Overnight variation in tidal expiratory flow limitation in COPD patients and its correction: an observational study

Tidal expiratory flow limitation (EFL ) is common among COPD patients. Whether EFL changes during sleep and can be abolished during home ventilation is not known. COPD patients considered for noninvasive ventilation used a ventilator which measured within-breath reactance change at 5 Hz (∆Xrs) and adjusted EPAP settings to abolish EFL . Participants flow limited (∆Xrs > 2.8) when supine underwent polysomnography (PSG) and were offered home ventilation for 2 weeks. The EPAP pressure that abolished EFL was measured and compared to that during supine wakefulness. Ventilator adherence and subjective patient perceptions were obtained after home use. Of 26 patients with supine EFL , 15 completed overnight PSG and 10 the home study. In single night and 2-week home studies, EFL within and between participants was highly variable. This was unrelated to sleep stage or body position with only 14.6% of sleep time spent within 1 cmH O of the awake screening pressure. Over 2 weeks, mean EPAP was almost half the mean maximum EPAP (11.7 vs 6.4 cmH O respectively). Group mean ∆Xrs was ≤ 2.8 for 77.3% of their home use with a mean time to abolish new EFL of 5.91 min. Adherence to the ventilator varied between 71 and 100% in prior NIV users and 36-100% for naïve users with most users rating therapy as comfortable. Tidal expiratory flow limitation varies significant during sleep in COPD patients. This can be controlled by auto-titrating the amount of EPAP delivered. This approach appears to be practical and well tolerated by patients. The trial was retrospectively registered at CT.gov NCT04725500.