Describe the term Humidification
Dry gases result in the loss of ciliary activity of the mucosa of the airway and can lead to mucosal damage as well as causing the secretions to be thick and difficult to clear. There are two methods of humidification available for patients on mechanical ventilator - (i) the heat and moisture exchanger (HME), and (ii) the heated humidifier. Heated humidifiers operate actively to increase the heat and water vapor content of inspired gas. HMEs operate passively by storing heat and moisture from the patient's exhaled gas and releasing it to the inhaled gas. If a patient has thick secretions, HMEs should not be used as it gets clogged. HMEs may be changed every 48 hours - although is some evidence that a longer period of use (upto a week) may be OK. The incidence of ventilator associated pneumonias may be less with the use of HMEs compared to heated humidifiers.