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The authors comment on past research showing nightly CPAP use to average an unsatisfactory duration, 4.6 hrs. They point out that these studies mixed multiple nights together and also combined the use patterns of consistent and inconsistent users. Their study was designed to separate out these factors. They studied 32 newly diagnosed patients at the University of Pennsylvania and Johns Hopkins Medical Schools, with obstructive sleep apnea of generally moderately severe degree though wide variability, with respiratory distres indices averaging 66 (SD=31) and low oxygen saturation averaging 68 (SD=15). All subjects used CPAP machines for nine weeks with a covert monitor of which they were unaware, tracking the amount of time the machine was used each night. Follow-ups were done monthly. The two sites differed in that patients at Johns Hopkins had higher respiratory distress indices (77) than those at the University of Pennsylvania (46) but otherwise their patients were similar. The authors observed what they termed a "bimodal distribution" of CPAP use, half the patients using it almost every night (over 90% of the time) and half the patients using it itermittently, anywhere from 2 to 79% of the nights. Consistent users also used CPAP longer each night (6.2 hrs) than intermittent users did (3.4 hrs) on the nights they used it. Patients in these two groups used CPAP for a similar duration on their first night, but by the fourth night the two groups had drawn apart in nightly hours of use, and continued to show these differences throughout the nine weeks. Attempts were made to find factors which distinguished the two groups of consistent and inconsistent users with very few findings. They did not differ on site, age, gender, years of education, marital status, employment status, type of employment, respiratory distress index prior to treatment, low oxygen saturation prior to treatment, MSLT results prior to treatment, chief complaint, level of CPAP pressure, or severity of pretreatment symptoms. Neither did they differ on side-effects in general, though the consistent users complained more of discomfort from the mask on the bridge of the nose. However, consistent users reported symptoms of sleep apnea (snoring, snorting, gasping, choking, tossing, turning) only half as often as inconsistent users, and inconsistent users reported more sleepiness while driving and working, along with poorer performance, than consistent users. Note that even with consistent use, about half the patients complained of excessive daytime sleepiness, but half of these said it happened only rarely, whereas 80% of inconsistent users complained of EDS. A majority of both groups found CPAP "inconvenient" and complained of nasal stuffiness and eye irritation.

The sleep medicine community voices a lot of concern over noncompliance with CPAP, which is felt to be its main drawback. However, it does not examine closely enough the process by which noncompliance develops. There tends to be an assumption that noncompliance is related to side-effects and might therefore be solved by technological improvements. These authors take a step in the right direction by examining more closely the process of developing noncompliance, at least to the extent of defining two separate groups of consistent and inconsistent users. Unsurprisingly, patients who use CPAP less often also use it for shorter periods when they use it at all. This is evidently the group that needs the closest attention, though we may also learn something about adaptation to CPAP by studying the group of consistent users. In fact, support groups which mix consistent and inconsistent users may be especially helpful to the latter. Inconsistent use develops very early in treatment, in the first few days, and therefore isn't adequately addressed by the kind of monthly follow-up which represents the usual practice--if that--with sleep clinics and home health care agencies. It may surprise some people that consistent and inconsistent users were so similar on so many factors, including pretreatment severity of illness, CPAP pressure, and even side-effects. However, those who have dealt with individuals in the throes of struggling through initial use of CPAP may not be so surprised. Those who have the most difficulty don't really have different side-effects from those who use it consistently, but they seem to have more trouble with those side-effects. This is probably a result of the virtual horror some people feel about the use of a mask--not only the claustrophobic reaction but the gross physical stigma of having a lifelong illness probably needing lifelong treatment of this sort. Here support groups can be especially helpful. Another possibility to keep in mind is that the excess symptoms of the inconsistent users may represent cause as well as result of the inconsistent use. A patient who experiences dramatic relief of symptoms after the first night of CPAP seems less likely to give up on it, whatever the side-effects, than one who experiences equivocal results, possibly no more than transient placebo effects. These individuals, who are not doing well with their basic illness symptoms on CPAP, deserve special and early attention from their sleep specialists--both because this pattern of symptoms signals a likelihood of inconsistent use and because the symptoms may reflect something wrong with the treatment itself, such as inappropriate pressure, emergence of periodic leg movements of sleep, comorbid narcolepsy, medication effects on alertness, allergies obstructing their airway, or any of the numerous other factors which may subtly disturb the continuity of deep sleep and cause daytime sleepiness regardless of appropriate CPAP treatment.

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