Continuous negative abdominal pressure decreases intra-abdominal and central venous pressure in ICU patients

We set out to investigate whether continuous negative abdominal pressure (CNAP) might be used to decrease abdominal pressure. We investigated the effects of CNAP on both intra-abdominal pressure (IAP) and central venous pressure (CVP) on 30 consecutive patients admitted to our ICU (age 62 ± 14 years, BMI 26.3 ± 4, SAPS II 40.4 ± 18). Patients with severe hemodynamic instability and/or with recent laparotomy were not studied. Measurements included bladder pressure as an index of IAP, CVP, invasive mean arterial pressure (APm) and heart rate (HR). Following baseline measurements (Basal), CNAP (Life Care – Nev 100, Respironics) was applied on the abdomen at three levels: CNAP =, CNAP -5 and CNAP -10, corresponding to negative pressure equal to baseline IAP, 5 or 10 cmH₂O lower than CNAP =, respectively. Results are as presented in Table 1.

Table 1

CVP was correlated with IAP (R² = 0.790, P < 0.001, multiple linear regression).

Given these results, we conclude that CNAP decreases IAP and CVP; the higher the negative pressure applied, the greater the changes. CVP decreases possibly because of a blood shift from the intrathoracic compartment.