C-Flex® Technology: Effects on Breathing Parameters and Inspiratory Flow Limitation

<i>Background:</i> Expiratory pressure relief continuous positive airway pressure (pressure relief CPAP, C-Flex®) is known to be as effective in the treatment of obstructive sleep apnea (OSA) as conventional CPAP while improving overall patients’ adherence. However, the effects of C-Flex on ventilation during sleep have not been studied yet. <i>Objective:</i> This study investigates the effects of pressure relief CPAP on respiratory parameters and possible inspiratory flow limitation with increased difference between inspiratory and expiratory pressure compared with conventional CPAP. <i>Methods:</i> In total, 24 patients were investigated both during conventional CPAP and during three C-Flex pressure relief settings in randomized order during rapid-eye-movement (REM) and non-REM (NREM) sleep. Airflow was monitored with a pneumotachograph; inspiratory flow limitation was assessed by analyzing airflow and esophageal pressure swings. <i>Results:</i> Using higher C-Flex gains, expiratory time decreased in favor of the inspiratory duty cycle while there was no significant change in tidal volume. Analysis of inspiratory flow limitation showed no significant difference between conventional CPAP and the C-Flex gains studied. <i>Conclusions:</i> The increase in the inspiratory duty cycle with C-Flex might either indicate an increase in the work of breathing or a decrease in the work of breathing due to a lower peak end-expiratory pressure and consecutive alleviation of passive expiration. Both treatments appeared equivalent regarding the occurrence of inspiratory flow limitation.