Pattern of cytokines and chemokines in exhaled breath condensate is related to the characteristics of mechanical ventilation

Introduction

Ventilator-associated lung injury (VALI) is an inflammatory response of the lung caused by mechanical ventilation (MV) and is related to tidal volumes (TV), positive end-expiratory pressure (PEEP) and peak pressures (P_peak) [1]. In experimental settings, VALI is characterized by a local inflammatory response measured in tissue or lavate. It is difficult to obtain this material in the critically ill [2]. Exhaled breath condensate (EBC) is obtained in patients on MV using an easy non-invasive technique. In this pilot study we examined the relation between levels of inflammatory proteins in EBC of patients on MV and characteristics of MV.

Methods

A prospective study was performed in 13 patients on MV. EBC was obtained from the connection-swiffle between ventilator and tube. IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, IFNγ, MCP-1 and MIP-1β were determined by multiplex immunoassay. Levels of inflammatory mediators were correlated with parameters of MV.

Results

In 13 (seven males) patients, 29 samples were obtained. Median age of the patients was 69 years, median APACHE II score 25 points. Samples were taken during MV: seven during pressure control (PC) and 22 during pressure support (PS) mode. Median P_peak was 18 cmH₂O, median PEEP 8 cmH₂O, median TV 7.22 ml/kg and median P/F ratio 33.62 kPa. Levels of all inflammatory proteins except for IL-12 were lower in patients on PC, reaching statistical significance for IL-17 (median PS 1.96 vs. PC 0.96, P = 0.002) and MCP-1 (median PS 0.72 vs. PC 0.38, P = 0.033). Significant lower levels were found in patients ventilated with TV ≤8 for MCP-1 (median TV ≤8 ml/kg 0.75 vs. TV >8 ml/kg 3.41, P = 0.032) and MIP-1β (median TV ≤8 ml/kg 0.00 vs. TV >8 ml/kg 1.30, P = 0.028). Levels of cytokines were lower in case of low P_peak (≤20 cmH₂O) reaching the level of statistical significance for IFNγ (median P_peak ≤20 cmH₂O 0.00 vs. > 20 cmH₂O 6.23, P = 0.025).

Conclusions

In a small group of patients, cytokine and chemokine patterns in EBC were related with characteristics of MV. MV with a TV ≤8 may limit inflammatory response.