Evaluation of regional pulmonary function using a bronchoscopic capnometer in patients with COPD

Background: Partial pressure of carbon dioxide (PCO 2 ) measured by capnometer is mainly used to evaluate the respiratory condition of the lungs under ventilator control. Recently, the use of bronchoscopy has been reported in the evaluation of lung function after lobectomy in patients with lung cancer and those with chronic obstruc‐ tive pulmonary disease (COPD), who underwent bronchoscopic lung volume reduction (BLVR). Objectives: To determine the usefulness of bronchoscopic capnometry to assess treatment sites for BLVR. Method: Twenty patients with COPD suspected of having lung cancer who underwent transbronchial biopsy were included. PCO 2 was measured at the healthy side of the segmental bronchus under room air with a capn‐ ometer. Distribution of the percentage of low attenuation area (%LAA) as measured by chest computed tomog‐ raphy (CT), was calculated and compared to end-tidal CO 2 (EtCO 2 ) distribution obtained by the capnometer. Results: All 20 patients displayed homogeneous patterns on CT, but the distribution of EtCO 2 as measured by capnometer was uneven in 3 patients. There was no significant correlation between %LAA and EtCO 2 in the 20 patients, but in 9 patients with higher %LAA values, %LAA correlation significantly with EtCO 2 (r = −0.437, p = 0.023). Conclusions: Capnography was useful in physiologically evaluating local ventilation and perfusion status of the lung. We recommend capnography as an adjunct to CT to assess functional heterogeneity in patients potentially undergoing BLVR.