The Correlation between Head of Bed Angle and Intra-Abdominal Pressure of Intubated Patients; a Pre-PostClinical Trial

The recommended position for measuring Intra-Abdominal Pressure (IAP) is the supine position.However, patients put in this position are prone to Ventilator-associated pneumonia. This study was done toevaluate the relationship between bed head angle and IAP measurements of intubated patients in the intensivecare unit.

In this clinical trial, seventy-six critically ill patients under mechanical ventilation were en-rolled. IAP measurement was performed every 8 hours for 24 hours using the KORN method in three differentdegrees of the head of bed (HOB) elevation (0◦, 15◦, and 30◦). Bland-Altman analysis was performed to identifythe bias and limits of agreement among the three HOBs. According to World Society of the Abdominal Com-partment Syndrome (WSACS), we can consider two IAP techniques equivalent if a bias of <1 mmHg and limitsof agreement of - 4 to +4 were found between them. Data were analyzed using SPSS statistical software (v. 19),and the significance level was considered as 0.05.

The prevalence of intra-abdominal hypertension was18.42%. Mean ± standard deviation (SD) of IAP were 8.44 ± 4.02 mmHg for HOB angle 0◦, 9.58 ± 4.52 for HOBangle 15◦, and 11.10 ± 4.73 for HOB angle 30o (p = 0.0001). The IAP measurement bias between HOB angle 0◦andHOB angle 15◦was 1.13 mmHg. This bias was 2.66 mmHg between HOB angle 0◦and HOB angle 30◦.

Conclusion:

 Elevation of HOB angle from 0 to 30 degree significantly increases IAP. It seems that the measurement ofIAP at HOB angle 15◦was more reliable than 30◦.