Non-invasive evaluation of the respiratory system’s static compliance during assisted ventilation at various pressure support levels

Spontaneous breathing activity during pressure support ventilation (PSV) is not beneficial for the assessment of static compliance (C st ). We designed a new scheme for determining C st during PSV and assessed its accuracy using a lung model. A Hamilton C3 ventilator was connected to an ASL5000 lung simulator that simulated different lung mechanics [system’s static compliance (C st ), 30 or 60 mL/cmH 2 O; airway resistance (R aw ), 5, 10, 15, or 20 cmH 2 O/(L·s)]. PSV and volume-controlled ventilation (VCV) underwent activation with tidal volume (V T ) values of 5, 7, and 10 ml/kg. Respiratory mechanics were obtained and corrected with virtual extrapolation by applying RC exp and relevant equations. The repeated change in pressure support (PS) level was set at ± 1 cmH 2 O. C st−PSV was determined from volume fluctuations resulting from PS level changes. The classic C st measurement was obtained with the end-inspiration approach during volume-controlled ventilation (C st−VCV ). Comparing the value of C st−VCV , similar values for C st−PSV were obtained at low PS level. By changing the PS level, the estimated C st−PSV resulted in a relatively high error of about 10–15%.The novel scheme provided reliable estimated results for C st during pressure support ventilation. Despite its limited accuracy affected by the spontaneous effort participation, this scheme may help in non-invasive, uninterrupted monitoring of C st .