Objective measurement of patterns of nasal CPAP use by patients with obstructive sleep apnea

Obstruction of the upper airway during sleep (OSAS) is widely treated by having patients self-administer nasal continuous positive airway pressure (CPAP). To obtain objective evidence of the patterns of CPAP use, information was gathered from two urban sites on 35 OSAS patients who were prescribed CPAP for a total of 3,743 days. Patients were given CPAP machines that contained a microprocessor and monitor that measured actual pressure at the mask for every minute of each 24-h day for an average of 106 days per patient. They were not aware of the monitor inside the CPAP machines. Monitor output was compared with patients' diagnostic status, pretreatment clinical and demographic characteristics, and follow-up self-reports of CPAP use, problems, side effects, and aspects of daytime fatigue and sleepiness. Patients attempted to use CPAP an average of 66 ± 37% of the days monitored. When CPAP was used, the mean duration of use was 4.88 ± 1.97 h. However, patients' reports of the duration of CPAP use overestimated actual use by 69 ± 110 min (p < 0.002). Both frequency and duration of CPAP use in the first month reliably predicted use in the third month (p < 0.0001). Although the majority (60%) of patients claimed to use CPAP nightly, only 16 of 35 (46%) met criteria for regular use, defined by at least 4 h of CPAP administered on 70% of the days monitored. Relative to less regular users, these 16 patients had more years of education (p = 0.05), and were more likely to work in professional occupations. At pretreatment they tended to report more episodes of daytime sleepiness (p = 0.062) and less ability to perform tasks (p = 0.069), and at follow-up after CPAP use they reported greater satisfaction with CPAP (p = 0.025) and an improved level of daytime energy (p = 0.046). The most frequently cited problems with CPAP were 'inconvenience' (54%) and 'stuffy nose' (46%), although the complaint that the mask caused 'claustrophobia' was the only problem identified significantly more often by the 19 patients who used CPAP less regularly (p < 0.02). Surprisingly, only 2 of the 35 patients studied used CPAP for at least 7 h on ≥ 70% of days, suggesting that frequent, long-duration, quality sleep is a relatively rare occurrence in OSAS patients treated with CPAP. We conclude that actual CPAP use by OSAS patients falls short of the therapeutic goal of providing quality sleep all night, every night, and that patients' self-reports are rather poor estimates of actual use within and between nights. Efforts to enhance CPAP use are needed, especially early in treatment.