Effect of nocturnal EPAP titration to abolish tidal expiratory flow limitation in COPD patients with chronic hypercapnia: a randomized, cross-over pilot study.

BACKGROUND: Tidal expiratory flow limitation (EFLT) promotes intrinsic PEEP (PEEPi) in patients with chronic obstructive pulmonary disease (COPD). Applying non-invasive ventilation (NIV) with an expiratory positive airway pressure (EPAP) matching PEEPi improves gas exchange, reduces work of breathing and ineffective efforts. We aimed to evaluate the effects of a novel NIV mode that continuously adjusts EPAP to the minimum level that abolishes EFLT. METHODS: This prospective, cross-over, open-label study randomized patients to one night of fixed-EPAP and one night of EFLT-abolishing-EPAP. The primary outcome was transcutaneous carbon dioxide pressure (PtcCO2). Secondary outcomes were: peripheral oxygen saturation (SpO2), frequency of ineffective efforts, breathing patterns and oscillatory mechanics. RESULTS: We screened 36 patients and included 12 in the analysis (age 72 ± 8 years, FEV1 38 ± 14%Pred). The median EPAP did not differ between the EFLT-abolishing-EPAP and the fixed-EPAP night (median (IQR) = 7.0 (6.0, 8.8) cmH2O during night vs 7.5 (6.5, 10.5) cmH2O, p = 0.365). We found no differences in mean PtcCO2 (44.9 (41.6, 57.2) mmHg vs 54.5 (51.1, 59.0), p = 0.365), the percentage of night time with PtcCO2 > 45 mm Hg was lower (62(8,100)% vs 98(94,100)%, p = 0.031) and ineffective efforts were fewer (126(93,205) vs 261(205,351) events/hour, p = 0.003) during the EFLT-abolishing-EPAP than during the fixed-EPAP night. We found no differences in oxygen saturation and lung mechanics between nights. CONCLUSION: An adaptive ventilation mode targeted to abolish EFLT has the potential to reduce hypercapnia and ineffective efforts in stable COPD patients receiving nocturnal NIV. TRIAL REGISTRATION: ClicalTrials.gov, NCT04497090. Registered 29 July 2020-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04497090 .

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

RATIONALE: In COPD patients, the development of tidal expiratory flow limitation (EFLT) 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 EFLT by a new automatic non-invasive ventilation (NIV) mode in stable hypercapnic COPD patients in the seated and supine positions. METHODS: Twenty-six hypercapnic COPD patients (mean±SD: FEV1%pred = 39.2 ±â€¯16.1, FEV1/FVC%pred = 46.3 ±â€¯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 EFLT breath-by-breath by using the forced oscillation technique optimized in real-time PEEP to the lowest pressure able to abolish EFLT (PEEPO). RESULTS: The ventilator was always able to identify a PEEPO. Its values were highly variable among patients and increased from median(iqr) 4.0 (0.03) (range: 4.0-8.3cmH2O) to 6 (6.1) cmH2O (range: 4.0-15.7 cmH2O) when patients moved from the seated to the supine position, respectively. PEEPO in supine position did not correlate to any spirometric or anthropometric variable. CONCLUSIONS: PEEPO 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.