This study was conducted on 24 mechanically ventilated patients with ARF on top of COPD admitted in RICU, critical care unit from the period of Jan 2003 to Aug 2003 they were divided into 3 groups according to mode of ventilation each group comprised 8 cases randomly. Each patient was subjected to bed side echocardiography arterial line insertion, central venous catheter and calculation of haemodynamic parameters obtained included LV dimension and RV diameter, HR, CO, ABP, CVP, PAP, SVR, DO2 and ABG analysis. These haemodynamic parameters were obtained during the different modes of ventilation with and without PEEP then after weaning as control.Group I: CMV : Compared to resting state on CMV mode: There was statistically significant increase in LVEDD, LVESD, LAD, HR, PAP, SaO2, CaO2, SVR, CVP and reduction in FS, EF, RVD, CO resulted in significant reduction in DO2 ; CMV with PEEP: When PEEP was added to CMV: PEEP resulted in significant reduction in DO2, Co, ABP, EF, FS and elevation of PAP, SVR, CVP. The significant elevation in SaO2, HR could not overcome the marked reduction in CO. Group II: SIMV: Compared to resting state there was statistically significant increase in LVEDD, LVESD, HR, RVD, CaO2, SaO2 FS, Co resulting in significant increase in Do2.compensate the decrease in EF; SIMV with PEEP: when PEEP was added it improved SaO2, CaO2, HR but significant decease in LVEDD, FS, EF, Co the end result was improvement of hypoxemia and minimal insignificant reduction of Do2 (0.5%). GROUP III : CPAP mode resulted in significant decrease in haemodynamic parameters that could not be overcomed by the increase in SaO2, CaO2 resulted in significant reduction in Do2 (6.3%).