Ascites: its effect upon static inflation of the respiratory system

This report presents a simple clinical method to quantify the pressure generated within ascites fluid and thus to examine the effect of that fluid upon lung volume. The intra-abdominal hydrostatic pressure (Pih) given in cm H2O is the height of the meniscus of a column of water above the anterior abdominal wall measured with the patient supine. Pih thus may be thought of as a pressure in excess of the height of the anterior abdominal wall. In 23 study subjects, Pih measured 7.0 +/- 4.8 cm H2O; Pih correlated inversely with all static volumes. Furthermore, abdominal compliance (measured as the ratio of 100 ml ascites fluid removed divided by the difference between Pih before and after fluid removal) correlated directly with functional residual capacity. We conclude that the effect of ascites upon respiratory function varies among patients; the variation may be explained in part by Pih.