Effect of different connection adapters on aerosol delivery in invasive ventilation setting; an in-vitro study

Introduction: Different aerosol generators are used during mechanical ventilation connected to spacers or adapters. The design and volume of these connections can significantly affect aerosol delivery. This study aimed to evaluate the impact of a variety of connections on aerosol delivery in invasive mechanical ventilation (IMV) setting. Methods: A ventilator was set at volume-controlled mode (Vt = 500 ml, f = 15/min, PEEP = 5 cm H20), and connected to a test lung model to simulate intubated mechanically ventilated adults with a 1:3 ratio of inspiratory to expiratory phase. An endotracheal tube of 8 mm inner diameter was used in this model, inserted between Y-piece and the breathing simulator. Ventilator settings were selected typically as those indicated for COPD patients in the intensive care unit when IMV is prescribed during acute exacerbations. Aerosol-generator was placed in dual limb IMV at Y-piece in the inspiratory limb. For nebulizer delivery; 1 ml respirable solution was nebulized using vibrating mesh nebulizer with three connection settings; I: T-piece, II: Combihaler (new and old version), and III: Combihaler with a pressurized metered-dose inhaler (pMDI). Only with connection III, two pMDI puffs, 100 μg salbutamol each, were actuated before nebulization of 1 ml of salbutamol solution. For pMDI delivery; pMDI puffs (100 μg per puff) were delivered using two connection settings I: pMDI T-piece adapter (2 and 5 pMDI salbutamol puffs), and II: Combihaler (2 pMDI salbutamol puffs only). 2 and 5 pMDI salbutamol puffs were delivered by pMDI T-piece adapter to determine the possible effect of aerosolized drug condensation on the T-piece. Fates of nebulized, and actuated-doses were determined. Results: No significant difference was observed between old and new Combihalers used to deliver nebulized doses with and without pMDI. The pMDI T-piece adapter delivered significantly higher pMDI aerosol than Combihaler (p < 0.05). The new Combihaler delivered a slightly higher pMDI dose than the old Combihaler. Conclusions: The antistatic property of the new Combihaler affected pMDI delivered dose similar to conventional spacer but does not affect the nebulized dose. Further clinical studies are needed to determine the bronchodilator effect of the pre-nebulization pMDI puffs on the nebulized dose.