CF patients see breathing problems while sleeping after transplant
About half of patients studied experienced apnea, airway obstruction
About half of people with cystic fibrosis (CF) had breathing difficulties during sleep a year after a lung transplant, although the severity was mild, according to the first study to address the issue.
Older age, being male, and having smaller static lung volume, which is when there is no flow of air through the airways, were independent predictors of post-transplant breathing problems. Despite these findings, excessive daytime sleepiness was not a concern, the researchers noted.
Still, having a lung transplant lengthened the time in deep sleep and increased blood oxygen levels during the night.
The study, “Sleep and Respiratory Parameters After Lung Transplantation in Adult Patients With Cystic Fibrosis,” was published in Clinical Transplantation.
In CF, the abnormal accumulation of thick and sticky mucus in the lungs and the resulting infections, inflammation, and tissue damage contribute to a progressive declines in lung health. Lung transplants can be a life-saving treatment option for CF patients with advanced lung disease whose illness fails to respond to available therapies.
Studying breathing problems
Previous work published by scientists at the University of Leuven in Belgium showed that, in people without CF, having a lung transplant may be followed by sleep-disordered breathing (SDB) — breathing difficulties that occur during sleep, such as reduced airflow (hypopnea) or a complete cessation of breathing (apnea). Here, researchers explore whether a lung transplant affects breathing patterns with CF.
“This is the first study to examine sleep in adult [CF patients] after [lung transplant],” the researchers wrote.
The study enrolled 62 CF patients (31 women) who had a lung transplant and a follow-up sleep study a year later to gauge breathing patterns during sleep. Ten patients had underwent a sleep study before and after the transplant. None received CFTR modulator therapy at the time of the follow-up.
The primary outcome was the apnea-hypopnea index (AHI), or the average number of apnea/hypopnea events per hour of sleep. SDB was defined as an AHI value of 5 or more.
A year after a lung transplant, the median AHI was in the normal range at 4.9. About half (48.4%) the patients tested positive for SDB, of whom roughly one in six (17.7%) had moderate to severe SDB, or an AHI value of 15 or more.
Seven patients with SDB showed predominantly central sleep apnea events, that is,, when the brain doesn’t send the right signals to the muscles that control breathing. The remaining had more obstructive events, or when the airflow was blocked.
Compared with those who breathe normally during sleep, patients with SDB were significantly older, male, and had better lung function. They also woke up more often during sleep, had more drops in blood oxygen levels, and had lower minimum blood oxygen levels.
Although scores for daytime sleepiness slightly worsened, based on the Epworth Sleepiness Scale, the changes were nonsignificant, “indicating the absence of excessive daytime sleepiness,” the researchers wrote.
According to statistical analyses, age, sex, and thoracic gas volume (TGV), the volume of gas in the thorax, were the best predictors of SDB.
In more detail, the AHI was 7.27 events per hour lower in female patients than with men. Each one-year increase in age was associated with an AHI rise of 0.29, while each 1 L drop in TGV predicted a higher AHI of 3.56 events per hour. The results remained the same when other lung volume measures replaced TGV in the models. TGV was also an independent predictor of higher AHI after a lung transplant among non-CF patients in the previous study, the researchers said.
As expected, lung function significantly improved after the transplant in the 10 patients with pre- and post-transplant assessments.
However, AHI rose significantly by a mean of 4.6, driven mainly by obstructive events. Researchers called the clinical relevance of the finding “uncertain,” given that daytime sleepiness didn’t significantly increase.
At the same time, there was a significant increase in slow-wave sleep, also known as deep sleep, which is associated with reduced muscle activity, regular breathing/heart rate, and minimal dreaming. Mean blood oxygen levels also improved, as did the amount of sleep when blood oxygen levels were in the normal range (above 90%).
“Our findings emphasize the need for further research to elucidate the effects of [lung transplant] on sleep and respiration in adult [CF patients],” wrote the researchers, who said the small sample size was a limitation of the study.
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