ABSTRACT
BACKGROUND: Transcutaneous measurements of arterial blood gases (ABG) may decrease the need for repeated arterial puncture in older patients treated for acute cardiac or pulmonary disorders. However, age-related changes in skin perfusion, metabolism, or thickness may alter the validity of the technique. OBJECTIVE: To analyse the agreement between transcutaneous and arterial measurement of PaO2 and PaCO2 in older adults. DESIGN: Prospective descriptive study performed in the intermediate-care unit of a geriatric university hospital and a pulmonary rehabilitation centre. METHODS: 40 patients, aged 82.5+/-8 years (66-97), hemodynamically stable, without vasopressor treatment, underwent simultaneous measurement of arterial blood gases (ABG) and transcutaneous CO2 (TcPCO2) and O2 (TcPO2) with a Radiometer TINA TCM3 capnograph, and a probe T degrees set at 43 degrees C. RESULTS: Correlation between PaCO2 and TcPCO2 was high (r2=0.86) with a low bias (-0.1 mm Hg) and limits of agreement quite compatible with clinical use: (8.3; -8.5 mm Hg). The probe was well tolerated without any cutaneous lesion even after prolonged recordings (up to 8 h). Conversely, although TcPO2 and PaO2 were significantly correlated, the variability around the regression line precludes the use of transcutaneous measurements for monitoring PaO2)in a clinical setting. CONCLUSION: In older subjects, TcPCO2 (but not TcPO2) measurements are reliable when repeated assessment of ABG is warranted.
