Effects of different body positions on intra-abdominal pressure and dynamic respiratory compliance

Intra-abdominal pressure (IAP) is an important parameter and prognostic indicator of the patient's underlying physiologic status [1]. Measurement of IAP via the bladder has been forwarded as the gold standard. The abdomen is considered primarily fluid in character and therefore it follows the law of Pascal. If this is true IAP should be the same regardless of the body position since fluid is not compressible. Putting the patient in the upright position is a common practice in patients with acute respiratory failure (e.g. lung oedema). This study will look at the effects of different body positions on IAP and dynamic compliance (Cdyn) in mechanically ventilated patients.