Hyperinflation on Chest Radiograph as a Marker of Low Adherence to Positive Airway Pressure Therapy in the Overlap Syndrome

Abstract

BACKGROUND: Positive airway pressure (PAP) in subjects with both obstructive sleep apnea and COPD reduces the risk of pulmonary hypertension, death, and hospitalizations from COPD exacerbations, but adherence to the intervention is low, similar to the experience with noninvasive ventilation in stable COPD. We sought to assess whether hyperinflation on chest radiographs contributes to low adherence to PAP therapy in the overlap syndrome. METHODS: Records of patients with a listed diagnosis of COPD at the time of polysomnography were reviewed. Overlap syndrome was diagnosed when COPD was clinically confirmed with spirometry showing a fixed airway obstruction and when the apnea-hypopnea index was > 5. Hyperinflation was evaluated by a review of the right diaphragm height on a lateral chest radiograph. Adherence was assessed clinically or through device download at a 3-month follow-up, and later adherence was assessed by telephone interviews. A receiver operating curve was used to determine whether diaphragm height was associated with adherence. RESULTS: Twenty-one of 41 subjects (51%) were considered adherent to PAP therapy at the 3-month visit. Adherent subjects were more overweight compared with non-adherent subjects (body mass index of 36.0 ؎ 5.7 vs 32.0 ؎ 5.7 kg/m 2 , P ‫؍‬ .03), sleepier at the onset (Epworth sleepiness scale score of 13.0 ؎ 5.8 vs 9.4 ؎ 5.4, P < .05), and less likely to have hyperinflation as defined by a right diaphragm height < 2.45 cm (33% vs 65%, P ‫؍‬ .04). The body mass index and initial sleepiness no longer predicted adherence beyond 3 months, but 35% of subjects with a right diaphragm height < 2.45 cm were adherent beyond 3 months compared with 75% of those with a right diaphragm height > 2.45 cm (P ‫؍‬ .04 by Fisher exact test). CONCLUSIONS: Hyperinflation is associated with decreased adherence to PAP therapy in the overlap syndrome.

A review of therapies for the overlap syndrome of obstructive sleep apnea and chronic obstructive pulmonary disease

“…Patients with emphysema have been found to have lower CPAP adherence compared with obese patients with daytime sleepiness. 87 OS is amenable to phenotyping. Figure 1 shows that patients with COPD may suffer from a spectrum of SRBD, the exact nature of which depends on the relative severity of the emphysema and obesity.…”

“…Most of these studies employed CPAP. Patients with emphysema have been found to have lower CPAP adherence compared with obese patients with daytime sleepiness 87 …”

Expiratory Time Constant and Sleep Apnea Severity in the Overlap Syndrome

“…Of the 48 subjects of the original cohort of patients with the overlap syndrome, 7 34 had complete full-night diagnostic polysomnography available for review. A mixed model analysis showed no significant differences in the time constant between sleep or wake stages, and there was no significant association between various variables and the time constant, except for a significant positive correlation with the percent of supine sleep ( Table 1).…”