Monitoring of PCO2 by skin surface sensors

The methodology of cutaneous PCO2 measurement and the results of the first clinical studies performed with a newly developed sensor are reported. The in vitro data of the sensor are: sensitivity 55 mV/decade; response time tau 90% = 50 s; drift less than 10% per 24 h; no measurable interference by oxygen and anesthetic gases. At a sensor temperature of 44 degrees C, the correlation between arterial PCO2 and cutaneous PCO2 is significant, with correlation coefficients above 0.95 both in case of neonates and adult patients. The cutaneous PCO2 is, however, consistently higher than arterial PCO2, and a correction of the cutaneous PCO2 value needs to be performed. At 44 degrees C, the time lag between changes of cutaneous PCO2 and arterial PCO2 is about 2-3 min as estimated from capnometric measurements. At lower sensor temperatures, the correlation between arterial and cutaneous PCO2 is still good; however, the physiological response time of the cutaneous PCO2 measurement becomes prohibitively long.