Humidification and Mucus Transport in Critical Patients: Clinical and Therapeutic Implications

Abstract

An adult man inhales more than 12,000 l of air per day, which may contain particles and microorganisms. The epithelium of the conducting airways, from the nose to the bronchioli, are anatomically and physiologically designed to protect the alveoli by providing clean, warmed and fully saturated air at this level, where an efficient gas exchange must occur, and by providing specific defense mechanisms, such as trapping particles and microorganisms in the mucus and mucociliary transport of these agents in the direction of the oropharynx, where they will be swallowed or expectorated. Mucociliary transport (MCT) is an important respiratory defense mechanism, which efficiency depends on the equilibrium among three major components: ciliary beating, airway surface liquid (the periciliary liquid and mucus), and the interaction between cilia and mucus. In the intensive care unit (ICU) and emergency department, many factors can increase the risks of mucus transport dysfunction. Among them, artificial inspired air conditioning is a basic factor with physiological and clinical impact in critically ill patients.