Objectives Given that cardiopulmonary resuscitation (CPR) is an aerosol-generating procedure, it is necessary to use a mechanical ventilator and reduce the number of providers involved in resuscitation for in-hospital cardiac arrest in coronavirus disease (COVID-19) patients or suspected COVID-19 patients. However, no study assessed the effect of changes in inspiratory time on flowrate and airway pressure during CPR. We herein aimed to determine changes in these parameters during CPR and identify appropriate ventilator management for adults during CPR. Methods We measured changes in tidal volume (Vt), peak inspiratory flow rate (PIFR), peak airway pressure (Ppeak), mean airway pressure (Pmean) according to changes in inspiratory time (0.75 s, 1.0 s and 1.5 s) with or without CPR. Vt of 500 mL was supplied (flowrate: 10 times/min) using a mechanical ventilator. Chest compressions were maintained at constant compression depth (53 ± 2 mm) and speed (102 ± 2/min) using a mechanical chest compression device. Results Median levels of respiratory physiological parameters during CPR were significantly different according to the inspiratory time (0.75 s vs. 1.5 s): PIFR (80.8 73.3 – 87.325 vs. 70.5 67 – 72.4 L/min, P < 0.001), Ppeak (54 48 – 59 vs. 47 45 – 49 cmH 2 O, P < 0.001), and Pmean (3.9 3.6 – 4.1 vs. 5.7 5.6 – 5.8 cmH 2 O, P < 0.001). Conclusions Changes in PIFR, Ppeak, and Pmean were associated with inspiratory time. PIFR and Ppeak values tended to decrease with increase in inspiratory time, while Pmean showed a contrasting trend. Increased inspiratory time in low-compliance cardiac arrest patients will help in reducing lung injury during adult CPR.