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

BACKGROUND: Tidal expiratory flow limitation (EFL(T)) is common among COPD patients. Whether EFL(T) changes during sleep and can be abolished during home ventilation is not known. METHODS: 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(T). 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(T) was measured and compared to that during supine wakefulness. Ventilator adherence and subjective patient perceptions were obtained after home use. RESULTS: Of 26 patients with supine EFL(T), 15 completed overnight PSG and 10 the home study. In single night and 2-week home studies, EFL(T) 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(2)O of the awake screening pressure. Over 2 weeks, mean EPAP was almost half the mean maximum EPAP (11.7 vs 6.4 cmH(2)O respectively). Group mean ∆Xrs was ≤ 2.8 for 77.3% of their home use with a mean time to abolish new EFL(T) 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. CONCLUSIONS: 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. Trial registration: The trial was retrospectively registered at CT.gov NCT04725500. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12931-021-01913-7.