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. 2020 Dec 18;8(Suppl 1):74.
doi: 10.1186/s40635-020-00356-6.

The effects of tidal volume size and driving pressure levels on pulmonary complement activation: an observational study in critically ill patients

Friso M de Beer  1   2   3 , Luuk Wieske  4   5   6 , Gerard van Mierlo  7 , Diana Wouters  7 , Sacha Zeerleder  8   7 , Lieuwe D Bos  4   5 , Nicole P Juffermans  4   5 , Marcus J Schultz  4   5   9   10 , Tom van der Poll  11   12 , Wim K Lagrand  4   5 , Janneke Horn  4   5 ; BASIC–study group
Collaborators, Affiliations

The effects of tidal volume size and driving pressure levels on pulmonary complement activation: an observational study in critically ill patients

Friso M de Beer et al. Intensive Care Med Exp. .

Abstract

Background: Mechanical ventilation can induce or even worsen lung injury, at least in part via overdistension caused by too large volumes or too high pressures. The complement system has been suggested to play a causative role in ventilator-induced lung injury.

Aims and methods: This was a single-center prospective study investigating associations between pulmonary levels of complement activation products and two ventilator settings, tidal volume (VT) and driving pressure (ΔP), in critically ill patients under invasive ventilation. A miniature bronchoalveolar lavage (BAL) was performed for determination of pulmonary levels of C5a, C3b/c, and C4b/c. The primary endpoint was the correlation between BAL fluid (BALF) levels of C5a and VT and ΔP. Levels of complement activation products were also compared between patients with and without ARDS or with and without pneumonia.

Results: Seventy-two patients were included. Median time from start of invasive ventilation till BAL was 27 [19 to 34] hours. Median VT and ΔP before BAL were 6.7 [IQR 6.1 to 7.6] ml/kg predicted bodyweight (PBW) and 15 [IQR 11 to 18] cm H2O, respectively. BALF levels of C5a, C3b/c and C4b/c were neither different between patients with or without ARDS, nor between patients with or without pneumonia. BALF levels of C5a, and also C3b/c and C4b/c, did not correlate with VT and ΔP. Median BALF levels of C5a, C3b/c, and C4b/c, and the effects of VT and ΔP on those levels, were not different between patients with or without ARDS, and in patients with or without pneumonia.

Conclusion: In this cohort of critically ill patients under invasive ventilation, pulmonary levels of complement activation products were independent of the size of VT and the level of ΔP. The associations were not different for patients with ARDS or with pneumonia. Pulmonary complement activation does not seem to play a major role in VILI, and not even in lung injury per se, in critically ill patients under invasive ventilation.

Keywords: Bronchoalveolar lavage; C5a; Complement; Complement activation; Complement component 5; Critical care; Driving pressure; Intensive care; Mechanical ventilation; Tidal volume.

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Conflict of interest statement

The authors declare that they have no competing interest.

Figures

Fig. 1
Fig. 1
Flow of patients. ICU intensive care unit, SIRS systemic inflammatory response syndrome, BASIC-study ‘Biomarker Analysis in Septic Intensive Care patients’-study, BAL bronchoalveolar lavage, BALF bronchoalveolar lavage fluid
Fig. 2
Fig. 2
Complement activation products C5a, C3b/c and C4b/c in BALF of patients without ARDS (open symbols) compared to patients with ARDS (closed symbols); and patients without pneumonia (open symbols) and with pneumonia (closed symbols). Individual data were plotted on a log-scale together with Tukey box plots. ARDS acute respiratory distress syndrome, C complement, BALF bronchoalveolar lavage fluid
Fig. 3
Fig. 3
Associations between complement activation products C5a, C3b/c and C4b/c in BALF and VT and ΔP used prior to BAL. C complement, VT tidal volume, ΔP driving pressures, BALF bronchoalveolar lavage fluid
See this image and copyright information in PMC

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