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 administ ration has been limited. The advantages of aerosol therapy include a smalle r dose, efficacy comparable with that observed with systemic administration of the drug, and a rapid onset of action. Inhaled drugs are delivered dire ctly to the respiratory tract, their systemic absorption is limited, and sy stemic side effects are minimized. Inhaled bronchodilators are routinely us ed with mechanically ventilated patients in the intensive care unit, but a variety of drugs ranging from antibiotics to surfactants has been administe red. Nebulizers and metered-dose inhalers (MDIs) are commonly used aerosol generators because they produce respirable particles with a mass median aer odynamic diameter (MMAD) between 1 and 5 mu m. Due to the limitation of ava ilable formulations, MDIs are chiefly used to deliver bronchodilators and s teroids, whereas nebulizers have greater versatility and can he used to adm inister bronchodilators, antibiotics, surfactant, mucokinetic agents, and o ther drugs. The delivery of inhaled drugs in mechanically ventilated patien ts differs from that in ambulatory patients in several respects. Until rece ntly, 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 ov erly pessimistic and that the endotracheal tube may actually facilitate gre ater aerosol delivery compared with the normal airway when a variety of var iables effecting aerosol delivery during mechanical ventilation are optimiz ed.