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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
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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
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 Electrodes
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
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 in Neonates