Transcutaneous carbon dioxide in severe COPD patients during bronchoscopic lung volume reduction

Patients undergoing bronchoscopy are usually monitored only by pulse oximetry, hence hypoventilation cannot be assessed. Transcutaneous carbon dioxide tension (TcPCO(2)) monitoring is a non-invasive technique to assess hypoventilation. Patients with severe chronic obstructive pulmonary disease (COPD) undergoing bronchoscopy are at increased risk for sedation-induced hypoventilation. The aim of the study was to measure TcPCO(2) using a digital sensor to examine the occurrence of hypoventilation during bronchoscopic lung volume reduction (BLVR).

Combined TcPCO(2) and SpO(2) saturation and arterial blood gases (ABG) were prospectively measured in 15 patients with severe COPD (Mean FEV(1) 29%) undergoing BLVR under conscious sedation with IV midazolam and IV alfentanil.

A highly significant correlation was noted between simultaneous ABG PCO(2) samplings and TcPCO(2) measured (R = 0.85, p < 0.001). Mean baseline TcPCO(2) level was 41.7 ± 10.3 mm Hg (±SD) (range 35-66 mmHg)], and peak measurement during the procedure was 61 ± 17.1 mm Hg (range 41-111 mmHg). The mean increase in TcPCO(2) during bronchoscopy was 19.2 (range 3.7-45 mmHg) [p < 0.0001]. Mean duration of significant hypercapnea (TcPCO(2) > 55 mmHg), observed in 7 (46%) patients, was 9 min (range 0-53).

Bronchoscopy performed under conscious sedation in patients with severe COPD is frequently associated with significant hypoventilation that can only be detected by TcPCO(2) monitoring. Combined measurement of SpO(2) and TcPCO(2) during bronchoscopy enhances patient safety, helps guide administration of sedation, and can alert physicians to the need for anesthesia reversal following completion of bronchoscopic interventions.