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. 2025 Mar 10;29(1):107.
doi: 10.1186/s13054-025-05325-7.

Individualized PEEP can improve both pulmonary hemodynamics and lung function in acute lung injury

Mayson L A Sousa  1   2   3   4 , Luca S Menga  5   6   7 , Annia Schreiber  5   6 , Mattia Docci  5   6 , Fernando Vieira  5   6 , Bhushan H Katira  8 , Mariangela Pellegrini  9   10 , Sebastian Dubo  11 , Ghislaine Douflé  6   12   13 , Eduardo L V Costa  14 , Martin Post  7   15 , Marcelo B P Amato  14 , Laurent Brochard  5   6
Affiliations

Individualized PEEP can improve both pulmonary hemodynamics and lung function in acute lung injury

Mayson L A Sousa et al. Crit Care. .

Abstract

Rationale: There are several approaches to select the optimal positive end-expiratory pressure (PEEP), resulting in different PEEP levels. The impact of different PEEP settings may extend beyond respiratory mechanics, affecting pulmonary hemodynamics.

Objectives: To compare PEEP levels obtained with three titration strategies-(i) highest respiratory system compliance (CRS), (ii) electrical impedance tomography (EIT) crossing point; (iii) positive end-expiratory transpulmonary pressure (PL)-in terms of regional respiratory mechanics and pulmonary hemodynamics.

Methods: Experimental studies in two porcine models of acute lung injury: (I) bilateral injury induced in both lungs, generating a highly recruitable model (n = 37); (II) asymmetrical injury, generating a poorly recruitable model (n = 13). In all experiments, a decremental PEEP titration was performed monitoring PL, EIT (collapse, overdistention, and regional ventilation), respiratory mechanics, and pulmonary and systemic hemodynamics.

Measurements and main results: PEEP titration methods resulted in different levels of median optimal PEEP in bilateral lung injury: 14(12-14) cmH2O for CRS, 11(10-12) cmH2O for EIT, and 8(8-10) cmH2O for PL, p < 0.001. Differences were less pronounced in asymmetrical lung injury. PEEP had a quadratic U-shape relationship with pulmonary artery pressure (R2 = 0.94, p < 0.001), right-ventricular systolic transmural pressure, and pulmonary vascular resistance. Minimum values of pulmonary vascular resistance were found around individualized PEEP, when ventilation distribution and pulmonary circulation were simultaneously optimized.

Conclusions: In porcine models of acute lung injury with variable lung recruitability, both low and high levels of PEEP can impair pulmonary hemodynamics. Optimized ventilation and hemodynamics can be obtained simultaneously at PEEP levels individualized based on respiratory mechanics, especially by EIT and esophageal pressure.

Keywords: Acute lung injury; Mechanical ventilation; Positive end-expiratory pressure; Pulmonary hemodynamics; Pulmonary vascular resistance.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare no competing interests. Ethical approval and consent to participate: The animal study protocol was approved by the Animal Care Committee of the Peter Gilgan Centre for Research and Learning (PGRLC) at The Hospital for Sick Children – SickKids, reference number 1000058058. Consent for publication: Not applicable.

Figures

Fig. 1
Fig. 1
Positive end-expiratory pressure (PEEP) titration in pigs with bilateral lung injury (n = 37) according to three strategies. Black solid line represents the average electrical impedance tomography (EIT) crossing point between collapse and overdistension. Black dashed line represents the average highest respiratory system compliance (CRS). Black dotted line represents the average end-expiratory transpulmonary pressure (PL) slightly positive. Error bars represent standard error
Fig. 2
Fig. 2
A The optimal positive end-expiratory pressure (PEEP) according to different PEEP titration strategies in pigs with bilateral lung injury (n = 37): CRS, highest respiratory system compliance; EIT, electrical impedance tomography crossing point; and PL, end-expiratory transpulmonary pressure slightly positive. * represents post-hoc p < 0.05. B Regional compliance in bilateral lung injury (n = 37). Black solid line represents the average EIT crossing point between collapse and overdistension. Black dashed line represents the average highest CRS. Black dotted line represents the average end-expiratory PL slightly positive. Error bars represent standard error
Fig. 3
Fig. 3
Pulmonary hemodynamics in bilateral lung injury (n = 37): A Mean pulmonary artery pressure (Mean PAP) at each level of positive end-expiratory pressure (PEEP). B Right ventricular (RV) systolic transmural pressure at each level of PEEP. Dots represent mean and error bars represent standard error. Red line represents quadratic regression, and grey area shaded represents 95% confidence interval. Black solid line represents the average electrical impedance tomography (EIT) crossing point between collapse and overdistension. Black dashed line represents the average highest respiratory system compliance (CRS). Black dotted line represents the average end-expiratory transpulmonary pressure (PL) slightly positive
Fig. 4
Fig. 4
Positive end-expiratory pressure (PEEP) titration in pigs with asymmetrical lung injury (n = 13) according to three strategies. Black solid line represents the average electrical impedance tomography (EIT) crossing point between collapse and overdistension. Black dashed line represents the average highest respiratory system compliance (CRS). Black dotted line represents the average end-expiratory transpulmonary pressure (PL) slightly positive. Error bars represent standard error
Fig. 5
Fig. 5
Optimal PEEP and regional respiratory system mechanics in asymmetrical lung injury (n = 13). A The optimal positive end-expiratory pressure (PEEP) according to different PEEP titration strategies in pigs with asymmetrical lung injury: CRS, highest respiratory system compliance; EIT, electrical impedance tomography crossing point; and PL, end-expiratory transpulmonary pressure slightly positive. * represents post-hoc p < 0.05. B Dependent (grey) versus non-dependent (orange) regions. C Left (grey) versus right (orange) regions. Surfactant lavage and high-stretch ventilation were performed in the left side (more injured), while the right side was kept collapsed (less injured). Black solid line represents the average EIT crossing point between collapse and overdistension. Black dashed line represents the average highest CRS. Black dotted line represents the average end-expiratory PL slightly positive. Error bars represent standard error
Fig. 6
Fig. 6
Pulmonary hemodynamics in asymmetrical lung injury (n = 13): A Mean pulmonary artery pressure (Mean PAP) at each level of positive end-expiratory pressure (PEEP). B Pulmonary vascular resistance (PVR) at each level of PEEP. Dots represent mean and error bars represent standard error. Red line represents quadratic regression, and grey shaded area represents 95% confidence interval. Black solid line represents the average electrical impedance tomography (EIT) crossing point between collapse and overdistension. Black dashed line represents the average highest respiratory system compliance (CRS). Black dotted line represents the average end-expiratory transpulmonary pressure (PL) slightly positive
Fig. 7
Fig. 7
Sensitivity analysis in 5 animals in volume-controlled ventilation. A Mean pulmonary artery pressure (Mean PAP) at each level of positive end-expiratory pressure (PEEP), n = 5. B End-tidal carbon dioxide (EtCO2) at each level of PEEP, n = 5. C Partial pressure of arterial carbon dioxide (PaCO2) at each level of PEEP measured in one of the experiments. Error bars represent standard error. Grey shaded area represents 95% confidence interval
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