Effects of PEEP on regional ventilation-perfusion mismatch in the acute respiratory distress syndrome

Bertrand Pavlovsky; Antonio Pesenti; Elena Spinelli; Gaetano Scaramuzzo; Ines Marongiu; Paola Tagliabue; Savino Spadaro; Giacomo Grasselli; Alain Mercat; Tommaso Mauri

doi:10.1186/s13054-022-04085-y

Effects of PEEP on regional ventilation-perfusion mismatch in the acute respiratory distress syndrome

Crit Care. 2022 Jul 11;26(1):211. doi: 10.1186/s13054-022-04085-y.

Authors

Bertrand Pavlovsky^{1

2}, Antonio Pesenti^{1

3}, Elena Spinelli¹, Gaetano Scaramuzzo⁴, Ines Marongiu³, Paola Tagliabue¹, Savino Spadaro⁴, Giacomo Grasselli^{1

3}, Alain Mercat^{2

5}, Tommaso Mauri^{6

7}

Affiliations

¹ Department of Anesthesia, Critical Care and Emergency, IRCCS (Institute for Treatment and Research) Ca' Granda Maggiore Policlinico Hospital Foundation, Via Sforza 35, 20122, Milan, Italy.
² Vent'Lab, Medical Intensive Care Unit Department, Angers University Hospital, Angers, France.
³ Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.
⁴ Intensive Care Unit, Department of Morphology, Surgery and Experimental Medicine, Sant'Anna University Hospital, Ferrara, Italy.
⁵ Department of Medicine, University of Angers, Angers, France.
⁶ Department of Anesthesia, Critical Care and Emergency, IRCCS (Institute for Treatment and Research) Ca' Granda Maggiore Policlinico Hospital Foundation, Via Sforza 35, 20122, Milan, Italy. tommaso.mauri@unimi.it.
⁷ Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy. tommaso.mauri@unimi.it.

Abstract

Purpose: In the acute respiratory distress syndrome (ARDS), decreasing Ventilation-Perfusion [Formula: see text] mismatch might enhance lung protection. We investigated the regional effects of higher Positive End Expiratory Pressure (PEEP) on [Formula: see text] mismatch and their correlation with recruitability. We aimed to verify whether PEEP improves regional [Formula: see text] mismatch, and to study the underlying mechanisms.

Methods: In fifteen patients with moderate and severe ARDS, two PEEP levels (5 and 15 cmH₂O) were applied in random order. [Formula: see text] mismatch was assessed by Electrical Impedance Tomography at each PEEP. Percentage of ventilation and perfusion reaching different ranges of [Formula: see text] ratios were analyzed in 3 gravitational lung regions, leading to precise assessment of their distribution throughout different [Formula: see text] mismatch compartments. Recruitability between the two PEEP levels was measured by the recruitment-to-inflation ratio method.

Results: In the non-dependent region, at higher PEEP, ventilation reaching the normal [Formula: see text] compartment (p = 0.018) increased, while it decreased in the high [Formula: see text] one (p = 0.023). In the middle region, at PEEP 15 cmH₂O, ventilation and perfusion to the low [Formula: see text] compartment decreased (p = 0.006 and p = 0.011) and perfusion to normal [Formula: see text] increased (p = 0.003). In the dependent lung, the percentage of blood flowing through the non-ventilated compartment decreased (p = 0.041). Regional [Formula: see text] mismatch improvement was correlated to lung recruitability and changes in regional tidal volume.

Conclusions: In patients with ARDS, higher PEEP optimizes the distribution of both ventilation (in the non-dependent areas) and perfusion (in the middle and dependent lung). Bedside measure of recruitability is associated with improved [Formula: see text] mismatch.

Keywords: Acute lung injury; COVID-19; Electrical impedance tomography; Multiple inert gas elimination technique; Recruitment-on-inflation ratio.

MeSH terms

Humans
Lung
Perfusion
Positive-Pressure Respiration / methods
Respiratory Distress Syndrome* / therapy
Respiratory Physiological Phenomena