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. 2021 Feb 24;25(1):81.
doi: 10.1186/s13054-021-03477-w.

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

Lorenzo Ball  1   2 , Chiara Robba  3 , Lorenzo Maiello  4 , Jacob Herrmann  5 , Sarah E Gerard  6 , Yi Xin  7 , Denise Battaglini  3 , Iole Brunetti  3 , Giuseppe Minetti  8 , Sara Seitun  8 , Antonio Vena  9 , Daniele Roberto Giacobbe  9 , Matteo Bassetti  9   10 , Patricia R M Rocco  11 , Maurizio Cereda  12 , Lucio Castellan  8 , Nicolò Patroniti  4   3 , Paolo Pelosi  4   3 ; GECOVID (GEnoa COVID-19) group
Collaborators, Affiliations

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

Lorenzo Ball et al. Crit Care. .

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.

Keywords: ARDS; COVID-19; CT scan; Mechanical ventilation; Respiratory system mechanics.

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Conflict of interest statement

Dr. Bassetti reports personal fees and other from Angelini, personal fees and other from AstraZeneca, other from Bayer, personal fees and other from Cubist, personal fees and other from Pfizer, personal fees and other from Menarini, personal fees and other from MSD, other from Nabriva, other from Paratek, other from Roche, other from Shionogi, other from Tetraphase, other from The Medicine Company, personal fees and other from Astellas Pharma Inc., personal fees from Gilead Sciences, personal fees from Teva, personal fees from Novartis, grants from Ranbaxy, personal fees from Correvio, personal fees from Molteni, personal fees from Thermo Fisher, outside the submitted work. Dr. Herrmann is cofounder and shareholder in OscillaVent, Inc, and consultant for ZOLL Medical Corporation, both outside the submitted work. Dr. Giacobbe reports personal fees from Stepstone Pharma GmbH, personal fees from MSD Italia, personal fees from Correvio Italia, outside the submitted work. Dr. Rocco reports personal fees from SANOFI as a DSMB member. All other authors declared no conflict of interest.

Figures

Fig. 1
Fig. 1
Distribution of alveolar recruitment. The dashed line represents the boundary of the third quartile (4.5%), defining the “recruiters” group
Fig. 2
Fig. 2
Distribution of aeration compartments, expressed as percent of the total lung mass, at PEEP of 8 and 16 cmH2O. Data are reported overall and stratified in the recruiter and non-recruiter groups. Bars represent means, error bars the standard error of mean. *Significant difference between the two PEEP levels (p < 0.05). PEEP: positive end-expiratory pressure
Fig. 3
Fig. 3
Histogram distribution of lung volume aeration along the Hounsfield units scale at the two PEEP levels. Data are reported overall (panel A) and stratified in the recruiter (panel B) and non-recruiter (panel C) groups. PEEP: positive end-expiratory pressure. Bars represent medians, error bars the interquartile ranges
Fig. 4
Fig. 4
Gas-exchange and respiratory mechanics data at PEEP of 8 and 16 cmH2O. Gray squares and lines represent individual patient data, red bars the median value. Dashed lines represent patients in the recruiter group, solid lines the non-recruiter group. PEEP: positive end-expiratory pressure
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