Auto-titrating external positive end-expiratory airway pressure to abolish expiratory flow limitation during tidal breathing in patients with severe chronic obstructive pulmonary disesase: a physiological study

Background The optimal non-invasive application of external positive end-expiratory pressure (EPAP) to abolish tidal-breathing expiratory flow limitation (EFLT) and minimise intrinsic PEEP (PEEPi) is challenging in COPD patients. We investigated whether auto-titrating EPAP, using the forced oscillation technique (FOT) to detect and abolish EFLT, would minimise PEEPi, work of breathing and neural respiratory drive (NRD) in patients with severe COPD. Methods Patients with COPD with chronic respiratory failure underwent auto-titration of EPAP using a FOT-based algorithm that detected EFLT. Once optimal EPAP was identified, manual titration was performed to assess NRD (using diaphragm and parasternal intercostal muscle electromyography, EMGdi and EMGpara, respectively), transdiaphragmatic inspiratory pressure swings (ΔPdi), transdiaphragmatic pressure-time product (PTPdi), and PEEPi, between EPAP levels 2 cmH2O below to 3 cmH2O above optimal EPAP. Results Of 10 patients enrolled (age 65±6 years; male 60%; body mass index 27.6±7.2 kg.m−2; %predicted FEV1 28.4±8.3), eight had EFLT, and optimal EPAP was 9 (range 4–13) cmH2O. NRD was reduced from baseline EPAP at 1 cmH2O below optimal EPAP on EMGdi and at optimal EPAP on EMGpara. In addition, at optimal EPAP, PEEPi (0.80±1.27 cmH2O versus 1.95± 1.70 cmH2O; p Conclusion Auto-titration of EPAP, using a FOT-based algorithm to abolish EFLT, minimises transdiaphragmatic pressure swings and NRD in patients with COPD and chronic respiratory failure.