Data downloads are crucial for adherence. In a recent study, the American Thoracic Society stated, “Providers need to be able to interpret adherence systems.”27
The clinic provides a summary report on each patient’s adherence. A provider interpretation is added, and the report is copied into the Computer Patient Record System.
After the report is downloaded, the provider checks for correct pressure and then for a large leak. A large leak is an unintentional leak (the total amount that leaks but not including leak from the mask) > 5% of the night. A leak of > 15 minutes was added to the super-user criteria, because some software provides the average time of a large leak per day in minutes.28 Many veterans sleep only 4 to 5 hours nightly (300 minutes × 5% = 15 minutes). Therefore, the leak should not be more than 5% or 15 minutes for a veteran sleeping 5 hours.
The machine indicates a percentage of leak on the patient self-check LED screen for adherence. There is no standardized leak criterion used by all flow-generator manufacturers. Every mask has venting designed to leak intentionally so that the patient does not rebreathe air CO2. The main concern is unintentional leaks above the intentional leak or venting threshold.
The ResMed CPAP (ResMed Corp, San Diego, CA) maximum intentional leak is 24 L/min.29 Above that level is large leak. The exact leak amount varies by interface (mask) based on pressure and mask type.2,12
The larger the interface surface area, the larger the leak. Unintentional leak is higher with the full-face mask than with the nasal mask, most likely because there is more opportunity for leakage with the larger surface area of the full-face mask. Nasal pillows seem to leak less because of their smaller surface area, but more studies on mask interfaces are needed to validate this finding.
Chin Strap
Adding a chin strap improved patient adherence, nightly duration of use, residual AHI, and leak in patients with sleep apnea.30 Other investigators reported reduced OSA, confirmed by polysomnography and nasopharyngolaryngoscopy, with use of only a chin strap.31 When a nasal mask with chin strap is used, the strap should be made to fit properly over the chin, not on the throat. Properly used chin straps significantly reduce leakage and residual AHI.30
A chin strap most likely reduces large leak and dry mouth.30 Dry mouth can result from mouth leak, which is commonly caused by nasal congestion or high pressure and mouth breathing. The nasal turbinates help humidify, warm, and cool the air. Heated humidification of PAP can help prevent dry mouth.
Asking the Right Questions
The clinician should ask several key questions at the first follow-up: How is it going with your PAP machine? Do you feel PAP therapy is helping you sleep? Do you feel better with PAP therapy? To a patient who states he or she is not doing well with therapy, the clinician should ask, What type of problems are you having? In many cases, poor adherence is attributable to a large leak from a poorly fitting mask. A large leak can also increase residual AHI and cause frequent arousals.30
Some machines cannot maintain the pressure of a large leak and will shut off and trigger an alarm that wakes the patient to readjust the mask. This situation causes some patients to discontinue CPAP/BPAP use. The mask leak must be adjusted. Another common complaint is morning dry mouth. This extreme dryness—a significant clue pointing to mouth leak caused in part by the mouth dropping open during sleep with PAP—should be addressed by fitting the patient with a chin strap.30 Dry mouth also can be caused by low humidity; increasing the humidity setting usually resolves the problem. However, as one study found, use of controlled heated humidification did not improve adherence or quality of life.32 In the same study, the nasopharyngeal dryness that resulted from CPAP therapy without humidification was reduced immediately and during the first weeks of treatment.All current PAP machines feature heated humidification.
Mouth breathing can also result from nasal congestion, allergic or vasomotor rhinitis, nasal turbinate hypertrophy, obstruction from a deviated septum, polyps, or air hunger/insufficient PAP pressure. Chronic rhinosinusitis is a problem that affects up to 12.5% of the U.S. population.33
Adherence is also increased with the elimination of leak and associated arousals. Patients are shown how to use their PAP machine’s heated humidity settings to obtain desired comfort levels. The clinician explains that the nasal turbinates heat and cool the air and that they can become swollen and irritated with PAP therapy. A heated hose may be prescribed to provide optimal humidification without condensation or water dripping into the hose (rainout).