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Effect of hypercapnia on spleen-related haemoglobin increase during apnea
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling. (Environmental Physiology Group)
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling. (Sportech Environmental Physiology Group)
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling. (Environmental Physiology Group)
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling. (Environmental Physiology Group)
2012 (Engelska)Ingår i: Diving and Hyperbaric Medicine, ISSN 1833-3516, Vol. 42, nr 1, s. 4-9Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
2012. Vol. 42, nr 1, s. 4-9
Nyckelord [en]
hypercapnia spleen contraction
Nationell ämneskategori
Fysiologi
Identifikatorer
URN: urn:nbn:se:miun:diva-15820ISI: 000301886700002PubMedID: 22437969Scopus ID: 2-s2.0-84858788803OAI: oai:DiVA.org:miun-15820DiVA, id: diva2:488792
Tillgänglig från: 2012-02-02 Skapad: 2012-02-02 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
Ingår i avhandling
1. Cardiovascular, hematological and dietary means to cope with environmentally induced hypoxia in humans
Öppna denna publikation i ny flik eller fönster >>Cardiovascular, hematological and dietary means to cope with environmentally induced hypoxia in humans
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Östersund: Mid Sweden University, 2015. s. 87
Serie
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 213
Nationell ämneskategori
Idrottsvetenskap Fysiologi
Identifikatorer
urn:nbn:se:miun:diva-25016 (URN)978-91-88025-01-2 (ISBN)
Handledare
Tillgänglig från: 2015-06-01 Skapad: 2015-06-01 Senast uppdaterad: 2018-01-11Bibliografiskt granskad
2. Initiation of spleen contraction resulting in natural blood boosting in humans
Öppna denna publikation i ny flik eller fönster >>Initiation of spleen contraction resulting in natural blood boosting in humans
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Östersund: Mid Sweden University, 2015. s. 87
Serie
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 217
Nyckelord
Acclimatization, altitude, apnea, breath-hold diving, hemoglobin, hypercapnia, hypoxia, triggers
Nationell ämneskategori
Hälsovetenskaper
Identifikatorer
urn:nbn:se:miun:diva-25518 (URN)978-91-88025-10-4 (ISBN)
Handledare
Tillgänglig från: 2015-07-13 Skapad: 2015-07-13 Senast uppdaterad: 2017-06-15Bibliografiskt granskad

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Richardson, MattEngan, HaraldLodin-Sundström, AngelicaSchagatay, Erika

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