| LinkExchange Member | Free Home Pages at GeoCities |
Article #6
For some audience responses to date, CLICK HERE
To return to main page, CLICK HERE
BiPAP (see Glossary) is used not only for people with sleep apnea but also for those with respiratory failure from other causes, such as neuromuscular disease. These patients often complain of air leakage through the mouth, just as do sleep apneics. The authors studied the effects of this phenomenon on sleep in six such patients, with two nights of overnight polysomnography, which included audio/videotaping of the face to monitor air leakage around the mask and through the mouth, also identifiable by measurement of mask pressure and estimated airflow into the mask. Four patients, partially sleep-deprived the night before, were also monitored during daytime naps.
Sleep architecture was abnormal in all patients, with decreased sleep efficiency, increased stage 1 sleep, and decreased rapid eye movement sleep, these abnormalities varying between patients from mild to severe. Arousal frequencies ranged from 8.4 to 143 per hour, averaging 46/hr, and were associated with air leakage in 60-99% of occurences, averaging 82% of the time. In other words, air leakage appeared capable of inducing as many arousals as do apneas and hypopneas in severely ill sleep apneics; in fact, the “air leakage distress index” (if there were such a term) averaged 37 arousals/hour!
All patients showed signs of air leakage throughout the night, but especially in slow-wave (deep) sleep. However, oxygen desaturations were infrequent, average saturation being 94% and average lowest saturation being 90% or more in five of the six. Only one patient, with gross leakage throughout the night, had severe desaturations, despite a chinstrap; she died several weeks later.
Arousals occurred usually towards the end of a leakage, especially during REM sleep, much less so during slow-wave sleep despite frequent air leakages during that stage. Presumably this represents different thresholds for arousal by external stimulation in slow-wave vs. REM sleep.
Air leakage also occurred during naps, but more briefly. None of the napping patients entered REM or slow-wave sleep.
Sleeping patients often terminated leakages by repositioning the jaw and swallowing, but a few minutes later the pattern would typically repeat itself.
The authors concluded that the major adverse effect of air leakage was sleep fragmentation, not desaturation. Patients appeared more resistant to this effect during deeper stages of sleep, but the occurrence of leakage-related arousals in lighter stages of sleep seemed to hinder patients entering the deeper stages. Insensitivity or habituation to leakage-related arousals would have the advantage of reducing sleep fragmentation but the disadvantage of allowing more disturbance of blood oxygenation.
Despite all this, patients were better able to sleep with BiPAP than without it. The authors suggested that mouthpieces or oronasal masks might further improve sleep. They suggested that the usefulness of chinstraps also be studied.
Even though this study does not concern sleep apnea directly, I consider it quite relevant to a common problem of patients with sleep apnea on CPAP or BiPAP: air leakage, whether through the mouth or around the mask.
This problem is one reason patients like myself try different masks. When I recently pointed this out to a home health care worker from whom I was buying (without trying) a $100 gel mask, he reassured me that the machine could largely compensate for such leaks with pressure increases. I now doubt this, though I have seen no data on it except for the authors’ comments that they could detect leakages from pressure fluctuations in the mask. However, the home care worker missed the point entirely that this “annoyance” could disrupt sleep as much as the apnea itself! After I took the gel mask home and tried it the first night, I discovered I had thrown my money away; it was worse than the old Respironics mask I had for years!
Leakage of air towards the eyes is an especially alarming consequence if it dries the eyes overnight, because the patient awakens in the morning with acutely painful eyes that take some time to clear up. When it happened to me, I thought I had somehow injured my eyes; I can’t remember anyone warning me about this.
However, the main point is that the leakages, and the muscular responses used to briefly control the leakages, represent internal and external stimuli contributing to arousals and sleep fragmentation, resulting in lighter and less restful sleep. In fact, it is not unlike the adverse effect on sleep of sleep apnea itself.
One patient reported being told by a home health care worker that she was just about the only one he knew complaining about air leakage. This seems to show how out of touch he was with the problems of his patients, who may be reluctant to make any complaints to a worker who is always in a hurry, reluctant to take time to listen, or maybe even judgmental that people who complain about anything must lack fortitude!
Sleep fragmentation and its converse, continuity of sleep, are multifactorial in cause. Apneas and hypopneas are a major cause of arousals and fragmentation, but so "trivial" an occurrence as air leakage may have an equally adverse effect on sleep, and it is quite possible that any number of other factors considered relatively minor--periodic leg movements of sleep, noise, the motions of a bed partner, the presence of pets in the bedroom, the symptoms of allergies and colds, the noise of a nearby airport--may contribute their portions of varying magnitude to the disruption of sleep. Therein may lie some of the explanation for persistent symptoms of excessive daytime sleepiness in patients under treatment with CPAP, and some of the day-to-day variation in this problem.
WHAT DO YOU THINK ABOUT THIS ARTICLE AND MY COMMENTS?
CAN YOU RELATE THIS MATERIAL TO ANY PERSONAL EXPERIENCES?
Get your own Free Home Page