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

Pan, Qing; Pan, Jie; Zhang, Zhongheng; Fang, Luping; Ge, Huiqing

Measurement of the static compliance of respiratory system (Cstat) 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. We proposed a method to measure the quasi-static respiratory compliance (Cqstat) under pressure control ventilation mode without the inspiratory pause maneuver. First, a screening strategy was applied to filter out the breaths affected strongly by the spontaneous breathing efforts or artefacts. Then, we performed a virtual extrapolation of flow-time waveform when the end-inspiration flow is not zero, to allow for the calculation of Cqstatfor each kept cycle. Finally, the output Cqstatwas obtained as the average of the smallest 40 Cqstatmeasurements. The proposed method was validated against golden standard Cstat measured from real ventilated patients, and compared with two reported algorithms. The golden standard Cstat was obtained by applying end-inspiratory pause maneuver under the volume-control mode. Sixty-nine measurements from 36 patients were analyzed. The Bland-Altman analysis showed that the bias of agreement for Cqstat versus the golden standard measurement was -0.267 mL/cmH2O (95% limits of agreement -4.279 to 4.844 mL/cmH2O). The linear regression analysis indicated a strong correlation (R2= 0.90) between the Cqstatand golden standard. The results showed that the Cqstatcan be well estimated from continuous ventilator waveforms including spontaneous breathing without inspiratory pause maneuver. The method is promising to provide continuous measurement for compliance of mechanical ventilation.