Assessment of respiratory system compliance under pressure control ventilation without an inspiratory pause maneuver

Objective. The measurement of the static compliance of the respiratory system (C_stat) during mechanical ventilation requires zero end-inspiratory flow. An inspiratory pause maneuver is needed if the zero end-inspiratory flow condition cannot be satisfied under normal ventilation.Approach. We propose a method to measure the quasi-static respiratory compliance (C_qstat) under pressure control ventilation mode without the inspiratory pause maneuver. First, a screening strategy was applied to filter out breaths affected strongly by spontaneous breathing efforts or artifacts. Then, we performed a virtual extrapolation of the flow-time waveform when the end-inspiratory flow was not zero, to allow for the calculation ofC_qstatfor each kept cycle. Finally, the outputC_qstatwas obtained as the average of the smallest 40C_qstatmeasurements. The proposed method was validated against the gold standardC_statmeasured from real clinical settings and compared with two reported algorithms. The gold standardC_statwas obtained by applying an end-inspiratory pause maneuver in the volume-control ventilation mode.Main results. Sixty-nine measurements from 36 patients were analyzed. The Bland-Altman analysis showed that the bias of agreement forC_qstatversus the gold standard measurement was -0.267 ml/cmH₂O (95% limits of agreement was -4.279 to 4.844 ml/cmH₂O). The linear regression analysis indicated a strong correlation (R² = 0.90) between theC_qstatand gold standard.Significance. The results showed that theC_qstatcan be accurately estimated from continuous ventilator waveforms, including spontaneous breathing without an inspiratory pause maneuver. This method promises to provide continuous measurements compliant with mechanical ventilation.