Evaluation of transcutaneous CO2 responses following acute changes in PaCO2 in healthy subjects

Respirology. 2009 Apr;14(3):436-42. doi: 10.1111/j.1440-1843.2008.01442.x. Epub 2009 Dec 16.


Background and objective: Transcutaneous blood gas-monitoring systems with miniaturized SpO(2) (peripheral blood oxygen saturation)/PCO(2) combined sensors (TOSCATM) have been widely used. There are no reports of the inter- and intra-individual variability in transcutaneous measurements of PaCO(2) (PtcCO(2)) in response to acute progressive changes in PaCO(2). This study examined inter- and intra-individual variability of PtcCO(2) measurements under semi-steady-state conditions, and characterized the behaviour of PtcCO(2) in response to acute progressive changes in PaCO(2).

Methods: Subjects breathed mixed gases through a mouthpiece connected to an automatic arterial blood gas controller. Using end-tidal PCO(2) and PO(2) as guides, PaCO(2) was controlled to increase and/or decrease between baseline and > or = 60 mm Hg, in a stepwise (n = 9) or progressive fashion (n = 6). Arterial blood was sampled when needed.

Results: Intra-individual correlation coefficients between PtcCO(2) and PaCO(2) were excellent in all subjects (0.971-0.989); however, the slope of the regression line varied among subjects (1.040-1.335). Bias and limits of agreement (+/- 2 SD from bias) between PtcCO(2) and PaCO(2) were -1.8 mm Hg and -7.7 to 4.1 mm Hg. Changes in PtcCO(2) in response to acute progressive changes in PaCO(2) also varied among subjects.

Conclusion: The PtcCO(2) measurement system allows reliable estimation of PaCO(2) in a given subject. However, caution is needed when comparing absolute values between subjects or when acute changes in PaCO(2) occur.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Gas Monitoring, Transcutaneous / methods*
  • Breath Tests / methods*
  • Carbon Dioxide / analysis
  • Carbon Dioxide / metabolism*
  • Exhalation / physiology*
  • Humans
  • Observer Variation
  • Oxygen / metabolism
  • Pulmonary Gas Exchange / physiology
  • Young Adult


  • Carbon Dioxide
  • Oxygen