miun.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Spleen contraction during 20 min normobaric hypoxia and 2 min apnea in humans
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development. (Environmental Physiology Group)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development. (Environmental Physiology Group)
2010 (English)In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 81, no 6, p. 545-549Article in journal (Refereed) Published
Abstract [en]

Introduction: Spleen contraction occurs in humans during exercise, apnea, and simulated altitude, resulting in ejection of stored red blood cells into circulation. The mechanisms responsible for initiating the contraction are not fully known: hypoxia is likely involved, but other, unknown factors may also contribute. To reveal the initiating factors, we studied its occurrence in two different situations involving similar reductions in arterial oxygen saturation (SaO2). We hypothesized that similar spleen responses would result if the level of hypoxia is the main factor involved. Methods: Five female and four male healthy volunteers performed two different trials on separate days: 1)20 min of normobaric hypoxic breathing (14.2% oxygen); and II) 2 min of apnea after a deep inspiration of air. Both trials started and ended with 10 min of sitting eupneic rest. Spleen diameter was intermittently measured via ultrasonic imaging in three dimensions to calculate volume. S aO2 and heart rate (HR) were recorded continuously with a pulse oximeter. Results: Exposures resulted in similar nadir SaO 2: 87% after normobaric hypoxia and 89% after apnea. During normobaric hypoxia, spleen volume was reduced by 16% and during apnea by 34%. HR increased by 7% during normobaric hypoxia, but fell by 25% during apnea. Discussion: Both normobaric hypoxia and apnea induced spleen contraction, but despite similar levels of SaO2 apnea evoked a significantly stronger response, possibly due to hypercapnia, faster desaturation, ortheapneic stimulus in itself. Spleen contraction may facilitate adaptation to altitude and to apneic diving by elevating blood gas storage capacity.

Place, publisher, year, edition, pages
2010. Vol. 81, no 6, p. 545-549
Keywords [en]
Altitude; Breath hold; Diving response; Hypoxia; Spleen contraction
National Category
Microbiology
Identifiers
URN: urn:nbn:se:miun:diva-10766DOI: 10.3357/ASEM.2682.2010ISI: 000278305400002PubMedID: 20540444Scopus ID: 2-s2.0-77952831855OAI: oai:DiVA.org:miun-10766DiVA, id: diva2:282859
Available from: 2009-12-22 Created: 2009-12-22 Last updated: 2017-12-12Bibliographically approved
In thesis
1. 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. p. 87
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 217
Keywords
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

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textPubMedScopus

Authority records BETA

Lodin-Sundström, AngelicaSchagatay, Erika

Search in DiVA

By author/editor
Lodin-Sundström, AngelicaSchagatay, Erika
By organisation
Department of Engineering and Sustainable Development
In the same journal
Aviation, Space and Environmental Medicine
Microbiology

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 393 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf