Interaction between intra-abdominal pressure and positive-end expiratory pressure

objective: the aim of this study was to quantify the interaction between increased intra-abdominal pressure and positive-end expiratory pressure. methods: in 30 mechanically ventilated icu patients with a fixed tidal volume, respiratory system plateau and abdominal pressure were measured at a positive-end expiratory pressure level of zero and 10 cm h2o. the measurements were repeated after placing a 5 kg weight on the patients' belly. results: after the addition of 5 kg to the patients' belly at zero positive-end expiratory pressure, both intra-abdominal pressure (p<0.001) and plateau pressures (p=0.005) increased significantly. increasing the positive-end expiratory pressure levels from zero to 10 cm h2o without weight on the belly did not result in any increase in intra-abdominal pressure (p=0.165). however, plateau pressures increased significantly (p< 0.001). increasing positive-end expiratory pressure from zero to 10 cm h2o and adding 5 kg to the belly increased intra-abdominal pressure from 8.7 to 16.8 (p<0.001) and plateau pressure from 18.26 to 27.2 (p<0.001). maintaining positive-end expiratory pressure at 10 cm h2o and placing 5 kg on the belly increased intra-abdominal pressure from 12.3 +/- 1.7 to 16.8 +/- 1.7 (p<0.001) but did not increase plateau pressure (26.6+/-1.2 to 27.2 +/-1.1 -p=0.83). conclusions: the addition of a 5kg weight onto the abdomen significantly increased both iap and the airway plateau pressure, confirming that intra-abdominal hypertension elevates the plateau pressure. however, plateau pressure alone cannot be considered a good indicator for the detection of elevated intra-abdominal pressure in patients under mechanical ventilation using peep. in these patients, the intra-abdominal pressure must also be measured.