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Cerebral hemodynamic and ventilatory responses to hypoxia, hypercapnia, and hypocapnia during 5 days at 4,350?m.

ABSTRACT: This study investigated the changes in cerebral near-infrared spectroscopy (NIRS) signals, cerebrovascular and ventilatory responses to hypoxia and CO2 during altitude exposure. At sea level (SL), after 24?hours and 5 days at 4,350?m, 11 healthy subjects were exposed to normoxia, isocapnic hypoxia, hypercapnia, and hypocapnia. The following parameters were measured: prefrontal tissue oxygenation index (TOI), oxy- (HbO2), deoxy- and total hemoglobin (HbTot) concentrations with NIRS, blood velocity in the middle cerebral artery (MCAv) with transcranial Doppler and ventilation. Smaller prefrontal deoxygenation and larger ?HbTot in response to hypoxia were observed at altitude compared with SL (day 5: ?HbO2-0.6±1.1 versus -1.8±1.3??mol/cmper mm?Hg and ?HbTot 1.4±1.3 versus 0.7±1.1??mol/cm per mm?Hg). The hypoxic MCAv and ventilatory responses were enhanced at altitude. Prefrontal oxygenation increased less in response to hypercapnia at altitude compared with SL (day 5: ?TOI 0.3±0.2 versus 0.5±0.3% mm?Hg). The hypercapnic MCAv and ventilatory responses were decreased and increased, respectively, at altitude. Hemodynamic responses to hypocapnia did not change at altitude. Short-term altitude exposure improves cerebral oxygenation in response to hypoxia but decreases it during hypercapnia. Although these changes may be relevant for conditions such as exercise or sleep at altitude, they were not associated with symptoms of acute mountain sickness.

SUBMITTER: Rupp T

PROVIDER: S-EPMC3887348 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Cerebral hemodynamic and ventilatory responses to hypoxia, hypercapnia, and hypocapnia during 5 days at 4,350 m.

Rupp Thomas T Esteve François F Bouzat Pierre P Lundby Carsten C Perrey Stéphane S Levy Patrick P Robach Paul P Verges Samuel S

Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism 20130925 1

This study investigated the changes in cerebral near-infrared spectroscopy (NIRS) signals, cerebrovascular and ventilatory responses to hypoxia and CO2 during altitude exposure. At sea level (SL), after 24 hours and 5 days at 4,350 m, 11 healthy subjects were exposed to normoxia, isocapnic hypoxia, hypercapnia, and hypocapnia. The following parameters were measured: prefrontal tissue oxygenation index (TOI), oxy- (HbO2), deoxy- and total hemoglobin (HbTot) concentrations with NIRS, blood velocit ...[more]

PMID: 24064493

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Project description:Backgroundγ-irradiation is used to treat red blood cell (RBC) concentrates (RCCs) transfused to immunosuppressed patients. This treatment damages RBCs and increases storage lesions. Several studies have shown the beneficial effect of reducing O2 content during RBC storage. The present research work investigated the effect of γ-irradiation on RCCs stored under normal and hypoxia/hypocapnia conditions.Materials and methodsO2 concentration (measured as oxyhaemoglobin fraction, sO2) and ABO-matched RCCs from whole blood donations, leukoreduced and prepared in phosphate, adenine, glucose, guanosine, saline and mannitol (PAGGSM) were pooled and split in two identical RCCs within 24 h post donation. One bag (Hx) was submitted to O2 and CO2 adsorption for 3 h on an orbital shaker at 22±2 °C and then transferred to a storage bag impermeable to gas. The other bag (Ctrl) was left as it was. The two bags were then stored at 4 °C. γ-irradiation (25 Gy) was applied at day 2 or 14, and the RCCs were stored until day 43. Different parameters (metabolites, haemolysis, morphology) were measured.ResultsStarting sO2 values were 63.7±18.4% (n=12) in Ctrl and 20.8±9.8% (n=12) in Hx bags, and reached 90.8±9.1% and 6.6±5.9% at day 43, respectively. As expected, an increase in glycolysis rate was observed after deoxygenation. Extracellular potassium concentrations were identical and reached around 70 mM at expiry with an irradiation-dependent kinetic release. No difference in haemolysis was observed after irradiation on day 2 in either group (<0.40%, p>0.9999). When irradiated at day 14, haemolysis was lower (p=0.033) in RCCs under hypoxia at the end of storage (day 28, 0.67±0.16%) compared to control (1.06±0.33%). Percentages of spherocytes were lower under hypoxia.DiscussionThe storage under hypoxia provided equivalent storage when RCCs were irradiated at day 2 and was advantageous when irradiated at day 14. In summary, O2-depletion of RCCs enable a better storage of RBCs, particularly when late irradiation is applied.

Dataset Information

Cerebral hemodynamic and ventilatory responses to hypoxia, hypercapnia, and hypocapnia during 5 days at 4,350?m.

Publications

Cerebral hemodynamic and ventilatory responses to hypoxia, hypercapnia, and hypocapnia during 5 days at 4,350 m.

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