Detection of hypoventilation during thoracoscopy: combined cutaneous carbon dioxide tension and oximetry monitoring with a new digital sensor

BACKGROUND: Changes in Paco(2) have not been described during thoracoscopy under sedation-assisted local anesthesia. We hypothesized that hypoventilation might occur secondary to administration of sedatives and decreased ventilation in one lung.Aim: Prospectively measure cutaneous carbon dioxide tension (Pcco(2)) in addition to pulse oximetric saturation (Spo(2)) using a new combined digital sensor to examine the occurrence of hypoventilation during thoracoscopy under sedation-assisted local anesthesia. SETTING: University hospital. METHODS: Following validation studies, Pcco(2) was prospectively measured in 16 consecutive patients undergoing thoracoscopy under sedation-assisted local anesthesia using a combined digital earlobe sensor measuring Spo(2) (percentage) and Pcco(2) (millimeters of mercury). All patients received supplemental oxygen. Routine BP monitoring and Spo(2) was continued. Patients received IV hydrocodone, 5 mg, and intermittent boluses or IV midazolam and pethidine. RESULTS: Mean baseline Pcco(2) measurement was 39.1 +/- 7.2 mm Hg (+/- SD) [range, 27.5 to 50.5 mm Hg], and peak measurement during the procedure was 52.3 +/- 10.3 mm Hg (range, 37.2 to 77 mm Hg) [p < 0.001]. Median and mean changes in Pcco(2) measurement from baseline were 13.0 mm Hg and 13.2 +/- 5.3 mm Hg (range, 5.5 to 27.8 mm Hg), respectively. Mean fall in Spo(2) during the procedure was 4.6 +/- 3.2% (range, 1 to 14%). CONCLUSIONS: Thoracoscopy performed under sedation-assisted local anesthesia is associated with significant hypoventilation. Combined measurement of Spo(2) and Pcco(2) during thoracoscopy is a novel approach in the monitoring of ventilation, enhancing patient safety, and might allow to guide the administration of sedation in a better way.