• Satoshi Fuke, Kenji Miyamoto, Hiroshi Ohira, Megumi Ohira, Nao Odajima, and Masaharu Nishimura.
• First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
• Respirology. 2009 Apr 1;14(3):436-42.

Background And ObjectiveTranscutaneous 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).MethodsSubjects 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.ResultsIntra-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.ConclusionThe 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.

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