Happy hypoxia in COVID-19 patients associated with hypoxic ventilatory depression

Abstract

Objective: Acute exposure to hypoxia generally increase the ventilation. However, some of COVID-19 patients who suffer from pneumonia are characterized by hypoxic ventilatory depression with loss of dyspnea which is called as happy hypoxia. This report describes the background and the clinical issues of happy hypoxia. Methods: The mechanisms to increase ventilation and dyspnea under hypoxia are explained. Further, clinical issues and characteristics in COVID-19 are reviewed. Results: Genetic factors are definitely concerned with chemosensitivity to hypoxia. Further disease factors including COVID-19 infection could influence the attenuation of the chemosensitivity. This can be attributed to either ventilatory depression due to the modulation of metabolic substrate, adenosine in the brain, or autonomic neuropathy including the dysfunction of the carotid body. Conclusions: COVID-19 patients must be carefully treated and/or monitored to avoid hypoxic ventilator depression. The clinical application of aminophylline will be an issue to be considered.