Article #79

Some patients come to refuse CPAP because of discomfort associated with breathing only through the nose; their complaints include dryness, burning, and congestion of the nasal passages. Leakage of air out of the mouth may play an important role in these side effects, because it results in air flowing only one way into the nose, drying the nasal lining and causing inflammation and increased nasal resistance to air flow.     As a result, a heated humidifier has become a standard part of the CPAP apparatus. However, this has not proven entirely satisfactory. It reduces the problems but often fails to eliminate them, especially in the presence of air leakage through the mouth. The humidifier also adds difficulty to keeping the equipment adequately clean and transporting it.     The purpose of this study was to evaluate the effect of nasal CPAP on the humidity of air breathed in, and the effect of adding heated humidification or replacing the standard nasal mask with a full face mask covering both nose and mouth.     The authors studied 25 patients with moderate to severe obstructive sleep apnea. Their Apnea Hypopnea Indices ranged from 13 to 102 events per hour, averaging 67. They had been on CPAP for about 3 years. CPAP pressures were in the moderate range of 6 to 15 cm of H2O, averaging 11-12. All had complained of nasal symptoms--chronic nasal obstruction, inflammation, or sneezing--which made the use of CPAP uncomfortable. Most had problems likely to lead to air leakage through the mouth--deviated nasal septum, chronic nasal inflammation, nasal polyps, or a past uvulopalatopharyngoplasty.     An instrument in the nasal mask measured the relative humidity and temperature of air breathed in. Another instrument measured mouth leakage of air.     Eight patients had these measurements done during a night in the sleep lab with CPAP without humidification for the first half of the night, then with humidification for the second half. Heated humidification always resulted in higher humidity of air breathed in than CPAP without humidification. With mouth closed, relative humidity during the first half of the night without the humidifier was 60%, versus 81% during the second half, with the humidifier. However, when mouth leakage of air occurred, humidity dropped dramatically, to 43%. Humidification lessened this, but only to the point of achieving humidity levels comparable to those with non-humidified CPAP with mouth closed (64%), so the effect of mouth leakage in lowering humidity of air breathed in through the nose was still apparent even with use of the humidifier.     In a second study, of 17 patients studied for three hours during the daytime, nasal CPAP with and without humidification was compared with the use of a full face mask covering both nose and mouth, thereby getting around the problem of mouth leakage of air. Subjects were instructed to spend 5 minutes under each of the three conditions (CPAP with humidifier, CPAP without humidifier, and CPAP with full face mask) with mouth open, to simulate nocturnal air leakage through the mouth.     The results of the second study, like those of the first, showed lowered humidity with CPAP turned on (63%) compared to normal breathing of room air (80%), and still lower humidity with mouth open (39%). Humidification prevented the drop of humidity with CPAP with mouth closed (82%), but not with mouth open (63%). In contrast, use of the full face mask maintained normal humidity regardless of CPAP use or mouth opening.     The authors concluded that use of a full face mask was more effective than heated humidification in preventing dryness of air breathed in with CPAP, especially in the case of air leaking out through the mouth. The occurrence of mouth leaks occupied almost one-third of total sleep time in patients with nasal complaints. At these times, humidification appeared inadequate to prevent dehydration. The full face mask eliminated any apparent need for the humidifier.     Unfortunately, the authors note, patients found the full face mask less comfortable than the nasal mask. They complained of a poor fit with the contours of the face, generatin esaon eede which required painultightening of the straps. Only two patients accepted long-term use of the full face mask. In either alternative, humidifier or full face mask, manufacturers need to improve the design.

Can such a relatively small, simply designed study on such an apparently minor issue as air humidity with CPAP really warrant such a lengthy summary as above?     Obviously, I think so, or I wouldn't have spent so much time detailing this study. It seems to be the general consensus that the main problem with CPAP is patient noncompliance or outright refusal. People resort to dubious, irreversible, painful, and sometimes harmful surgical alternatives because they consider "intolerable" an effective and essentially harmless mechanism like CPAP, generally lower in side effects than most medications.     Perhaps one aspect of CPAP that makes any side effects especially intolerable is the prospect of lifelong use. However, I suspect that a more important element is the fact that whatever side effects it has tend to disturb and disrupt sleep--the very thing that CPAP is intended to prevent!     Nevertheless, this study does serve to strengthen a point that I find myself making frequently to people writing me with complaints about CPAP, often it seems without ever bringing them to the attention of their own sleep doctors!     The important point is that one doesn't just find CPAP "intolerable" without specific problems, many of which have at least the possibility of finding specific solutions. Usually arrival at such solutions requires open interchange of information with one's sleep doctor and home care technician; sometimes one can also learn a lot from other patients, whether through casual conversations in the doctor's waiting room or more structured groups such as AWAKE. Finally, there are plenty of resources on the Internet to help you learn about potential solutions to various problems with CPAP. Trivial as these may seem, to the extent that they can prevent people from using CPAP regularly, they can become a matter of life and death.     In summary, I believe that no one should give up on CPAP as treatment for sleep apnea until they have given it a "full, fair trial"--which means making every effort, whether by use of humidification, different delivery devices like full face mask or nasal prongs, or any of a multitude of other potential solutiont to problems which come up.

"Suns may set and rise again; for us, when our brief light has set, there's the sleep of one ever lasting night." Caius Valerius Catullus, 87-54 B.C.

 

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