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

Background: Changes in PaCO2 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 (PeCO(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, PcCO2 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 PcCO2 (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 PcCO2 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 PcCO2 measurement from baseline were 13.0 mm Hg and 13.2 +/- 5.3 mm Hg (range, 5.5 to 27.8 min 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 PcCO2 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.