Effects of Acute Hypobaric Hypoxia Exposure on Cardiovascular Function in Unacclimatized Healthy Subjects: A “Rapid Ascent” Hypobaric Chamber Study

Sigrid Theunissen, Costantino Balestra, Sébastien Bolognési, Guy Borgers, Dirk Vissenaeken, Georges Obeid, Peter Germonpré, Patrick M. Honoré and David De Bels
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Sigrid Theunissen: Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), 1160 Brussels, Belgium
Costantino Balestra: Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), 1160 Brussels, Belgium
Sébastien Bolognési: Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), 1160 Brussels, Belgium
Guy Borgers: Hypobaric Centre, Queen Astrid Military Hospital, 1120 Brussels, Belgium
Dirk Vissenaeken: Hypobaric Centre, Queen Astrid Military Hospital, 1120 Brussels, Belgium
Georges Obeid: Military Hospital Queen Elizabeth, 1120 Brussels, Belgium
Peter Germonpré: Military Hospital Queen Elizabeth, 1120 Brussels, Belgium
Patrick M. Honoré: Department of Intensive Care Medicine, CHU-Brugmann, 1020 Brussels, Belgium
David De Bels: Department of Intensive Care Medicine, CHU-Brugmann, 1020 Brussels, Belgium

IJERPH, 2022, vol. 19, issue 9, 1-11

Abstract: Background: This study aimed to observe the effects of a fast acute ascent to simulated high altitudes on cardiovascular function both in the main arteries and in peripheral circulation. Methods: We examined 17 healthy volunteers, between 18 and 50 years old, at sea level, at 3842 m of hypobaric hypoxia and after return to sea level. Cardiac output (CO) was measured with Doppler transthoracic echocardiography. Oxygen delivery was estimated as the product of CO and peripheral oxygen saturation (SpO 2 ). The brachial artery’s flow-mediated dilation (FMD) was measured with the ultrasound method. Post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography. Results: During altitude stay, peripheral oxygen saturation decreased (84.9 ± 4.2% of pre-ascent values; p < 0.001). None of the volunteers presented any hypoxia-related symptoms. Nevertheless, an increase in cardiac output (143.2 ± 36.2% of pre-ascent values, p < 0.001) and oxygen delivery index (120.6 ± 28.4% of pre-ascent values; p > 0.05) was observed. FMD decreased (97.3 ± 4.5% of pre-ascent values; p < 0.05) and PORH did not change throughout the whole experiment. Τhe observed changes disappeared after return to sea level, and normoxia re-ensued. Conclusions: Acute exposure to hypobaric hypoxia resulted in decreased oxygen saturation and increased compensatory heart rate, cardiac output and oxygen delivery. Pre-occlusion vascular diameters increase probably due to the reduction in systemic vascular resistance preventing flow-mediated dilation from increasing. Mean Arterial Pressure possibly decrease for the same reason without altering post-occlusive reactive hyperemia throughout the whole experiment, which shows that compensation mechanisms that increase oxygen delivery are effective.

Keywords: hypobaric; nitric oxide; vascular reactions; breathing; extreme environments; human; permissive hypoxemia (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
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