Hypoxic Exercise Exacerbates Hypoxemia and Acute Mountain Sickness in Obesity: A Case Analysis

Temporary hypoxemia at high altitude in an intensive care unit physician

A 42-year-old pediatric intensive care unit physician traveled to Nepal and took a helicopter trip to Everest Base Camp. The helicopter reached an altitude of 5500 m during flight and descended at different destinations with varying altitudes. At Hotel Everest View at 3820 m, his oxygen saturation was 79%. He had mild tachypnea and deep breathing but was able to walk around, jump, and take photographs. He returned to Kathmandu (altitude, 1324 m) without using any supplemental oxygen during the entire trip. Based on calculations with the alveolar gas equation, he observed that he and his fellow passengers probably had hypoxemia during the trip. In summary, temporary hypoxemia associated with high altitude in healthy individuals without cardiorespiratory compromise may not require oxygen therapy. In contrast, intensive care unit patients who have respiratory failure may have similar oxygen saturation levels but may require oxygen therapy and mechanical ventilation. The oxygen saturation level must be interpreted in consideration of the clinical scenario before deciding about the need for oxygen therapy.

Effects of Acute Exposure and Acclimatization to High-Altitude on Oxygen Saturation and Related Cardiorespiratory Fitness in Health and Disease

Maximal values of aerobic power (VO₂max) and peripheral oxygen saturation (SpO₂max) decline in parallel with gain in altitude. Whereas this relationship has been well investigated when acutely exposed to high altitude, potential benefits of acclimatization on SpO₂ and related VO₂max in healthy and diseased individuals have been much less considered. Therefore, this narrative review was primarily aimed to identify relevant literature reporting altitude-dependent changes in determinants, in particular SpO₂, of VO₂max and effects of acclimatization in athletes, healthy non-athletes, and patients suffering from cardiovascular, respiratory and/or metabolic diseases. Moreover, focus was set on potential differences with regard to baseline exercise performance, age and sex. Main findings of this review emphasize the close association between individual SpO₂ and VO₂max, and demonstrate similar altitude effects (acute and during acclimatization) in healthy people and those suffering from cardiovascular and metabolic diseases. However, in patients with ventilatory constrains, i.e., chronic obstructive pulmonary disease, steep decline in SpO₂ and V̇O₂max and reduced potential to acclimatize stress the already low exercise performance. Finally, implications for prevention and therapy are briefly discussed.