Albuterol delivery from a metered-dose inhaler with spacer is reduced following short-duration manual ventilation in a neonatal ventilator-lung model

INTRODUCTION: Albuterol aerosol is commonly administered to mechanically ventilated neonates via metered-dose inhaler (MDI) with spacer. The spacer increases the dead space in the ventilation circuit, and some institutions limit the amount of time the spacer remains in line, to minimize carbon dioxide retention and the risk of hypercarbia. However, minimizing the amount of time the spacer remains in line might also limit albuterol delivery to the patient. OBJECTIVE: To determine whether limiting the amount of time the spacer is left in line after MDI actuation significantly reduces albuterol delivery. METHODS: We conducted a bench study with a neonatal ventilator-lung model that included a Bird VIP ventilator, in a time-cycled, pressure-limited, continuous-flow mode, with settings to simulate a 1-kg infant with moderate lung disease: peak inspiratory pressure 25 cm H2O, positive end-expiratory pressure 4 cm H2O, respiratory rate 30 breaths/min, inspiratory time 0.35 s, tidal volume approximately 7 mL. The circuit was attached to a 3.0-mm inner-diameter endotracheal tube and a neonatal test lung. We tested 5 methods of MDI albuterol administration. The first 3 methods used a spacer attached to the ETT and either 5, 15, or 30 manual breaths (flow 6 L/min, respiratory rate 30 breaths/min, peak inspiratory pressure 25 cm H2O) were delivered after each MDI actuation (2 actuations). The final 2 methods used an in-line spacer (placed between the circuit Y-piece and the endotracheal tube) with the spacer kept in line for 30 or 60 s after each actuation (2 actuations). A breathing filter was placed between the ETT and test lung to trap the aerosolized albuterol. RESULTS: Mean +/- SD albuterol delivery was 2.3 +/- 0.5%, 3.6 +/- 1.8%, and 5.1 +/- 1.3% after 5, 15, and 30 manual breaths, respectively (p < or = 0.05 for 30 breaths vs 5 and 15 breaths). Albuterol delivery was 3.7 +/- 1.3% when the spacer was left in line for 30 s, versus 3.7 +/- 0.6% when it was left in line for 60 s. CONCLUSIONS: Limiting the time that the spacer was left in line after each MDI actuation significantly reduced albuterol delivery in our neonatal ventilator-lung model.