Background A large proportion of patients with a SARS-Cov-2-associated respiratory failure develop an acute respiratory distress syndrome (ARDS). It has been recently suggested that SARS-Cov-2-associated ARDS may differ from usual non-SARS-Cov-2-associated ARDS by higher respiratory system compliance ( C RS ), lower potential for recruitment with positive end-expiratory pressure (PEEP) contrasting with severe shunt fraction. The purpose of the study was to systematically assess respiratory mechanics and recruitability in SARS-Cov-2-associated ARDS. Methods Gas exchanges, C RS and hemodynamics were assessed at 2 levels of PEEP (15 cmH 2 O and 5 cmH 2 O) within 36 h (day1) and from 4 to 6 days (day 5) after intubation. The recruited volume was computed as the difference between the volume expired from PEEP 15 to 5 cmH 2 O and the volume predicted by compliance at PEEP 5 cmH 2 O (or above airway opening pressure). The recruitment-to-inflation (R/I) ratio (i.e. the ratio between the recruited lung compliance and C RS at PEEP 5 cmH 2 O) was used to assess lung recruitability. A R/I ratio value higher than or equal to 0.5 was used to define highly recruitable patients. Results The R/I ratio was calculated in 25 of the 26 enrolled patients at day 1 and in 15 patients at day 5. At day 1, 16 (64%) were considered as highly recruitable (R/I ratio median [interquartile range] 0.7 [0.55–0.94]) and 9 (36%) were considered as poorly recruitable (R/I ratio 0.41 [0.31–0.48]). The PaO 2 /FiO 2 ratio at PEEP 15 cmH 2 O was higher compared to PEEP 5 cmH 2 O only in highly recruitable patients (173 [139–236] vs 135 [89–167] mmHg; p < 0.01). Neither PaO 2 /FiO 2 or C RS measured at PEEP 15 cmH 2 O or at PEEP 5 cmH 2 O nor changes in PaO 2 /FiO 2 or C RS in response to PEEP changes allowed to identify highly or poorly recruitable patients. Conclusion In this series of 25 patients with SARS-Cov-2 associated ARDS, 64% were considered as highly recruitable and only 36% as poorly recruitable based on the R/I ratio performed on the day of intubation. This observation suggests that a systematic R/I ratio assessment may help to guide initial PEEP titration to limit harmful effect of unnecessary high PEEP in the context of Covid-19 crisis.
【저자키워드】 COVID-19, SARS-CoV-2, Respiratory failure, acute respiratory distress syndrome, mechanical ventilation, Respiratory mechanics, Positive end-expiratory pressure, Recruitability, 【초록키워드】 ARDS, intubation, airway, Patient, Compliance, Respiratory system, recruitment, change, patients, acute respiratory distress, Shunt, PEEP, Lung recruitability, observation, Volume, Lung compliance, syndrome, help, fraction, limit, initial, Result, enrolled, predicted, identify, performed, was used, develop, proportion, recruited, median, calculated, changes in, suggested, to define, expired, PaO, were assessed, 【제목키워드】 acute respiratory distress, PEEP, syndrome,