As a respiratory therapist, I am accustomed to thinking about humidification. When we give oxygen therapy, it is usually humidified. When we administer most kinds of inhalation therapy, we typically add humidification. The upper airway is very efficient at adding humidity to any air we breathe in. But in the normal environment, the air we breathe in has some humidity. When we add gases from piped in sources, those gases are dry. So we add humidity so as not to add to the humidification burden of the upper airway when we administer gases that are completely devoid of humidity.

Certainly, whenever the upper airway is bypassed with an endotracheal tube or tracheostomy, humidification to 100% humidity at body temperature is a common objective for any short term therapy. The human body has such an amazing adaptability that people with permanent trachs can often eventually get along without supplemental humidity.

All this leads to the question of whether you should use the humidifier in your CPAP or BiPAP machine (we will collectively call them CPAP). Obviously, if your physician’s prescription includes the use of the humidifier, then use it. But if not, then consider this line of reasoning. The typical home CPAP machine is using room air as its source. Therefore the reason for adding humidity to a desiccated source gas does not apply to the home CPAP situation. Also, the upper airway is not bypassed in home CPAP, so that reason also does not apply. If you use the CPAP machine at night and you breathed room air without supplemental humidity all day, why do you need supplemental humidity to breathe the same air during the night? That’s right, you don’t.

But if more humidity is better, why not use it, even though it might not be necessary? You shouldn’t use it because water in your home CPAP machine causes problems. The first is the potential to get an infection from your humidifier. If your humidifier is a “passover” type, then the risk of infection is pretty low if you are careful to keep the humidifier clean and it never tips over. However, with some humidifiers, the gas goes through the water in a “cascade” type of design. This makes the humidifier much more efficient, but also more dangerous as a source of infection. When the air exits the water, it can carry tiny little drops of water that can carry a microbe from the water into the air that is carried down into your lungs. If you start with a sterile humidifier chamber and add sterile water to it (not your typical home situation), you immediately have some microbes in the water. As the room air is drawn into the machine and through the humidifier, additional microbes are added to the water. There are several types of microbes that love to grow in water. Water loving microbes will double in number every 20 minutes from multiplication. So, naturally, if you use the humidifier on your CPAP machine, be sure to empty it out before refilling, and frequently clean and disinfect it, your hose, and your mask.

Also, if your CPAP machine gets tipped over, the water can enter your CPAP machine. This can cause damage to your machine, but also can infect your machine with microbes.

In addition, unless you are using sterile distilled water to add to your humidifier chamber, you will get hard water deposits over time on your humidifier chamber. This makes it more difficult to properly clean and disinfect the chamber.

In final, I can recommend using the humidifier on your CPAP machine in only two situations. First, if your physician’s prescription includes humidification. Second, if you live in the north, it is winter when the air in your house has low humidity AND you meet these conditions:

• You frequently clean and disinfect your humidifier chamber, hose, and mask.
• You empty out the water before adding more water.
• You only add water that is clean and has not been sitting around growing microbes.