Effects of non-invasive pressure support ventilation (NI-PSV) on ventilation and respiratory effort in very low birth weight infants

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 H ₂O 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.