A schematic representation of the electric circuit analogue of the pulmonary circulation. (a) Pulmonary artery pressure decay after occlusion of the balloon during a respiratory hold in the presence of mechanical ventilation. (b) An additional trace using 20 data point moving average smoothing of the original trace (collected at 100 Hz) is superimposed on the curves. This further facilitates the visual estimation of the capillary pressure by defining more precisely the point of divergence of the occluded and nonoccluded curves. In addition, an exponential curve has been fitted onto the curve 0.3–2 s after occlusion. This fitted curve has been extrapolated to the time of occlusion to provide the capillary pressure. Pcap, pulmonary capillary pressure. Reproduced with permission from Takala .