The effect of different reference transducer positions on intra-abdominal pressure measurement: a multicenter analysis.

ABSTRACT

OBJECTIVE: To investigate the effect of different reference transducer positions on intra-abdominal pressure (IAP) measurement. Three reference levels were studied the symphysis pubis; the phlebostatic axis; and the midaxillary line at the level of the iliac crest. DESIGN: Prospective cohort study. SETTING: The intensive care units of participating hospitals PATIENTS AND PARTICIPANTS: One hundred thirty-two critically ill patients at risk for intra-abdominal hypertension (IAH). INTERVENTIONS: In each patient, three sets of IAP measurements were obtained in the supine position, using the different reference levels. The IAP measurements obtained at the different reference levels were compared using a paired t-test and Bland-Altman statistics were calculated. MEASUREMENTS AND RESULTS: IAP(phlebostatic) (9.9 +/- 4.67 mmHg) and IAP(pubis) (8.4 +/- 4.60 mmHg) were significantly lower that IAP(midax) (12.2 +/- 4.66 mmHg; p < 0.0001 for both comparisons). The bias between the IAP(midax) and IAP(pubis) was 3.8 mmHg (95% CI 3.5-4.1) and 2.3 mmHg (95% CI 1.9-2.6) between the IAP(midax) and the IAP(phlebostatic). The precision was 3.03 and 3.40, respectively. CONCLUSIONS: In the supine position, IAP(midax) is higher than both IAP(phlebostatic) and IAP(pubis), differences found to be clinically significant; therefore, the symphysis pubis or phlebostatic axis reference lines are not interchangeable with the midaxillary level.