It's estimated that 10% to 30% of people who have had an acute COVID-19 infection will experience persistent symptoms, referred to as post-COVID condition. This condition is confirmed three months after the onset of COVID-19 and characterized by physical, neurocognitive, and psychiatric symptoms that persist for more than two months and cannot be explained by an alternative diagnosis. A randomized, sham-control, double-blind trial was conducted to evaluate the effects of hyperbaric oxygen therapy on patients who have post-COVID condition.

Patients ages 18 or older who had persistent symptoms after a confirmed COVID-19 infection were randomized to receive 40 daily sessions of either hyperbaric oxygen therapy or sham therapy. A total of 73 patients (37 in the hyperbaric oxygen therapy group and 36 in the control group) completed the protocol and were included in the analysis. There was a significant group-by-time interaction in the global cognitive score after hyperbaric oxygen therapy compared with the sham therapy. The hyperbaric oxygen therapy group also showed improvements in physical limitations and energy, sleep, psychological symptoms (somatization, depression, and anxiety), and pain interference symptoms. There were no significant differences in adverse effects in the two groups, and none of the patients discontinued treatment because of adverse effects.

Clinical outcomes were associated with increased cerebral blood flow and brain microstructural changes in the frontal, parietal, and limbic regions associated with cognitive and emotional roles.

There were several limitations of the study: the sample size was small; the optimal number of hyperbaric oxygen therapy sessions for maximal therapeutic effect hasn't yet been determined; and long-term results have yet to be collected.