Sleep apnea describes repeated pauses or reductions in breathing during sleep. The total AHI is only part of the picture: the type of event and its cause help determine treatment.
Obstructive sleep apnea
In an obstructive apnea, the upper airway is blocked while breathing effort continues. CPAP treats this by helping hold the airway open. Anatomy, sleep state and other factors can influence the tendency to obstruction.
An obstructive event is not simply defined by snoring. Sleep-study airflow and effort signals help establish the pattern.
Central sleep apnea
During a central apnea, airflow and breathing effort are absent. This reflects a disturbance in breathing control rather than the same airway-collapse mechanism. Relevant contexts include heart failure, certain medicines, altitude and other medical conditions; sometimes no cause is identified.
A few pauses around sleep transitions do not by themselves establish a central sleep apnea syndrome. The frequency, timing, wider recording and clinical circumstances matter. Sleep studies also recognise mixed events, which contain both central and obstructive components.
Treatment-emergent central sleep apnea
Central events may emerge or persist when PAP treats previously obstructive sleep apnea. This is called treatment-emergent central sleep apnea, sometimes described as complex sleep apnea.
Some cases improve with continued treatment and monitoring, while others need a different plan. There is no universal number of weeks that everyone should wait without review. Symptoms, event burden, leak, medicines and associated disease affect the decision.
A device's clear-airway label is an estimate, not direct proof that breathing effort stopped. The clinician may need to review the original study or obtain further testing before assigning a diagnosis.
Treatment is selected by cause
It is inaccurate to say that CPAP never helps central sleep apnea or that every central event requires bilevel ST. Current AASM recommendations distinguish causes and consider different therapies, with varying certainty of evidence.
Heart failure adds specific constraints. ASV requires a specialist decision, attention to current device contraindications and safety notices, and, in reduced-ejection-fraction heart failure, experienced-centre care with close monitoring under current AASM guidance.
If new central flags appear, bring the trend and symptoms to the prescribing team. Do not independently raise pressure, stop prescribed medicines or buy a different mode based on the label alone.
Related reading: Central events after starting CPAP: what to review