Emergent central sleep apnea during CPAP therapy-clinical implications

CPAP emergent central sleep apnea (CSA) (classified as treatment emergent CSA) is a well-recognized phenomenon that has been included in the current edition of the International Classification of Sleep Disorders (1). It is defined as the presence of primarily obstructive sleep apnea (OSA) on the diagnostic sleep study, significant resolution of obstructive events with CPAP titration but emergence or persistence of central events during PAP treatment with a central apnea index (CAI) ≥5/hr and greater than 50% of events being central and the results cannot be better explained by another CSA disorder. The European Respiratory Society has recently clarified the diagnostic criteria (2). It refines the definition to state that central events should be rare on the diagnostic study which I believe should be defined as a CAI less than 5/hr. If the CAI is greater than 5/hr on the diagnostic study then a CAI greater than 5/hr during the titration study is really CPAP resistant CSA (defined as treatment resistant CSA by the European Respiratory Society) and not true CPAP emergent CSA.