Critical Care (Feb 2021)

Computed tomography assessment of PEEP-induced alveolar recruitment in patients with severe COVID-19 pneumonia

  • Lorenzo Ball,
  • Chiara Robba,
  • Lorenzo Maiello,
  • Jacob Herrmann,
  • Sarah E. Gerard,
  • Yi Xin,
  • Denise Battaglini,
  • Iole Brunetti,
  • Giuseppe Minetti,
  • Sara Seitun,
  • Antonio Vena,
  • Daniele Roberto Giacobbe,
  • Matteo Bassetti,
  • Patricia R. M. Rocco,
  • Maurizio Cereda,
  • Lucio Castellan,
  • Nicolò Patroniti,
  • Paolo Pelosi,
  • GECOVID (GEnoa COVID-19) group

DOI
https://doi.org/10.1186/s13054-021-03477-w
Journal volume & issue
Vol. 25, no. 1
pp. 1 – 10

Abstract

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Abstract Background There is a paucity of data concerning the optimal ventilator management in patients with COVID-19 pneumonia; particularly, the optimal levels of positive-end expiratory pressure (PEEP) are unknown. We aimed to investigate the effects of two levels of PEEP on alveolar recruitment in critically ill patients with severe COVID-19 pneumonia. Methods A single-center cohort study was conducted in a 39-bed intensive care unit at a university-affiliated hospital in Genoa, Italy. Chest computed tomography (CT) was performed to quantify aeration at 8 and 16 cmH2O PEEP. The primary endpoint was the amount of alveolar recruitment, defined as the change in the non-aerated compartment at the two PEEP levels on CT scan. Results Forty-two patients were included in this analysis. Alveolar recruitment was median [interquartile range] 2.7 [0.7–4.5] % of lung weight and was not associated with excess lung weight, PaO2/FiO2 ratio, respiratory system compliance, inflammatory and thrombophilia markers. Patients in the upper quartile of recruitment (recruiters), compared to non-recruiters, had comparable clinical characteristics, lung weight and gas volume. Alveolar recruitment was not different in patients with lower versus higher respiratory system compliance. In a subgroup of 20 patients with available gas exchange data, increasing PEEP decreased respiratory system compliance (median difference, MD − 9 ml/cmH2O, 95% CI from − 12 to − 6 ml/cmH2O, p < 0.001) and the ventilatory ratio (MD − 0.1, 95% CI from − 0.3 to − 0.1, p = 0.003), increased PaO2 with FiO2 = 0.5 (MD 24 mmHg, 95% CI from 12 to 51 mmHg, p < 0.001), but did not change PaO2 with FiO2 = 1.0 (MD 7 mmHg, 95% CI from − 12 to 49 mmHg, p = 0.313). Moreover, alveolar recruitment was not correlated with improvement of oxygenation or venous admixture. Conclusions In patients with severe COVID-19 pneumonia, higher PEEP resulted in limited alveolar recruitment. These findings suggest limiting PEEP strictly to the values necessary to maintain oxygenation, thus avoiding the use of higher PEEP levels.

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