According to the data from a small Israeli trial, patients with long covid showed some improvement after breathing pure oxygen in a high-air-pressure environment. In the trial, researchers randomly assigned 73 patients experiencing post-covid symptoms for the last three months into two groups, i.e., hyperbaric oxygen therapy (HBOT) group or a placebo treatment group. 

According to a report published in the Scientific Reports of the journal ‘Nature’, the HBOT group participants showed "significant improvement" in thinking skills, energy, sleep, psychiatric symptoms, and pain in comparison to participants in the placebo group after the last session of the 40-day regimen. 

The researchers stated that young and middle-aged adults who were infected with earlier versions of the Omicron variant of the coronavirus were likely to have "strong" protection against reinfection with the currently dominant Omicron BA.4 and BA.5 subvariants.

(Source: https://www.hindustantimes.com/lifestyle/health/highpressure-oxygen-shows-promise-in-long-covid-earlier-omicron-infection-may-protect-against-subvariants-101657849843297.html )