Hypoxemia without dyspnea in COVID-19

Abstract

Dyspnea may not be a major symptom of the disease. There are many reports that some patients with COVID-19 did not complain of dyspnea. There is no consensus on the clinical significance of hypoxemia without dyspnea. Several studies suggest that patients with hypoxemia without dyspnea are not protected against the development of adverse COVID-19 outcomes. It is unclear whether hypoxemia with and without dyspnea are two distinct COVID-19 phenotypes or two phases of the disease. There is currently no consensus on the terminology of this condition, its definition, and its mechanisms of formation. It has not been established whether hypoxemia without dyspnea is associated with a favorable outcome of the disease or not. The question of the absence of respiratory response to hypoxia improves the prognosis in such patients remains unresolved. Analysis of currently available data on the mechanisms of hypoxemia development and related manifestations of dyspnea in SARS-CoV-2 virus infection. “Silent hypoxemia” can be observed both in the initial manifestations of respiratory failure and in progression of the disease. Clinical significance of “silent hypoxemia” is that the decrease in physiologic responses and the absence of dyspnea allow patients to feel normal, thus denying the severity of their condition and masking the true severity of the disease. In addition, in elderly patients and patients with diabetes mellitus, suppression of respiratory function in response to hypoxia and the development of “silent hypoxemia” with rapid decompensation should be expected. The attitude to patients with “asymptomatic carriage” of the virus should be reconsidered and comprehensive monitoring of such patients with mandatory pulse oximetry or arterial blood gas test composition should be carried out.