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

Chest. 2005 Feb;127(2):585-8. doi: 10.1378/chest.127.2.585.


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.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anesthesia, Local*
  • Blood Gas Monitoring, Transcutaneous / instrumentation*
  • Conscious Sedation*
  • Female
  • Humans
  • Hydrocodone / administration & dosage
  • Hydrocodone / adverse effects
  • Hypoventilation / diagnosis*
  • Infusions, Intravenous
  • Intraoperative Complications / diagnosis*
  • Male
  • Meperidine / administration & dosage
  • Meperidine / adverse effects
  • Midazolam / administration & dosage
  • Midazolam / adverse effects
  • Middle Aged
  • Monitoring, Intraoperative / instrumentation*
  • Oximetry / instrumentation*
  • Prospective Studies
  • Risk Factors
  • Signal Processing, Computer-Assisted / instrumentation*
  • Thoracoscopy*


  • Hydrocodone
  • Meperidine
  • Midazolam