Effect of Therapeutic Hypercapnia on Inflammatory Responses to One-lung Ventilation in Lobectomy Patients

Background: One-lung ventilation (OLV) can result in local and systemic inflammation. This prospective, randomized trial was to evaluate the effect of therapeutic hypercapnia on lung injury after OLV. Method: Fifty patients aged 20 to 60 yr undergoing lobectomy were randomly provided with air or carbon dioxide (partial pressure of carbon dioxide: 35 to 45 mmHg or 60 to 70 mmHg). Peak pressure, plateau pressure, and lung compliance were recorded. Bronchoalveolar lavage fluid (BALF) and blood samples were collected. Adverse events were monitored. The primary outcome was the concentration of BALF tumor necrosis factor, and the secondary outcomes were serum cytokine concentrations. Results: The BALF tumor necrosis factor was lower in the carbon dioxide group than in the air group (median [range], 51.1 [42.8 to 76.6] vs. 71.2 [44.8 to 92.7]; P = 0.034). Patients in the carbon dioxide group had lower concentrations of serum and BALF interleukin (IL)-1, IL-6, and IL-8, but higher serum concentrations of IL-10, accompanied by reduced numbers of cells and neutrophils as well as lower concentrations of protein in the BALF. Also, patients in the carbon dioxide group had lower peak (mean SD, 22.2 +/- 2.9 vs. 29.8 +/- 4.6) and plateau pressures (20.5 +/- 2.4 vs. 27.1 +/- 2.9), but higher dynamic compliance (46.6 +/- 5.8 vs. 38.9 +/- 6.5). Furthermore, patients in the carbon dioxide group had higher postoperation oxygenation index values. Ten patients experienced slightly increased blood pressure and heart rate during OLV in the carbon dioxide group. Conclusion: Under intravenous anesthesia, therapeutic hypercapnia inhibits local and systematic inflammation and improves respiratory function after OLV in lobectomy patients without severe complications.