Background and objective: Intra-abdominal hypertension (IAH) is a frequent plentiful problem in patients admitted to critical care units. It ranges from a surge incidence of morbidity and mortality to a particular need for nursing health care, so recognition of the occurrence of IAH is a very critical issue for critical care nurses and physician. This study aimed to recognize the effects of various body position with the various head of bed elevation on the intra-abdominal pressure (IAP) in patients with mechanical ventilation. Methods: Design: A non-randomized, prospective observational study was used. Setting: Trauma and general intensive care units at Assuit University Hospitals. Method: In a prospective observational study, during the third day of mechanical ventilation, 60 patients were screened for IAP via a urinary catheter, in two various body positions in three separate degrees of the head of the bed (HOB) elevation (0 • , 15• , and 30 • ). The position was changed at least 4 hours apart over a 24-h period.Results: In lateral recumbence, IAP measurements were significantly elevated compared to supine position, they were 19.70 ± 3.09 mmHg versus 16.00 ± 3.14 (p < .001), 22.80 ± 3.56 mmHg versus 19.03 ± 2.95 (p < .001), and 26.08 ± 3.59 mmHg versus 21.46 ± 2.90 versus (p < .001) at 0 • , 15• , and 30• respectively. The mean of IAP difference was 3.7 ± 3.0 mmHg at 0 • , 3.8 ± 1.00 mmHg at 15• , and 5.5 ± 1.01 mmHg at 30 • (p < .005).Conclusions: IAP reading is significantly elevated by changing from supine to lateral position especially with HOB elevation and significantly correlated with mortality rate in patients with mechanical ventilation