Pure Central Sleep Apnea: description of a case series at tertiary hospital in Portugal

Central Sleep Apnea (CSA) is an uncommon sleep breathing disorder which diagnosis is based on sleep-related symptoms plus nocturnal polysomnography (PSG) revealing ≥5 central apneas/hypopneas per hour of sleep, with central events being >50% of respiratory events. Although CSA and Obstructive Sleep Apnea (OSA) might coexist, pure CSA is uncommon. The aim of this work was to describe a CSA case series without OSA criteria (obstructive apnea/hypopneas index [AHI] ≤5/h) followed at a reference tertiary hospital in Portugal. Treatment-emergent CSA was excluded. Eight cases were identified. Their age range was 22-86 years, and 5 were male. Daytime sleepiness and witnessed apneas were frequently reported. According to PSG, CSA was classified as: mild (n=1; central AHI= 13/h), moderate (n=2; central AHI= 17.8-22.1/h) and severe (n=5; central AHI 35.8-45.2/h). Cheyne-Stokes breathing (CSB) was present in 3 cases. The majority was normocapnic, only one patient had daytime hypocapnia. Relevant medical conditions (heart failure, arterial fibrillation and chronic kidney disease) were identified in 5 patients, which included CSB cases. The remaining were classified as primary CSA after extensive etiological study, in the absence of pharmacological contribution or secondary cause. Moderate to severe CSA initiated positive airway pressure (PAP) therapy: continuous PAP (n=2), BiLevel-ST (n=1) and adaptive servo-ventilation (n=4, with LVEF=46-60%). Four cases had optimal PAP adherence and symptom improvement. CSA without OSA at a diagnosis PSG is infrequent in most Sleep Medical Centres and their management can be difficult. The authors described 8 cases reflecting different phenotypes and treatment approaches.