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Volume 15 No. 04
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Accepted Papers

Scientific Investigations

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

Yuan Chang, MD1; Liyue Xu, MD2,3; Fang Han, MD2; Brendan T. Keenan, MS3; Elizabeth Kneeland-Szanto, MBA3; Rongbao Zhang, MD2; Wei Zhang, MD4; Yongbo Yu, BS4; Yuhua Zuo, BS2; Allan I. Pack, MBChB, PhD3; Samuel T. Kuna, MD3,5
1Department of Respiratory Medicine, Peking University International Hospital, Beijing, China; 2Department of Respiratory Medicine, Peking University People's Hospital, Beijing, China; 3Department of Medicine and Center for Sleep and Circadian Neurobiology, University of Pennsylvania, Philadelphia, Pennsylvania; 4PKU-UPenn Sleep Center, Peking University International Hospital, Beijing, China; 5Department of Medicine, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania

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).


Ninety adults with COPD (89.0% males, mean ± standard deviation age 66.5 ± 7.8 years, body mass index 27.5 ± 5.8 kg/m2, forced expiratory volume in the first second/forced vital capacity [FEV1/ FVC] 53.5 ± 12.4%, FEV1 54.0 ± 18.4% predicted) underwent unattended HSAT followed by an in-laboratory PSG with simultaneous PM recording.


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 (P < .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 (P = .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, P < .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 (P < .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 (P < .0001).


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.


Chang Y, Xu L, Han F, Keenan BT, Kneeland-Szanto E, Zhang R, Zhang W, Yu Y, Zuo Y, Pack AI, Kuna ST. Validation of the Nox-T3 portable monitor for diagnosis of obstructive sleep apnea in patients with chronic obstructive pulmonary disease. J Clin Sleep Med. 2019;15(4):587–596.

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