Improving CPAP Compliance With Humidification

Vol. 17 •Issue 9 • Page 28
Improving CPAP Compliance With Humidification

CPAP is commonly used in the sleep care industry, but most caregivers have learned it is far easier to prescribe its use than to get patients to use it. Compliance, defined, generally means there is continued use of CPAP treatments for more than 70 percent of the time and for greater than four hours a night. Most current research indicates compliance does not come close to the target. In fact, only 50 to 70 percent of those for whom CPAP has been prescribed stay compliant.

Reasons people cite for not using the CPAP generally fall into a few categories. Nearly 75 percent complain of dryness and congestion with a sore nose and throat. This is caused because the patients are exposed to cold, dry air, known to cause rhinnorhea and congestion. Dry airflow provided by CPAP equipment can exceed the body’s natural ability to heat and humidify the incoming air.

Numerous users complain the congestion caused by CPAP equipment encourages oral breathing. This in turn allows the pressurized air supplied by CPAP to escape through the mouth (mouth leak as we call it in the industry). Mouth leak is a considerable problem for CPAP users. It is a big problem too. Patients receiving dry air from CPAP equipment will mouth leak for an average of 30 percent of their total sleep time.

This also contributes to an additional problem. When air escapes through the mouth, the flow provided by the CPAP unit increases, and the increased flow exacerbates subsequent drying of the nasal mucosa. As the body attempts to counteract this drying process by supplying more heat and moisture to the mucosal tissues, the nasal congestion continues to worsen, encouraging even further mouth breathing and mouth leak. It becomes a vicious cycle—and ultimately the patient can abandon the CPAP unit altogether.

Dry Mucosal Lining

Regular use of CPAP may cause continual mucosal drying, resulting in morphological changes to the nasal mucosa. The removal of moisture from the epithelial surface results in inflammation of the deeper epithelial layers. Adhesion and clumping of the cilia has also been observed.

Patients also commonly complain about poor mask fit. This can result in pain and in abrasions to the bridge of the nose and pressure sores. Poor fits also create air leaks, again causing the CPAP unit to deliver increasing flows of dry air.

Some people have reported allergies, aerophagia, claustrophobia and chest discomfort associated with their CPAP. And a major issue for many people is the embarrassment of having to wear a mask to bed. It can be a romance breaker, among other things.

All of these side effects greatly impact CPAP treatment compliance. For many patients, any benefits do not appear to offset the inconvenience.

Since studies have shown compliance patterns can be defined within the first few nights of CPAP usage, it is extremely important for caregivers to work diligently to achieve optimal conditions right from the offset.

Key Recommendations

Three common factors have been identified as keys to patient acceptance and compliance in these first-nights. These are:

Patient education; Use of heated humidification; and Optimal mask comfort.

Numerous researchers have studied the effects of patient education relative to CPAP compliance. Most studies indicate that any extra efforts to support and assist new CPAP patients will lead to increased compliance. In fact, even the simplest interventions have helped increase patient compliance.

Widely used compliance monitoring and programs allow those involved in patient support to determine whether their interventions are working.

Patient education aides are widely available, including video and printed literature explaining the benefits of CPAP and guidelines for CPAP use. Support groups and educational clinics designed to educate and encourage patient compliance have shown increased compliance rates as well.

One of the best methods to prevent dropout rates for CPAP use is for caregivers to add humidity to the air supplied by CPAP. When discussing humidity, caregivers can refer to either relative humidity or absolute humidity.

Absolute humidity (AH) is the amount of water vapor per liter of gas, measured in mg/L.

Relative humidity (RH) is the amount of moisture expressed as a percentage of the total moisture capacity of the gas.

As gas temperature increases, its capacity to hold moisture increases. If the relative humidity were to remain the same, the amount of moisture would increase as the temperature increased. Hayes and Richards et al. showed that by supplying “heated” humidification to the air provided by CPAP equipment, there was an increase in nasal mucosal blood flux. Since the tissues no longer experience the rush of blood to the nasal mucosa, the increase in congestion was minimized as a result.

Further Study

By using mouth breathing to simulate mouth leaks, Richards et al. showed that even if normal mouth breathing occurred with air that had passed through a heated humidifier, nasal resistance was similar to that as seen for nasal breathing.

Maria Martins de Araujo et al. showed that heated humidification significantly attenuated the decrease in relative humidity caused by mouth leak. Their research has shown that heated humidification coupled with CPAP can prevent or diminish mucosal dehydration, thus reducing nasal dryness and discomfort. This, in turn, can lead to increased patient compliance.

The evidence provided above seems to show that the addition of heated humidification to CPAP will decrease nasal side effects and thereby also lower the time spent mouth leaking. A direct result of this is increased compliance to treatment.

Clinical studies by Rakotonanahary, Massie et al. showed that patients who were not receiving heated humidification but had nasal problems used their machines for an average of 3.51 hours per day. When they were given heated humidification, the patients’ CPAP use increased to 5.38 hours per day. Further, patients who received heated humidification were significantly more compliant with their CPAP therapy than those who did not.

Cold humidification has often been used as a treatment for patients who complain of nasal symptoms after the initiation of CPAP treatment. However, there is no evidence currently available to support the use cold-passover humidification in CPAP. Richards et al. showed that nasal airway resistance was increased to a similar level regardless of whether a patient was receiving no humidity or cold-passover humidity.

Cold Water Studies

Two studies that looked at possible increases in compliance with CPAP therapy with cold-passover humidification have been unable to show a significant increase in the average hourly use of CPAP.

Heated humidification is relatively safe. Extensive research has shown that heated passover humidifiers do not produce aerosols. Moisture is added to the air in the form of molecular water vapor. The water vapor particulate is so small it is impossible for bacteria and viruses to use the vapor as a transport medium.

Use of distilled water further ensures there is no nutrient in the water for any pathogen to use for multiplication. With the use of a passover humidifier, even if the water does become contaminated, this contamination cannot be transported via water vapor to the patient.

One of the biggest myths surrounding CPAP use is that heated humidification should be given only after patients develop nasal symptoms. Remembering that compliance is often determined in the first few nights of use, the best results might well be achieved if any and all potential discomforts are alleviated in those first nights.

It seems logical that if side effects can be reduced, then compliance of prescribed CPAP will increase. In light of this thinking, caregivers might best serve their patients by recommending heated humidification from the offset. This would normally be done during the patient’s CPAP titration in the sleep laboratory.

Kline et al. reported there is ample evidence to support this addition by showing that using humidification in line with CPAP significantly improved subject compliance with the treatment. But more importantly, their study concerned the dropout of participants. The sleep lab patients receiving heated humidification had significantly less discomfort than the group not receiving any form of humidification and generally maintained their compliance.

Lifetime Therapy Ahead

Since CPAP treatment for OSA is an intrusive therapy and a lifelong commitment, anything that boosts compliance carries patient benefits such as improved ability to concentrate, alertness, normalization of blood pressure and decreased risk of cardiovascular consequences.

In order to improve patient acceptance and compliance, caregivers must educate patients about what to expect and benefits and consequences of use and non-use. Caregivers also have a duty to ensure their patients will receive the optimum treatment available. Heated humidification and a comfortable interface are certainly a part of this process.


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Joseph Anderson is a Virginia practitioner.