Arousals from Sleep Possible Cause of Apnea in Some Patients

Arousals from Sleep Possible Cause of Apnea in Some Patients
By Michael Smith, North American Correspondent, MedPage Today
Published: January 05, 2009
Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston. Earn CME/CE credit
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TORONTO, Jan. 5 -- In patients with heart failure and central sleep apnea, arousals may cause the sleep disorder rather than defending against it, researchers here said. Action Points
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In obstructive sleep apnea, arousals from sleep are seen as a defense mechanism to re-start breathing; their frequency typically declines when the apnea is treated, according to Douglas Bradley, M.D., of the University of Toronto, and colleagues.


But in a large randomized trial of patients with heart failure, treating central sleep apnea with continuous positive airway pressure (CPAP) had no effect on arousals, although the number of apneas and hypopneas fell significantly, Dr. Bradley and colleagues reported in the Jan. 1 issue of Sleep.


And, unlike in obstructive apnea, there was no effect on sleep structure, the researchers said.


The results of the multicenter Canadian Continuous Positive Airway Pressure for Patients with Central Sleep Apnea and Heart Failure trial suggest that "unlike [in obstructive sleep apnea], arousals from sleep in [central sleep apnea] are not protective, but probably have the opposite effect: they appear to be causative," Dr. Bradley said in a statement.


"Future studies should explore preventing arousals from sleep in order to treat [central sleep apnea]," he added.


The researchers noted that in obstructive sleep apnea, the arousal ends the apnea, but in central sleep apnea, the arousal often comes several breaths after the incident has ended.


Their study randomized 258 patients with central sleep apnea, class II to IV heart failure, and a left ventricular ejection fraction of the less than 40% to either optimal heart failure therapy with CPAP or optimal therapy alone.


The primary endpoint was the combined rate of all-cause mortality and heart transplant.


The researchers reported in 2005 that CPAP brought no survival benefit, although the intervention attenuated the central sleep apnea, improved nocturnal oxygenation, increased ejection fraction, lowered norepinephrine levels, and increased the distance walked in six minutes.


The current analysis looked more closely at the central sleep apnea, which is a failure of respiratory control. In contrast, in obstructive sleep apnea, control of respiration is not affected, but the patient struggles against a physical blockage.


The researchers looked at differences from baseline in sleep apnea, sleep structure, and arousals at a polysomnographic examination three months into the study.


The early comparison was chosen, the researchers said, to include the largest possible number of participants -- 205 -- but results were similar when they looked at the 71 patients still in the study at two years.


Analysis showed:

In the control groups, there was no change in the apnea-hypopnea index or the frequency of arousals.
In volunteers who got CPAP, the overall apnea-hypopnea index (including both central and obstructive events) fell from an average of 38.9 incidents an hour to 17.6, a change that was significant at P<0.001.
Apneas and hypopneas regarded as central in nature fell 55%, from 35.4 an hour to 16.1, which was also significant at P<0.001.
Arousals remained high -- 28.8 arousals per hour at baseline compared with 24.3 on CPAP.

There was no significant effect on any aspect of sleep structure, including such variables as time in bed, total sleep time, sleep efficiency, or time spent in any of the stages of sleep, the researchers found.


Taken together with results from other, smaller studies, the results suggest arousals in heart failure patients with central sleep apnea are "not entirely a consequence of central apneas and hypopneas," the researchers said.


Instead, "such arousals may be incidental to, or play a causative or aggravating role" in the pathogenesis of the condition, they said.



The study was supported by the Canadian Institutes of Health Research (CIHR), Respironics Inc., ResMed Inc., and Tyco Healthcare Inc.

Various researchers were supported by awards or fellowships from Mahidol University in Bangkok, the Toronto Rehabilitation Institute, the Fonds de la Recherche en Santé du Québec, and the Heart and Stroke Foundation of Ontario.


Aside from the industry support -- a requirement of grant support from the CIHR -- the researchers reported no conflicts.

rested gal wrote:....... I think what the future studies about central sleep apnea should be exploring (other studies have already been doing this) is optimizing "CPAP" treatment for heart failure patients and others with Central Sleep Apnea by using the currently available ASV machines. Not plain CPAP machines.

rooster wrote:Debjax,

After your comments I did a second read of the summary and agree with you. If it is the case that arousals trigger apneas then we are dealing with something I never saw discussed in the forum. I temper my comments.

Thanks,