Impact of Different Positive End-Expiratory Pressures on Lung Mechanics in the Setting of Moderately Elevated Intra-Abdominal Pressure and Acute Lung Injury in a Porcine Model

Mascha O Fiedler; Emilis Simeliunas; B Luise Deutsch; Dovile Diktanaite; Alexander Harms; Maik Brune; Maximilian Dietrich; Florian Uhle; Markus A Weigand; Armin Kalenka

doi:10.3390/jcm10020306

Impact of Different Positive End-Expiratory Pressures on Lung Mechanics in the Setting of Moderately Elevated Intra-Abdominal Pressure and Acute Lung Injury in a Porcine Model

J Clin Med. 2021 Jan 15;10(2):306. doi: 10.3390/jcm10020306.

Authors

Mascha O Fiedler^{1

2}, Emilis Simeliunas^{1

3}, B Luise Deutsch⁴, Dovile Diktanaite^{1

3}, Alexander Harms⁵, Maik Brune⁶, Maximilian Dietrich¹, Florian Uhle¹, Markus A Weigand^{1

2}, Armin Kalenka^{2

7

8}

Affiliations

¹ Department of Anesthesiology, Heidelberg University Hospital, 69120 Heidelberg, Germany.
² Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), 69120 Heidelberg, Germany.
³ Department of Anesthesiology, Kantonsspital Lucerne, 6004 Lucerne, Switzerland.
⁴ Faculty of Medicine, Justus Liebig University, 35392 Giessen, Germany.
⁵ Institute of Pathology, University Hospital Heidelberg, 69120 Heidelberg, Germany.
⁶ Department of Internal Medicine I and Clinical Chemistry, University Hospital Heidelberg, 69120 Heidelberg, Germany.
⁷ Department of Anesthesiology and Intensive Care Medicine, Hospital Bergstrasse, 64646 Heppenheim, Germany.
⁸ Faculty of Medicine, University of Heidelberg, 69120 Heidelberg, Germany.

Abstract

The effects of a moderately elevated intra-abdominal pressure (IAP) on lung mechanics in acute respiratory distress syndrome (ARDS) have still not been fully analyzed. Moreover, the optimal positive end-expiratory pressure (PEEP) in elevated IAP and ARDS is unclear. In this paper, 18 pigs under general anesthesia received a double hit lung injury. After saline lung lavage and 2 h of injurious mechanical ventilation to induce an acute lung injury (ALI), an intra-abdominal balloon was filled until an IAP of 10 mmHg was generated. Animals were randomly assigned to one of three groups (group A = PEEP 5, B = PEEP 10 and C = PEEP 15 cmH₂O) and ventilated for 6 h. We measured end-expiratory lung volume (EELV) per kg bodyweight, driving pressure (ΔP), transpulmonary pressure (ΔP_L), static lung compliance (C_stat), oxygenation (P/F ratio) and cardiac index (CI). In group A, we found increases in ΔP (22 ± 1 vs. 28 ± 2 cmH₂O; p = 0.006) and ΔP_L (16 ± 1 vs. 22 ± 2 cmH₂O; p = 0.007), with no change in EELV/kg (15 ± 1 vs. 14 ± 1 mL/kg) when comparing hours 0 and 6. In group B, there was no change in ΔP (26 ± 2 vs. 25 ± 2 cmH₂O), ΔP_L (19 ± 2 vs. 18 ± 2 cmH₂O), C_stat (21 ± 3 vs. 21 ± 2 cmH₂O/mL) or EELV/kg (12 ± 2 vs. 13 ± 3 mL/kg). ΔP and ΔP_L were significantly lower after 6 h when comparing between group C and A (21 ± 1 vs. 28 ± 2 cmH₂O; p = 0.020) and (14 ± 1 vs. 22 ± 2 cmH₂O; p = 0.013)). The EELV/kg increased over time in group C (13 ± 1 vs. 19 ± 2 mL/kg; p = 0.034). The P/F ratio increased in all groups over time. CI decreased in groups B and C. The global lung injury score did not significantly differ between groups (A: 0.25 ± 0.05, B: 0.21 ± 0.02, C: 0.22 ± 0.03). In this model of ALI, elevated IAP, ΔP and ΔP_L increased further over time in the group with a PEEP of 5 cmH₂O applied over 6 h. This was not the case in the groups with a PEEP of 10 and 15 cmH₂O. Although ΔP and ΔP_L were significantly lower after 6 hours in group C compared to group A, we could not show significant differences in histological lung injury score.

Keywords: ALI; ARDS; PEEP; end-expiratory lung volume; intraabdominal pressure; transpulmonary pressure.