Validation of the Nox-T3 Portable Monitor for Diagnosis of Obstructive Sleep Apnea in Patients With Chronic Obstructive Pulmonary Disease.

STUDY OBJECTIVES

Clinical practice guidelines recommend polysomnography (PSG) for diagnosis of obstructive sleep apnea (OSA) in patients with major comorbidities. We evaluated home sleep apnea testing (HSAT) using a type 3 portable monitor (PM, Nox-T3, Nox Medical, Reykjavik, Iceland) to diagnose OSA in adults with chronic obstructive pulmonary disease (COPD).

METHODS

Ninety adults with COPD (89.0% males, mean ± standard deviation age 66.5 ± 7.8 years, body mass index 27.5 ± 5.8 kg/m, forced expiratory volume in the first second/forced vital capacity [FEV/ FVC] 53.5 ± 12.4%, FEV 54.0 ± 18.4% predicted) underwent unattended HSAT followed by an in-laboratory PSG with simultaneous PM recording.

RESULTS

Scoring hypopneas with a ≥ 4% oxygen desaturation, the apnea-hypopnea index (AHI) was 16.7 ± 20.6 events/h on HSAT, 20.0 ± 23.3 events/h on in-laboratory PM, and 21.2 ± 26.2 events/h on PSG ( < .0001). Bland-Altman analysis of AHI on HSAT versus PSG showed a mean difference (95% confidence interval) of -5.08 (-7.73, -2.42) events/h ( = .0003) and limits of agreement (± 2 standard deviations) of -30.00 to 19.85 events/h; HSAT underestimated AHI to a greater extent for more severe values (rho = -.529, < .0001). Using an AHI ≥ 5 events/h to diagnose OSA, HSAT had 95% sensitivity, 78% specificity, 88% positive predictive value, and 89% negative predictive value compared to PSG. Mean oxygen saturation was 93.2 ± 3.7% on PSG, 91.0 ± 3.3% on in-laboratory PM, and 90.8 ± 4.0% on HSAT ( < .0001). Percentage time oxygen saturation ≤ 88% was 17.9 ± 26.4% on HSAT, 17.4 ± 25.5% on in-laboratory PM, and 10.0 ± 21.1% on PSG ( < .0001).

CONCLUSIONS

The Nox-T3 PM can be used to diagnose OSA in patients with COPD but, most likely due to differences among pulse oximeters, a greater number of patients with COPD and without OSA qualified for nocturnal oxygen treatment using this PM than PSG.