Regional peak flow as a novel approach to assess regional pulmonary mechanics by electrical impedance tomography: an observational validation study

BACKGROUND: Spontaneous breathing efforts during mechanical ventilation are a widely accepted weaning approach for acute respiratory distress syndrome (ARDS) patients. These efforts can be too vigorous, possibly inflicting lung and diaphragm damage. Higher positive end expiratory pressure (PEEP) levels can be used to lower the magnitude of vigorous breathing efforts. Nevertheless, PEEP titrating tools are lacking in spontaneous mechanical ventilation (SMV). Therefore, the aim is to develop an electrical impedance tomography (EIT) algorithm for quantifying regional lung mechanics independent from a stable plateau pressure phase based on regional peak flow (RPF) by EIT, which is hypothetically applicable in SMV and to validate this algorithm in patients on controlled mechanical ventilation (CMV). METHODS: The RPF algorithm quantifies a cumulative overdistension (OD(RPF)) and collapse (CL(RPF)) rate and is validated in a prospective cohort of mechanically ventilated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) patients on CMV. OD(RPF) and CL(RPF) are compared with compliance-based cumulative overdistension (OD(P500)) and collapse (CL(P500)) rates from the Pulmovista 500 EIT device at multiple PEEP levels (PEEP 10 cmH(2)O to PEEP 24 cmH(2)O) in EIT measurements from CMV patients by linear mixed models, Bland-Altman analysis and intraclass correlation coefficient (ICC). RESULTS: Seventy-eight patients were included. Linear mixed models revealed an association between OD(RPF) and OD(P500) of 1.02 (0.98–1.07, P<0.001) and between CL(RPF) and CL(P500) of 0.93 (0.80–1.05, P<0.001). ICC values ranged from 0.78 to 0.86 (P<0.001) for OD(RPF) and OD(P500) and from 0.70 to 0.85 (P<0.001) for CL(RPF) and CL(P500) (PEEP 10 to PEEP 24). The mean bias between OD(RPF) and OD(P500) in these PEEP levels ranged from 0.80% to 4.19% and from −1.31% to 0.13% between CL(RPF) and CL(P500). CONCLUSIONS: A RPF approach for quantifying regional lung mechanics showed a moderate to good agreement in coronavirus disease 2019 (COVID-19) related ARDS patients on CMV compared to the compliance-based approach. This, in addition to being independent of a plateau pressure phase, indicates that the RPF approach is a valid method to explore for quantifying regional lung mechanics in SMV.