Transcutaneous Monitoring and Pulse Oximetry RC 290

TCM: PO2 and PCO2 via Skin Electrodes Continuous and non-invasive Digital readout plus hard copy TCM values show values of O2 and CO2 at tissue level These values are a affected both by lung function and perfusion TCM used more in infants than adults because infants have thinner skin and less sub-Q fat

TCM System

TCM Electrodes PO2 is a Clark electrode PCO2 is a Severinghaus electrode Electrodes should not be placed over bone Electrodes may be heated to “arterialize” the site Heated electrodes need to be moved every 4-8 hours Water or a sealant solution should be placed on the skin to prevent an air bubble from forming between the skin and electrode Electrodes usually “sloped”, ie 2 point calibration

TCM Monitor Unit Controls for electrode temperature and high and low limits for alarms Digital display of TCM values Power or energy indicator (shows how much is being used to heat electrode This is the perfusion monitor!

Power/Energy Level Changes After the unit is started and stabilizes, the relative heating power indicator is zeroed If it starts to have a positive deflection, this means it is taking more power to keep the electrode heated to the set temperature This means perfusion has increased!

Power/Energy Level Changes (cont.) If relative power starts to have a negative deflection, this means it is taking less energy to keep the electrode at the set temperature This indicates decreased perfusion! TCM values and arterial values have poor correlation with decreased perfusion!

If relative heat energy does not have a negative deflection, correlation between TCM and arterial values is good Decreased TCM PO2 without negative deflection of relative heat energy usually indicates a pulmonary problem

A negative deflection in relative heating power with a drop in TCM PO2 usually indicates a perfusion problem Not a lung problem!

TCM Uses Making ventilator changes Effects of activities on infant Feeding, handling, etc Effects of respiratory therapies O2 changes, PD & P, suctioning , etc Identifying the direction of shunt in PDA

Shunt Direction in PDA Using TCM Two TCM PO2 electrodes One is placed pre-ductal and the other is post-ductal If difference is greater than 15 mmhg, PDA is R-L

TCM Does Not Replace ABGs It does cut down on the number of ABGs and is a good indicator of when they need to be done

Pulse Oximetry in Neonates Advantages Less costly than TCM Less maintenance than TCM Disadvantages Does not give a direct indication of perfusion Can not assess ventilation/PCO2 Does not give good indication of hyperoxia Alarms should be set between 92% and 95%

Pulse Oximetry Is Used More for Surveillance than Diagnosis

Time to relax!