Intra-abdominal pressure measurements in lateral decubitus versus supine position

Intra-abdominal pressure (IAP) has traditionally been measured in the supine position, however, measuring the pressure in lateral semi-recumbent position has not been studied.

A single centre prospective 1-day study.

10 patients admitted for more then 24 hours who were mechanically ventilated and had an indwelling urinary catheter.

Inclusion criteria included were age > 18 years, sedated to a RASS score of -5 and mechanically ventilated. The pressures were measured via the bladder with the mid-axillary line as zero reference point. When patients were nursed in lateral decubitus, pressures were measured and compared immediately to the supine position.

10 patients were included with a total of 60 measurements.The male/female ratio was 9:1 with a mean APACHE Pi score of 11.5 [95% CI 4.8-22.4], SAPS 2 of 31.5 [95% CI 8.9-35.8] and SOFA score of 4.0 [95% CI 1.8-7.2]. Four patients were medical and 6 were surgical. The mean IAP at different time intervals (morning, afternoon and evening) in lateral and supine position were 10.9 +/- 2.0 (in mmHg) vs 6.6 +/- 3.2 (SD with p < 0.001); 11.0 +/- 4.0 vs 5.4 +/- 2.2 (p < 0.0005) and 11.6 +/- 3.8 vs 7.8 +/- 3.0 (p< 0.001). Overall, the LSP did not change significantly (p= 0.76), but the SP did (p=0.006) with the afternoon reading being significantly lower than the evening measurement. However, the trend in the difference (LSP minus SP) was not significant (p=0.43).

There was a significant statistical difference in the pressures measured in LSP versus SP.The LSP position should not be used to measure IAP.