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.

Electrochemical sensors for invasive and non-invasive monitoring of blood gases.

The need for continuous monitoring of blood gases in critically ill patients has become more and more evident during the past years. Electrochemical sensors appear to be most appropriate for such measurements because of their simplicity, ease of use and low cost. Intravascular sensors and skin surface sensors for pO2 and pCO2 are available today in different degrees of technical maturity.

Interference of anesthetic gases at skin surface sensors for oxygen and carbon dioxide.

Several variables may account for the response of electrochemical skin surface PO2 sensors to anesthetic gases: cathode material and size, pH of the electrolyte and membrane material. These variables cannot be chosen arbitrarily and their influence has been tested with two types of sensors. In one type (LSC), a large size cathode (mm range) and a membrane with low permeability for oxygen such as mono-axially oriented polyethylene is used.

An electrochemical sensor for continuous intravascular oxygen monitoring.

The intravascular PO2 sensor described in this paper essentialal routine use. The small dimensions of the sensor permit its introduction into the vessel through a conventional guiding catheter size 4 F or larger. With 5 F catheters, simultaneous blood sampling and/or blood pressure measurement is possible.

Principle and characteristics of the ROCHE tissue pH electrode.

A miniaturized probe for continuous measurement of tissue (interstitial fluid) pH is described. The electrode design follows closely the concept described by Stamm and co-workers. The pH sensitive tip has a length of 1 mm and is made of a Li-Ba-Si glass of low electrical resistivity.

A fast stabliization technique for oxygen sensors with low cathode current densities.

After application of the polarization voltage to a newly prepared oxygen sensor, an initial stabilization of several minutes to a few hours is required. The electrochemical phenomena accounting for this stabilization process are discussed. By far the slowest reaction is the change of the oxidation state of the noble metal cathode after application of the polarization voltage.

Reliability of cutaneous oxygen measurement by skin sensors with large-size cathodes.

The oxygen partial pressure may be measured cutaneously by directly heated PO2 sensors attached to the surface of the skin. The use of a large-size cathods (diameter 4 mm) allows one to obtain an average PO2 value over a sufficiently large skin area. The permeability of the membrane for oxygen has to be kept low to prevent a disturbance of the oxygen profile in the cutaneous tissue as a result of the oxygen consumption of the sensor.

Skin sensors for continuous oxygen monitoring of newborns.

Since the introduction of the technique of cutaneous1 pO2 measurement by directly heated oxygen sensors in 1972, the clinical applications and limitations of this new method have been extensively investigated. The method has proven to be of particular value in monitoring of high risk newborns as it affords the possibility of continuously monitoring clinically significant changes in the oxygenation state of the newborn. In this paper, methodological criteria for the assessment of the reliability of cutaneous pO2 monitoring are discussed.

An instrument for the rapid determination of L-lactate in biological fluids.

An analyzer for lactate has been developed based upon an electrochemical-enzymatic method. It allows the determination of lactate within 2 to 3 minutes after sample collection. The instrument is capable of performing up to 20 measurements per hour.