Variability of breathing during wakefulness while using CPAP predicts adherence

The standard therapy for obstructive sleep apnoea (OSA) is continuous positive airway pressure (CPAP) therapy. However, long-term adherence remains at ~50% despite improvements in behavioural and educational interventions. Based on prior work, we explored whether regularity of breathing during wakefulness might be a physiologic predictor of CPAP adherence.

Of the 117 consecutive patients who were diagnosed with OSA and prescribed CPAP, 79 CPAP naïve patients were enrolled in this prospective study. During CPAP initiation, respiratory signals were collected using respiratory inductance plethysmography while wearing CPAP during wakefulness in a seated position. Breathing regularity was assessed by the coefficient of variation (CV) for breath-by-breath estimated tidal volume (V_T ) and total duration of respiratory cycle (Ttot). In a derivation group (n = 36), we determined the cut-off CV value which predicted poor CPAP adherence at the first month of therapy, and verified the validity of this predetermined cut-off value in the remaining participants (validation group; n = 43).

In the derivation group, the CV for estimated V_T was significantly higher in patients with poor adherence than with good adherence (median (interquartile range): 44.2 (33.4-57.4) vs 26.0 (20.4-33.2), P < 0.001). The CV cut-off value for estimated V_T for poor CPAP adherence was 34.0, according to a receiver-operating characteristic (ROC) curve. In the validation group, the CV value for estimated V_T >34.0 confirmed to be predicting poor CPAP adherence (sensitivity, 0.78; specificity, 0.83).

At the initiation of therapy, breathing regularity during wakefulness while wearing CPAP is an objective predictor of short-term CPAP adherence.