HME Filter

Heat/Moisture Exchange (HME) filters are a type of stoma cover which help laryngectomees partially restore functions previously performed by our noses and upper airways. They might be thought of as "artificial noses." As the name implies, an ?exchange? of heat and moisture occurs in the HME filter as a laryngectomee inhales and exhales. During exhalation, warmth and humidity are conveyed from the lungs and deposited into the filter. During inhalation, the warmth and moisture are picked back up by incoming air and returned to the lungs.
Before the laryngectomy, the upper half of the breathing system filtered, humidified and warmed incoming air. It also provided resistance so that the lungs fully inflated. This helped maintain lung capacity, and facilitated an efficient exchange of gasses in the lungs (oxygen added to the blood stream and carbon dioxide removed). Prior to the laryngectomy, by the time the inhaled air reached the lungs it was saturated with moisture and its temperature was close to the body temperature of 98 degrees Fahrenheit (37 Celsius). Air at 100% relative humidity and 98 degrees is ideal for oxygen/carbon dioxide gas exchange. After the laryngectomy, the incoming air was dirtier, drier and cooler.

The resistance function of the nose and upper airway might be a little more difficult to understand than dirtier, drier and cooler air and the problems those produce for laryngectomees.