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Cardiovascular and hematological responses to voluntary apnea in humans
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with cardiovascular and hematological responses to voluntary apnea in

humans, with a special focus on O2 usage and storage. Humans, and many other air‐breathing

animals, respond to apnea (breath holding) with a collection of interacting cardiovascular

reflexes, which are collectively called the diving response. In humans, the main characteristics of

the diving response are a reduction in heart rate (bradycardia), decreased cardiac output,

peripheral vasoconstriction and increased arterial blood pressure. Another response during

apnea in mammals, more recently also observed in man, is a transient increase in hemoglobin

concentration across a series of apneas, probably due a reduction in spleen size. There may also

be long‐term effects on erythropoiesis in the apneic diver, as suggested by high hemoglobin

levels observed in divers. The focus of the included studies are the short transient diving

response (I), the more slowly occurring transient hematological changes to apnea, most likely

related to a reduction in spleen size (II), and the possible effects of repeated apnea on serum

erythropoietin concentration (III).

I) The aim was to study the effects of body immersion on the O2‐conserving effect of the

human diving response. The results showed that, regardless of body immersion, apnea with face

immersion causes a stronger cardiovascular diving response compared to during apnea alone,

leading to a smaller reduction in arterial oxygen saturation levels. Thus the diving response is

triggered and conserves O2 even during whole‐body immersion, which has previously only been

observed during apnea without whole‐body immersion.

II) The aim was to study hematological responses to voluntary repeated maximal‐duration

apneas in divers and non‐divers. Increases in hemoglobin concentration were found across a

series of 3 apneas in elite breath‐hold divers, elite cross‐country skiers and untrained subjects.

However a larger increase in hemoglobin was found in divers compared to non‐divers, which

suggests a possible training effect of their extensive apnea‐specific training. In contrast, physical

endurance training does not appear to affect the hematological response to apnea.

III) The aim was to study the effects of serial voluntary apnea on the serum erythropoietin

concentration. In a comparison between elite breath‐hold divers and subjects untrained in apnea,

divers were found to have a 5% higher resting hemoglobin concentration. An average maximum

increase in erythropoietin of 24 % was found in untrained subjects after 15 maximal duration

apneas, preceded by 1 min of hyperventilation. This suggests a possible erythropoietic effect of

apnea‐induced hypoxia, which may connect the increased resting hemoglobin found in divers to

their apnea‐specific training.

It was concluded from these studies that man responds to apnea with a series of different

adjustments in order to limit O2 usage and increase O2 storage: The classical diving response is

effectively restricting O2‐consumption also during full immersion, the spleen related hemoglobin

increase occurs in both divers and non‐divers with different levels of physiological training, but

is more prominent in divers, and finally, the observed high levels of hemoglobin concentration in

divers may be related to enhanced erythropoiesis during dive training.

Place, publisher, year, edition, pages
Sundsvall: Mittuniversitetet , 2007. , p. 47
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 28
National Category
Microbiology
Identifiers
URN: urn:nbn:se:miun:diva-9328ISBN: 978-91-85317-70-7 (print)OAI: oai:DiVA.org:miun-9328DiVA, id: diva2:227243
Presentation
(English)
Available from: 2009-07-10 Created: 2009-07-10 Last updated: 2011-04-05Bibliographically approved
List of papers
1. Oxygen-conserving effect of the diving response in the immersed human
Open this publication in new window or tab >>Oxygen-conserving effect of the diving response in the immersed human
2009 (English)In: Diving and hyperbaric medicine, ISSN 1833-3516, Vol. 39, no 4, p. 193-199Article in journal (Refereed) Published
Abstract [en]

Research involving the human diving response has often simulated diving by apneic face immersion. However, no comparisons of cardiovascular responses and their oxygen- conserving function have been made between simulated diving and apneic face immersion when the body is constantly immersed as during diving. We compared the diving response and its effects on arterial oxygen saturation during apneas in horizontal dry body and immersed body positions. Both air and water temperatures were 23ºC. Twelve near-maximal apneas of the same duration were completed by 17 subjects. Four series of 3 apneas each were conducted: dry body apnea (DA), dry body, face-immersion apnea (DFIA), immersed body apnea (IA), and immersed body, face-immersion apnea (IFIA). Heart rate, skin capillary blood flow, arterial blood pressure, arterial hemoglobin saturation, lung volume and end-tidal PACO2 and PAO2 were recorded non-invasively and responses during apneas were compared among series. Cardiovascular responses showed similar patterns in all series. Face immersion led to a greater reduction in heart rate during apnea, regardless of body immersion. Both DFIA and DA resulted in a transient skin vasoconstriction, more pronounced during DFIA (p<0.001). During body immersion skin vasoconstriction was constant, and neither IA nor IFIA reduced blood flow further. Less arterial desaturation occurred after both FIA series, suggesting an oxygen-conserving effect of the more powerful diving response associated with face immersion in both body positions. We conclude that a similar oxygen-conserving diving response is triggered by apnea and face immersion during full-body immersion in cool water, as in the dry body model.

Keyword
Apnea, bradycardia, oxygen conservation, vasoconstriction, immersion
National Category
Microbiology
Identifiers
urn:nbn:se:miun:diva-6186 (URN)000273113700004 ()2-s2.0-75149148221 (Scopus ID)1903 (Local ID)1903 (Archive number)1903 (OAI)
Available from: 2009-01-29 Created: 2009-01-29 Last updated: 2010-06-14Bibliographically approved
2. Increase of hemoglobin concentration after maximal apneas in divers, skiers and untrained humans
Open this publication in new window or tab >>Increase of hemoglobin concentration after maximal apneas in divers, skiers and untrained humans
Show others...
2005 (English)In: Canadian Journal of Applied Physiology, ISSN 1066-7814, Vol. 30, no 3, p. 276-281Article in journal (Refereed) Published
Abstract [en]

Apnea is physiologically stressful and can within a short time frame pose a threat to survival. To sustain prolonged apnea, oxygen use should be minimized and its storage maximized. Two mechanisms known to have this effect are the cardiovascular diving response, directing the available oxygen selectively to the heart and brain, and spleen contraction increasing the circulating erythrocyte volume and thereby gas storage capacity. Spleen contraction is also observed after maximal exercise, and is thought to enhance aerobic performance. While the cardiovascular diving response is known to be more pronounced after apnea training, spleen contraction has not been studied in conjunction with apnea training or other types of training. The aim of the present investigation is to study the hematological responses to apnea performed during rest by elite apneic divers, by elite cross-country skiers and by untrained subjects. After 20 min of rest, subjects performed 3 maximal apneas spaced by 2 min normal breathing intervals. Blood samples were drawn before, directly after, and 10 min after the apnea series and hemoglobin concentration was measured. All groups responded to maximal apneas with an increase in hemoglobin concentration, which had disappeared after 10 min of recovery. The increase in hemoglobin concentration was more pronounced in the apneic divers (4g/L) than in skiers (3g/L) and untrained subjects (2g/L; P < 0.05). All groups prolonged their apneic times through the series, but the increase was most evident for the divers versus both the skiers (P < 0.05) and untrained subjects (P < 0.01). The results suggest that these responses could be more pronounced as a result of apnea training.

Keyword
apnea, hemoglobin, endurance training, cross country skiing, spleen contraction
National Category
Microbiology Biological Sciences Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-1688 (URN)000229602800002 ()1516 (Local ID)1516 (Archive number)1516 (OAI)
Note
VR-Medicine, ExternalAvailable from: 2008-09-30 Created: 2009-07-27 Last updated: 2011-04-06Bibliographically approved
3. Increased erythropoietin concentration after repeated apneas in humans
Open this publication in new window or tab >>Increased erythropoietin concentration after repeated apneas in humans
2008 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 102, no 5, p. 609-613Article in journal (Refereed) Published
Abstract [en]

Hypoxia-induced increases in red blood cell production have been found in both altitudeadapted populations and acclimatized lowlanders. This process is mediated by erythropoietin (EPO) released mainly by the hypoxic kidney. We have previously observed high hemoglobin concentrations in elite breath-hold divers and our aim was to investigate whether apnea-induced hypoxia could increase EPO concentration. Ten healthy volunteers performed 15 voluntary maximal duration apneas, divided into three seriesof five apneas, each series separated by 10 min of rest. Apneas within series were separated by 2 min and preceded by 1 min of hyperventilation to increase apnea duration and arterial oxygen desaturation. When EPO concentration after serial apneas was compared to baseline values, an average maximum increase of 24% was found (P<0.01). No changes in EPO concentration were observed during a control day without apnea, eliminating possible effects of a diurnal rhythm or blood loss. We therefore conclude that serial apneas increase circulating EPO concentration in humans.

Keyword
Erythropoiesis, breath holding, desaturation, diving response, bradycardia
National Category
Microbiology Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-3335 (URN)10.1007/s00421-007-0639-9 (DOI)000252540300015 ()18097682 (PubMedID)2-s2.0-38649119768 (Scopus ID)3340 (Local ID)3340 (Archive number)3340 (OAI)
Note
VR-Medicine, ExternalAvailable from: 2008-11-29 Created: 2008-11-13 Last updated: 2017-12-12Bibliographically approved

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