Background
The early biological impact of short-term mechanical ventilation on healthy lungs is unknown. We aimed to characterize the immediate tidal volume (VT)-related changes on lung injury biomarkers in patients with healthy lungs and low risk of pulmonary complications.
Methods
Twenty-eight healthy patients for knee replacement surgery were prospectively randomized to volume-controlled ventilation with VT 6 (VT6) or 10 (VT10) mL/kg predicted body weight. General anesthesia and other ventilatory parameters (positive end-expiratory pressure 5 cmH2O, FiO2 0.5, respiratory rate titrated for normocapnia) were managed similarly in the two groups. Exhaled breath condensate (EBC) and blood samples were collected for nitrite, nitrate, tumor necrosis factor α, interleukins-1β, 6, 8, 10, 11, neutrophil elastase (NE), and Clara Cell protein 16 (CC16) measurements, at the onset of ventilation and 60 min later.
Results
No significant differences in biomarkers were detected between the VT groups at any time. The coefficient of variation of EBC nitrite and nitrate decreased in the VT6 but increased in the VT10 group after 60-min ventilation. Sixty minute ventilation significantly increased plasma NE levels in the VT6 (35.2 ± 30.4 vs. 56.4 ± 51.7 ng/mL, P = 0.008) and CC16 levels in the VT10 group (16.4 ± 8.8 vs. 18.7 ± 9.5 ng/mL, P = 0.015). EBC nitrite correlated with plateau pressure (r = 0.27, P = 0.042) and plasma NE (r = 0.44, P = 0.001). Plasma CC16 correlated with compliance (r = 0.34, P = 0.014).
Conclusion
No tidal volume-related changes were observed in the selected lung injury biomarkers of patients with healthy lungs after 60-min ventilation. Plasma NE and plasma CC16 might indicate atelectrauma and lung distention, respectively.