Transcutaneously and Arterially Measured PO₂ in Adult Intensive Care Patients

Abstract

The advantage of PO₂ measurement using skin surface electrodes is that it is a simple and noninvasive method which allows continuous recordings to be made. This advantage has made the procedure valuable in treating intensive care patients, and transcutaneous PO₂ measurement has become established as a routine method in neonatology [1, 2]. On the other hand, there are a number of interfering factors associated with determining the PO₂ on the surface of the skin, particularly in the case of critically ill patients, such as severe blood pressure fluctuation in hemodynamically unstable patients, reduced skin circulation due to restricted cardiac output, and skin perfusion changes induced by vasoactive drugs. These factors, along with the fact that the PO₂ permeability of the adult skin is considerably less than that of a neonate, can limit the application of transcutaneous (tc) PO₂ measurement in adult patients undergoing intensive care. A number of questions thus arise:

• 1. To what extent can tcPO₂ values provide information on the arterial blood gases?

• 2. Can the correlation regularly observed between higher arterial PO₂ (PaO₂) values and lower tcPO₂ values be compared interindividually?

• 3. To what extent is PO₂ measurement affected by the diminished blood flow in low output syndrome or by vasoactive drugs?

• 4. How does the critically ill patient with reduced skin perfusion tolerate local monitoring under the sensors?