Fig. 4
From: The neglected role of abdominal compliance in organ-organ interactions
Estimation of abdominal compliance (Cab) during the respiratory abdominal variation test (RAVT) in intermittent positive pressure ventilation (IPPV)‐mode. The graph shows the smoothed average of a continuous intra-abdominal pressure (IAP) tracing (CiMON, Pulsion Medical System, Munich, Germany) obtained during the RAVT in IPPV mode. The tidal volume (VT) was increased stepwise from 250 to 1000 ml with increments of 250 ml. At each VT, the following parameters were recorded: end‐expiratory IAP (IAPee), end‐inspiratory IAP (IAPei), IAP and ∆IAP. With increasing VT mainly the IAPei increases whereas IAPee remains relatively unchanged. During the RAVT, the diaphragm is displaced caudally and an additional volume is added to the abdominal cavity. The ∆IAV is probably correlated to the ∆VT observed between the start and the end of the RAVT (= 750 ml). The slope of the curve connecting the IAPei at each VT can be used to estimate the Cab. The CabRAVT in the sample shown can be calculated as follows: CabRAVT = ∆VT/∆IAPei = 750/(13.6 − 11.5) = 357.1 ml/mmHg and this correlates well with the CabVT:CabVT = VT/∆IAP = 1000/(13.6 − 11) = 384.6 ml/mmHg. Adapted from [3] with permission