[Invasive or transcutaneous measurements of oxygen saturation and blood gases? An evaluation of pulse oximetry and transcutaneous measurement of PO2 and PCO2 during rest and exercise].

Arterial and transcutaneous measurements of the oxygen saturation (SO2), the partial pressure of oxygen (PO2) and the partial pressure of carbon dioxide (PCO2 were compared during rest before and after cycling, and during submaximal and maximal exercise, in 12 adult patients with cystic fibrosis. SO2 was measured non-invasively using two different pulse oximeters (Radiometer and Ohmeda, respectively) and PO2 and PCO2 were registered with a transcutaneous electrode (Radiometer). The coefficients of correlation between arterial and transcutaneous values were respectively 0.95 (Radiometer) and 0.85 (Ohmeda) for SO2, 0.77 for PO2, and 0.75 for PCO2. On average the differences between arterial and transcutaneous values were small, but varied by 3-4% (2SD) for SO2, 2.0 kPa for PO2 and 1.0 kPa for PCO2. Our results indicate that pulse oximetry is a reasonably good way of detecting severe arterial hypoxemia during work, whereas the transcutaneous measurements of PO2 and PCO2 show such large variations that this method cannot be recommended for clinical use.