Automatic tailoring of the lowest PEEP to abolish tidal expiratory flow limitation in seated and supine COPD patients

Abstract Rationale In COPD patients, the development of tidal expiratory flow limitation (EFL T ) results in intrinsic positive end-expiratory pressure (PEEPi), leading to increased work of breathing and worsening patient-ventilator interaction. An external PEEP can mitigate these consequences but how to optimize its value it is still unknown. Objective To measure the minimum PEEP able to abolish EFL T by a new automatic non-invasive ventilation (NIV) mode in stable hypercapnic COPD patients in the seated and supine positions. Methods and measurements: Twenty-six hypercapnic COPD patients (FEV 1 %pred = 39.2 ± 16.1, FEV 1 /FVC%pred = 46.3 ± 16.3%) were studied while receiving NIV during two consecutive 15-min periods with patients studied seated in the first and supine in the second. A ventilator able to identify EFL T breath-by-breath by using the forced oscillation technique optimized in real-time PEEP to the lowest pressure able to abolish EFL T (PEEP O ). Results The ventilator was always able to identify a PEEP O . Its values were highly variable among patients and increased from 4.0 (0.03) (range: 4.0–8.3cmH 2 O) to 6 (6.1) cmH 2 O (range: 4.0–15.7 cmH 2 O) when patients moved from the seated to the supine position, respectively. PEEP O in supine position did not correlate to any spirometric or anthropometric variable. Conclusions PEEP O in COPD patients is highly variable and increases in supine position. It is not predicted by spirometric nor anthropometric variables, but had a considerable variability among the patients. We suggest that PEEPo may be used as a phenotyping variable in COPD patients.