Transcutaneous Oxygen (TcPO2) Monitors
Jonathan M. Klein, MD
Peer Review Status: Internally Peer Reviewed
The transcutaneous PO2 monitor (TCM allows for non-invasive measurement of arterial oxygen tension. The prerequisite for accurate correlation of an arterial PO2 value with a transcutaneous PO2 value is creation of constant local vasodilatation by heating the skin. This causes maximal blood flow in the skin with little or no difference between the PO2 value at the arterial and venous ends of the capillary.
The transcutaneous PO2 monitor consists of a combined platinum and silver electrode covered by an oxygen-permeable hydrophobic membrane, with a reservoir of phosphate buffer and potassium chloride trapped inside the electrode. A small heating element is located inside the silver anode. The oxygen monitor consists of a TcPO2 channel, for which high and low alarm limits can be set, a temperature display channel and a heat channel.
The TCM sensor is applied by the nurse to the anterior chest wall or other acceptable site and heated to 44°C. The site will be changed every four hours to avoid erythema and burns to the infant's skin. The electrode will be calibrated by the blood gas technician and recalibrated every eight hours.
The nurse will record the TCM value on the nurse's notes at least once an hour. When correlating the transcutaneous PO2 with an arterial or capillary blood gas sample, the value from the TCM should be recorded 15 seconds after obtaining the blood sample.
An order should be written documenting the desired range of transcutaneous oxygen levels for a given patient. The optimal range for most premature infants will be 50 to 70 mm Hg. Higher limits may be appropriate for large preterm or term infants, especially those at risk of pulmonary hypertension.
If the patient's transcutaneous PO2 stays outside of these limits for more than two to three minutes, the nurse shall increase or decrease the FiO2 by no more than 0.05 until the patient's reading returns to the desired range.
If a change in FiO2 is required for more than five minutes, the House Officer shall be notified of the change in the infant's condition. The change in FiO2 and response of the infant will be documented in the nurse's notes.