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What You Should Know About CPAP Humidification

Tracy R. Nasca

I have learned a lot about CPAP humidification from my friends at Fisher and Paykel Healthcare. They introduced the first heated humidifier for use in-line with a CPAP device in 1992. I think it is important for sleep apnea patients who use CPAP therapy to have a thorough understanding of how and why it is necessary to use humidification. Thanks to Fisher & Paykel who generously shared this information for me to pass on to you.

Humidifiers are used to moisten the air brought in through your CPAP. There are two basic types: passive (cold water) or heated. Pressurized air, exiting from the CPAP, is passed through a humidification chamber containing distilled water and then routed through tubing to your mask, thereby delivering air with additional moisture. Most patients prefer the heated versions, as they can also be used cold if needed.

If typical room air is at 20 degrees Celsius containing about 10mg H2O per liter of gas, and the body supplies the remaining heat and moisture required for efficient gas exchanges, what happens during CPAP therapy? Read on to find out!

The nasal airway is unable to maintain sufficient warmth and humidity for the increased gas flow of CPAP therapy. As a result, the patient's airways lose moisture and will eventually exhibit symptoms consistent with upper airy dryness and inflammation such as dry nose, dry throat, headache, chest discomfort, bleeding nose, dry cracked lips, breakdown of the soft tissue around the nares (nostril) and infections of the nose, throat and sinuses may also occur.

When the patient falls asleep using CPAP, mouth leak may occur. Because incoming air is able to travel directly out through the mouth without first going to the lungs, unidirectional airflow occurs.

The increased flow of cold dry air through the nasal passages causes mucosal drying and rebound congestion. Swelling occurs in rebound congestion and results in a decrease in nasal airway diameter and as a result increased nasal airway resistance occurs (NAR).

Increase in nasal airway resistance (NAR) leads to an increase in mouth leak as the patient begins to mouth breathe and the vicious cycle continues. Research (Am. Thoracic Society) revealed that heated CPAP humidification reduces NAR by supplying the required humidity to the air that the nose is unable to supply.

Research also noted that cold passover humidification caused little change in patient response, but that heated humidification minimized the increase in NAR.

If you live in a humid environment you probably have air conditioning and dehumidifiers operating, so the air which passes through your CPAP is cold and dry. This causes an increase in the occurrence of nasal symptoms and may result in discomfort. CPAP humidification helps! Even in humid environments, the nasal airways are unable to provide sufficient humidity to humidify the increased airflow of CPAP therapy. Thisresults in the nasal mucosa being stripped of the moisture required to humidify the air.

The nasal airway is highly vascular, enabling it to be easily dried out by cold dry air.

Cleaning instructions, according to Fisher & Paykel, include a daily 10 minute soak in warm soapy water. Disinfect weekly in vinegar and water solution of 3 parts water, 1 part vinegar.

Is it possible for a patient to catch an infection from a humidifier? Research says, "no". In fact the environment in the heated humidifier chamber under most operating conditions is such that the majority of pathogens are rapidly killed.

Studies show that even if pathogens were able to exist in the humidification chamber, they would not be able to be transported to the patient. The humidity from the chamber is in vapor form, which is too small for a bacteria or virus to travel in!

Passover humidification (both cool and heated) is molecular humidity in that what exits either a cold or heated unit is water vapor or water molecules that are in the .0001 micron size.

Bacteria (.2 to 10 microns) and virus (.017 to .3 microns) are much larger. Therefore it would be physically impossible for water molecules to transport either bacteria or virus even if the chamber was full of GUNK! In other words, there is NO means of transport.

Heated humidification adds the additional safety net in that it will kill off 90% of the pathogens within 10 minutes of achieving full temperature.

Distilled water is cleaner and lengthens the life of the humidifier; there is no medium for growth of anything in distilled water. All manufacturers recommend it. Depending on the quality, tap water is not necessarily harmful for use in humidifiers, but well water can be harmful to the chamber if there are a lot of deposits in it.

The information included on this site is for educational purposes only. It is not intended nor implied to be a substitute for professional medical advice. Contact your physician or health care provider when you have health related questions. Never disregard or delay medical advice because of information you have obtained on this site.