Inspiratory flow limitation identified obstruction and breath cycling before, during, and after Cheyne Stokes breathing

Introduction: We recently showed crescendo-decrescendo inspiratory flow limitation (IFL) with Cheyne-Stokes breathing (CSB) hyperpnoea. This suggests obstructive in addition to previously conjectured central pathogenesis. The association, if any, of CSB with respiration before and after CSB remains poorly described. Aim: We used a patented automated breath-by-breath algorithm to quantify IFL before, during, and after CSB. Methods: Diagnostic ambulatory sleep polygraphs (Remmers Sleep Recorder, Sagatech Electronics, Ltd., Calgary, Canada) where interpreting physicians identified CSB were further assessed by two biomedical engineers (VP and RSP). Where CSB was confirmed IFL and cyclic periodicity were assessed before, during, and after CSB. Results: From 66 774 ambulatory sleep polygraphs referred for diagnostic interpretation 30 studies were identified with potential CSB by interpreting clinicians, but only 19 studies by engineers. 9 of these 19 studies showed transitions from and to inspiratory flow limited breathing with CSB suggesting persistent obstruction. Attenuated but similarly timed IFL identified cycling was seen in breathing before and after CSB. Mean individual CSB cycle times remained highly consistent (range 34.4 to 64.4 s with individual coefficients of variance Conclusions: IFL with similarly timed respiratory cycling occurs before, during, and after CSB suggesting persistent obstruction. As a mechanistic model of treatment-emergent central apnoea CPAP may reduce IFL braking of cyclic hyperventilation so worsening CSB.