OBJECTIVE: This study compares patient-ventilator synchrony, work of breathing and patient effort in neonates during different modes of patient-triggered ventilation. DESIGN: Clinically stable neonates received intermittent mandatory ventilation (IMV), synchronized intermittent mandatory ventilation (SIMV), pressure assist/control ventilation (A/C), and pressure support ventilation (PSV) in a random order for 20 mins. With each mode patient-ventilator synchrony, work of breathing, and patient effort were evaluated. SETTING: Neonatal level III intensive care unit of a university hospital. Measurements and RESULTS: Seven clinically stable neonates (31.4 +/- 2 wks gestation, weighing 1.49 +/- 0.38 kg) were randomly ventilated with the above four modes using a Bird VIP ventilator. Esophageal pressure, airway pressure, and flow were measured using a CP-100 neonatal monitor (Bicore). Data for five consecutive breaths in each mode were analyzed. Patient effort and work of breathing differed significantly among modes of ventilation. The inspiratory pressure time product was least with A/C (0.54 +/- 0.29 cm H(2)O.sec) and increased with PSV (0.60 +/- 0.39 cm H(2)O.sec), SIMV (1.46 +/- 0.55 cm H(2)O.sec), and IMV (2.74 +/- 1.05 cm H(2)O.sec) (p <.05). A similar trend was observed for work of breathing, with work least during A/C (0.07 +/- 0.04 joules per liter [J/L]), followed by PSV (0.17 +/- 0.14 J/L), SIMV (0.33 +/- 0.13 J/L), and IMV (0.41 +/- 0.16 J/L) (p <.05). Marked dyssynchrony between patient-initiated and ventilator-initiated inspiration occurred only during IMV. CONCLUSION: Asynchrony can be avoided by the use of assisted, patient triggered modes of ventilation and, of the available modes, pressure A/C results in the least effort and work of breathing for clinically stable neonates.