Late Breaking Abstract - Improved aerosol drug delivery during adult invasive mechanical ventilation with independent humidity control

Aerosol therapy is commonly performed during invasive mechanical ventilation (IMV). Although heated humidification is standard practice during IMV, studies suggest that it greatly limits the delivered dose. In this study, we aimed to investigate whether the delivered dose and thus the lung deposited dose can be increased by decoupling humidity control from heating during aerosol drug delivery. In a bench study setup, albuterol sulfate solution was nebulized into an adult IMV circuit with a vibrating-mesh nebulizer. An absolute humidifier with decoupled heating and humidification was tested at 0 mg/L and 25 mg/L of added humidity during nebulization and compared to two conventional pass-over humidifiers with no independent humidity control. The drug deposition on a filter between the test lung and the endotracheal tube was quantified with a UV-vis spectrometer as the delivered dose. The size distribution of the aerosol entering the test lung was also measured and used to predict the lung deposited dose. The absolute humidifier at 0 mg/L led to a significantly higher delivered dose (37.2%) than the pass-over humidifiers (21.2% and 24.1%), while the absolute humidifier at 25 mg/L led to a comparable dose (24.9%) as one of the pass-over humidifiers. All these test scenarios achieved sufficient humidity (>33 mg/L) in the gas flow during nebulization. Regional lung deposition simulations suggest that around 40% of the measured delivered dose would deposit in healthy lungs. In conclusion, we found that the delivered dose and thus the lung deposited dose can be improved significantly by enabling independent humidity control inside the adult IMV circuit during aerosol drug delivery.