The purpose of this study was to examine the relationship between night-to-night variability and nightly duration of continuous positive airway pressure (CPAP) therapy over the first 9 weeks of treatment and to determine when patients begin to establish a nonadherent pattern of use. Data were analyzed from a study of daily CPAP use covertly monitored in 32 diagnosed patients with obstructive sleep apnea (OSA) using a microprocessor monitor encased in a CPAP machine. Patterns of CPAP use were bimodal, based on the frequency of nightly use. Approximately half the subjects were consistent users of CPAP, applying it > 90% of the nights for an average of 6.22 +/- 1.21 hours per night, while the other half comprised intermittent users who had a wide range of daily use averaging 3.45 +/- 1.94 hours per night on the nights CPAP was used. The percent of days skipped was significantly correlated with decreased nightly duration (rho = -0.73, p < 0.0001). Analysis of the night-to-night pattern of use revealed that the two groups differed significantly in the nightly duration of CPAP use by the fourth day of treatment (p = 0.001). Exploration of factors that potentially differentiate the two groups revealed no reliable predictors. However, intermittent users continued to report significantly greater OSA symptoms (snoring, snorting, and apnea) posttreatment, suggesting that they continued to experience sleep disordered breathing.

A~traet Carbon monoxide was shown to be competitive with 02 in oxygen sensing by perfused carotid bodies isolated from cats, afferent electrical activity increasing with either decreasing Oz or increasing CO. The CO-induced increase in afferent activity was fully reversed by bright light. At submaximal light intensities the extent of reversal, after correcting to equal light intensity of light quanta at each wavelength, was maximal for light of 432 + 2 and 590 + 2 nm, with a ratio (432/590) of approximately 6. This spectrum is characteristic of the CO compound of mitochondrial cytochrome a 3. The photo-reversible inhibition of oxygen sensing activity by CO accounts for at least 80% of the oxygen chemosensory activity of the carotid body.

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