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The sleep medicine community is much concerned over the “low compliance” of sleep apneic patients with their CPAP, which is supposed to be used all night every night and even during naps, but often gets used much less, sometimes not every night, sometimes only for part of the night. However, the authors have observed some patients do well using CPAP as little as two or three hours a day, suggesting that only partial treatment may be effective. Their study was designed to test this possibility.
Their subjects consisted of 27 patients referred for suspicion of OSAS who had undergone a full-night in-lab polysomnogram, resulting in recommendation of CPAP when the subject had disabling daytime sleepiness or a Movement Arousal Index or MAI of 24 or greater (representing the appearance of alpha rhythm with increased muscular activity in the midst of sleep—what we would probably consider one type of “arousal” not necessarily related to movement at all). These 27 subjects included only one female. They were middle-aged (49 years SD=+/-9) and obese (Body Mass Index=33, SD=+/-7). They had a wide-ranging but overall severe Respiratory Distress Index of 51/hour (SD=+/-21), a sleep fragmentation MAI of 41/hour (SD=+/-15), an increased proportion of stage 1 Non-REM sleep (29%, SD=+/-23%) at the expense of stages 3-4 Non-REM sleep (5%, SD=+/-4%), and had low mean oxygen saturation (90%, SD=+/-6%) and minimum oxygen saturation (63%, SD=+/-12%).
After 2-3 nights on CPAP at low pressure (5 cm H2O) to allow them to get used to the device, subjects underwent a second polysomnogram in which the CPAP pressure was progresively increased to suppress snoring, movement arousals, apneas, and hypopneas. The therapeutic pressure was found to average 7.8 cm H2O (SD=+/-2.7), under which the Respiratory Distress Index and Movement Arousal Index both fell into the normal range (10/hr +/-11 and 9.1/hr +/-6.0 respectively) and the average and minimum oxygen saturations rose to 95% (SD=+/-2%) and 86% (SD=+/-8%) respectively. Sleep architecture also improved, though this reached significance only for amount of stage 3, which increased from 3% (SD=+/-3) to 9% (+/-7). This treatment was continued for four hours, after which the mask was withdrawn, the CPAP discontinued, and the patients allowed to resume sleeping.
The second half of night, after CPAP had been used and then stopped, was compared with the second half of the first night’s polysomnogram, when no CPAP was used at all. Note that these two nights occurred about a month apart. There was a significant, though partial, improvement in the sleep of the second half of the night during which CPAP had been applied for the first half, compared to the second half of the night spent entirely without CPAP. These improvements consisted in the following statistically significant changes: mean oxygen saturation increased from 90% (SD=+/-5%) to 94% (SD=+/-3%), minimum oxygen saturation increased from 63% (SD=+/-20) to 80% (SD=+/-12), Respiratory Distress Index fell from 58/hr (SD=+/-20) to 35/hr (SD=22), Movement Arousal Index fell from 46/hr (SD=+/-21) to 29/hr (SD=+/-16), but sleep architecture was essentially unchanged, with high levels of stage 12 and low levels of stage 3 and 4 non-REM sleep.
One might crudely characterize the change from the 2nd half of the first night, without any CPAP, to the second half of the second night, after 4 hours of CPAP, as showing a 36-40% drop in the indices of respiratory events and arousals, and a 4-27% increase in the oxygen saturation measures. None of these changes, except for the mean oxygen saturation, brought the patients into the normal range during the second half of the night after CPAP. In contrast, the improvement (during a different part of the night) while using CPAP brought the Respiratory Distress Index down to 10.4 (SD=+/-10.90 and the Movement Arousal Index down to 9.1 (SD=+/-6), though I call to your attention the substantial variability indicating that some patients were showing abnormal indices even during CPAP.
The authors noted that there was a carryover effect of improvement from the first half of the night using CPAP to the second half of the night without it, but with considerable deterioration in the indices of sleep as soon as the CPAP was discontinued. They remarked that this carry-over (or “residual”) effect of part-night CPAP had not previously been documented, though there have been full-night withdrawal studies with mixed results. The trend was to find a complete loss of CPAP benefits within a day to a few days after stopping the treatment.
The authors point out that other studies of CPAP withdrawal used subjects who had been on CPAP for a considerable time, whereas in their study subjects had received CPAP for only a total of 4 hours and on only one night. This may on the one hand make the occurrence of any residual effect more impressive. At least, it calls into question any explanation of improvement on the basis of resolving pharyngeal edema. They preferred to attribute the residual improvement to the reduced sleep fragmentation during the first half of the night, which could reduce airway collapsibility during the remainder of the night, since it is known that sleep fragmentation can increase airway collapsibility, perhaps contributing to the phenomenon of increasing frequency of apneas as the night wears on.
The concluded by suggesting that this residual improvement in apnea after four hours of use might help account for some patient’s stopping use of CPAP halfway through the night, the second half being less disturbing to them that it would otherwise have been without the prior CPAP, but the overall quality of the night’s sleep remaining much inferior to what would have eventuated had the patient used CPAP throughout the entire night.
This idea about non-compliance comes as a new one to me and I’m not sure what to think about it yet. I don’t know about other people, but I myself find sleeping, even napping, without my CPAP machine extremely uncomfortable, characterized by frequent full awakenings choking, gasping, breathing rapidly, heart pounding, etc. One would actually prefer not to sleep at all if one weren’t overwhelming tired; it happens rarely, mostly while engaged in unexpectedly long visits to relatives or friends, or riding as a passenger on a long (that is, one hour) car drivefor which I had never seen my way through to purchasing a battery power supply. In other words, my experience of sleeping without the CPAP would certainly motivate me to put it on and keep it on under all but a few infrequent circumstances. On the other hand, were my symptoms at night milder, I might find a partial degree of relief sufficient to feel I was sleeping “okay” without the CPAP after I had my nightly “dose” of a few hours. Quite possibly I would go unaware of any memory or cognitive or mood disturbance that persisted during the day as related to my partial use of CPAP. Certainly, unless I took my blood pressure regularly, I wouldn‘t be aware of any adverse effects on blood pressure. And unless I were reminded frequently, I would probably manage to suppress and deny all “alarmist” talk about heart attacks, strokes, and auto accidents and consequences of incompletely controlled sleep apnea.
I might be satisfied with the way I slept and felt and my spouse, once soundly asleep, might be less bothered by my snoring, but my future prospects of survival might suffer to say nothing of my current functioning. After all, don’t a lot of people take a nap now and then, or get tired at certain times of the day? What exactly defines the difference between normal and abnormal degrees of such activities? Thus it can be easy to deny that even obvious behavioral problems exist. Alas, we are not only endangering ourselves but others, on the road, and are creating a problematic situation for our fellow sufferers from sleep apnea who, when they say they are taking treatment, really are using it religiously. How are authorities to know which CPAP users are actually taking the treatment in an effective way and which are not? Performance tests could become quite complicated and arguable; monitors can be deceived.
As you can see, I am strongly in favor of following the standard advice to use CPAP all night, every night, and for naps as well, not matter how “well” one feels using it less. Furthermore, if any other pattern of usage is going on, this should be made absolutely clear to the sleep doctor and all caretakers and support groupsthe patient is involved with, so that they may, first of all, help solve any practical impediments to consistent CPAP use and, probably more important, exert pressure against the forces of denial that lead many people with many different chronic illnesses to avoid treatment or take less of it than they are supposed to, to prove to themselves that they aren’t really all that ill.
&nbap; Finally, to close this commentary with less of a harangue, I find the experimental situation set up the authors interesting for the fact that their patients were “virginal” to CPAP that second night. This would seem to be a point of particular interest in what may well become a lifelong career of CPAP use, and deserves extra close examination. Is it possible that, rather than seeing merely the effect of a few good hours of consollidated sleep, coupled with some resultant improvement in upper airway muscular rigidity, we are seeing the “turning on” of a process of recovery of the sleep apnea itself. That is, just as single dose of an antibiotic may yield surprisingly rapid and marked effects on an infection, which will nevertheless recur shortly if the antibiotic is not continued, we may be witnessing a major systemic change that will accumulate with time. It is obvious that this change does not progress to recovery without need for CPAP within any short time, such as weeks or months, but it still seems possible that lengthy, consistent use of CPAP with other therapeutic measures may eventually result in decreasing pressure needs and even eventual independence of CPAP itself—I note this because the slightest possibility of such an encouraging course of events would itself do much to encourage more thorough compliance with treatment than the most horrific inventory of consequences for improper use, coupled with the prospect of a life sentence of nocturnal “invalidism.”
WHAT DO YOU THINK ABOUT THIS
ARTICLE AND MY COMMENTS ON IT? CAN YOU RELATE IT TO ANY PERSONAL EXPERIENCES?
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