Introduction & Objective: passive respiratory exercises are used to prevent from accumulation of secretions, lung collapse and the incidence of ventilator-associated pneumonia in ICUs. This  study is aimed to compare the effects of manual percussion and mechanical vibrations on cardiopulmonary functions of mechanically ventilated patients.

Materials &Methods: This randomized crossover clinical study was conducted on 21 mechanically ventilated patients hospitalized in intensive care units who were selected based on convenience sampling. Both methods of manual percussion and mechanical vibrations were applied for the patients.Cardiopulmonary function parameters were assessed before and four times after the intervention. Data was analyzed by Stata software version 11, descriptive and analytical statistics and paired t-test.

Results: There was no significant difference between the effects of manual percussion and mechanical vibration on heart rate, systolic and diastolic blood pressure, mean arterial pressure, airway resistance and arterial oxygen saturation. However, there was a significant difference between the effects of manual percussion and mechanical vibration on pulmonary compliance at minute 15 after intervention (P = 0.044) that is, manual percussion increased pulmonary compliance more than mechanical vibrations.

Conclusions: Both manual percussion and mechanical vibration improve cardiopulmonary function and do not cause complications for the patients. Both methods can be used according to the patient's condition and possibilities of units. However, mechanical vibration cannot substitute for because of manual percussion its failure in increasing pulmonary compliance.