1. Transcutaneous Monitoring and Pulse Oximetry
RC 290

2. 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

3. TCM System

4. 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

5. 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!

6. 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!

7. 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!

8. 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

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

10. 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

11. 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

12. 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

13. 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%

14. Pulse Oximetry Is Used More for Surveillance than Diagnosis

15. Time to relax!