The MODEM trial is a cluster-randomized, cluster-crossover clinical trial comparing the effectiveness of three ventilator modes (volume control vs pressure control vs adaptive pressure control) for mechanical ventilation of critically ill adults at multiple centers. A total of 4,785 critically ill adults receiving invasive mechanical ventilation in intensive care units will be enrolled and included in the primary analysis. Each study unit will be assigned to a ventilator mode and will switch between modes every 2 months in an order determined by randomization. Enrolled patients will be assigned to receive volume control, pressure control, or adaptive pressure control according to the mode assigned to the unit at the time they were enrolled. The primary outcome will be ventilator-free days in the first 28 days, and the secondary outcome will be all-cause, 28-day in-hospital mortality.