Source: Medscape Today News: August 12, 2011Obstructive Sleep Apnea Recurs Quickly When CPAP Withdrawn
Laurie Barclay, MD
August 11, 2011 — Obstructive sleep apnea (OSA) recurs quickly when continuous positive airway pressure (CPAP) is withdrawn, according to the results of a randomized controlled trial reported online August 10 in the American Journal of Respiratory and Critical Care Medicine.
"In patients with [OSA] who are established on CPAP treatment, withdrawal of the therapy is associated with a rapid recurrence of OSA and sleepiness within a few days," lead study author Malcolm Kohler, MD, senior consultant at the Sleep Disorders Centre and Pulmonary Division of the University Hospital in Zurich, Switzerland, said in a news release. "After 14 days of CPAP withdrawal, OSA patients experienced considerable increases in heart rate and blood pressure as well as a deterioration in vascular function."
The study goals were to validate a new strategy to assess the physiological effects of OSA and to study new therapies during a period of CPAP withdrawal, as well as to evaluate the effects of CPAP withdrawal. In this trial, 41 patients with OSA treated with CPAP were assigned to either CPAP withdrawal (subtherapeutic CPAP) or to continue CPAP for 2 weeks. Measurements included polysomnography, sleepiness, psychomotor performance, endothelial function assessed by flow-mediated dilatation, blood pressure (BP), heart rate (HR), urinary catecholamines, and blood markers of systemic inflammation and metabolism.
Within a few days after CPAP was withdrawn, patients in that group had recurrence of OSA and of subjective sleepiness. However, psychomotor performance did not deteriorate significantly during the 2-week study.
Compared with the therapeutic CPAP group, the CPAP withdrawal group had a significant reduction in endothelial function (mean difference in change, −3.2%; 95% confidence interval [CI], −4.5 to −1.9%; P < .001). The CPAP withdrawal group also had significant increases in morning systolic BP (mean difference in change, +8.5 mm Hg; 95% CI, +1.7 to +15.3 mm Hg; P = .016), morning diastolic BP (mean difference in change, +6.9 mm Hg; 95% CI, +1.9 to +11.9 mm Hg; P = .008), and morning HR (mean difference in change, +6.3beats per minute [bpm]; 95% CI, +0.4 to +12.2 bpm; P = .035).
During CPAP withdrawal, levels of urinary catecholamines increased, but there was no change in markers of systemic inflammation, insulin resistance, or blood lipids.
"We have shown that CPAP withdrawal leads to a return of OSA within the first night off CPAP," Dr. Kohler said. "In addition to strongly suggesting that OSA patients should bring along their CPAP machines on holiday, these findings have implications for OSA research going forward. CPAP withdrawal represents a new way to investigate the physiological effects of OSA and evaluate novel treatments."
Limitations of this study include potential lack of blinding of participants (ie, those randomized to subtherapeutic CPAP may have realized their group allocation) and withdrawal period of only 2 weeks for ethical reasons.
"This is the first randomized controlled study investigating the effects of a 2-week CPAP withdrawal on OSA severity, sleepiness, psychomotor performance, and measures of cardiovascular risk," the study authors write. "We found that CPAP withdrawal was associated with a return of OSA by the first night, an increase in subjective sleepiness, progressively impaired endothelial function, and increased urinary catecholamines, blood pressure, as well as with an increased heart rate at 2 weeks." But, "CPAP withdrawal was not associated with significant deterioration in psychomotor performance, systemic inflammation, insulin resistance, or blood lipids" within this same timeframe.
"The severity of OSA did not increase further after the first week of CPAP withdrawal," the study authors go on to explain. "This suggests that the duration of any future trial using this model, and purely investigating the treatment effects on the severity of sleep-disordered breathing, could be as short as a few nights."
They strongly urge that any OSA patients participating in a CPAP withdrawal study not drive for the duration of the trial.
"The CPAP withdrawal model seems to be a useful addition to the armamentarium of study paradigms investigating the physiological consequences of OSA such as the introduction of 'simulated OSA' in healthy humans," conclude the study authors. "Thus, the CPAP withdrawal model seems to be [most] suitable when the short-term physiological effects of OSA and responses to novel treatments need to be investigated."
The study was supported by the Swiss National Science Foundation and the Swiss Society of Pneumology.The study authors have disclosed no relevant financial relationships.
Am J Respir Res Crit Care Med. Published August 10, 2011.
Cheers,
Jess
