| 1. |
- Linnarsson, D., et al.
(författare)
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Breathing volumes and gas exchange during simulated rapid free ascent from 100 msw
- 1993
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 74:3, s. 1293-1298
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Tidskriftsartikel (refereegranskat)abstract
- The crew of a disabled submarine can be rescued by means of free ascent through the water to the surface. Pulmonary gas exchange was studied during simulated rapid free ascent in subjects standing immersed to the neck in a pressure chamber. The pressure was rapidly increased to 1.1 MPa [100 meters seawater (msw)] followed by decompression at 0.03 MPa/s (3 msw/s). Effective inspired tidal volume, as estimated by an Ar dilution method, fell gradually to zero during decompression from 20 to 0 msw. Directly determined expired tidal volumes were increased up to two to three times at the time of return to surface pressure compared with pre- and postdecompression volumes. End-tidal PCO2 was increased on compression and fell to a nadir of 3.4 kPa (25 Torr) at the time of return to surface pressure. Thus, intrapulmonary gas expansion caused simultaneous inspiratory hypoventilation and expiratory hyperventilation. If O2-enriched gas is to be used to reduce the risk of decompression sickness, it should be administered early during decompression to alter the intrapulmonary gas composition. The time course of arterial PCO2 changes as reflected by end-tidal values during short-lasting compression/decompression would act to promote inert gas supersaturation in the brain.
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| 2. |
- Adolfsson, Peter, 1963, et al.
(författare)
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Accuracy and reliability of continuous glucose monitoring in individuals with type 1 diabetes during recreational diving
- 2009
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Ingår i: Diabetes Technology & Therapeutics. - : Mary Ann Liebert. - 1557-8593 .- 1520-9156. ; 11:8, s. 493-7
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: This study evaluated the accuracy and function of the Continuous Glucose Monitoring System (CGMS, Minneapolis, MN) during recreational scuba diving in individuals with type 1 diabetes. METHODS: Twenty-four adults, 12 with type 1 diabetes and 12 healthy controls, were studied during five recreational scuba dives performed on three consecutive days. All the participants used the CGMS on all the days and during all the dives. Comparisons were made between plasma glucose at specific time intervals and the CGMS. RESULTS: The recording by the CGMS was robust, with few sensor problems. The mean sensor survival time was >48 h. Eighty-five percent of the individuals used one sensor during the entire length of the trial. The overall mean absolute difference (MAD) within the group with diabetes was 14.4 +/- 6%, and the corresponding daily figures were 23.2 +/- 19.3% on day 1, 11.6 +/- 4.5% on day 2, and 11.2 +/- 5.7% on day 3. A significant improvement regarding MAD when day 1 was compared with day 2 and 3 (P < 0.05). With a limit set at 70 mg/dL, hypoglycemia pre- and post-dive was detected with a positive predictive value of 0.39, negative predictive value of 0.98, sensitivity of 0.64, and specificity of 0.94. CONCLUSIONS: We demonstrate that the CGMS was used with accuracy in such difficult conditions as scuba diving and provided robust information on glucose variations.
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| 3. |
- Berglund, B, et al.
(författare)
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Erythropoietin concentrations during 10 days of normobaric hypoxia under controlled environmental circumstances.
- 2002
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 174, s. 225-
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Tidskriftsartikel (refereegranskat)abstract
- Serum erythropoietin levels (s-[epo]), haemoglobin concentration ([Hb]), haematocrit (hct), and ferritin concentration ([fer]) were measured in seven healthy male volunteers (20-23 years) exposed continuously to hypoxia (PO(2) 14 kPa) for 10 days. Serum erythropoietin concentration increased significantly from 9.5 +/- 3.51 to 33.6 +/- 11.64 U L(-1) (P < 0.05) after 2 days of hypoxia. Thereafter, s-[epo] decreased. However, after 10 days s-[epo] was 18.7 +/- 5.83 U L(-1) which was still increased above the pre-hypoxia level (P < 0.05). Serum haemoglobin concentration and hct increased over the 10 days of hypoxia, [Hb] from 152 +/- 8.9 to 168 +/- 9.2 gL(-1) (P < 0.001), and hct from 43 +/- 2.4 to 49 +/- 2.6% (P < 0.001). Ferritin concentration decreased significantly during the hypoxic exposure from 82 +/- 46.9 to 44 +/- 31.7 mmol L(-1) after 10 days (P < 0.01). In conclusion, the initial increase of s-[epo] under controlled normobaric hypoxia was marked, 353%, and levelled off after 5-10 days at 62-97% above normoxia level. There was also a significant increase in [Hb] and hct and a decrease in [fer] after 10 days of exposure to normobaric hypoxia.
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| 4. |
- Gennser, Mikael, et al.
(författare)
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Effects of dietary lipids on frequency and force in atrial muscle at 10 MPa
- 1987
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Ingår i: Undersea biomedical research. - 0093-5387. ; 14:1, s. 31-43
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneously beating atrial preparations, from rats fed different lipid diets, were compressed to 10 MPa. The following observations were made: Different lipid diets altered the ratio of omega-6/omega-3 polyunsaturated fatty acids of the cardiac phospholipids. Beating frequency and twitch tension at surface pressure was unaffected by the diets. Compression to 10 MPa caused a decrease in spontaneous beating frequency and an increased twitch tension in all preparations. The decrease in beating frequency was inversely related to the omega-6/omega-3 ratio. Pressure induced increase in twitch tension was not affected by the diets. N2O dissolved in the tissue bath solution partly counteracted the pressure-induced changes.
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| 5. |
- Gennser, Mikael, et al.
(författare)
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Effects of hydrostatic pressure and inert gases on twitch tension
- 1989
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Ingår i: Undersea biomedical research. - 0093-5387. ; 16:6, s. 415-426
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Tidskriftsartikel (refereegranskat)abstract
- Effect of pressure and inert gases on the twitch tension (Tmax) was measured on electrically stimulated and spontaneously beating rat atria. In stimulated preparations, pressurization to 10 MPa increased Tmax by 20-60% depending on the stimulating frequency (60-240 beats/min). The introduction of 5 MPa N2 or 5 MPa H2 at 10 MPa hydrostatic pressure decreased the Tmax by 17 +/- 6% and 13 +/- 6%, respectively. Gas effect did not depend on the stimulating frequency. Nitrous oxide (0.15 and 0.45 MPa) decreased Tmax both at "surface" and at 10 MPa. Nitrous oxide effect was slightly potentiated at pressure. In spontaneously beating preparations, compression to 10 and 15 MPa decreased beating frequency (BF) by 24 +/- 10% and 31 +/- 8% and increased Tmax by 60 +/- 35% and 105 +/- 33%, respectively. The tension increase is partly due to the direct pressure effect and partly due to the negative force-frequency relation in the rat atria. Introduction of inert gas increased BF and decreased Tmax. The potency of the gases was in the same order for both variables: He less than H2 less than N2.
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| 6. |
- Gennser, Mikael, et al.
(författare)
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Effects of hydrostatic pressure, H2, N2, and He, on beating frequency of rat atria
- 1989
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Ingår i: Undersea biomedical research. - 0093-5387. ; 16:2, s. 153-164
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Tidskriftsartikel (refereegranskat)abstract
- Hydrostatic compression to 15 MPa caused a drop in spontaneous beating frequency (BF) of isolated rat atria kept in tris solution at 37 degrees C by 30.6 +/- 7.2%. Introduction of superfusing solutions equilibrated with hydrogen (PH2: 4.9, 9, and 14 MPa, respectively), increased the BF in proportion to the hydrogen content. A hydrogen partial pressure equal to the hydrostatic pressure was calculated to reduce the bradycardia by 52.0 +/- 19.5%. Effects of nitrogen (PN2: 5 and 14 MPa) and helium (PHe: 13 and 14 MPa) were also tested. Nitrogen was found to be 1.7-2 times and helium 0.2 times as effective as hydrogen in reducing the bradycardia. Preparations compressed at 27 degrees C exhibited a more pronounced bradycardia than those kept at 37 degrees C, but 5 MPa N2 and 9 MPa H2 reversed the bradycardia to the same extent at 27 degrees C as at 37 degrees C. Tests with 4 MPa H2 showed the effect on BF to be similar, whether the gas was added during an intermediate stop in the compression (4.6 MPa) or at 10 MPa pressure. An additional hydrostatic pressure increase from 10 to 12.5 MPa eliminated the BF increase of 4 MPa hydrogen added at 10 MPa. The findings are discussed in view of the possible use of hydrogen as a breathing gas in deep sea diving.
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| 7. |
- Gennser, Mikael, et al.
(författare)
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Effects of hyperbaric pressure and temperature on atria from ectotherm animals (Rana pipiens and Anguilla anguilla)
- 1990
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Ingår i: Comparative Biochemistry and Physiology - Part A. - : Elsevier BV. - 0300-9629. ; 95:2, s. 219-228
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Tidskriftsartikel (refereegranskat)abstract
- 1. Spontaneously beating atria from frogs (R. pipiens) and eels (A. anguilla) were compressed hydraulically to 10 MPa. Effects on beating frequency and twitch tension were studied. 2. At low temperatures (8-10 degrees C) compression to 10 MPa caused a slowing of the beat frequency. No effects were noted at higher temperatures (16-24 degrees C). Twitch tension was decreased by pressure at low temperatures and increased at high temperatures. 3. Differences were noted between preparations from cold and warm acclimatized frogs, and from silver and yellow eels, respectively. 4. The effect of temperature acclimatization on pressure and temperature sensitivity is discussed in relation to data on cardiac phospholipid fatty acid composition.
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| 8. |
- Padoan, S, et al.
(författare)
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Reduced voluntary non-visual suppression of the vestibulo-ocular reflex gain during nitrous oxide narcosis
- 1992
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Ingår i: Aviation Space and Environmental Medicine. - 0095-6562. ; 63:10, s. 80-875
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Tidskriftsartikel (refereegranskat)abstract
- The effect of subanesthetic nitrous oxide (N2O) narcosis (21%) on the vestibulo-ocular reflex (VOR) and on voluntary non-visual suppression of the VOR was studied in 12 subjects, using a velocity step rotational test. Gain and time constant of the VOR were calculated by computer. During tests, the subjects were required either to perform mental arithmetic or to attempt to follow an imaginary target rotating with them in the dark. Voluntary non-visual suppression of gain was significantly reduced during exposure to N2O, though there was no statistically significant effect of N2O on gain per se. The time constant was unaffected either by voluntary suppression or by N2O. The reducing effect of N2O on voluntary non-visual suppression of VOR gain is assumed to be due to reduced alertness. Reduced voluntary non-visual suppression of VOR may imply reduced visual-vestibular interaction, which might be one explanation of the complaints of dizziness associated with fatigue or with ingestion of certain sedatives.
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