IS TRANSCUTANEOUS PO2 MONITORING DURING EXERCISE A RELIABLE ALTERNATIVE TO ARTERIAL PO2 MEASUREMENTS

Arterial PO2 measurement during exercise is an important part in the e valuation of pulmonary disease but requires an intra-arterial cannula. However, in clinical work it would be preferable to assess PO2 non-in vasively. To evaluate such a technique, simultaneous measurements of t ranscutaneous PO2 (tcPO(2)) and arterial PO2 (PaO2), sampled from an i ndwelling arterial radial cannula, were made before, during and after a fatigue or symptom-limited bicycle exercise test in 16 patients refe rred to hospital because of dyspnoea. In total 181 paired measurements were made. Mean values (range) of PaO2 and tcPO(2) were 11.2 kPa (5-1 6) and 9.5 (5-13.3), respectively. The correlation coefficient between PaO2 and TcPO2 was only 0.36 (P<10(-5)). By normalizing the values of tcPO(2) and PaO2 to corresponding values at supine rest before exerci se, the correlation coefficient increased to 0.80 (P<10(-6)). Using Pa O2 as golden standard, tcPO(2) described the trend in pO(2) during exe rcise reasonably well in all cases and this information is often suffi cient for assessing the degree of pulmonary insufficiency. Thus, trans cutaneous blood gas monitoring during exercise is useful for clinical evaluation of pulmonary disease, but a single arterial blood sample at rest before exercise is recommended for baseline correlation.