Mask interface and CPAP adherence.

511 A 72-year-old retired nurse with family history of obstructive sleep apnea, loud snoring, witnessed apneas, excessive daytime sleepiness, and inability to concentrate underwent polysomnography. The patient has history of hypertension, multiple urogynecological procedures for genitourinary prolapse, and has history of atrial fibrillation and congestive heart failure. On examination, the patient had a body mass index of 31.8 kg/m,2 well controlled blood pressure, normal nasal passageway, and no evidence for decompensated heart failure. Cardiovascular examination revealed normal heart sounds and no murmurs, while respiratory examination revealed bilateral normal breath sounds. Abdominal examination was normal, and skin examination was normal as well. Examination of fingers revealed the following nail findings shown in image below (Fig. 1). Polysomnography revealed severe obstructive sleep apnea with an apnea-hypopnea index of 33.2 per hour, and lowest oxygen saturation of 82% by finger pulse oximetry. The patient underwent continuous positive airway pressure titration on a second night, which was marked by significant improvement in AHI to 3 per hour while on CPAP of 8 cm H2O with a silicone nasal mask. The patient complained of suffocation, and polysomnography revealed marked reduction in sleep efficiency despite improvement in sleep disordered breathing. The day following the CPAP titration, the patient called the lab coordinator to complain about a “skin rash” on her face, nasal burning, itching, and rhinorrhea. Examination during a followup clinic visit on the same day did not reveal any maculopapular rash, however skin impressions demarcating the areas of mask contact around the nose were identified. A “skin allergy patch” was constructed using a piece of the nasal mask material and affixed onto the ventral aspect of the patient’s forearm using adhesive tape to discern any evidence of skin contact allergies. On a follow-up visit 2 days later, there was no evidence of any skin change underneath the patch. Which one or more of the following are likely to explain the patient’s intolerance to CPAP mask interface?