RESUMO
BACKGROUND: Nasal continuous positive airway pressure (NCPAP) is used to provide support to non-intubated infants, but it often fails. Pressure support ventilation (PSV) is a mode of synchronized ventilation that can supplement the spontaneous breathing effort, but it is unknown if it is effective in non-intubated very low birth weight (VLBW) infants. OBJECTIVES: To compare the acute physiological effects of non-invasive PSV (NI-PSV) versus NCPAP on tidal volume (V(T)), minute ventilation (V(E)), gas exchange, breathing effort, and chest wall distortion in VLBW infants. METHODS: Stable preterm infants of birth weight less 1,250 g were studied during consecutive 2 hr periods of NCPAP and NI-PSV in random sequence. VT, V(E), and thoraco-abdominal synchrony were measured using respiratory inductance plethysmography. Breathing effort was measured by esophageal manometry. Gas exchange was measured by pulse oximetry and transcutaneous PCO2. RESULTS: Fifteen infants of birth weight (mean +/- SD) 808 +/- 201 g and 25.9 +/- 1.8 weeks gestational age were studied while on NCPAP 5.3 +/- 0.6 cm H2O and on NI-PSV with 7.9 +/- 1.3 cm H2O above NCPAP of pressure support. There were no differences in VT, V(E), PCO2 or hypoxemia episodes. Peak and minute inspiratory effort were significantly reduced in NI-PSV mode as compared to NCPAP. There was a significant reduction in indices of chest wall asynchrony in NI-PSV mode. CONCLUSION: When compared to NCPAP, NI-PSV did not increase minute ventilation, but it effectively unloaded the patient's respiratory pump as indicated by a lower inspiratory effort and reduced chest wall distortion.
