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

Prashant N Chhajed, Bruno Kaegi, Rajeevan Rajasekaran, Michael Tamm
Chest. 2005 Feb;127(2):585-8.

• 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.
  
  
• AIMS
  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%).
  
  
• CONCLUSION
  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.

2 - Cutaneous carbon dioxide monitoring in adults.

Prashant N Chhajed, Ludwig T Heuss, Michael Tamm
Current Opinion in Anaesthesiology. 17(6):521-525, December 2004.

• PURPOSE OF REVIEW
  Arterial blood gas analysis is the 'gold standard' method to measure the arterial partial pressure of carbon dioxide (PaCO2). However, arterial sampling including arterial catheterization is invasive
  and expensive. Cutaneous carbon dioxide tension (PcCO2) measurement is used as a noninvasive surrogate measure of PaCO2, which is used to either estimate PaCO2 or determine trend changes
  in the measurement. There has been considerable progress in the technical aspects of PcCO2 monitoring in the last few years. In this article, we evaluate recent developments and the renewed interest in the subject of PcCO2 monitoring in adults and discuss the technical aspects, clinical applications and the future outlook for this technique in the clinical setting.
  
  
• RECENT FINDINGS
  With evolution in technology, PcCO2 monitoring is now less cumbersome than before. Combined PcCO2 measurement and pulse oximetry is now possible with a single earlobe sensor.
  
  
• SUMMARY
  The clinical settings in which PcCO2 monitoring can be applied include patient monitoring during
  and after anaesthesia, patients receiving noninvasive ventilation, post extubation, endoscopy
  under sedation, the sleep laboratory and the lung function laboratory. Although there is an
  overlap of the clinical indications when both PcCO2 and end-tidal carbon dioxide monitoring may
  be used, it is our opinion that both these methods have independent indications and are sometimes also complementary to each other in patient care.
  
  (C) 2004 Lippincott Williams & Wilkins, Inc.

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