Background: Measurements of transcutaneous carbon dioxide tension (PtcCO2) with current devices are proven to provide clinically acceptable agreement with measurements of partial arterial carbon dioxide tension (PaCO2) in several settings but not during cardiopulmonary exercise testing (CPET). Objectives: The primary objective of this study was to investigate the agreement between PaCO2 and PtcCO2 measurements (using a Tosca 500 with a Tosca sensor 92) during CPET. A secondary objective was to investigate the agreement between arterial and transcutaneous oxygen saturation (SaO2, SpO2) as measured with this sensor during CPET. Methods: In patients with various pulmonary diseases, PtcCO2 and SpO2 were continuously measured and compared with arterial blood gas samples during CPET. A maximum bias of 0.5 kPa and 95% limits of agreement (LOA) of 1 kPa between carbon dioxide pressure (PCO2) measurements were determined as clinically acceptable. Results: In total 101 ‘paired’ arterial and transcutaneous measurements were obtained from 21 patients. Bias between PaCO2 and PtcCO2 was –0.03 kPa with LOA from –0.78 to 0.71 kPa. Bias between SaO2 and SpO2 was –1.0% with LOA from –2.83 to 0.83%. Conclusions: Transcutaneous estimations of PCO2 and SpO2 are accurate and can be used in CPET, circumvening the need for arterial cannulation.

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