Longitudinal comparison study of pressure relief (C-Flex) vs. CPAP in OSA patients.

BACKGROUND: Continuous positive airway pressure (CPAP) devices with the option of flexible pressure delivery (e.g., C-Flex) are thought to provide an improved degree of comfort and result in better therapeutic adherence while maintaining standard CPAP efficacy. The purpose of this study was to compare adherence and subjective measures of comfort between C-Flex and CPAP treatment. METHODS: The study was an international, multisite, single-blinded study with participants randomized to either C-Flex or CPAP. Participants completed subjective measures of sleepiness and comfort at baseline, and at 30-, 90-, and 180-day follow-ups. Additionally, compliance data were downloaded from the device at each follow-up. Repeated measures analysis of variance was used to assess the effects of treatment. RESULTS: There were 138 men and 46 women (average age of 48 +/- 9.2, average Epworth Sleepiness Scale score of 14.9 +/- 3.6, and average diagnostic apnea/hypopnea index (AHI) of 51.9 +/- 27.7). C-Flex and CPAP groups were comparable on baseline measures, achieved comparable AHI on titration, and had comparable PAP pressure requirements. C-Flex users had comparable average hours of use per night and total nights of use across the study, but had a trend (p < .07) toward achieving greater total hours of utilization. While both groups had comparable decreases in sleepiness, C-Flex users reported on visual analog scales greater comfort (64.3 vs. 57.4; p = .01). CONCLUSIONS: The results of this study demonstrated that C-Flex has comparable resolution of respiratory indices and adherence. Furthermore, C-Flex users reported greater mask comfort.

The length-force relationship of the human genioglossus in patients with obstructive sleep apnea.

During sleep, patients with obstructive sleep apnea (OSA) have repetitive episodes of upper airway collapse, which are terminated by increased activity of upper airway dilator muscles. The repetitive activation of the genioglossus (GG) may result in muscle remodeling. We hypothesized that OSA patients have an altered length-force relationship, increased force generation and/or decreased force maintenance as compared with control subjects. The GG length-force relationship was determined in 12 patients with OSA and 12 normal control subjects. The optimum length of the GG (LO) was at a longer muscle length in OSA patients than in control subjects. At longer muscle lengths, OSA patients produced greater percentages of their maximum protrusion force than control subjects. Force maintenance was not significantly different between the two groups. We conclude that in OSA patients relative to normal controls, the length-force relationship of the GG is altered, specifically at longer muscle lengths. We speculate that the GG is remodeled in OSA patients and that this facilitates airway re-opening to terminate obstructive events.