RecruitingClinical trialVentilator Pressure and Optimization of Compliance and HemodynamicsIn preterm infants \< 34 weeks' gestation at birth receiving respiratory support with invasive positive pressure ventilation, the positive end-expiratory pressure (PEEP) of best compliance will increase the cardiac output and improve oxygenation. This study may emphasize using point-of-care echocardiography along with electrical impedance tomography (EIT) to optimize ventilator settings in preterm infants. Infants will be randomized to a 4-hour crossover period of increasing and decreasing PEEP in random order from baseline to determine compliance, oxygenation, and cardiac hemodynamics at each step using echocardiography (ECHO) and EIT measurements. There will be a 15-minute washout period after changes prior to data collection.