| 1. |
- Pernett, Frank, et al.
(author)
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Spleen Contraction During Sudden Eupneic Hypoxia Elevates Hemoglobin Concentration
- 2021
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In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
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Journal article (peer-reviewed)abstract
- The spleen contracts progressively during moderate normobaric hypoxia exposure of 20 min, which elevates hemoglobin concentration (Hb). However, acute hypoxia exposure could be shorter and more severe when oxygen systems fail during, e.g., high-altitude sky diving, aircraft cabin pressure drop, balloon flights, extreme altitude climbing, and in some maladies. We aimed to evaluate the speed and magnitude of spleen contraction during short exposure to extreme eupneic hypoxia and its subsequent recovery on oxygen. Eight female and seven male volunteers were exposed to normobaric hypoxia (10% oxygen) for 10 min during sitting rest, followed by 10 min on 100% oxygen. Heart rate (HR), arterial oxygen saturation (SpO(2)), and mean arterial blood pressure (MAP) were measured continuously. The spleen was measured via ultrasonic imaging every minute for volume calculations, and venous blood samples were drawn before and after exposure for hemoglobin concentration (Hb). Mean (SD) spleen volume was 279 (115) mL before exposure, 219 (75) mL (21% reduction; P = 0.005) at 3 min of exposure, and 201 (93) mL after 10 min exposure to hypoxia (28% reduction; P < 0.001). Hb was 138.8 (7.6) g center dot L-1 before and 142.9 (8.1) g center dot L-1 after 10 min of exposure (2.9% increase; P < 0.001). SpO(2) was 96.4 (1.7)% before exposure and 74.7 (8.4)% during the last minute of exposure (22.5% reduction; P < 0.001). HR increased from 80 (14) to 90 (17) bpm during exposure (12% increase, P < 0.05). MAP remained unchanged. After 10 min recovery on oxygen, values had been restored for spleen volume and Hb, while SpO(2) was higher and HR lower compared with before hypoxia exposure. We concluded that acute normobaric hypoxia of only 10 min caused significant spleen volume contraction with Hb increase. This rapid spleen response, evident already after 3 min of exposure, could have a protective effect during sudden exposure to severe hypoxia.
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| 2. |
- Rodríguez-Zamora, Lara, 1985-, et al.
(author)
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Blood lactate accumulation during competitive freediving and synchronized swimming
- 2018
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In: Undersea & Hyperbaric Medicine. - : Undersea and Hyperbaric Medical Society, Inc.. - 1066-2936. ; 45:1, s. 55-63
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Journal article (peer-reviewed)abstract
- A number of competitive water sports are performed while breath-holding (apnea). Such performances put large demands on the anaerobic system, but the study of lactate accumulation in apneic sports is limited. We therefore aimed to determine and compare the net lactate accumulation (NLA) during competition events in six disciplines of competitive freediving (FD) and three disciplines of synchronized swimming (SSW). The FD disciplines were: static apnea (STA; n = 14); dynamic apnea (DYN; n = 19); dynamic apnea no fins (DNF; n = 16); constant weight (CWT; n = 12); constant weight no fins (CNF; n = 8); free immersion (FIM; n =10). The SSW disciplines were solo (n = 21), duet (n = 31) and team (n = 34). Capillary blood lactate concentration was measured before and three minutes after competition performances, and apneic duration and performance variables were recorded. In all nine disciplines NLA was observed. The highest mean (SD) NLA (mmol·L-1) was found in CNF at 6.3 (2.2), followed by CWT at 5.9 (2.3) and SSW solo at 5 (1.9). STA showed the lowest NLA 0.7 (0.7) mmol·L-1 compared to all other disciplines (P ⟨ 0.001). The NLA recorded shows that sports involving apnea involve high levels of anaerobic activity. The highest NLA was related to both work done by large muscle groups and long apneic periods, suggesting that NLA is influenced by both the type of work and apnea duration, with lower NLA in SSW due to shorter apneic episodes with intermittent breathing.
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| 3. |
- Schagatay, Erika, 1961-, et al.
(author)
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Spleen Volume and Contraction During Apnea in Mt. Everest Climbers and Everest Base Camp Trekkers
- 2020
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In: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 21:1, s. 84-91
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Journal article (peer-reviewed)abstract
- The human spleen can contract and transiently boost the blood with stored erythrocytes. We measured spleen volume and contraction during apneas in two groups, each containing 12 Caucasian participants (each 3 women): one group planning to summit Mt. Everest (8848 m; "Climbers") and another trekking to Everest Base Camp (5300 m; "Trekkers"). Tests were done in Kathmandu (1370 m) 1-3 days after arrival, before the Climb/Trek. Age, height, weight, vital capacity, resting heart rate, and arterial oxygen saturation were similar between groups (not significant). After 15 minutes of sitting rest, all participants performed a 1-minute apnea and, after 2 minutes of rest, 1 maximal duration apnea was performed. Six of the climbers did a third apnea and hemoglobin concentration (Hb) was measured. Three axial spleen diameters were measured by ultrasonic imaging before and after the apneas for spleen volume calculation. Mean (standard deviation) baseline spleen volume was larger in Climbers [367 (181) mL] than in Trekkers [228 (70) mL; p = 0.022]. Spleen contraction occurred during apneas in both groups, with about twice the magnitude in Climbers. Three apneas in six of the Climbers resulted in a spleen volume reduction from 348 (145) to 202 (91) mL (p = 0.005) and an Hb elevation from 147.9 (13.1) to 153.3 (11.3) g/L (p = 0.024). Maximal apneic duration was longer in Climbers [88 (23) seconds vs. 67 (18) seconds in Trekkers; p = 0.023]. We concluded that a large spleen characterizes Climbers, suggesting that spleen function may be important for high-altitude climbing performance.
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| 4. |
- Blakeson, Magdalene C., et al.
(author)
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Illness Incidence, Psychological Characteristics, and Sleep in Dogsled Drivers During the Iditarod Trail Sled Dog Race
- 2022
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In: Wilderness & environmental medicine (Print). - : Elsevier BV. - 1080-6032 .- 1545-1534. ; 33:1, s. 92-96
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Journal article (peer-reviewed)abstract
- Introduction: Every March, dogsled drivers (mushers) compete in a 1569-km race across Alaska, involving physical exertion, mental exertion, and sleep deprivation for up to 2 wk. These factors may increase mushers’ vulnerability to illness, making them a relevant study population for acute infection risk factors. Specifically, the influence of psychological factors on illness risk during prolonged physical exertion has rarely been investigated. The aim of this study was to examine the relationship between psychological characteristics, sleep deprivation, and illness incidence in Iditarod mushers. Methods: Fourteen mushers completed 4 psychological instruments to assess state and trait anxiety, resilience and perceived stress, and self-reported upper respiratory symptoms (URS) in the month before the race. Mushers self-reported sleep duration and URS during the race. Results: State and trait anxiety, resilience, and perceived stress did not differ between mushers with and without pre- and in-race URS (P>0.05). However, all mushers who reported in-race URS had reported URS ≤9 d before the race, and the onset of symptoms during the race typically occurred shortly after a rest period. Sleep duration was higher in mushers who reported in-race URS, both before (4.9±0.3 h, P=0.016) and during illness (5.9±1.3 h, P=0.006), vs mushers without in-race URS (3.4±0.8 h). Conclusions: This study highlights recent illness, rest periods, and greater sleep requirements as potential risk factors for URS onset during a multiday endurance challenge, whereas psychological factors were not associated with URS.
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| 5. |
- Danielsson, Tatiana
(author)
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Further Investigations of Convergence Results for Homogenization Problems with Various Combinations of Scales
- 2020
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Doctoral thesis (other academic/artistic)abstract
- This thesis is based on six papers. We study the homogenization of selected parabolic problems with one or more microscopic scales in space and time, respectively. The approaches are prepared by means of certain methods, like two-scale convergence, multiscale convergence and also the evolution setting of multiscale convergence and very weak multiscale convergence. Paper I treats a linear parabolic homogenization problem with rapid spatial and temporal oscillations in perforated domains. Suitable results of two-scale convergence type are established. Paper II deals with further development of compactness results which can be used in the homogenization procedure engaging a certain limit condition. The homogenization procedure deals with a parabolic problem with a certain matching between a fast spatial and a fast temporal scale and a coefficient passing to zero that the time derivative is multiplied with. Papers III and IV are further generalizations of Paper II and investigate homogenization problems with different types of matching between the microscopic scales. Papers III and IV deal with one and two rapid scales in both space and time respectively. Paper V treats the nonlinearity of monotone parabolic problems with an arbitrary number of spatial and temporal scales by applying the perturbed test functions method together with multiscale convergence and very weak multiscale convergence adapted to the evolution setting. In Paper VI we discuss the relation between two-scale convergence and the unfolding method and potential extensions of existing results. The papers above are summarized in Chapter 4. Chapter 1 gives a brief introduction to the topic and Chapters 2 and 3 are surveys over some important previous results.
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| 6. |
- de Asis Fernandez, Fran, et al.
(author)
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Hook Breathing Facilitates SaO(2) Recovery After Deep Dives in Freedivers With Slow Recovery
- 2019
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In: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 10
-
Journal article (peer-reviewed)abstract
- (SaO2)To facilitate recovery from hypoxia, many freedivers use a breathing method called "hook breathing" (HB) after diving, involving an interrupted exhale to build up intrapulmonary pressure. Some divers experience a delay in recovery of arterial oxygen saturation (SaO2) after diving, interpreted as symptoms of mild pulmonary edema, and facilitated recovery may be especially important in this group to avoid hypoxic "blackout." We examined the influence of HB on recovery of (SaO2) in freedivers with slow recovery (SR) and fast recovery (FR) of (SaO2) after deep "free immersion" (FIM) apnea dives to 30 m depth. Twenty-two male freedivers, with a mean (SD) personal best in the discipline FIM of 57(26) m, performed two 30 m deep dives, one followed by HB and one using normal breathing (NB) during recovery, at different days and weighted order. (SaO2) and heart rate (HR) were measured via pulse oximetry during recovery. The SR group (n = 5) had a faster (SaO2) recovery using HB, while the FR group (n = 17) showed no difference between breathing techniques. At 105 s, the SR group reached a mean (SD) SaO(2) of 95(5)% using HB, while using NB, their (SaO2) was 87(5)% (p < 0.05), and 105-120 s after surfacing(SaO2) was higher with HB (p < 0.05). In SR subjects, the average time needed to reach 95% (SaO2) with HB was 60 s, while it was 120 s at NB (p < 0.05). HR was similar in the SR group, while it was initially elevated at HB in the FR group (p < 0.05). We conclude that HB efficiently increases (SaO2) recovery in SR individuals, but not in the FR group. The proposed mechanism is that increased pulmonary pressure with HB will reverse any pulmonary edema and facilitate oxygen uptake in divers with delayed recovery.
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| 7. |
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| 8. |
- Engan, Harald, et al.
(author)
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Spleen contraction and Hb elevation after dietary nitrate intake
- 2020
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In: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 129:6, s. 1324-1329
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Journal article (peer-reviewed)abstract
- Ingestion of dietary nitrate ([Formula: see text]) is associated with improved exercise tolerance and reduced oxygen (O2) cost of exercise, ascribed to enhanced mitochondrial efficiency, muscle contractile function, or other factors. Nitrate ingestion has also been found to attenuate the reduction in arterial oxygen saturation ([Formula: see text]) during apnea and to prolong apneic duration. The spleen serves as a dynamic blood pool expelling erythrocytes into the circulation during apnea, and [Formula: see text] and nitric oxide donors may induce vasoactive effects in the mesenteric and splanchnic circulation. Our aim was to investigate the effect of ingestion of concentrated organic [Formula: see text]-rich beetroot juice (BR) on spleen volume and spleen contraction during apnea, and the resulting hemoglobin (Hb) concentration. Eight volunteers performed two apneas of submaximal and maximal duration during prone rest ∼2.5 h after ingesting 70 mL of BR (∼5 mmol [Formula: see text]) or placebo (PL; ∼0.003 mmol [Formula: see text]), on separate days in weighted order. Heart rate and [Formula: see text] were monitored continuously and spleen diameters were measured every minute for triaxial volume calculation. Capillary Hb samples were collected at baseline and after the maximal apnea. Baseline spleen volume was reduced by 66 mL after BR ingestion (22.9%; P = 0.026) and Hb was elevated (+3.0%; P = 0.015). During apneas, spleen contraction and Hb increase were similar between BR and PL conditions (NS). The study shows that dietary [Formula: see text]reduces spleen volume at rest, resulting in increased Hb. This spleen-induced Hb elevation following [Formula: see text] ingestions represents a novel mechanism that could enhance performance in conditions involving exercise, apnea, and hypoxia.NEW & NOTEWORTHY This is the first study to examine changes of spleen volume and circulating Hb following dietary [Formula: see text] supplementation. After dietary [Formula: see text] ingestion, the spleen volume at rest was reduced and Hb was elevated. The spleen contains a dynamic red blood cell reservoir, which can be mobilized and facilitate oxygen transport during various types of physiological stress. This study has revealed an additional, previously unexplored mechanism possibly contributing to the ergogenic effects of dietary [Formula: see text].
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| 9. |
- Holmström, Pontus K., et al.
(author)
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Differential splenic responses to hyperoxic breathing at high altitude in Sherpa and lowlanders
- 2024
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In: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 109:4, s. 535-548
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Journal article (peer-reviewed)abstract
- The human spleen contracts in response to stress-induced catecholamine secretion, resulting in a temporary rise in haemoglobin concentration ([Hb]). Recent findings highlighted enhanced splenic response to exercise at high altitude in Sherpa, possibly due to a blunted splenic response to hypoxia. To explore the potential blunted splenic contraction in Sherpas at high altitude, we examined changes in spleen volume during hyperoxic breathing, comparing acclimatized Sherpa with acclimatized individuals of lowland ancestry. Our study included 14 non-Sherpa (7 female) residing at altitude for a mean continuous duration of 3 months and 46 Sherpa (24 female) with an average of 4 years altitude exposure. Participants underwent a hyperoxic breathing test at altitude (4300 m; barrometric pressure = ∼430 torr; (Formula presented.) = ∼90 torr). Throughout the test, we measured spleen volume using ultrasonography and monitored oxygen saturation ((Formula presented.)). During rest, Sherpa exhibited larger spleens (226 ± 70 mL) compared to non-Sherpa (165 ± 34 mL; P < 0.001; effect size (ES) = 0.95, 95% CI: 0.3–1.6). In response to hyperoxia, non-Sherpa demonstrated 22 ± 12% increase in spleen size (35 ± 17 mL, 95% CI: 20.7–48.9; P < 0.001; ES = 1.8, 95% CI: 0.93–2.66), while spleen size remained unchanged in Sherpa (−2 ± 13 mL, 95% CI: −2.4 to 7.3; P = 0.640; ES = 0.18, 95% CI: −0.10 to 0.47). Our findings suggest that Sherpa and non-Sherpas of lowland ancestry exhibit distinct variations in spleen volume during hyperoxia at high altitude, potentially indicating two distinct splenic functions. In Sherpa, this phenomenon may signify a diminished splenic response to altitude-related hypoxia at rest, potentially contributing to enhanced splenic contractions during physical stress. Conversely, non-Sherpa experienced a transient increase in spleen size during hyperoxia, indicating an active tonic contraction, which may influence early altitude acclimatization in lowlanders by raising [Hb].
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| 10. |
- Holmström, Pontus K., et al.
(author)
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Enhanced splenic volume and contraction in elite endurance athletes
- 2021
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In: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 131:2, s. 474-486
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Journal article (peer-reviewed)abstract
- Splenic contraction, which leads to ejection of stored erythrocytes, is greater in athletes involved in regular freediving or high-altitude activities. As this response facilitates oxygen-carrying capacity, similar characteristics may be expected of elite endurance athletes. Therefore, our aims were to compare resting and apnea-induced splenic volume in endurance athletes and untrained individuals, and to assess the athletes' exercise-induced splenic volume. Twelve elite biathletes (7 women) and 12 controls (6 women) performed a maximal effort apnea in a seated position. In addition, the biathletes completed a maximal roller-skiing time trial. Splenic dimensions were measured by ultrasonic imaging for subsequent volume calculations, whereas Hb was analyzed from capillary blood samples and cardiorespiratory variables were monitored continuously. Baseline splenic volume was larger in the biathletes (214 +/- 56 mL) compared with controls (157 +/- 39 mL, P = 0.008) and apnea-induced splenic contraction was also greater in the biathletes (46 +/- 20 mL vs. 30 +/- 16 mL, P = 0.035). Hb increased immediately after apnea in the biathletes (4.5 +/- 4.8%, P = 0.029) but not in the controls (-0.7 +/- 3.1%, P = 0.999). Increases in exercise-induced splenic contraction (P = 0.008) and Hb (P = 0.001) were greater compared with the apnea-induced responses among the athletes. Baseline splenic volume tended to be correlated with <(V)over dot>o(2max) (r= 0.584, P = 0.059). We conclude that elite biathletes have greater splenic volume with a greater ability to contract and elevate Hb compared with untrained individuals. These characteristics may transiently enhance O-2-carrying capacity and possibly increase O-2 uptake, thereby helping biathletes to cope with high intermittent O-2 demands and severe O-2 deficits that occur during biathlon training and competition. NEW & NOTEWORTHY This study demonstrates that elite biathletes have larger splenic volume, apnea-induced splenic contraction, and Hb elevation compared with untrained individuals, which is likely functional to cope with high O-2 demands and substantial O-2 deficits. We believe that enhanced splenic contraction may be of importance during competitions involving crosscountry skiing, to regulate circulating Hb and enhance O-2-carrying capacity, which may protect Ca-O2, and increase O-2 uptake.
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| 11. |
- Holmström, Pontus
(author)
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Protective Responses to Freediving Reveal High-Altitude Tolerance
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- High-altitude mountaineers - just as freedivers - are exposed to hypoxia. During freediving, the diving response leads to reduced oxygen consumption, and splenic contraction increases circulating hemoglobin concentration (Hb), which enhances freediving performance. It is unknown whether these responses relate with altitude-induced responses and what role the spleen has at high-altitude. My thesis aimed to explore whether associations exist between these apnea-induced responses and tolerance to high-altitude. In five studies, I investigated the diving response and splenic contraction during apnea in a range of groups, including recreational trekkers, elite climbers, indigenous Sherpa (living high and living low) and endurance athletes, at low-altitude and at high-altitude. My primary finding was striking: the diving response and splenic size were associated with tolerance to high-altitude; lowlanders with a strong diving response and large spleen showed less symptoms of acute mountain sickness at high-altitude. I also found that groups often exposed to high-altitude have larger spleens compared with groups who reside at sea-level. Interestingly, the Sherpa living high had larger spleens compared with Sherpa living low. Another important finding was that the spleen is reduced in size by ~14% per 1000 m of ascent in lowlanders, which was associated with enhanced baseline Hb. I also found that endurance athletes, who are dependent on efficient oxygen delivery, have larger spleens compared with untrained individuals. I conclude, that a strong diving response and a large spleen may be characteristics of high-altitude tolerant lowlanders, and could possibly be used to predict high-altitude sensitivity. Studies 1-4 suggest that a large spleen is a favourable trait in several groups to tolerate high-altitude hypoxia, likely by its ability to regulate circulating Hb. Sherpa had larger spleens compared with lowlanders, indicating that genetic factors influence splenic size, while the finding that Sherpa living high had larger spleens than Sherpa living low indicate that splenic size also is influenced by environmental exposure. Study 4 revealed a tonic splenic contraction in lowlanders at high-altitude, suggesting that the Hb regulating function may be important before EPO-induced red cell increase occurs, thereby aiding individual acclimatization.
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| 12. |
- Holmström, Pontus, et al.
(author)
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Spleen Size and Function in Sherpa Living High, Sherpa Living Low and Nepalese Lowlanders
- 2020
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In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 11
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Journal article (peer-reviewed)abstract
- High-altitude (HA) natives have evolved some beneficial responses leading to superior work capacity at HA compared to native lowlanders. Our aim was to study two responses potentially protective against hypoxia: the spleen contraction elevating hemoglobin concentration (Hb) and the cardiovascular diving response in Sherpa highlanders, compared to lowlanders. Male participants were recruited from three groups: (1) 21 Sherpa living at HA (SH); (2) seven Sherpa living at low altitude (SL); and (3) ten native Nepalese lowlanders (NL). They performed three apneas spaced by a two-min rest at low altitude (1370 m). Their peripheral oxygen saturation (SpO(2)), heart rate (HR), and spleen volume were measured across the apnea protocol. Spleen volume at rest was 198 +/- 56 mL in SH and 159 +/- 35 mL in SL (p= 0.047). The spleen was larger in Sherpa groups compared to the 129 +/- 22 mL in NL (p< 0.001 compared to SH;p= 0.046 compared to SL). Spleen contraction occurred in all groups during apnea, but it was greater in Sherpa groups compared to NL (p< 0.001). HR was lower in Sherpa groups compared to NL both during rest (SL:p< 0.001; SH:p= 0.003) and during maximal apneas (SL:p< 0.001; SH:p= 0.06). The apnea-induced HR reduction was 8 +/- 8% in SH, 10 +/- 4% in SL (NS), and 18 +/- 6% in NL (SH:p= 0.005; SL:p= 0.021 compared to NL). Resting SpO(2)was similar in all groups. The progressively decreasing baseline spleen size across SH, SL, and NL suggests a role of the spleen at HA and further that both genetic predisposition and environmental exposure determine human spleen size. The similar HR responses of SH and SL suggest that a genetic component is involved in determining the cardiovascular diving response.
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| 13. |
- Holmström, Pontus, et al.
(author)
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Test–retest reliability of splenic volume assessment by ultrasonography
- 2022
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 12:1
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Journal article (peer-reviewed)abstract
- While MRI and CT are the gold standards for assessments of splenic size in clinical settings, ultrasonography is particularly suited due to its portability, cost efficiency and easy utilization. However, ultrasonography is associated with subjective assessment, potentially resulting in increased variation. We used a test–retest design aiming to determine the reliability of splenic measurements assessed by ultrasonography during apnea. In addition, we compared reliability between different equations for volume calculations: Koga, Prolate ellipsoid and Pilström. Twelve healthy participants (6 women) performed two tests separated by 15 min, comprising a maximal voluntary apnea in a seated position. Splenic dimensions were measured via ultrasonography for 5 min before and immediately following apnea. Resting splenic volume displayed high test–retest reliability between tests (Pilström: 157 ± 39 mL vs 156 ± 34 mL, p = .651, ICC = .970, p < .001, CV = 2.98 ± 0.1%; Prolate ellipsoid: 154 ± 37 mL vs 144 ± 43 mL, p = .122, ICC = .942, p < .001, CV = 5.47 ± 0.3%; Koga: 142 ± 37 mL vs 140 ± 59 mL, p = .845, ICC = .859, p < .001, CV = 9.72 ± 1.4%). Apnea-induced volumes displayed similar reliability (127 ± 29 mL vs 129 ± 28 mL, p = .359, ICC = .967, p < .001, CV = 3.14 ± 3.1%). Reliability was also high between equations (Pilström vs Prolate ellipsoid: ICC = .818, p < .001, CV = 7.33 ± 0.3%, bias = − 3.1 mL, LoA = − 46.9 to 40.7 mL; Pilström vs Koga: ICC = .618, p < .01, CV = 11.83 ± 1.1%, bias = − 14.8 mL, LoA = − 76.9 to 47.3 mL). We conclude that splenic ultrasonographic measurements have practical applications during laboratory and field-based research as a reliable method detecting splenic volume change consistently between repeated tests. The Pilström equation displayed similar reliability compared to the prolate ellipsoid formula and slightly higher compared to the Koga formula and may be particularly useful to account for individual differences in splenic dimensions.
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| 14. |
- Holmström, Pontus, et al.
(author)
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The effects of high altitude ascent on splenic contraction and the diving response during voluntary apnea
- 2021
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In: Experimental Physiology. - 0958-0670 .- 1469-445X. ; 106:1, s. 160-174
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Journal article (peer-reviewed)abstract
- Voluntary apnea causes splenic contraction and reductions in heart rate (HR; bradycardia), and subsequent transient increases in hemoglobin concentration ([Hb]). Ascent to high altitude (HA) induces systemic hypoxia and reductions in oxygen saturation (SpO2 ), which may cause tonic splenic contraction, which may contribute to hematological acclimatization associated with HA ascent. We measured resting cardiorespiratory variables (HR, SpO2 , [Hb]) and resting splenic volume (via ultrasound) during incremental ascent from 1400 m (day 0), to 3440 m (day 3), 4240 m (day 7), and 5160 m (day 10) in non-acclimatized native lowlanders during assent to HA in the Nepal Himalaya. In addition, apnea-induced responses in HR, SpO2 and splenic volume were measured before and after two separate voluntary maximal apneas (A1-A2) at 1400 m, 3440 m and 4240 m. Resting spleen volume decreased -14.3% (-15.2 mL)/1000 m with ascent, from 140±41 mL (1400 m), to 108±28 mL (3440 m; P > 0.99), 94±22 mL (4240 m; P = 0.009) and 84±28 mL (5160 m; P = 0.029), with concomitant increases in [Hb] from 125±18.3 g/L (1400 m) to 128±10.4 g/L (3440 m), 138.8±12.7 g/L (4240 m) and 157.5±8 g/L (5160 m; P = 0.021). Apnea-induced splenic contraction was 50±15 mL (1400 m), 44±17 mL (3440 m; P > 0.99) and 26±8 mL (4240 m; P = 0.002), but was not consistently associated with increases in [Hb]. The apnea-induced bradycardia was more pronounced at 3440 m (A1:P = 0.04; A2:P = 0.094) and at 4240 m (A1:P = 0.037 A2:P = 0.006) compared to values at 1400 m. We conclude that hypoxia-induced splenic contraction at rest (a) may contribute to restoring arterial oxygen content through its [Hb]-enhancing contractile function and (b) eliminates further apnea-induced [Hb] increases in hypoxia. We suggest that tonic splenic contraction may contribute to hematological acclimatization early in HA ascent in humans.
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| 15. |
- Holmström, Pontus, et al.
(author)
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The Magnitude of Diving Bradycardia During Apnea at Low-Altitude Reveals Tolerance to High Altitude Hypoxia
- 2019
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In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 10, s. 1-12
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Journal article (peer-reviewed)abstract
- Acute mountain sickness (AMS) is a potentially life-threatening illness that may develop during exposure to hypoxia at high altitude (HA). Susceptibility to AMS is highly individual, and the ability to predict it is limited. Apneic diving also induces hypoxia, and we aimed to investigate whether protective physiological responses, i.e., the cardiovascular diving response and spleen contraction, induced during apnea at low-altitude could predict individual susceptibility to AMS. Eighteen participants (eight females) performed three static apneas in air, the first at a fixed limit of 60 s (A1) and two of maximal duration (A2-A3), spaced by 2 min, while SaO(2), heart rate (HR) and spleen volume were measured continuously. Tests were conducted in Kathmandu (1470 m) before a 14 day trek to mount Everest Base Camp (5360 m). During the trek, participants reported AMS symptoms daily using the Lake Louise Questionnaire (LLQ). The apnea-induced HR-reduction (diving bradycardia) was negatively correlated with the accumulated LLQ score in A1 (r(s) = -0.628, p= 0.005) and A3 (r(s) = -0.488, p = 0.040) and positively correlated with SaO(2) at 4410 m (A1: r = 0.655, p = 0.003; A2: r = 0.471, p = 0.049; A3: r = 0.635, p = 0.005). Baseline spleen volume correlated negatively with LLQ score (r(s) = -0.479, p = 0.044), but no correlation was found between apnea-induced spleen volume reduction with LLQ score (r(s) = 0.350, p = 0.155). The association between the diving bradycardia and spleen size with AMS symptoms suggests links between physiological responses to HA and apnea. Measuring individual responses to apnea at sea-level could provide means to predict AMS susceptibility prior to ascent.
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| 16. |
- Lindblom, Hampus, et al.
(author)
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Effect of exercise intensity and apnea on splenic contraction and hemoglobin increase in well-trained cross-country skiers
- 2024
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In: European Journal of Applied Physiology. - : Springer Nature. - 1439-6319 .- 1439-6327. ; 124:7, s. 2057-2067
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Journal article (peer-reviewed)abstract
- The human spleen acts as a reservoir for red blood cells, which is mobilized into the systemic circulation during various conditions such as hypoxia and physical exertion. Cross-country (XC) skiers, renowned for their exceptional aerobic capacity, are regularly exposed to high-intensity exercise and local oxygen deficits. We investigated a putative dose-dependent relationship between splenic contraction and concomitant hemoglobin concentration ([Hb]) elevation across four exercise intensities in well-trained XC skiers. Fourteen male XC skiers voluntarily participated in a 2-day protocol, encompassing a serial apnea test and a VO2max test (day 1), followed by three submaximal exercise intensities on a roller skiing treadmill corresponding to 55, 70, and 85% of VO2max (day 2). Spleen volume was measured via ultrasonic imaging, and venous blood samples were used to determine [Hb] levels. Baseline spleen volume was similar (266(35) mL) for all conditions (NS). Notably, all conditions induced significant splenic contractions and transient [Hb] elevations. The VO2max test exhibited the most pronounced splenic contraction (35.8%, p < 0.001) and a [Hb] increase of 8.1%, while the 85% exercise intensity led to 27.1% contraction and the greatest [Hb] increase (8.3%, < 0.001) compared to baseline. The apnea test induced relatively smaller responses (splenic contraction: 20.4%, [Hb] = 3.3%, p < 0.001), akin to the response observed at the 70% exercise intensity (splenic contraction = 23%, [Hb] = 6.4%, p < 0,001) and 55% (splenic contraction = 20.0%, [Hb] = 4.8%, p < 0.001). This study shows a discernible dose-dependent relationship between splenic contraction and [Hb] increase with levels of exercise, effectively distinguishing between submaximal and maximal exercise intensity.
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| 17. |
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| 18. |
- Lodin-Sundström, Angelica, 1981-, et al.
(author)
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Splenic contraction is enhanced by exercise at simulated high altitude
- 2021
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 121:6, s. 1725-1732
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Journal article (peer-reviewed)abstract
- Purpose: Splenic contraction increases circulating hemoglobin (Hb) with advantages during hypoxia. As both hypoxia and exercise have been shown to be important separate triggers of splenic contraction we aimed to investigate if the spleen response to simulated high altitude (HA) is enhanced by superimposing exercise. Method: Fourteen healthy volunteers (seven females) performed the following protocol in a normobaric environment sitting on an ergometer cycle: 20 min rest in normoxia; 20 min rest while breathing hypoxic gas simulating an altitude of 3500 m; 10 min exercise at an individually set intensity while breathing the hypoxic gas; 20 min rest in hypoxia; and finally 20 min rest in normoxia. Spleen measurements were collected by ultrasonic imaging and venous Hb measured at the end of each intervention. Result: Mean ± SD baseline spleen volume during normoxic rest was 280 ± 107 mL, the volume was reduced by 22% during rest in hypoxia to 217 ± 92 mL (p < 0.001) and by 33% during exercise in hypoxia (189 mL; p < 0.001). Hb was 140.7 ± 7.0 g/L during normoxic rest and 141.3 ± 7.4 g/L during hypoxic rest (NS), but increased by 5.3% during hypoxic exercise (148.6 ± 6.3 g/L; p < 0.001). Spleen volume and Hb were stepwise changed back to baseline at cessation of exercise and return to normoxia. Conclusion: Splenic contraction is induced by hypoxia and further enhanced by superimposing exercise, and reduced when exercise ceases, in a step-wise manner, showing that the tonic but partial contraction observed in long-term field expeditions to HA may occur also in the short term. This “graded response” may be beneficial during acclimatization to HA, to cope with moderate chronic hypoxia during rest while allowing additional enhancement of oxygen carrying capacity to overcome short bouts of extreme hypoxia caused by exercise.
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| 19. |
- McKnight, J. Chris, et al.
(author)
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When the human brain goes diving : using near-infrared spectroscopy to measure cerebral and systemic cardiovascular responses to deep, breath-hold diving in elite freedivers
- 2021
-
In: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 376:1831
-
Journal article (peer-reviewed)abstract
- Continuous measurements of haemodynamic and oxygenation changes in free living animals remain elusive. However, developments in biomedical technologies may help to fill this knowledge gap. One such technology is continuous-wave near-infrared spectroscopy (CW-NIRS)-a wearable and non-invasive optical technology. Here, we develop a marinized CW-NIRS system and deploy it on elite competition freedivers to test its capacity to function during deep freediving to 107 m depth. We use the oxyhaemoglobin and deoxyhaemoglobin concentration changes measured with CW-NIRS to monitor cerebral haemodynamic changes and oxygenation, arterial saturation and heart rate. Furthermore, using concentration changes in oxyhaemoglobin engendered by cardiac pulsation, we demonstrate the ability to conduct additional feature exploration of cardiac-dependent haemodynamic changes. Freedivers showed cerebral haemodynamic changes characteristic of apnoeic diving, while some divers also showed considerable elevations in venous blood volumes close to the end of diving. Some freedivers also showed pronounced arterial deoxygenation, the most extreme of which resulted in an arterial saturation of 25%. Freedivers also displayed heart rate changes that were comparable to diving mammals both in magnitude and patterns of change. Finally, changes in cardiac waveform associated with heart rates less than 40 bpm were associated with changes indicative of a reduction in vascular compliance. The success here of CW-NIRS to non-invasively measure a suite of physiological phenomenon in a deep-diving mammal highlights its efficacy as a future physiological monitoring tool for human freedivers as well as free living animals. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.
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| 20. |
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| 21. |
- Mulder, Eric, et al.
(author)
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Case Studies in Physiology : Is blackout in breath-hold diving related to cardiac arrhythmias?
- 2023
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In: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 134:4, s. 951-956
-
Journal article (peer-reviewed)abstract
- Syncope or "blackout" (BO) in breath-hold diving (freediving) is generally considered to be caused by hypoxia. However, it has been suggested that cardiac arrhythmias affecting the pumping effectivity could contribute to BO. BO is fairly common in competitive freediving, where athletes aim for maximal performance. We recorded heart rate (HR) during a static apnea (STA) competition, to reveal if arrhythmias occur. Four male freedivers with STA personal best (PB) of 349 ± 43 s, volunteered during national championships, where they performed STA floating face down in a shallow indoor pool. A non-coded Polar T31 chest strap recorded R-R intervals and a water- and pressure-proof pulse oximeter arterial oxygen saturation. Three divers produced STA near their PB without problems, whereas one diver ended with BO at 5 min 17s, which was 12 s beyond his PB. He was immediately brought up by safety divers and resumed breathing within 10 s. All divers attained similar lowest diving HR (47 ± 4 beats/min), but HR recordings displayed a different pattern for the diver ending with BO. After a short tachycardia, the three successful divers developed bradycardia, which became more pronounced during the second half of the apnea. The fourth diver developed pronounced bradycardia earlier, and at 2.5 min into the apnea, HR started alternating between approximately 50 and 140 beats/min, until the diver lost consciousness. At resumed breathing, HR returned to baseline. Nadir oxygen saturation was similar for all divers. We speculate that arrhythmia could have contributed to BO, by lowering stroke volume leading to a systolic blood pressure drop, affecting brain perfusion.NEW & NOTEWORTHY Heart rate during prolonged breath-holding until the point of loss of consciousness has not previously been published. The recordings show that blackout was preceded by a period of persistent alterations in R-R intervals, whereby an ectopic beat followed every normal heartbeat. Explanations for this deviating heart rate pattern could be either premature atrial contractions or premature ventricular contractions following every atrial beat, i.e., bigeminy, which could have compromised cardiac pumping function and caused/contributed to blackout.
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| 22. |
- Mulder, Eric, et al.
(author)
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Effects of dynamic apnea training on diving bradycardia and short distance swimming performance
- 2022
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In: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 62:8, s. 1037-1044
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Apnea training enhances bradycardia and improves competitive apnea performance, and has been proposed as a training method for other sports, such as swimming. We evaluated the effects of apneic underwater swimming, i.e. dynamic apnea (DYN), in 9 competitive swimmers (TR) who completed ten DYN sessions over 2 weeks.METHODS: TR performed pre- and post-training tests including a static apnea test with continuous heart rate (HR) and peripheral oxygen saturation measurements, all-out 50m and 100m freestyle tests and an all-out DYN test. Control groups were competitive swimmers (SC; n=10) that trained swimming without DYN, and a non-swimmer group (AC; n=10) performing only static apnea tests.RESULTS: Post-training, TR mean±SD time for 50m freestyle improved from 25.51±2.01s to 24.64±2.02s (p<0.01) and for 100m from 55.5±4.2s to 54.1±4.4s (p<0.05). SC also improved their 100m time from 56.7±3.3s to 56.0±3.1s (p<0.01; p=0.07 between groups). Only TR performed DYN tests; DYN distance increased from 62.1±11.5m to 70.9±18.9m (p<0.05) while DYN speed decreased from 0.74±0.14m/s to 0.64±0.18m/s (p<0.01). Static apnea duration did not change in any of the groups, but HR-reduction was enhanced posttraining only in TR (24.8±14.8% to 31.1±10.9%, p<0.01; p<0.001 between groups).CONCLUSIONS: We conclude that 2 weeks of DYN training enhanced DYN performance, which may be caused by the enhanced apnea-induced diving bradycardia. Further research is required to determine whether DYN training enhances short distance freestyle swimming performance.
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| 23. |
- Mulder, Eric, et al.
(author)
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First Evaluation of a Newly Constructed Underwater Pulse Oximeter for Use in Breath-Holding Activities
- 2021
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In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
-
Journal article (peer-reviewed)abstract
- Studying risk factors in freediving, such as hypoxic blackout, requires development of new methods to enable remote underwater monitoring of physiological variables. We aimed to construct and evaluate a new water- and pressure proof pulse oximeter for use in freediving research. The study consisted of three parts: (I) A submersible pulse oximeter (SUB) was developed on a ruggedized platform for recording of physiological parameters in challenging environments. Two MAX30102 sensors were used to record plethysmograms, and included red and infra-red emitters, diode drivers, photodiode, photodiode amplifier, analog to digital converter, and controller. (II) We equipped 20 volunteers with two transmission pulse oximeters (TPULS) and SUB to the fingers. Arterial oxygen saturation (SpO(2)) and heart rate (HR) were recorded, while breathing room air (21% O-2) and subsequently a hypoxic gas (10.7% O-2) at rest in dry conditions. Bland-Altman analysis was used to evaluate bias and precision of SUB relative to SpO(2) values from TPULS. (III) Six freedivers were monitored with one TPULS and SUB placed at the forehead, during a maximal effort immersed static apnea. For dry baseline measurements (n = 20), SpO(2) bias ranged between -0.8 and -0.6%, precision between 1.0 and 1.5%; HR bias ranged between 1.1 and 1.0 bpm, precision between 1.4 and 1.9 bpm. For the hypoxic episode, SpO(2) bias ranged between -2.5 and -3.6%, precision between 3.6 and 3.7%; HR bias ranged between 1.4 and 1.9 bpm, precision between 2.0 and 2.1 bpm. Freedivers (n = 6) performed an apnea of 184 +/- 53 s. Desaturation- and resaturation response time of SpO(2) was approximately 15 and 12 s shorter in SUB compared to TPULS, respectively. Lowest SpO(2) values were 76 +/- 10% for TPULS and 74 +/- 13% for SUB. HR traces for both pulse oximeters showed similar patterns. For static apneas, dropout rate was larger for SUB (18%) than for TPULS (<1%). SUB produced similar SpO(2) and HR values as TPULS, both during normoxic and hypoxic breathing (n = 20), and submersed static apneas (n = 6). SUB responds more quickly to changes in oxygen saturation when sensors were placed at the forehead. Further development of SUB is needed to limit signal loss, and its function should be tested at greater depth and lower saturation.
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| 24. |
- Mulder, Eric
(author)
-
Identifying Risk Factors and Safety Strategies in Freediving through Physiological Research and Wearable Technology
- 2024
-
Doctoral thesis (other academic/artistic)abstract
- Freediving, underwater diving while breath-holding, imposes unique physiological challenges to the human body. This includes immersion, changes in hydrostatic pressure, hypercapnia, and hypoxia. Severe hypoxia can cause loss of consciousness, known as hypoxic blackout, and without immediate assistance drowning may occur. The aim of this thesis was to identify factors increasing the risk of hypoxic blackout, to determine if physiological responses mitigated these risks and to explore potential interventions that could promote safe freediving. This was done by utilizing a prototype water- and pressure-proof pulse oximeter (SUB) to measure heart rate (HR) and arterial oxygen saturation (SpO2) under various real-world freediving conditions, and through laboratory investigation of the effects of apnea- recovery pacing on repeated apneas, focusing on arterial, cerebral, and muscle oxygenation. Study 1 demonstrated the SUB's ability to record HR and SpO2 during deep sea dives up to 82 meters, marking an important advancement in underwater monitoring technology. Study 2 showed that deeper dives resulted in greater oxygen desaturation, potentially increasing the risk of hypoxic blackout, not only due to pressure effects on gas exchange, but also from increased physical exertion. In addition, some individuals experienced hypoxia upon reaching maximum depth, when hyperoxia is expected, suggesting that gas exchange may be compromised, which could increase the risk of blackout during ascent. In Study 3, a persistent cardiac arrhythmia preceded a blackout, suggesting that arrhythmias may be a contributing factor to increased risk of blackout. Study 4 showed that brain oxygen homeostasis was maintained across a series of submaximal apneas with equal dive-to-rest ratio, without progressive oxygen desaturation occurring, suggesting that pacing strategies can be effectively used to maintain safety in repeated freediving and should be individually tailored. Collectively, these studies confirm that well- trained freedivers exhibit a remarkable tolerance to hypoxia. However, the risk of hypoxic blackout is highly individual, suggesting that establishing a definitive blackout threshold based on SpO2 may be challenging. It is therefore concluded that there is a need for enhanced safety protocols in freediving, including personalized physiological monitoring, which could be enabled by innovative wearable technologies like the SUB to mitigate the risk of blackout in freediving.
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| 25. |
- Mulder, Eric, et al.
(author)
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New scientific methods in breath-hold diving research
- 2021
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In: Freiberg Online Geoscience (FOG). - 1434-7512. ; 58, s. 115-125
-
Journal article (peer-reviewed)abstract
- Physiological field research on breath-hold divers (freedivers) is challenging as divers are exposed to hyperbaric environments hostile to classical physiological measurement methods. Two main challenges are; I) The need of developing methods allowing measurements of physiological variables underwater at depth, II) To accompany the studied freediver in the water. The rapid vertical descent and ascent makes it impossible for researchers to use SCUBA to follow the participants to depth. We present new approaches in scientific diving to meet these demands. Our methods development of underwater technology has included water- and pressure-proof dataloggers to record and store data from a 12 lead ECG (250Hz) and photoplethysmograms from two SpO2 probes using red- and infrared signals (30Hz), combined with ambient pressure and temperature loggers. We previously used SCUBA to enable real-time blood pressure and ECG measurements on freedivers, by waiting for them at the bottom of their pre-determined depth. A breath-hold diving approach for the researcher was found to be superior due to enhanced flexibility in contrast to a heavy, static SCUBA setup. A method was developed in order to perform such scientific freediving safely, the basis being diving in e.g., the professional Japanese Ama divers. Combining the use of novel wearable water- and pressureproof physiological measurement methods with “scientific freediving”, seems to provide optimal work flexibility for both our study participants and the researcher, and may be the preferred approach for our future research.
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| 26. |
- Mulder, Eric, et al.
(author)
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Reply to Lemaître and Costalat
- 2023
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In: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 135:4, s. 728-729
-
Journal article (peer-reviewed)
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| 27. |
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| 28. |
- Mulder, Eric, et al.
(author)
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Underwater pulse oximetry reveals increased rate of arterial oxygen desaturation across repeated freedives to 11 metres of freshwater
- 2023
-
In: Diving and Hyperbaric Medicine. - : Diving and Hyperbaric Medicine Journal. - 1833-3516 .- 2209-1491. ; 53:1, s. 16-23
-
Journal article (peer-reviewed)abstract
- INTRODUCTION: Recreational freedivers typically perform repeated dives to moderate depths with short recovery intervals. According to freediving standards, these recovery intervals should be twice the dive duration; however, this has yet to be supported by scientific evidence. METHODS: Six recreational freedivers performed three freedives to 11 metres of freshwater (mfw), separated by 2 min 30 s recovery intervals, while an underwater pulse oximeter measured peripheral oxygen saturation (SpO2) and heart rate (HR). RESULTS: Median dive durations were 54.0 s, 103.0 s and 75.5 s (all dives median 81.5 s). Median baseline HR was 76.0 beats per minute (bpm), which decreased during dives to 48.0 bpm in dive one, 40.5 bpm in dive two and 48.5 bpm in dive three (all P < 0.05 from baseline). Median pre-dive baseline SpO2 was 99.5%. SpO2 remained similar to baseline for the first half of the dives, after which the rate of desaturation increased during the second half of the dives with each subsequent dive. Lowest median SpO2 after dive one was 97.0%, after dive two 83.5% (P < 0.05 from baseline) and after dive three 82.5% (P < 0.01 from baseline). SpO2 had returned to baseline within 20 s after all dives. CONCLUSIONS: We speculate that the enhanced rate of arterial oxygen desaturation across the serial dives may be attributed to a remaining 'oxygen debt', leading to progressively increased oxygen extraction by desaturated muscles. Despite being twice the dive duration, the recovery period may be too short to allow full recovery and to sustain prolonged serial diving, thus does not guarantee safe diving. Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.
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| 29. |
- Mulder, Eric, et al.
(author)
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Unlocking the depths : multiple factors contribute to risk for hypoxic blackout during deep freediving
- 2023
-
In: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 123:11, s. 2483-2493
-
Journal article (peer-reviewed)abstract
- Purpose: To examine the effect of freediving depth on risk for hypoxic blackout by recording arterial oxygen saturation (SpO2) and heart rate (HR) during deep and shallow dives in the sea. Methods: Fourteen competitive freedivers conducted open-water training dives wearing a water-/pressure proof pulse oximeter continuously recording HR and SpO2. Dives were divided into deep (> 35 m) and shallow (10–25 m) post-hoc and data from one deep and one shallow dive from 10 divers were compared. Results: Mean ± SD depth was 53 ± 14 m for deep and 17 ± 4 m for shallow dives. Respective dive durations (120 ± 18 s and 116 ± 43 s) did not differ. Deep dives resulted in lower minimum SpO2 (58 ± 17%) compared with shallow dives (74 ± 17%; P = 0.029). Overall diving HR was 7 bpm higher in deep dives (P = 0.002) although minimum HR was similar in both types of dives (39 bpm). Three divers desaturated early at depth, of which two exhibited severe hypoxia (SpO2 ≤ 65%) upon resurfacing. Additionally, four divers developed severe hypoxia after dives. Conclusions: Despite similar dive durations, oxygen desaturation was greater during deep dives, confirming increased risk of hypoxic blackout with increased depth. In addition to the rapid drop in alveolar pressure and oxygen uptake during ascent, several other risk factors associated with deep freediving were identified, including higher swimming effort and oxygen consumption, a compromised diving response, an autonomic conflict possibly causing arrhythmias, and compromised oxygen uptake at depth by lung compression possibly leading to atelectasis or pulmonary edema in some individuals. Individuals with elevated risk could likely be identified using wearable technology.
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| 30. |
- Mulder, Eric, et al.
(author)
-
Using Underwater Pulse Oximetry in Freediving to Extreme Depths to Study Risk of Hypoxic Blackout and Diving Response Phases
- 2021
-
In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
-
Journal article (peer-reviewed)abstract
- Deep freediving exposes humans to hypoxia and dramatic changes in pressure. The effect of depth on gas exchange may enhance risk of hypoxic blackout (BO) during the last part of the ascent. Our aim was to investigate arterial oxygen saturation (SpO2) and heart rate (HR) in shallow and deep freedives, central variables, which have rarely been studied underwater in deep freediving. Four male elite competitive freedivers volunteered to wear a newly developed underwater pulse oximeter for continuous monitoring of SpO2 and HR during self-initiated training in the sea. Two probes were placed on the temples, connected to a recording unit on the back of the freediver. Divers performed one “shallow” and one “deep” constant weight dive with fins. Plethysmograms were recorded at 30 Hz, and SpO2 and HR were extracted. Mean ± SD depth of shallow dives was 19 ± 3 m, and 73 ± 12 m for deep dives. Duration was 82 ± 36 s in shallow and 150 ± 27 s in deep dives. All divers desaturated more during deeper dives (nadir 55 ± 10%) compared to shallow dives (nadir 80 ± 22%) with a lowest SpO2 of 44% in one deep dive. HR showed a “diving response,” with similar lowest HR of 42 bpm in shallow and deep dives; the lowest value (28 bpm) was observed in one shallow dive. HR increased before dives, followed by a decline, and upon resurfacing a peak after which HR normalized. During deep dives, HR was influenced by the level of exertion across different diving phases; after an initial drop, a second HR decline occurred during the passive “free fall” phase. The underwater pulse oximeter allowed successful SpO2 and HR monitoring in freedives to 82 m depth – deeper than ever recorded before. Divers’ enhanced desaturation during deep dives was likely related to increased exertion and extended duration, but the rapid extreme desaturation to below 50% near surfacing could result from the diminishing pressure, in line with the hypothesis that risk of hypoxic BO may increase during ascent. Recordings also indicated that the diving response is not powerful enough to fully override the exercise-induced tachycardia during active swimming. Pulse oximetry monitoring of essential variables underwater may be an important step to increase freediving safety.
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| 31. |
- Patrician, Alexander, 1989-, et al.
(author)
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Association Between Arterial Oxygen Saturation and Lung Ultrasound B-Lines After Competitive Deep Breath-Hold Diving
- 2021
-
In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
-
Journal article (peer-reviewed)abstract
- Breath-hold diving (freediving) is an underwater sport that is associated with elevated hydrostatic pressure, which has a compressive effect on the lungs that can lead to the development of pulmonary edema. Pulmonary edema reduces oxygen uptake and thereby the recovery from the hypoxia developed during freediving, and increases the risk of hypoxic syncope. We aimed to examine the efficacy of SpO2, via pulse-oximetry, as a tool to detect pulmonary edema by comparing it to lung ultrasound B-line measurements after deep diving. SpO2 and B-lines were collected in 40 freedivers participating in an international deep freediving competition. SpO2 was measured within 17 ± 6 min and lung B-lines using ultrasound within 44 ± 15 min after surfacing. A specific symptoms questionnaire was used during SpO2 measurements. We found a negative correlation between B-line score and minimum SpO2 (rs = −0.491; p = 0.002) and mean SpO2 (rs = −0.335; p = 0.046). B-line scores were positively correlated with depth (rs = 0.408; p = 0.013), confirming that extra-vascular lung water is increased with deeper dives. Compared to dives that were asymptomatic, symptomatic dives had a 27% greater B-line score, and both a lower mean and minimum SpO2 (all p < 0.05). Indeed, a minimum SpO2 ≤ 95% after a deep dive has a positive predictive value of 29% and a negative predictive value of 100% regarding symptoms. We concluded that elevated B-line scores are associated with reduced SpO2 after dives, suggesting that SpO2 via pulse oximetry could be a useful screening tool to detect increased extra-vascular lung water. The practical application is not to diagnose pulmonary edema based on SpO2 – as pulse oximetry is inexact – rather, to utilize it as a tool to determine which divers require further evaluation before returning to deep freediving.
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| 32. |
- Patrician, Alexander, 1989-, et al.
(author)
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The Effect of Dietary Nitrate on Nocturnal Sleep-Disordered Breathing and Arterial Oxygen Desaturation at High Altitude
- 2018
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In: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 19:1, s. 21-27
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Journal article (peer-reviewed)abstract
- Patrician, Alexander, Harald Engan, David Lundsten, Ludger Grote, Helena Vigetun-Haughey, and Erika Schagatay. The effect of dietary nitrate on nocturnal sleep-disordered breathing and arterial oxygen desaturation at high altitude. High Alt Med Biol 00:000-000, 2017.Sleep-disordered breathing and fluctuations in arterial oxygen saturation (SaO(2)) are common during sleep among lowlanders ascending to high altitude. Dietary nitrate (NO3-) supplementation has been shown to lower the O-2 consumption in various conditions. Our objective was to investigate whether dietary NO3- could reduce sleep-disordered breathing and SaO(2) desaturation during sleep at altitude. Cardiorespiratory responses during sleep were measured in 10 healthy lowlanders at 330m and then again in the Himalayas at 3700-4900m. Each subject received two 70mL shots of either beetroot juice (BR; approximate to 5.0mmol NO3- per shot) or placebo (PL: approximate to 0.003mmol NO3- per shot) in a single-blinded, weighted order over two consecutive nights at altitude. At 2.5-4.5 hours into sleep at altitude, BR increased the SaO(2) desaturation drop (4.2 [0.1]% with PL vs. 5.3 [0.4]% with BR; p=0.024) and decreased the SaO(2) desaturation duration (14.1 [0.9] seconds with PL to 11.1 [0.9] seconds with BR; p=0.0.041). There was a reduction in breaths with flow limitation (p=0.025), but no changes in Apnea-Hypopnea Index (AHI), mean and minimum SaO(2). The study suggests BR supplementation does not improve AHI or oxygenation, but may increase fluctuations in arterial O-2 saturation during sleep at altitude in native lowlanders.
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| 33. |
- Pernett, Frank, 1970-, et al.
(author)
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Effects of hyperventilation on oxygenation, apnea breaking points, diving response, and spleen contraction during serial static apneas
- 2023
-
In: European Journal of Applied Physiology. - : Springer Nature. - 1439-6319 .- 1439-6327. ; 123:8, s. 1809-1824
-
Journal article (peer-reviewed)abstract
- PurposeHyperventilation is considered a major risk factor for hypoxic blackout during breath-hold diving, as it delays the apnea breaking point. However, little is known about how it affects oxygenation, the diving response, and spleen contraction during serial breath-holding.Methods18 volunteers with little or no experience in freediving performed two series of 5 apneas with cold facial immersion to maximal duration at 2-min intervals. In one series, apnea was preceded by normal breathing and in the other by 15 s of hyperventilation. End-tidal oxygen and end-tidal carbon dioxide were measured before and after every apnea, and peripheral oxygen saturation, heart rate, breathing movements, and skin blood flow were measured continuously. Spleen dimensions were measured every 15 s.ResultsApnea duration was longer after hyperventilation (133 vs 111 s). Hyperventilation reduced pre-apnea end-tidal CO2 (17.4 vs 29.0 mmHg) and post-apnea end-tidal CO2 (38.5 vs 40.3 mmHg), and delayed onset of involuntary breathing movements (112 vs 89 s). End-tidal O2 after apnea was lower in the hyperventilation trial (83.4 vs 89.4 mmHg) and so was the peripheral oxygen saturation nadir after apnea (90.6 vs 93.6%). During hyperventilation, the nadir peripheral oxygen saturation was lower in the last apnea than in the first (94.0% vs 86.7%). There were no differences in diving response or spleen volume reduction between conditions or across series.ConclusionsSerial apneas revealed a previously undescribed aspect of hyperventilation; a progressively increased desaturation across the series, not observed after normal breathing and could heighten the risk of a blackout.
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| 34. |
- Pernett, Frank, 1970-
(author)
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Hypoxic Blackout in Serial Freediving – Protective Mechanisms and Risk Factors
- 2024
-
Doctoral thesis (other academic/artistic)abstract
- Breath-hold diving or freediving exposes the body to stressors such as low oxygen and high carbon dioxide levels in the blood, increased hydrostatic pressure, and cold. The reduction in blood oxygen levels is considered a primary factor for loss of consciousness while diving. This is known as hypoxic blackout. My thesis aimed to enhance the understanding of the factors that lead to hypoxic blackout in serial freediving. This includes studying the physiological mechanisms that protect the body against hypoxia and exploring how hyperventilation affects those mechanisms, with a specific focus on repetitive dives. The protective mechanisms, splenic contraction (Studies I, II) and diving bradycardia (Studies II and IV), were tested in experimental conditions. The effect of hyperventilation on simulated serial dives (Study II) was investigated, and a strategy to identify actual hyperventilation during diving was developed and explored (Study III). A static apnea test allowing identification of individuals at particular risk for blackout was developed (Study IV).The results showed that hypoxia-induced splenic contraction occurs rapidly enough to be protective in long-duration breath-holds (Study I). Serial simulated dives, preceded by short-term hyperventilation, lead to longer apnea duration and progressive oxygen desaturation (Study II). Despite the more severe desaturation resulting from hyperventilation, these consecutive apneas do not show an augmented diving response or splenic contraction. Hyperventilation was also observed when divers intended to avoid it (Studies II, III, and IV). Therefore, the possibility of estimating hyperventilation from the signal of a force sensor attached to a chest belt was explored (Study III). A stronger diving bradycardia and a bigger spleen were found to be protective against hypoxia and are related to slower oxygen desaturation (Study IV). The main conclusion is that oxygenation is impaired by the accumulation of an oxygen debt when consecutive dives are preceded by hyperventilation. The protective mechanisms, such as splenic contraction and the diving response, are beneficial at the individual level but do not offset the increased risk across a series of dives. However, splenic contraction does offer protection even during the first dive of a series. A chest belt-mounted force sensor could be used to identify when freedivers are hyperventilating. Additionally, a novel static apnea ramp test is effective in identifying freedivers who are at a high risk of faster desaturation during freediving.
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| 35. |
- Rixen, M., et al.
(author)
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First Real-Life Data on the Diving Response in Healthy Children
- 2024
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In: Pediatric Cardiology. - : Springer Nature. - 0172-0643 .- 1432-1971. ; 45:2, s. 314-322
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Journal article (peer-reviewed)abstract
- Swimming and diving are popular recreational activities, representing an effective option in maintaining and improving cardiovascular fitness in healthy people. To date, only little is known about the cardiovascular adaption to submersion in children. This study was conducted to improve an understanding thereof. We used a stepwise apnea protocol with apnea at rest, apnea with facial immersion, and at last apnea during whole body submersion. Continuous measurement of heart rate, oxygen saturation, and peripheral resistance index was done. Physiologic data and analysis of influencing factors on heart rate, oxygen saturation, and peripheral vascular tone response are reported. The current study presents the first data of physiologic diving response in children. Data showed that facial or whole body submersion leads to a major drop in heart rate, and increase of peripheral resistance, while the oxygen saturation seems to be unaffected by static apnea in most children, with apnea times of up to 75 s without change in oxygen saturation.
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| 38. |
- Schagatay, Erika, 1961-
(author)
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Predicting performance in competitive apnea diving, Part III: depth
- 2011
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In: Diving and Hyperbaric Medicine. - 1833-3516. ; 41:4, s. 216-228
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Research review (peer-reviewed)abstract
- Part I described the physiological factors defining the limits of static apnea, while Part II examined performance in dynamic distance swimming. This paper reviews the factors determining performance in the depth disciplines, where hydrostatic pressure is added to the stressors associated with apneaduration and physical work. Apneic duration is essential for performance in all disciplines, and is prolonged by any means that increases gas storage or tolerance to asphyxia, or that reduces metabolic rate. For underwater distance swimming, the main challenge is to restrict metabolism despite the work of swimming, and to redirect blood flow to allow the most vital functions. Here, work economy, local tissue energy and oxygen stores, anaerobic capacity of the muscles, and possibly technical improvements will be essential for further development. In the depth disciplines, direct pressure effects causing barotrauma, the narcotic effects of gases, decompression sickness (DCS) and possibly air embolism during ascent need to be taken into account, as does the risk of hypoxia when the dive cannot be rapidly interrupted before the surface is reached again. While in most deep divers apneic duration is not the main limitation thus far, greater depths may call for exceptionally long apneas and slower ascents to avoid DCS. Narcotic effects may also affect the ultimate depth limit, which elite divers predict to he around 156 metres' sea water. for constant weight with tins. To reach these depths, serious physiological challenges have to be met, technical developments are likely to be needed and safety procedures must be developed concomitantly.
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| 39. |
- Schagatay, Erika, 1961-, et al.
(author)
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Repeated freediving – An efficient and safe method to rescue subjects trapped in cars underwater
- 2019
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In: Safety Science. - : Elsevier BV. - 0925-7535 .- 1879-1042. ; 118, s. 752-756
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Journal article (peer-reviewed)abstract
- A method based on repeated freediving was developed to rescue subjects trapped in cars underwater – a scenario leading to 5–6 annual deaths in Sweden, and thousands globally. We determined rescue time and whether the divers were at risk of hypoxic blackout. Cars containing 5 kg negatively buoyant rescue-dummies strapped with seatbelts were placed on 5 m and 8 m depth. Eight freediving-instructors made 230 freedives, working in pairs with one diver always at the surface. For each rescue, two freedivers, equipped with mask, snorkel, fins, weight-belt, wetsuit and a buoy with belt-cutter and glass-breaker freedived alternating in turns between the divers. They accomplished a maximum of one of the following tasks per dive; (1) Finding the car; (2) Marking car with buoy; (3) Opening door/crushing window. (4) Opening/cutting belt; (5) Retrieving dummy to surface; (6) Transporting dummy to shore. Dummies were retrieved to shore from 5 m depth within a mean (SD) duration of 4 min 16 s (1 min 36 s) and from 8 m within 6 min 22 s (2 min 13 s; P < 0.05). Mean dive duration was 28(7)s (14–46 s), with 3 dives over 40 s duration. Freedivers arterial oxygen saturation (SaO2) levels were measured in dives of 30, 35, 40 and 45 s using pulse oximetry. Mean (SD) SaO2 at 20 s after surfacing was 90% for 45 s dives. This allows rapid recovery and gives a safety margin to the 50% SaO2 level when divers may risk blackout. We concluded that repeated freediving is efficient for rescuing victims trapped in cars underwater within their survival time, and following recommended methods and dive durations, rescue divers are not exposed to risk.
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| 41. |
- Schagatay, Erika, 1961-, et al.
(author)
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Spleen contraction elevates hemoglobin concentration at high altitude during rest and exercise
- 2020
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 120, s. 2693-2704
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Journal article (peer-reviewed)abstract
- Purpose: Hypoxia and exercise are known to separately trigger spleen contraction, leading to release of stored erythrocytes. We studied spleen volume and hemoglobin concentration (Hb) during rest and exercise at three altitudes. Methods: Eleven healthy lowlanders did a 5-min modified Harvard step test at 1370, 3700 and 4200 m altitude. Spleen volume was measured via ultrasonic imaging and capillary Hb with Hemocue during rest and after the step test, and arterial oxygen saturation (SaO2), heart rate (HR), expiratory CO2 (ETCO2) and respiratory rate (RR) across the test. Results: Resting spleen volume was reduced with increasing altitude and further reduced with exercise at all altitudes. Mean (SE) baseline spleen volume at 1370 m was 252 (20) mL and after exercise, it was 199 (15) mL (P < 0.01). At 3700 m, baseline spleen volume was 231 (22) mL and after exercise 166 (12) mL (P < 0.05). At 4200 m baseline volume was 210 (23) mL and after exercise 172 (20) mL (P < 0.05). After 10 min, spleen volume increased to baseline at all altitudes (NS). Baseline Hb increased with altitude from 138.9 (6.1) g/L at 1370 m, to 141.2 (4.1) at 3700 m and 152.4 (4.0) at 4200 m (P < 0.01). At all altitudes Hb increased from baseline during exercise to 146.8 (5.7) g/L at 1370 m, 150.4 (3.8) g/L at 3700 m and 157.3 (3.8) g/L at 4200 m (all P < 0.05 from baseline). Hb had returned to baseline after 10 min rest at all altitudes (NS). The spleen-derived Hb elevation during exercise was smaller at 4200 m compared to 3700 m (P < 0.05). Cardiorespiratory variables were also affected by altitude during both rest and exercise. Conclusions: The spleen contracts and mobilizes stored red blood cells during rest at high altitude and contracts further during exercise, to increase oxygen delivery to tissues during acute hypoxia. The attenuated Hb response to exercise at the highest altitude is likely due to the greater recruitment of the spleen reserve during rest, and that maximal spleen contraction is reached with exercise.
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