Using a portable monitoring device for diagnosing obstructive sleep apnea in patients with multiple co-existing medical illnesses.

To, Kin Wang; Chan, Tat On; Chan, Wing Chi; Choo, Kah Lin; Hui, David S C

INTRODUCTION The existing guidelines recommends type III devices should be used in patients without significant co-morbidities. OBJECTIVES This study explored the reliability of using a type III device in patients with significant medical conditions to diagnose sleep apnea. METHODS Patients had an overnight sleep study conducted simultaneously with both polysomnogram (PSG) and a type III (NOX-T3) monitoring device. All patients had stable multiple co-existing medical illnesses without any changes in medications and conditions within one month of sleep study. RESULTS Between July 2019 to March 2020, there were altogether 74 patients recruited with analyzable data. Five major disease groups were identified in the cohort: psychiatric illnesses, stroke, ischemic heart diseases (IHD) and chronic kidney diseases (CKD). Psychiatric patients with medications were found to have the lowest AHI (23.7/hr) and arousal index (46.6/hr). The CKD group had the highest mean arousal index (71.4/hr) and obstructive apnea count (110.2). NOX-T3 respiratory event index (REI) was significantly lower than the PSG AHI (mean REI 31.4 vs mean AHI: 42.2). The number of patients with no/mild/moderate/severe OSA diagnosed by NOX-T3 and PSG were 7/17/19/31 and 5/11/20/38 respectively. CONCLUSION NOX-T3 device can reliably diagnose OSA in patients with different stable co-existing medical conditions. There is a tendency for underestimation of the severity of the OSA with NOX-T3 in patients with co-existing medical conditions especially with sedative medications. A positive NOX-T3 reliably diagnose OSA whereas a negative NOX-T3 result need to be interpreted with caution.