Distinguishing central sleep apnea (CSA) from obstructive sleep apnea (OSA) can be clinically important because different types of apnea may require different treatment approaches. Academically, this distinction is important for investigating the pathological mechanism of different types of sleep apnea. Conventional polysomnography (PSG) with recording of chest and abdominal movement may overestimate the frequency of CSA, leading to inappropriate treatment of sleep-disordered breathing. We hypothesized that diaphragm electromyogram (EMGdi) could be a useful technique to assess neural respiratory drive and respiratory effort and, therefore, to distinguish accurately CSA from OSA.
A multipair esophageal electrode catheter mounted with a balloon was used to record the EMGdi and esophageal pressure (Pes) during overnight PSG. Nineteen patients were included in the study, 12 of whom had previously been identified as having central apnea-hypopnea on a diagnostic PSG undertaken for symptoms that suggest OSA and 7 of whom were known to have heart failure.
A good relationship was found between the swing of Pes and the root mean (± SD) square of the EMGdi during OSA events (0.89 ± 0.10). About one third of CSA events diagnosed by uncalibrated respiratory inductance plethysmography could not be confirmed by Pes or EMGdi. No difference was found in the number of CSAs diagnosed by Pes (1,319) vs EMGdi (1,293; p > 0.01).
We conclude that both Pes and EMGdi measurements are useful in accurately differentiating central from obstructive respiratory events. Conventional PSG with recording of chest and abdominal movement overestimates the frequency of CSA events.