In vitro performance of spacers for aerosol delivery during adult mechanical ventilation

Background: During mechanical ventilation, different aerosol generators are employed with various interfaces. The objective of this study was to evaluate the performance of a range of spacers, including a new device called Combihaler® designed for connection with both nebulizers and pressurized Metered-Dose Inhalers (pMDIs).

Methods: To assess the spacers, we used a ventilator and the Dual Adult Training and Test Lung (model 5600i, Michigan Instruments). Ventilation parameters were measured with and without spacers in volume-controlled and pressure-controlled mode. A filter was placed at the end of the endotracheal tube to measure aerosol delivery. Amikacin (1 g/8 mL) and salbutamol (5 mg/5 mL) were nebulized with an Aeroneb Solo® connected to its T-adapter or the Combihaler® spacer. Salbutamol (100 μg/actuation with 10 actuations) and beclomethasone (250 μg/actuation with 10 actuations) were delivered with a pMDI connected to a Minispacer®, an ACE® spacer, or a Combihaler® spacer. Drug delivery measurements were performed in volume-controlled mode in dry and humidified conditions. Drug deposits on the filter were assayed.

Results: The use of spacers and the T-adapter did not change the ventilation parameters (p>0.9). Aerosol delivery of salbutamol and Amikacin by nebulization increased up to three-fold with the Combihaler® compared with the T-adapter in humidified and nonhumidified conditions (p<0.05). Aerosol delivery of salbutamol and beclometasone by pMDI increased up to three-fold with the Combihaler® and the ACE® spacer compared with the Minispacer® in humidified and nonhumidified conditions (p<0.05). Aerosol delivery by pMDIs and vibrating mesh nebulizers using either a T-adapter or spacers was reduced by up to 62.5% in a humidified circuit compared with a nonhumidified circuit.

Conclusion: Aerosol delivery via pMDIs and vibrating mesh nebulizers is greater with large spacers (Combihaler® and ACE®) than with smaller spacers (Minispacer®) or a T-adapter, in both humidified and nonhumidified conditions. In humidified conditions, the aerosol delivery decreased with all spacers.