Am J Respir Crit Care Med. 2022 Nov 15. doi: 10.1164/rccm.202204-0629OC. Online ahead of print.
ABSTRACT
RATIONALE: The respective effects of PEEP and pressure support delivered through the helmet interface in hypoxemic patients need to be better understood.
OBJECTIVES: To assess the respective effects of helmet pressure support (NIV) and continuous positive-airway pressure (CPAP) compared to high-flow nasal oxygen (HFNO) on effort to breathe, lung inflation and gas exchange in hypoxemic patients (PaO2/FiO2≤200).
METHODS: Fifteen patients underwent 1-hour phases (constant FiO2) of HFNO (60 L/min), helmet NIV (PEEP=14 cmH2O, pressure support=12 cmH2O) and CPAP (PEEP=14 cmH2O) in randomized sequence.
MEASUREMENTS: Inspiratory esophageal (ΔPES) and transpulmonary pressure (ΔPL) swings were used as surrogates for inspiratory effort and lung distension, respectively. Tidal volume (VT) and end-expiratory lung volume were assessed with electrical impedance tomography.
MAIN RESULTS: ΔPES was lower during NIV vs. CPAP and HFNO (5[3-9] cmH2O vs. 13[10-19] vs. 10[8-13], p=0.001 and p=0.01). ΔPL was not statistically different between treatments. PaO2/FiO2 ratio was significantly higher during NIV and CPAP vs. HFNO (166[136-215] and 175[158-281] vs. 120[107-149], p=0.002 and p=0.001). NIV and CPAP similarly increased VT vs. HFNO (mean change: 70%[95%CI: 17-122], p=0.02; 93% [95%CI: 30-155], p=0.002) and end-expiratory lung volume (mean change: 198%[95%CI: 67-330], p=0.001; 263%[95%CI: 121-407], p=0.001), mostly due to increased aeration/ventilation in dorsal lung regions. During HFNO, 14/15 patients had pendelluft involving>10% of VT: pendelluft was mitigated by CPAP and further by NIV.
CONCLUSIONS: Compared to HFNO, helmet NIV, but not CPAP, reduced ΔPES. CPAP and NIV similarly increased oxygenation, end-expiratory lung volume and VT, without affecting ΔPL. NIV, and to a lesser extent, CPAP, mitigated pendelluft. Clinical trial registration available at www.
CLINICALTRIALS: gov, ID: NCT04241861.
PMID:36378814 | DOI:10.1164/rccm.202204-0629OC
