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Short-term effects of normobaric hypoxia on the human spleen
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
Responsible organisation
2008 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 104, no 2, 395-399 p.Article in journal (Refereed) Published
Abstract [en]

Spleen contraction resulting in an increase in circulating erythrocytes has been shown to occur during apnea. This effect, however, has not previously been studied during normobaric hypoxia whilst breathing. After 20 min of horizontal rest and normoxic breathing, five subjects underwent 20-min of normobaric hypoxic breathing (12.8% oxygen) followed by 10 min of normoxic breathing. Ultrasound measurements of spleen volume and samples for venous hemoglobin concentration (Hb) and hematocrit (Hct) were taken simultaneously at short intervals from 20 min before until 10 min after the hypoxic period. Heart rate, arterial oxygen saturation (SaO2) and respiration rate were recorded continuously. During hypoxia, a reduction in SaO2 by 34% (P < 0.01) was accompanied by an 18% reduction in spleen volume and a 2.1% increase in both Hb and Hct (P < 0.05). Heart rate increased 28% above baseline (P < 0.05). Within 3 min after hypoxia SaO2 had returned to pre-hypoxic levels, and spleen volume, Hb and Hct had all returned to pre-hypoxic levels within 10 min. Respiratory rate remained stable throughout the protocol. This study of short-term exposure to eupneic normobaric hypoxia suggests that hypoxia plays a key role in triggering spleen contraction and subsequent release of stored erythrocytes in humans. This response could be beneficial during early altitude acclimatization.

Place, publisher, year, edition, pages
2008. Vol. 104, no 2, 395-399 p.
Keyword [en]
Hypoxia, Spleen, Hemoglobin, Hematocrit, Ultrasound
National Category
Biological Sciences Sport and Fitness Sciences Microbiology
Identifiers
URN: urn:nbn:se:miun:diva-4361DOI: 10.1007/s00421-007-0623-4ISI: 000258609300033PubMedID: 18043933Scopus ID: 2-s2.0-50449084381Local ID: 5527OAI: oai:DiVA.org:miun-4361DiVA: diva2:29393
Conference
2nd International Conference on Environmental Ergonomics, 2007, Piran, Slovenia
Note
nd International Conference on Environmental Ergonomics, Piran, SLOVENIAAvailable from: 2008-11-29 Created: 2008-11-19 Last updated: 2015-07-13Bibliographically approved
In thesis
1. Hematological changes arising from spleen contraction during apnea and altitude in humans
Open this publication in new window or tab >>Hematological changes arising from spleen contraction during apnea and altitude in humans
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Östersund: Mid Sweden University, 2008. 49 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 57
Keyword
Hypoxia, hypercapnia, hemoglobin, hematocrit, breath-hold diving
National Category
Microbiology Sport and Fitness Sciences Physiology
Identifiers
urn:nbn:se:miun:diva-7786 (URN)978-91-86073-03-9 (ISBN)
Public defence
(English)
Supervisors
Available from: 2009-07-09 Created: 2008-12-15 Last updated: 2009-07-09Bibliographically approved
2. Initiation of spleen contraction resulting in natural blood boosting in humans
Open this publication in new window or tab >>Initiation of spleen contraction resulting in natural blood boosting in humans
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The spleen has been shown to contract in apneic situations in humans as well as in other diving mammals, expelling its stored red blood cell content into circulation. This natural blood boosting may increase the circulating hemoglobin concentration (Hb) by up to 10%, which would enhance the oxygen carrying capacity and likely increase performance. However, the triggers of this response in humans have not been fully clarified. Study I was therefore focused on the effect of hypoxia as a trigger of spleen contraction. It was found that 20 min of normobaric hypoxic breathing evoked a substantial reduction in spleen volume showing that hypoxia is an important trigger for spleen contraction. Knowing the role of hypoxia, Study II compared two different hypoxic situations – a 2 min apnea and 20 min normobaric hypoxic breathing – which resulted in the same level of arterial hemoglobin desaturation. Apnea evoked a twice as great spleen volume reduction, implying that variables other than hypoxia were likely involved in triggering spleen contraction. This may be hypercapnia which is present during apnea but not during normobaric hypoxic breathing. Study III therefore investigated the effects of breathing gas mixtures containing different proportions of CO2 prior to maximal apneas. Pre-breathing mixtures with higher percentages of CO2 resulted in greater spleen contraction, thus demonstrating hypercapnia's likely role as a trigger in addition to hypoxia. Study IV explored whether an all-or-nothing threshold stimulus for triggering spleen contraction existed, or if contraction was graded in relation to the magnitude of triggering stimuli. Exercise was therefore performed in an already hypoxic state during normobaria. Rest in hypoxia produced a moderate spleen volume reduction, with an enhanced spleen contraction resulting after hypoxic exercise, with a concomitant increase in Hb. This implies that spleen contraction is a graded response related to the magnitude of the stimuli. This could be beneficial in environments with varying oxygen content or work loads. Study V examined the possibility that spleen contraction is part of the acclimatization to altitude, during an expedition to summit Mt Everest. The long-term high altitude exposure, combined with physical work on the mountain, had no effects on resting spleen volume but resulted in a stronger spleen contraction, when provoked by apnea or exercise. This indicates that acclimatization to altitude may enhance the contractile capacity of the spleen, which may be beneficial for the climber. From these studies I concluded that hypoxia is an important trigger for spleen contraction but that hypercapnia also contributes in apneic situations. The spleen contraction likely provides a graded expulsion of erythrocytes in response to these stimuli, causing a temporary increase in gas storage capacity that may facilitate activities such as freediving and climbing. The storage of erythrocytes during rest serves to reduce blood viscosity, which would also be beneficial for the climber or diver. The human spleen contraction appears to become stronger with acclimatization, with beneficial effects at altitude. Such an upgraded response could be beneficial both in sports and diseases involving hypoxia.

Place, publisher, year, edition, pages
Östersund: Mid Sweden University, 2015. 87 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 217
Keyword
Acclimatization, altitude, apnea, breath-hold diving, hemoglobin, hypercapnia, hypoxia, triggers
National Category
Health Sciences
Identifiers
urn:nbn:se:miun:diva-25518 (URN)978-91-88025-10-4 (ISBN)
Supervisors
Available from: 2015-07-13 Created: 2015-07-13 Last updated: 2017-06-15Bibliographically approved

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