['In neonates, during spontaneous breathing with demand-type continuous positive airway pressure (CPAP), high airway resistance caused by small endotracheal tubes, time delay for triggering, and rapid respiratory frequency may result in patient-ventilator asynchrony. Such asynchrony may alter normal breathing patterns and thoracoabdominal synchrony. We, therefore, studied whether pressure support ventilation (PSV) could augment spontaneous breathing and improve synchrony between the rib cage (RC) and the abdominal (AB) motions in nine postoperative neonates with congenital heart disease. Three successive levels of PSV (0, 5, and 10 cm H2O) were used randomly. With increasing levels of PSV, the tidal volume (VT) increased and the respiratory frequency decreased, associated with an increase in minute ventilation. To assess thoracoabdominal synchrony, maximum compartment amplitude (MCA)/VT (MCA = AB + RC) and the phase delay of the RC-to-AB motion during inspiration (the ratio of the time delay to the inspiratory time) were measured using respiratory inductive plethysmography. When the motions of the RC and AB were out of phase, MCA/VT exceeded 1.0. MCA/VT decreased significantly from 1.3 +/- 0.3 without PSV to 1.0 +/- 0.0 with PSV of 10 cm H2O. The phase delay and paradoxical motion of the RC observed in seven of the nine cases without PSV also disappeared with PSV of 10 cm H2O. In conclusion, PSV can effectively augment spontaneous breathing with better thoracoabdominal synchrony in neonates.'] Does pressure support ventilation augment spontaneous breathing with improved thoracoabdominal synchrony in neonates with congenital heart disease?