Objective: To investigate the possibility of artificially decreasing intra-abdominal pressure (IAP) by applying continuous negative pressure around the abdomen.
Material and methods: We investigated the effects of negative extra-abdominal pressure (NEXAP) on IAP and central venous pressure (CVP) in 30 patients admitted to our intensive care unit (age 57+/-17 years, BMI 26.1+/-4.0 kg/m2, SAPS II 41.8+/-17.0). Patients with severe hemodynamic instability and/or those admitted following a laparotomy were not studied. Measurements included bladder pressure as an estimate of IAP, CVP, invasive mean arterial pressure (MAP) and heart rate (HR). In five patients extensive hemodynamic measurements were also taken using a Swan-Ganz catheter. Following measurements at baseline (Basal), NEXAP (Life Care - Nev 100, Respironics) was applied on the abdomen, in random order, at a pressure equal to IAP (NEXAP0), 5 cmH(2)O (NEXAP-5) or 10 cmH(2)O (NEXAP-10) more negative than NEXAP0.
Results: Basal IAP ranged from 4 to 22 mmHg. NEXAP decreased IAP from 8.7+/-4.3 mmHg to 6+/-4.2 (Basal vs NEXAP0 p<0.001). There was a further decrease of IAP when more negative pressure was applied: 4.3+/-3.2 mmHg, 3.8+/-3.7 mmHg (NEXAP-5 and NEXAP-10 vs NEXAP0, respectively, p<0.001). Similarly, CVP decreased from 9.3+/-3.4 mmHg to 7.5+/-3.8 (Basal vs NEXAP-10, p<0.001). The lower the IAP when NEXAP was applied, the lower the CVP (r2=0.778, p<0.001, multiple linear regression). When measured, cardiac output did not significantly change with NEXAP.
Conclusions: Negative extra-abdominal pressure may be applied in critically ill patients to decrease intra-abdominal pressure non-invasively.