Is preoperative hypercapnia a justified exclusion criterion for lung volume reduction surgery?

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was whether potential surgical candidates for lung volume reduction surgery (LVRS), who have preoperative hypercapnia, should be excluded on this basis. Using the reported search, 45 papers were found, of which 14 represented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. Of these, seven papers showed a significant (P < 0.05) improvement in postoperative forced expiratory volume in 1 second (FEV1) at up to 6 months in hypercapnic patients. There were six papers which found significant decreases in postoperative arterial carbon dioxide partial pressures (PaCO2) levels following LVRS up to 6 months. There were three papers which showed significant (P < 0.05) improvements in the 6-min walk test in hypercapnic patients following LVRS. Only two papers showed an increased operative mortality in the hypercapnic group compared to the normocapnic group, while nine papers did not find a difference in perioperative mortality. The only randomized controlled study, the landmark NETT study, excluded patients with severe hypercapnia (PaCO2 >55 mmHg and >60 mmHg) and the mean PaCO2 in the surgical and medical group were 43.3 ± 5.9 and 43.0 ± 5.8, respectively. We conclude that the evidence is not strong enough to consider hypercapnia in isolation as high risk or unsuitable for LVRS.