Changes of FRC during noninvasive ventilation in spontaneous breathing subjects can be determined by the oxygen washin/washout method

Recently, the feasibility of the oxygen washin/washout method for determination of functional residual capacity (FRC) in intubated, spontaneously breathing patients has been shown. During noninvasive ventilation using a face-mask the technique has not been validated so far. The aim of this study was to determine if the technique is able to follow FRC changes caused by change of body positions and application of continuous positive airway pressure in spontaneously breathing subjects wearing a face mask.