Aerosol delivery via noninvasive ventilation: role of models and bioanalysis

Non-invasive ventilation (NIV) is external support for respiration to assist breathing in case of respiratory failure (either hypercapnic or hypoxemic) without patient intubation. Nowadays, medicated aerosols are normally delivered to mechanically ventilated patients by nebulizers and pressurized metered-dose inhaler (pMDI) attached to adapter or spacer that fit into the ventilated circuit. Studies with obstructive lung disease patients have shown that aerosol delivery during mechanical ventilation is possible and of benefit. There are several models for investigating the aerosol delivery and deposition during mechanical ventilation such as in vitro, in vivo, and ex vivo models, these models depend on the technique used for quantitative or qualitative measurement of the deposited aerosol. In vitro models could be used for calculating the total emitted doses from different aerosol-generating devices or for aerodynamic characterization of the deposited inhaled medications. In vivo models dependents of extracting drugs from biological samples for measuring its concentration and bioavailability (pharmacokinetic model) or be dependent on the imaging technique of the radioactive aerosol. Applying different methods to predict aerosol efficiency before starting NIV and to quantify aerosol delivery during NIV are promising approaches that guide clinicians to avoid treatment failure before and during patient therapy.