DEAR DR. ROACH: My husband is considering a hyperbaric chamber to see if it can possibly help him for possible post-COVID symptoms. He contracted COVID this past July, and his atrial fibrillation also started to act up at this time. He spent a week in the hospital and was so weak that he had to use a wheelchair to get home.

Two days after arriving home, my husband spent a week or so in a local hospital with continued pneumonia symptoms and sepsis. Then he went to rehab for three weeks to get his strength back. He is now in a research study following the replacement of his aortic valve this past spring and has fainted twice after completing the exercises that they ask him to do.

He says that his head is foggy and swirly, and he feels as if he is going to fall over almost constantly. He has been told by various doctors that he may be oxygen-deficient and that a hyperbaric chamber may possibly help him.

Can you tell us what you know about these chambers?

• J.W.

ANSWER: Hyperbaric oxygen uses extremely high oxygen pressures to dissolve oxygen into the blood plasma. (The red blood cells get nearly 100% saturated in people with normal lungs, but high oxygen, which is way above atmospheric pressure, can force more oxygen into the fluid component of the blood.) The extra oxygen is useful for a limited number of indications, including air embolism, decompression sickness, gangrene as well as some other severe infections, carbon monoxide poisoning and some types of nonhealing ulcers.

The experimental evidence on using hyperbaric oxygen in people with persistent COVID symptoms appeared to be promising, with one initial study of 40 sessions showing a benefit. Unfortunately, a more-recent larger trial (of only 10 sessions) showed no improvement in symptoms compared to a placebo group. (The placebo group went into the chamber but didn’t get hyperbaric oxygen, and neither the subjects nor the investigators knew who got which treatment.) Even the placebo group improved significantly. This may represent the natural history of long COVID, or it may represent the expectation that people will get better. It could also be that more than 10 sessions are needed to receive a benefit.

I’ve had many patients with persistent symptoms after COVID, especially those who had very severe COVID. More research needs to be done to find new ways to help.

ToYourGoodHealth@med.cornell.edu.