Mechanical ventilation induces changes in exhaled breath condensate of patients without lung injury

Measurement of biomarkers in exhaled breath condensate (EBC) may be useful for monitoring lung inflammation and injury in mechanically ventilated patients. The aim of this study was to analyze changes in biomarkers of inflammation in EBC associated with prolonged mechanical ventilation.

EBC samples were collected from critically ill patients weaning from mechanical ventilation without lung disease and from healthy nonsmokers. The following parameters were measured: pH after helium deaeration, nitrogen oxide and 8-isoprostane concentrations.

EBC was obtained from 10 patients and 20 controls. Ventilation time before the start of sample collection was 250 (85-714)h. The post-deaeration pH of EBC samples was significantly lower in ventilated patients than controls (7.50 [7.28-7.70] vs 8.07 [7.60-8.40]; P=0.008). Ventilation time before sample collection inversely correlated with pH (r=-0.636; P=0.048). A significantly higher concentration of nitrogen oxide (muM) was seen in ventilated patients vs controls (66.22 [22.26-83.13] vs 15.06 [10.73-23.30]; P=0.002), whereas levels of 8-isoprostane (pg/mL) were not significantly different between both groups (5.73 [4.0-11.4] vs 9.09 [6.63-11.43]; P=0.169). The nitrogen oxide concentration correlated negatively with dynamic compliance (r=-0.952; P<0.001) and positively with respiratory rate (r=0.683; P=0.029).

EBC analysis is a non-invasive technique that can be used to monitor ventilated patients. Mechanically ventilated patients had higher EBC acidity and nitrogen oxide concentrations. Duration of ventilation correlated with breath condensate pH.