Critical Care (Aug 2020)

Respiratory physiology of COVID-19-induced respiratory failure compared to ARDS of other etiologies

  • Domenico Luca Grieco,
  • Filippo Bongiovanni,
  • Lu Chen,
  • Luca S. Menga,
  • Salvatore Lucio Cutuli,
  • Gabriele Pintaudi,
  • Simone Carelli,
  • Teresa Michi,
  • Flava Torrini,
  • Gianmarco Lombardi,
  • Gian Marco Anzellotti,
  • Gennaro De Pascale,
  • Andrea Urbani,
  • Maria Grazia Bocci,
  • Eloisa S. Tanzarella,
  • Giuseppe Bello,
  • Antonio M. Dell’Anna,
  • Salvatore M. Maggiore,
  • Laurent Brochard,
  • Massimo Antonelli

DOI
https://doi.org/10.1186/s13054-020-03253-2
Journal volume & issue
Vol. 24, no. 1
pp. 1 – 11

Abstract

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Abstract Background Whether respiratory physiology of COVID-19-induced respiratory failure is different from acute respiratory distress syndrome (ARDS) of other etiologies is unclear. We conducted a single-center study to describe respiratory mechanics and response to positive end-expiratory pressure (PEEP) in COVID-19 ARDS and to compare COVID-19 patients to matched-control subjects with ARDS from other causes. Methods Thirty consecutive COVID-19 patients admitted to an intensive care unit in Rome, Italy, and fulfilling moderate-to-severe ARDS criteria were enrolled within 24 h from endotracheal intubation. Gas exchange, respiratory mechanics, and ventilatory ratio were measured at PEEP of 15 and 5 cmH2O. A single-breath derecruitment maneuver was performed to assess recruitability. After 1:1 matching based on PaO2/FiO2, FiO2, PEEP, and tidal volume, COVID-19 patients were compared to subjects affected by ARDS of other etiologies who underwent the same procedures in a previous study. Results Thirty COVID-19 patients were successfully matched with 30 ARDS from other etiologies. At low PEEP, median [25th–75th percentiles] PaO2/FiO2 in the two groups was 119 mmHg [101–142] and 116 mmHg [87–154]. Average compliance (41 ml/cmH2O [32–52] vs. 36 ml/cmH2O [27–42], p = 0.045) and ventilatory ratio (2.1 [1.7–2.3] vs. 1.6 [1.4–2.1], p = 0.032) were slightly higher in COVID-19 patients. Inter-individual variability (ratio of standard deviation to mean) of compliance was 36% in COVID-19 patients and 31% in other ARDS. In COVID-19 patients, PaO2/FiO2 was linearly correlated with respiratory system compliance (r = 0.52 p = 0.003). High PEEP improved PaO2/FiO2 in both cohorts, but more remarkably in COVID-19 patients (p = 0.005). Recruitability was not different between cohorts (p = 0.39) and was highly inter-individually variable (72% in COVID-19 patients and 64% in ARDS from other causes). In COVID-19 patients, recruitability was independent from oxygenation and respiratory mechanics changes due to PEEP. Conclusions Early after establishment of mechanical ventilation, COVID-19 patients follow ARDS physiology, with compliance reduction related to the degree of hypoxemia, and inter-individually variable respiratory mechanics and recruitability. Physiological differences between ARDS from COVID-19 and other causes appear small.

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