BLOOD-GAS MEASUREMENT DURING EXERCISE - A COMPARATIVE-STUDY BETWEEN ARTERIALIZED EARLOBE SAMPLING AND DIRECT ARTERIAL PUNCTURE IN ADULTS

Sampling arterialized earlobe blood is thought to be easier and less p ainful than direct arterial puncture, and to allow measurement of bloo d gas values during exercise without the need to insert an arterial ca nnula. However, arterialized earlobe oxygen tension (PO2) often undere stimates arterial PO2, at rest, and is not fully validated during exer cise. We have therefore conducted a prospective study to compare value s of PO2 and carbon dioxide tension (PCO2) and the discomfort experien ced by adult subjects undergoing the two methods of blood sampling dur ing exercise. Seventy consecutive adult patients were studied. Blood s amples were drawn simultaneously from the radial artery and arterializ ed earlobe of each patient during the last minute of an 8 min exercise . Values of PO2 and PCO2 were measured by means of blood gas electrode s. The correlation coefficients between the two samples were 0.92 for PO2 and 0.91 for PCO2. However, the bias and the limits of agreement b etween the two methods were wide for PO2 (mean+/-2sD of the difference s between the two methods: 0.63+/-1.50 kPa (4.7+/-11.2 mmHg)). The bia s and the limits of agreement were smaller for PCO2. Patients felt tha t the earlobe method was not associated with less discomfort than radi al artery puncture. We conclude that arterialized earlobe blood oxygen tension is not a good substitute for arterial oxygen tension during e xercise, and should not be used to assess arterial oxygen tension in a dults during exercise.