Hypoxemia in individuals with mild-to-moderate obesity at simulated altitude: implications for an exaggerated ventilatory response

Introduction: Individuals with obesity are more hypoxemic (lower PaO2) relative to those without obesity. Rapid ascent to high altitude also causes hypoxemia. However, the magnitude of hypoxemia in individuals with obesity at high altitude is unknown but could be more severe compared with those without obesity due to the additive effects of obesity- and altitude-related causes of hypoxemia. To test this hypothesis, we compared PaO2 in individuals with vs. without obesity at a simulated altitude of 12,000ft. Methods: 19 younger otherwise healthy individuals were studied for 24 hours in a hypobaric environmental chamber: 10 without obesity (age: 35±7yr; BMI: 25.0±3.8 kg/m2) and 9 with mild-to-moderate obesity (age: 35±6yr; BMI: 37.3±4.2kg/m2). PaO2 (arterial puncture), ventilation (V̇E, pneumotachograph), and self-reported symptoms of acute mountain sickness (AMS, Lake Louise score) were measured at sea level (Pb: ~760mmHg) and at a simulated altitude of 12,000ft (Pb: ~483mmHg). Results: PaO2 was lower (p<0.001) in those with (84.5±8.0mmHg) vs. without obesity (96.1±6.8 mmHg) at sea level; however, PaO2 was not significantly different between groups at 12,000ft (with obesity: 47.8±6.0mmHg; without obesity: 51.2±5.6mmHg, p=0.265). While V̇E was similar between groups at sea level (with obesity: 14.8±5.0L/min; without obesity: 11.3±3.3L/min, p=0.114), V̇E was higher (p=0.029) in those with (58.3±8.4L/min) vs. without (47.2±9.0L/min) obesity at 12,000ft, which may reflect a greater hypoxic ventilatory response in those with obesity relative to those without obesity. Lastly, seven individuals with obesity and four individuals without obesity had AMS scores of ≥4 at 12,000ft. Conclusion: We demonstrated that the magnitude of hypoxemia at high altitude was similar between those with and without obesity, but this was at the expense of an exaggerated ventilatory response in those with obesity. While perhaps an appropriate compensatory ventilatory response to a hypoxic stimulus, this finding could have implications for younger healthy individuals with mild-to-moderate obesity traveling to higher elevations where they could be more likely to develop severe dyspnea and/or AMS. Further investigation of the degree of hypoxemia at high altitude is required in older individuals with a greater magnitude of obesity. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.