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Objective: To observe the method of mechanical ventilation in the chest compressions during cardiopulmonary resuscitation (CPR), and to explore the influence of the flow pattern selection of square-wave and decelerating-wave on airway pressure of patients., Methods: A prospective self-pairing study was conducted. Forty patients undergoing CPR admitted to Department of Emergency of Lishui City Central Hospital from January 2011 to February 2013 were enrolled. Using Respironics Eisprit ventilator, the working mode and parameters of ventilator were set reasonably according to previous research, while the chest compressions was performed in a stable state by the same doctor,. Each patient received different flow, waves, including square-wave and decelerating-wave, and the highest peak airway pressure was recorded as a pair of data when the time-pressure and time-flow waveform were frozen. Two pairs of data by different doctors were collected in each patient. Eighty pairs of data from 40 patients were collected for statistical analysis by paired t test., Results: The highest peak airway pressure of decelerating-wave was (38.15 ± 5.99) cmH₂O (1 cmH₂O=0.098 kPa), which was (5.71 ± 1.98) cmH₂O lower than that of square wave [(43.86 ± 6.68) cmH₂O] with significantly statistical difference (t=22.010, P=0.000). 73.75% patients undergoing square wave with peak airway pressure over 40 cmH₂O were found, but only 45.00% patients were found in decelerating-wave., Conclusions: Because decelerating-wave used in mechanical ventilation during CPR can obviously reduce the peak airway pressure, the occurrence of barotrauma, and the probability of triggering high pressure ventilator alarm, and improve the compliance of ventilator, so decelerating-wave is more reasonable than square-wave.