Coefficient of variation (COVA) during continuous intra-abdominal pressure (IAP) and abdominal perfusion pressure (APP) monitoring

Introduction

Definitions for intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) stand or fall with the reproducibility and accuracy of the IAP measurement. The aim of this study is to validate a novel fully-automated continuous technique to measure IAP via a balloon-tipped catheter connected to an IAP monitor (Spiegelberg, Hamburg, Germany) versus a novel bladder FoleyManometer (Holtech Medical, Copenhagen, Denmark), and to look for the COVA (SD divided by mean) for IAP and APP during different 24 hour monitoring periods.

Methods

IAP was estimated using two different methods: via the bladder (IBP) with a FoleyManometer and via a balloon-tipped gastric catheter (IGP) connected to an IAP monitor. For each 24 hour period, 12 measurement were noted. In total 645 paired measurements were performed in 15 sedated and mechanically ventilated ICU patients. The male/female ratio was 1/1, age 60 ± 9 years, APACHE II score 20.2 ± 8.6, and SAPS II score 49.4 ± 16.7.

Results

The values for IAP (mmHg) were 9.7 ± 3.2 (IGP) vs 9.8 ± 3.1 (IBP), and 72.1 ± 16.5 for APP. There was a good correlation: IBP = 0.85 × IGP + 1.6 (R² = 0.79, P < 0.0001). Bland and Altman analysis showed good agreement: IGP was almost identical to IBP with a mean bias of -0.1 ± 1.5(SD) mmHg (95% confidence interval [CI], -0.2 to 0); the limits of agreement (LA) were -3.1 to 2.9 mmHg (95% CI, -3.3 to -2.9 for the lower LA and 2.7 to 3.1 for the upper LA). The COVA was 18.7 ± 7.4% for IGP and 17.1 ± 12.7% for IBP. The global bias (IAPmax minus IAPmin) was 5.6 ± 2.6 mmHg for IGP and 3 ± 2.4 mmHg for IBP, the global variance (GLOVA), defined as global bias divided by the mean, was 61.6 ± 26.9% for IGP and 32.8 ± 24.3% for IBP. The COVA, global bias and GLOVA were 14.5 ± 6%, 32.8 ± 12.8 mmHg and 46.5 ± 17.9%, respectively, for APP.

Conclusion

Estimation of IAP via IGP or IBP is feasible. The novel IGP method is less time consuming, fully automated (autocalibration), and allows a continuous trend. The FoleyManometer offers a cost-effective alternative. Both are accurate and reproducible. The COVA for the obtained parameters in sedated patients is around 15–20% in a 24 hour period and thus varies substantially. These variations may even be more pronounced in nonsedated patients. Therefore IAP and APP are continuous variables like any other pressure and should be monitored as often as possible during the day to adapt treatment accordingly.

Figure 1