After three years of follow-up, 39.0% for the 123 people randomly assigned to nocturnal oxygen needed long-term oxygen therapy or had died versus 42.0% for the 119 who received their nighttime air from a sham concentrator, a non-significant difference, researchers report in the New England Journal of Medicine.
In addition, "Nocturnal oxygen had no observed effect on secondary outcomes, including exacerbation and hospitalization rates and quality of life," the researchers write. "Furthermore, the duration of exposure to nocturnal oxygen did not modify the overall effect of therapy."
However, the trial, known as INOX, was underpowered. The research team had expected to enroll 600 volunteers at the 28 centers across four countries. Instead, recruitment and retention problems limited enrollment.
"Randomized trials of oxygen therapy are difficult to conduct," lead author Dr. Yves Lacasse of Laval University in Quebec, Canada, told Reuters Health by email. "Among the 20 published or ongoing trials that we referred to in our recent review of home oxygen in COPD, 11 recruited less than 50 patients, three were stopped prematurely and one (the Long-Term Oxygen Treatment Trial) was redesigned after 7 months of recruitment and the randomization of only 34 patients."
The two earlier trials attempting to see if supplemental oxygen slowed the progress of COPD to the point of delaying severe daytime hypoxemia were also underpowered and also had negative results.
Nonetheless, the "data are accumulating," Dr. Lacasse said. "There is no indication that nocturnal oxygen has a positive or negative effect on survival or progression to long-term oxygen therapy in patients with COPD. Consequently, there is no reason for physicians to screen for nocturnal hypoxemia in COPD."
Nocturnal oxygen therapy in COPD is widely used despite the lack of scientific evidence regarding its efficacy, said Dr. Lacasse. "For instance, when we started the trial, about 20% of the patients with a primary diagnosis of COPD receiving oxygen therapy through our respiratory home care program were receiving home oxygen for nocturnal utilization only."
The treatment has been an extension of the fact that it has been known since the early 1980s that daytime oxygen therapy can increase survival in COPD patients with severe chronic daytime hypoxemia.
In the INOX study, all the patients had COPD, did not appear to be poised to need long-term oxygen therapy, and did not have sleep apnea, among other exclusion criteria.
All had nocturnal desaturation, according to nightly home oximetry recordings. The air, either from the oxygenator or the sham device, was delivered through nasal cannulae. The amount of oxygen delivered was up to 4 L per minute, with the goal of having nocturnal oxygen saturation of more than 90% for at least 90% of the time.
"The rationale for giving oxygen at night when nocturnal desaturation is found in patients with COPD is that the progression of COPD to its end stages of severe hypoxemia, right heart failure, and death is thought to result from the severity of desaturation occurring during sleep," said Dr. Lacasse. "In addition, nocturnal oxygen desaturation in patients with COPD induces systemic inflammation that may also contribute to the pathogenesis of pulmonary hypertension and cardiovascular diseases."
"Patients with COPD may desaturate during sleep even if they don't suffer from sleep apnea," he added. "The most likely mechanisms of nocturnal desaturation in COPD are alveolar hypoventilation (particularly during rapid-eye-movement sleep) and ventilation-perfusion mismatch."
Many factors led to low recruitment in the blinded study, Dr. Lacasse said. One is the broad acceptance that oxygen therapy is useful. "Also, patients for whom oxygen therapy is considered have, by definition, severe COPD and are usually frail. This situation complicates their follow-up within the frame of clinical studies and increases the probability of withdrawal."
By Gene Emery
SOURCE: https://bit.ly/3hqQ7qK The New England Journal of Medicine, online September 16, 2020.
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