This book assesses the most appropriate forms of aerosol therapy for critically ill patients. Aerosol therapy is applied for the treatment of several pulmonary diseases in addition to some promising applications intended for systemic absorption. Nowadays, aerosol delivery to clinically stable patients in the outpatient settings is done easily with a lot of focus on patient counseling and enhancement of lung deposition. A lot of guidelines are available for several diseases and it could offer adequate guidance to the therapists concerning escalation or de-escalation of therapy to enhance treatment efficiency and safety. However, in critically ill patients aerosol delivery is mostly done by the choice of the respiratory therapist only according to his knowledge.