Duration of ventricular ejection during spontaneous breathing and positive pressure ventilation in newborn infants

Experimental manipulations of intrathoracic pressure at the investigational level have been shown to result in demonstrable changes in ventricular outputs. To assess whether these changes are detectable in the clinical setting of newborn infants, we evaluated changes in the duration of left and right ventricular ejection during spontaneous breathing and during positive pressure ventilation. This was accomplished by measuring left and right ventricular ejection times (VETs) using echocardiography. Values from cardiac cycles during peak inspiration were compared to cycles that occurred during expiration. In 6 infants breathing spontaneously, the mean duration of right VET increased by 4.0% at peak inspiration, while the concomitant mean left VET decreased by 3.3%. In 14 infants requiring positive pressure ventilation, the mean duration of right VET decreased by 7.2% at peak inspiration, while the left VET increased by 2.5%. We conclude that changes in intrathoracic pressure associated with spontaneous breathing and with positive pressure ventilation result in detectable changes in ventricular ejection in the newborn infant.