Aerosol therapy in mechanically ventilated patients: recent advances and new techniques

Therapeutic aerosols are commonly used in mechanically ventilated patients, yet information regarding their efficacy and optimal technique of administration has been limited. The advantages of aerosol therapy include a smaller dose, efficacy comparable with that observed with systemic administration of the drug, and a rapid onset of action. Inhaled drugs are delivered directly to the respiratory tract, their systemic absorption is limited, and systemic side effects are minimized. Inhaled bronchodilators are routinely used with mechanically ventilated patients in the intensive care unit, but a variety of drugs ranging from antibiotics to surfactants has been administered. Nebulizers and metered-dose inhalers (MDIs) are commonly used aerosol generators because they produce respirable particles with a mass median aerodynamic diameter (MMAD) between 1 and 5 mum. Due to the limitation of available formulations, MDIs are chiefly used to deliver bronchodilators and steroids, whereas nebulizers have greater versatility and can be used to administer bronchodilators, antibiotics, surfactant, mucokinetic agents, and other drugs. The delivery of inhaled drugs in mechanically ventilated patients differs from that in ambulatory patients in several respects. Until recently, the consensus of opinion was that the efficiency of aerosol delivery to the lower respiratory tract in mechanically ventilated patients was much lower that that in ambulatory patients. Data suggest that this might be overly pessimistic and that the endotracheal tube may actually facilitate greater aerosol delivery compared with the normal airway when a variety of variables effecting aerosol delivery during mechanical ventilation are optimized.