A host of persistent symptoms includes abnormal heartbeats and a heightened risk of developing cardiovascular dysfunction.
A team of researchers ran a small study analyzing how inhaling highly pressurized, pure oxygen affects the heart function of long COVID patients.
They found that hyperbaric oxygen therapy may help the heart improve cardiovascular contractions in this population.
Professor Marina Leitman, MD, of the Sackler School of Medicine at Tel Aviv University and Shamir Medical Center, Be’er Ya’akov, Israel, who led this study, presented her team’s findings in May 2023 at EACVI 2023, a conference held by the European Society of Cardiology (ESC), though they have not yet been peer-reviewed.
How to measure cardiac function
The study’s authors assessed global longitudinal strain (GLS), a sensitive but uncommon measure of cardiac function.
Medical News Today spoke about GLS with Dr. Jayne Morgan, a cardiologist and clinical director of the COVID Task Force at the Piedmont Healthcare Corporation in Atlanta, Georgia, who was not involved in the present study.
“GLS is a measure of cardiac function that can guide a physician’s expectations of the clinical course in patients who may have normal left ventricular function yet remain symptomatic. An abnormal GLS value can be associated with an increased long term cardiac risk for patients,” Dr. Morgan explained.
A healthy heart will show a GLS value of around -20%, meaning that the heart is contracting and relaxing properly in the longitudinal direction.
A lower GLS value indicates that the heart is not functioning as effectively as it should.
Long COVID and heart concerns
While most people who have COVID-19 fully recover, about 10-20% of them develop long COVIDTrusted Source, also known as post-COVID syndrome. This can be diagnosed at least three months after someone develops initial COVID-19 symptoms.
Those with long COVID can also face a greater risk of developing heart disease, heart failure, and related conditions.
According to a 2022 studyTrusted Source, such symptoms have even manifested in people with no previous heart problems or high risk of cardiovascular disease.
How does hyperbaric oxygen therapy work?
HBOT involves breathing 100% oxygen while lying in a hyperbaric chamber, a tube that holds one person. The air we normally breathe consists of 21% oxygen.
The air pressure inside the chamber is elevated to a higher level than normal air pressure. The increased pressure helps the lungs and oxygen-deprived tissues absorb more oxygen, which promotes healing.
In the U.S., the Food and Drug Administration (FDA) regulates hyperbaric chambersTrusted Source and the oxygen used in HBOT.
HBOT is an established treatment for non-healing wounds, radiation injury, and decompression sickness in divers. Another small study published in 2021 found that this treatment may help treat long COVID symptoms.
However, the FDA has not currently cleared this therapy for treating COVID-19 or related conditions.
The study’s methods
Dr. Leitman and her cohorts enlisted 60 long COVID patients with symptoms persisting for at least three months after having mild to moderate COVID-19. They included hospitalized and non-hospitalized individuals.
The researchers randomly assigned the subjects to HBOT or a sham procedure in a 1:1 ratio. Each person had five sessions weekly over eight weeks.
The HBOT group received 100% oxygen at a pressure of 2 atmospheres for 90 minutes, with 5-minute breaks every 20 minutes. The sham group had 21% oxygen at 1 atmosphere for 90 minutes with no break.
Further, all the participants underwent echocardiography to measure GLS before the first HBOT session and 1 to 3 weeks after the last.
At the study’s baseline, 29 out of the 60 participants had an average GLS value of -17.8%. Sixteen were in the HBOT group, and 13 were in the sham group.
The Study’s Results
After the treatments, the average GLS among the intervention group increased to -20.2%. Among the sham group, the average GLS also increased to -19.1%. Only the former measurement was significantly different from the measurement at the start of the study.
Dr. Leitman observed that almost half of long COVID patients had impaired cardiac function at baseline according to GLS.
However, all the study participants had a normal ejection fraction, which is the standard measure of how well the heart contracts and relaxes while pumping blood.
“This means that ejection fraction is not sensitive enough to identify long COVID patients with reduced heart function,” Dr. Leitman said.
Oxygen therapy may be beneficial
Dr. Morgan said the study’s findings “appear to trend toward positive outcomes with hyperbaric oxygen therapy.”
However, she cautioned that “Hyperbaric oxygen is not a generalized standard therapy and will require further scrutiny.” Further, she noted that some research has raised “concern over a possible increase in arrythmias.”
Dr. Leitman and fellow researchers concluded that hyperbaric oxygen therapy can be beneficial in long COVID patients.
“More studies are needed to determine which patients will benefit the most, but it may be that all long COVID patients should have an assessment of global longitudinal strain and be offered hyperbaric oxygen therapy if heart function is reduced,” she added.
Dr. Leitman also hopes that further studies can gather long-term results and help health experts determine the optimal number of HBOT sessions.