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Cardiovascular, hematological and dietary means to cope with environmentally induced hypoxia in humans
Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Östersund: Mid Sweden University , 2015. , 87 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 213
National Category
Sport and Fitness Sciences Physiology
Identifiers
URN: urn:nbn:se:miun:diva-25016ISBN: 978-91-88025-01-2 (print)OAI: oai:DiVA.org:miun-25016DiVA: diva2:815534
Supervisors
Available from: 2015-06-01 Created: 2015-06-01 Last updated: 2015-06-15Bibliographically approved
List of papers
1. Effects of two weeks of daily apnea training on diving response, spleen contraction, and erythropoiesis in novel subjects.
Open this publication in new window or tab >>Effects of two weeks of daily apnea training on diving response, spleen contraction, and erythropoiesis in novel subjects.
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2013 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 23, no 3, 340-348 p.Article in journal (Refereed) Published
Abstract [en]

Three potentially protective responses to hypoxia have been reported to be enhanced in divers: (1) the diving response, (2) the blood-boosting spleen contraction, and (3) a long-term enhancement of hemoglobin concentration (Hb). Longitudinal studies, however, have been lacking except concerning the diving response. Ten untrained subjects followed a 2-week training program with 10 maximal effort apneas per day, with pre- and posttraining measurements during three maximal duration apneas, and an additional post-training series when the apneic duration was kept identical to that before training. Cardiorespiratory parameters and venous blood samples were collected across tests, and spleen diameters were measured via ultrasound imaging. Maximal apneic duration increased by 44 s (P < 0.05). Diving bradycardia developed 3 s earlier and was more pronounced after training (P < 0.05). Spleen contraction during apneas was similar during all tests. The arterial hemoglobin desaturation (SaO(2)) nadir after apnea was 84% pretraining and 89% after the duration-mimicked apneas post-training (P < 0.05), while it was 72% (P < 0.05) after maximal apneas post-training. Baseline Hb remained unchanged after training, but reticulocyte count increased by 15% (P < 0.05). We concluded that the attenuated SaO(2) decrease during mimic apneas was due mainly to the earlier and more pronounced diving bradycardia, as no enhancement of spleen contraction or Hb had occurred. Increased reticulocyte count suggests augmented erythropoiesis.

Keyword
Asphyxia; Bradycardia; Breath-hold training; Diving reflex; Reticulocytes; Spleen contraction
National Category
Physiology
Identifiers
urn:nbn:se:miun:diva-15819 (URN)10.1111/j.1600-0838.2011.01391.x (DOI)000318787900019 ()2-s2.0-84877660891 (Scopus ID)
Note

Article first published online: 29 SEP 2011

Available from: 2012-02-02 Created: 2012-02-02 Last updated: 2015-06-01Bibliographically approved
2. The effect of climbing mount everest on spleen contraction and increase in hemoglobin concentration during breath holding and exercise
Open this publication in new window or tab >>The effect of climbing mount everest on spleen contraction and increase in hemoglobin concentration during breath holding and exercise
2014 (English)In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 15, no 1, 52-57 p.Article in journal (Refereed) Published
Abstract [en]

Release of stored red blood cells resulting from spleen contraction improves human performance in various hypoxic situations. This study determined spleen volume resulting from two contraction-evoking stimuli: breath holding and exercise before and after altitude acclimatization during a Mount Everest ascent (8848m). Eight climbers performed the following protocol before and after the climb: 5min ambient air respiration at 1370m during rest, 20min oxygen respiration, 20min ambient air respiration at 1370m, three maximal-effort breath holds spaced by 2min, 10min ambient air respiration, 5min of cycling at 100 W, and finally 10min ambient air respiration. We measured spleen volume by ultrasound and capillary hemoglobin (HB) concentration after each exposure, and heart rate (HR) and arterial oxygen saturation (Sao2) continuously. Mean (SD) baseline spleen volume was unchanged at 213 (101) mL before and 206 (52) mL after the climb. Before the climb, spleen volume was reduced to 184 (83) mL after three breath holds, and after the climb three breath holds resulted in a spleen volume of 132 (26) mL (p=0.032). After exercise, the preclimb spleen volume was 186 (89) mL vs. 112 (389) mL) after the climb (p=0.003). Breath hold duration and cardiovascular responses were unchanged after the climb. We concluded that spleen contraction may be enhanced by altitude acclimatization, probably reflecting both the acclimatization to chronic hypoxic exposure and acute hypoxia during physical work. © Copyright 2014, Mary Ann Liebert, Inc. 2014.

Keyword
Acclimatization, Apnea, Hematology, Hypobaric hypoxia, Red cell volume
National Category
Sport and Fitness Sciences Hematology Physiology
Identifiers
urn:nbn:se:miun:diva-22041 (URN)10.1089/ham.2013.1061 (DOI)000333464100008 ()2-s2.0-84897141698 (Scopus ID)
Note

Language of Original Document: English

Available from: 2014-06-02 Created: 2014-05-30 Last updated: 2015-07-13Bibliographically approved
3. Effect of hypercapnia on spleen-related haemoglobin increase during apnea
Open this publication in new window or tab >>Effect of hypercapnia on spleen-related haemoglobin increase during apnea
2012 (English)In: Diving and Hyperbaric Medicine, ISSN 1833-3516, Vol. 42, no 1, 4-9 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND:

Splenic contraction associated with apnea causes increased haemoglobin concentration and haematocrit (Hct), an effect that may promote prolonged breath-holding. Hypoxia has been shown to augment this effect, but hypercapnic influences have not been investigated previously.

METHODS:

Eight non-divers performed three series of apneas on separate days after inspiration of oxygen with different carbon dioxide (CO₂) levels. Each series consisted of three apneas 2 minutes apart: one with pre-breathing of 5% CO₂ in oxygen (O₂, 'Hypercapnia'); one with pre-breathing of 100% O₂ ('Normocapnia'); and one with hyperventilation of 100% O₂ ('Hypocapnia'). The apnea durations were repeated identically in all trials, determined from the maximum duration attained in the CO₂ trial. A fourth trial, breathing 5% CO₂ in O₂ for the same duration as these apneas was also performed ('Eupneic hypercapnia'). In three subjects, spleen size was measured using ultrasonic imaging.

RESULTS:

Haemoglobin increased by 4% after apneas in the 'Hypercapnia' trial (P = 0.002) and by 3% in the 'Normocapnia' trial (P = 0.011), while the 'Hypocapnia' and 'Eupneic hypercapnia' trials showed no changes. The 'easy' phase of apnea, i.e., the period without involuntary breathing movements, was longest in the 'Hypocapnia' trial and shortest in the 'Hypercapnia' trial. A decrease in spleen size was evident in the hypercapnic trial, whereas in the hypocapnia trial spleen size increased, while only minor changes occurred in the other trials. No differences were observed between trials in the cardiovascular diving response.

CONCLUSION:

There appears to be a dose-response effect of CO₂ on triggering splenic contraction during apnea in the absence of hypoxia.

Keyword
hypercapnia spleen contraction
National Category
Physiology
Identifiers
urn:nbn:se:miun:diva-15820 (URN)000301886700002 ()22437969 (PubMedID)2-s2.0-84858788803 (Scopus ID)
Available from: 2012-02-02 Created: 2012-02-02 Last updated: 2015-07-13Bibliographically approved
4. Acute dietary nitrate supplementation improves dry static apnea performance
Open this publication in new window or tab >>Acute dietary nitrate supplementation improves dry static apnea performance
2012 (English)In: Respiratory Physiology & Neurobiology, ISSN 1569-9048, E-ISSN 1878-1519, Vol. 182, no 2-3, 53-59 p.Article in journal (Refereed) Published
Abstract [en]

Acute dietary nitrate (NO3-) supplementation has been reported to lower resting blood pressure, reduce the oxygen (O-2) cost of sub-maximal exercise, and improve exercise tolerance. Given the proposed effects of NO3- on tissue oxygenation and metabolic rate, it is possible that NO3- supplementation might enhance the duration of resting apnea. If so, this might have important applications both in medicine and sport. We investigated the effects of acute NO3- supplementation on pre-apnea blood pressure, apneic duration, and the heart rate (HR) and arterial O-2 saturation (SaO(2)) responses to sub-maximal and maximal apneas in twelve well-trained apnea divers. Subjects were assigned in a randomized, double blind, crossover design to receive 70 ml of beetroot juice (BR; containing similar to 5.0 mmol of nitrate) and placebo juice (PL; similar to 0.003 mmol of nitrate) treatments. At 2.5 h post-ingestion, the subjects completed a series of two 2-min (sub-maximal) static apneas separated by 3 min of rest, followed by a maximal effort apnea. Relative to PL, BR reduced resting mean arterial pressure by 2% (PL: 86 +/- 7 vs. BR: 84 +/- 6 mmHg; P = 0.04). The mean nadir for SaO(2) after the two sub-maximal apneas was 97.2 +/- 1.6% in PL and 98.5 +/- 0.9% in BR (P = 0.03) while the reduction in HR from baseline was not significantly different between PL and BR. Importantly, BR increased maximal apneic duration by 11% (PL: 250 +/- 58 vs. BR: 278 +/- 64 s; P = 0.04). In the longer maximal apneas in BR, the magnitude of the reductions in HR and SaO(2) were greater than in PL (P <= 0.05). The results suggest that acute dietary NO3- supplementation may increase apneic duration by reducing metabolic costs. (c) 2012 Elsevier B.V. All rights reserved.

Keyword
Oxygen consumption, Diving response, Hypoxia, Breath-hold, Blood pressure
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-17065 (URN)10.1016/j.resp.2012.05.007 (DOI)000306636200001 ()2-s2.0-84862885023 (Scopus ID)
Available from: 2012-10-01 Created: 2012-09-26 Last updated: 2015-06-01Bibliographically approved

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