Quantitative investigation of additional mask leakage during CPAP therapy.

The occurrence of mask leakages during the administration of nasal continuous positive airway pressure (CPAP) therapy for treating obstructive sleep apnoea syndrome (OSAS) leads to decreased compliance. Because of exhalation valves, all mask systems have a predefined amount of systematic mask leakage, thereby complicating measurement of any additional spontaneous leakage occurring during the night. In fact, relatively few studies have investigated the impact and amount of mask leakage in patients using CPAP. Using a fourth-order polynomial, systematic leakage was modelled as the nonlinear relationship between mask pressure and leakage through the exhalation valves. The total leakage was measured in 22 patients, and additional leakage was calculated by subtracting the systematic from the measured total leakage during the night. A mean additional leakage of 6.9±7.4 l/min was found; however, some patients showed rather high mask leakages (up to 37.4 l/min) with high mask pressures, possibly indicating that not all nasal masks are equally suited for higher CPAP pressures. The relevant mask leakages that were observed in some cases stress the importance of thorough monitoring of patients receiving CPAP therapy. Furthermore, all investigated patients were trained very extensively in our sleep lab, possibly indicating that intensive training may be an important factor for the rather low additional mask leakages. [ABSTRACT FROM AUTHOR]