Case Report of Sleep-Related Hypoventilation Complicated by Obstructive Sleep Apnea and Substance Use Disorder

Sleep-related hypoventilation (SRH) is characterized by inadequate ventilation during sleep, leading to elevated partial pressure of arterial carbon dioxide (PaCO 2 ). The etiology of the condition is multifactorial, with obesity hypoventilation syndrome (OHS), chest wall deformities, neuromuscular diseases, and medical conditions such as stroke being the most common underlying factors. The condition often coexists with obstructive sleep apnea (OSA), and it is often overlooked clinically. Substance abuse is also an important contributing factor to SRH. Nevertheless, due to the fact that patients frequently conceal their history of substance abuse, and the underlying cause becomes obscured after detoxification, relevant case reports are infrequent. We present a 53-year-old man with poor sleep and snoring. Polysomnography (PSG) revealed severe OSA with atypical features, such as a higher frequency of respiratory events during non-rapid eye movement (NREM) sleep than during REM sleep and an ataxic respiratory pattern. A detailed review of the patient's medical history revealed a 15-year history of heroin abuse, with a 5-year period of abstinence. Following a thorough evaluation that excluded other potential secondary causes, the patient was diagnosed with severe OSA and substance (heroin)-related sleep-related hypoventilation, based on the patient's medical history and the characteristic findings from the PSG. Following treatment with noninvasive positive pressure ventilation and medication, the patient exhibited a marked improvement in both nocturnal and daytime oxygen saturation levels, with complete resolution of symptoms. This case highlights the critical importance of thorough history taking, meticulous PSG interpretation, and adjunctive overnight CO 2 monitoring for early identification of SRH and accurate etiologic differentiation, thereby preventing misdiagnosis.