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- Brändström, Helge, 1953-
(författare)
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Accidental hypothermia and local cold injury : physiological and epidemiological studies on risk
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: (Papers I and II) The objectives were to first determine incidence and contributing factors to cold-related injuries in northern Sweden, both those that led to hospitalization and those that led to fatality. (Papers III and IV) A further aim was to assess post-cooling hand-rewarming responses and effects of training in a cold environment, both on fingertip rewarming and on function of the autonomic nervous system, to evaluate if there was adaptation related to prolonged occupational cold exposure.Methods: In a retrospective analysis, cases of accidental cold-related injury with hospital admission in northern Sweden during 2000-2007 were analyzed (Paper I). Cases of fatal hypothermia in the same region during 1992-2008 were analyzed (Paper II). A cohort of volunteers was studied before and after many months of occupational cold exposure. Subject hand rewarming response was measured after a cold hand immersion provocation and categorized as slow, moderate or normal in rewarming speed. This cold provocation and rewarming assessment was performed before and after their winter training. (Paper III). Heart rate variability (HRV) was analyzed from the same cold provocation/recovery sequences (Paper IV).Results: (Paper I) For the 379 cases of hospitalization for cold-related injury, annual incidences for hypothermia, frostbite, and drowning were 3.4/100,000, 1.5/100,000, and 1.0/100,000 inhabitants, respectively. Male gender was more frequent for all categories. Annual frequencies for hypothermia hospitalizations increased during the study period. Hypothermia degree and distribution of cases were 20 % mild (between 32 and 35ºC), 40% moderate (31.9 to 28ºC), and 24% severe (< 28ºC), while 12% had temperatures over 35.0ºC. (Paper II) The 207 cases of fatal hypothermia showed an annual incidence of 1.35 per 100,000 inhabitants, 72% in rural areas, 93% outdoors, 40% found within 100 meters of a building. Paradoxical undressing was documented in 30%. Ethanol was detected in femoral vein blood in 43%. Contributing co-morbidity was common including heart disease, previous stroke, dementia, psychiatric disease, alcoholism, and recent trauma. (Paper III) Post-training, baseline fingertip temperatures and cold recovery variables in terms of final rewarming fingertip temperature and vasodilation time increased significantly in moderate and slow rewarmers. Cold-related injury (frostbite) during winter training occured disproportionately more often in slow rewarmers (4 of the 5 injuries). (Paper IV) At ‘pre- winter-training’, normal rewarmers had higher power for low frequency and high frequency heart rate variability. After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low frequency and high frequency heart rate variability components. Conclusions: Hypothermia and cold injury continues to cause injury and hospitalization in the northern region of Sweden. Assessment and management is not standardized across hospitals. With the identification of groups at high risk for fatal hypothermia, it should be possible to reduce the incidence, particularly for highest risk subjects; rural, living alone, alcohol-imbibing, and psychiatric diagnosis-carrying citizens. Long-term cold-weather training may affect hand rewarming patters after a cold provocation, and a warmer baseline hand temperature with faster rewarming after a cold provocation may be associated with less general risk for frostbite. Heart rate variability results support the conclusion that cold adaptation in the autonomic nervous system occurred in both groups, though the biological significance of this is not yet clear.
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| 2. |
- Erelund, Sofia, 1983-
(författare)
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Heart and lung function - in health and disease : methodological studies in clinical physiology
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The human heart and lungs constitute an intricate and dynamic system. Various clinical physiological examinations can be used to evaluate cardio-pulmonary function and identify abnormalities. Thus, it is important to understand how normal physiology presents, to be able to identify pathological findings. To distinguish normal from abnormal findings in a patient population compared to healthy controls, adequate, accurate and up-to-date reference materials are required. There is currently a lack of well-established sex and age specific reference materials that clearly state boundaries of normality for electrocardiography (ECG) variables. For lung function examinations there are several different reference materials available, being discordant between ethnicities. In addition, the relation between lung function, age, sex, and height has generally been difficult to model in an optimal way. This highlights the need for more adequate sex-specific models regarding age- and height-dependency of spirometry variables. Heart rate variability (HRV) is a method for evaluating the autonomic nervous system (ANS) and its influence on heart rate and blood pressure. Autonomic disturbances are characterized by an imbalance between the sympathetic and the parasympathetic nervous systems. It is well known that decreased HRV is associated with increased mortality. Autonomic imbalances are also associated with various pathological conditions, of which rheumatoid arthritis (RA) and ischemic heart disease (IHD) are studied in this thesis.The purpose of this thesis was to describe the properties of different clinical physiological examinations and to investigate reference values relating to cardiovascular and pulmonary function in healthy individuals regarding age and sex. In addition, the aim was to assess the relationship between HRV, RA and CVD both cross sectionally and longitudinally. In a subjectively healthy population (n=219) of varying age, there were age and sex-dependent differences in ECG examinations. This emphasizes former findings and supports the need to establish age- and sex-specific reference values in the future. Lung function examinations in subjectively healthy persons (n=285) support and emphasize that the reference values presented by the Global Lung function Initiative (GLI) underestimate the pulmonary function in the adult Swedish population. The study showed that the model used in GLI can be updated with new values that are specific for the Caucasian population in Sweden. Patients with RA (n=50) presented with lower HRV than healthy controls (n=100) during autonomic provocation tests, both at baseline examinations and after five years. This indicates a cardiac autonomic imbalance. Furthermore, increased systolic blood pressure was associated with reduced HRV, thus a decrease in HRV could be a risk marker for developing arterial hypertension in this patient group.Females with IHD (n=197) presented with lower HRV compared to controls (n=141) at baseline, and a higher mortality rate after 15 years. The higher mortality rate was only present in females < 60 years of age. For measurements obtained in the upright position, HRV was higher in females that died during follow-up compared to those who were alive. This thesis emphasizes the importance of validated and updated sex- and age- specific reference materials, and models that are well suited for different clinical physiological examinations. Additionally, HRV examinations exposed changes in the ANS related to RA as well as IHD, where findings were shown to be persistent over time and particularly pronounced during provocations. In the future, HRV assessment could be a useful tool to identify the increased risk of developing hypertension in patients with RA, or to customize treatment based on ANS response as the field of personalized medicine continues to evolve.
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| 3. |
- Lundström, Anna, 1984-
(författare)
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Autonomic cardiac control in long QT syndrome : clinical studies of arrhythmogenic triggers
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Long QT syndrome (LQTS) is an inherited cardiac disease characterized by prolonged cardiac repolarization and an increased risk for life-threatening arrhythmias. These arrhythmias are typically triggered by adrenergic stimuli, such as physical activity and intense emotions, implicating that the sympathetic part of the autonomic nervous system (ANS) is involved in arrhythmogenesis. However, symptoms also commonly occur swimming and diving, situations associated with dual activation of both branches of the ANS. This observation suggests that both sympathetic and parasympathetic physiological responses may contribute to the initiation of arrhythmias in individuals with LQTS.Aim: The overall aim of this thesis was to describe the cardiac autonomic response in LQTS patients during daily activities, exercise, and swimming, as well as to assess the presence of arrhythmias during activities in water. Methods: In all 4 studies electrocardiograms (ECGs) were recorded. In study I and II, a 24-hour ECG (Holter) system was used. In study III and IV, a waterproof 2-lead ECG device (Actiwave-Cardio) was used. In study I, ECGs were collected from adult LQTS patients (n = 44) and healthy controls (n = 44) during a submaximal bicycle exercise stress test. In study II, annual 24-hour ECG recordings (n = 575) during ordinary daily living was retrospectively collected in children with LQTS (n = 116). In study III, children with LQTS type 1 (LQT1) (n = 15) and age and sex matched healthy controls (n = 15) performed face immersion (FI), swimming, diving, and whole-body submersion (WBS). In study IV, healthy adolescents aged 15 years performed FI (n = 54) and ice-water immersion (IWI) of the body (n = 20).Heart rate responses and spectral analysis of heart rate variability (HRV) were assessed. HRV measures the beat-to-beat variation of the RR intervals of the heart, making it possible to non-invasively analyze the cardiac autonomic influence on the heart. The total power (PTOT) reflects all the variation during the recorded period. The high frequency (HF) component reflects parasympathetic activity, while the low frequency (LF) is influenced by both the sympathetic and parasympathetic activity.Results: In study I, LQTS patients had a decreased heart rate reduction and a lower PTOT, LF and HF than controls during the post-exercise phase. LQTS patients off beta-blocker (BB) treatment showed a lower HF and higher LF/HF ratio compared to LQTS patients on BB treatment. In study II, a correlation between heart rate and changes in HRV parameters was observed. At higher heart rates, the whole cohort of LQTS patients, as well as the subgroup of LQTS patients off BB, had lower HRV values than controls. A pattern was observed indicating that LQT1 patients had lower HF in the age group of 1-10 years, with this trend shifting as age increased, resulting in lower HF in the LQT2 patients aged 15-18 years. LQT1 girls aged 10-18 years had lower PTOT than LQT1 boys. Study III showed that LQT1 patients had a smaller reduction in heart rate during FI and WBS than controls. LQT1 patients had a lower HRV before, during and after FI and WBS than controls. In study IV, in healthy adolescents, supraventricular extrasystoles were relatively common during both FI and IWI, and 2 of 54 had ventricular bigeminy during FI. FI resulted in a more pronounced heart rate reduction compared to IWI.Conclusions: The results of these studies indicate that individuals with LQTS have an aberrant cardiac response to activities that affects the ANS. After exercise and in response to water activities, the parasympathetic effect on both the heart rate and HRV appears depressed in LQTS patients. Additionally, during everyday activities, LQTS patients generally have lower HRV values at higher heart rates compared to controls. These findings suggest that both branches of the ANS might be involved in arrhythmogenesis in this patient group, and that an increased understanding of the ANS role could improve patient management and treatment. The results from the ice-water study indicate that the ventricular arrhythmia risk is likely higher during whole-body submersion with apnea. The absence of arrhythmias in beta-blocked LQT1 patients indicates effective protection by their current treatment.
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