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. 2025 Aug 19.
doi: 10.1111/anae.16725. Online ahead of print.

Individual and combined effects of chemical and mechanical power on postoperative pulmonary complications: a secondary analysis of the REPEAT study

Lukas M Müller-Wirtz  1   2 , Thijs A Lilien  3 , William M Patterson  2 , Sascha Ott  4   5 , Roland C E Francis  1 , Marcelo Gama de Abreu  6   7 , Ary Serpa Neto  8   9 , Reinout A Bem  3 , David M P van Meenen  10   11 , Marcus J Schultz  11   12 ; REPEAT investigators
Collaborators, Affiliations

Individual and combined effects of chemical and mechanical power on postoperative pulmonary complications: a secondary analysis of the REPEAT study

Lukas M Müller-Wirtz et al. Anaesthesia. .

Abstract

Introduction: Intra-operative supplemental oxygen and mechanical ventilation expose the lungs to potentially injurious energy. This can be quantified as 'chemical power' and 'mechanical power', respectively. In this study, we sought to determine if intra-operative chemical and mechanical power, individually and/or in combination, are associated with postoperative pulmonary complications.

Methods: Using an individual patient data analysis of three randomised clinical trials of intra-operative ventilation, we summarised intra-operative chemical and mechanical power using time-weighted averages. We evaluated the association between intra-operative chemical and mechanical power and a collapsed composite of postoperative pulmonary complications using multivariable logistic regression to estimate the odds ratios related to the effect of 1 J.min-1 increase in chemical or mechanical power with adjustment for demographic and intra-operative characteristics. We also included an interaction term to assess for potential synergistic effects of chemical and mechanical power on postoperative pulmonary complications.

Results: Of 3837 patients recruited to three individual trials, 2492 with full datasets were included in the analysis. Intra-operative time-weighted average (SD) chemical power was 10.2 (3.9) J.min-1 and mechanical power was 10.5 (4.4) J.min-1. An increase of 1 J.min-1 in chemical power was associated with 8% higher odds of postoperative pulmonary complications (OR 1.08, 95%CI 1.05-1.10, p < 0.001), while the same increase in mechanical power raised odds by 5% (OR 1.05, 95%CI 1.02-1.08, p = 0.003). We did not find evidence of a significant interaction between chemical and mechanical power (p = 0.40), suggestive of an additive rather than synergistic effect on postoperative pulmonary complications.

Discussion: Both chemical and mechanical power are independently associated with postoperative pulmonary complications. Further work is required to determine causality.

Keywords: anaesthesia; chemical power; mechanical power; oxygen; postoperative complications.

Plain language summary

When people have surgery, they often need extra oxygen and a machine to help them breathe. But this can sometimes put stress on the lungs and cause problems afterward. In this study, doctors wanted to see if the amount of energy used by the oxygen and the breathing machine (called ‘chemical power’ and ‘mechanical power’) could be linked to lung problems after surgery. Doctors looked at data from three big studies involving patients who had surgery with breathing support. They measured how much chemical and mechanical power was used during surgery and averaged it over time. Then, they checked to see if people who had more of this power used during surgery were more likely to have breathing or lung problems afterward. They also checked if using both types of power together made things worse. Out of 3837 patients, 2492 had complete information and were included in the study. On average, the chemical power used was about 10.2 and the mechanical power was about 10.5 (measured in special units called Joules per minute). For every small increase in chemical power, the chance of lung problems after surgery went up by 8%. For the same increase in mechanical power, the chance went up by 5%. The two types of power didn't seem to make each other worse when used together. The study showed that both chemical and mechanical power during surgery can raise the risk of lung problems afterward. More research is needed to understand if one causes the other, or if something else is going on.

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References

    1. Gattinoni L, Tonetti T, Cressoni M, et al. Ventilator‐related causes of lung injury: the mechanical power. Intensive Care Med 2016; 42: 1567–1575. https://doi.org/10.1007/s00134‐016‐4505‐2.
    1. Chiumello D, Gotti M, Guanziroli M, et al. Bedside calculation of mechanical power during volume‐ and pressure‐controlled mechanical ventilation. Crit Care 2020; 24: 417. https://doi.org/10.1186/s13054‐020‐03116‐w.
    1. Schuijt MTU, Hol L, Nijbroek SG, et al. Associations of dynamic driving pressure and mechanical power with postoperative pulmonary complications–post hoc analysis of two randomised clinical trials in open abdominal surgery. eClinicalMedicine 2022; 47: 101397. https://doi.org/10.1016/j.eclinm.2022.101397.
    1. Elefterion B, Cirenei C, Kipnis E, et al. Intraoperative mechanical power and postoperative pulmonary complications in noncardiothoracic elective surgery patients: a 10‐year retrospective cohort study. Anesthesiology 2024; 140: 399–408. https://doi.org/10.1097/ALN.0000000000004848.
    1. Hol L, Gasteiger L, Mazzinari G, Schultz MJ. Building evidence in perioperative mechanical ventilation – 10 years of randomized trials. Curr Anesthesiol Rep 2024; 15: 7. https://doi.org/10.1007/s40140‐024‐00685‐2.

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