Aim: The aim of the study was to evaluate the effect of different grades of increased intraabdominal hypertension (IAH) on the respiratory mechanics. Material and Methods:In this prospective observational clinical study, the influence of intaabdominal pressure (IAP) on respiratory parameters was assessed in 20 patients requiring mechanical ventilation with IAH grade I, 20 patients with IAH grade II, and 20 patients with grade III IAH. Respiratory parameters were measured and recorded by a computerized system incorporated into the mechanical ventilator.Results: A statistical difference was noticed between IAP and the dynamic respiratory parameters among the groups. Regarding the respiratory parameters positive correlation between the IAP on one hand, and peak airway pressure and resistance on the other hand was notable: IAP increased and so did pressures and the resistance in the respiratory pathways. Also the correlation between IAP, on one hand and the compliance and peripheral saturation with oxygen on the other hand, was negative. Referring the mean pulmonary pressure there wasn't correlation among IAP and mean pulmonary pressure in the groups. Conclusion:IAP leads to impairment of the respiratory mechanics. An increase of the level of IAP is followed by an increase in the altering effects upon the respiratory system.