Inhaled drug therapy during mechanical ventilation

In mechanically ventilated patients, drug delivery by inhalation is a common route of administration for an increasing number of pharmacologic agents. Inhalation of a therapeutic aerosol has advantages compared with other routes of drug administration with respect to convenience, ease of delivery, and safety. As with any drug, administration of an inhaled agent to a targeted site in an appropriate amount is essential for a therapeutic effect. Drug delivery is influenced by the physicochemical properties of the aerosolized drug, characteristics of the aerosol-generating device, technique of aerosol delivery, mechanical ventilator parameters, and airway anatomy. Lower respiratory tract deposition is diminished in ventilator-dependent patients due to losses arising from aerosol impaction on the ventilator circuit and endotracheal tube. For optimal drug delivery, the clinician should be familiar with the aerosol-generating device and technique of delivery, including mechanical ventilator parameters. Therapeutic gases such as nitric oxide and helium have been used as pharmacologic adjuncts during mechanical ventilation. Lower respiratory tract delivery of a therapeutic gas is influenced simply by gas diffusion. However, delivery of such agents to the mechanically ventilated patient is complicated by the requirement for specialized gas blenders and monitoring equipment. Inhaled drug delivery has the potential to modify the underlying respiratory pathophysiology while producing few systemic effects. In the future, the number of agents that can be administered by the inhalation route to mechanically ventilated patients will continue to expand.