Transcutaneous Blood Gas MonitoringA Multi-Disciplinary Clinical Competency New England Medical Center Respiratory Care Programs Rev 1 03-01-01
Transcutaneous Monitoring: Target Population Neonates, infants, and small children • Transcutaneous monitoring measures skin-surface PO2 and PCO2 • Estimates arterial partial pressure of oxygen and carbon dioxide (PaO2 and PaCO2) • Induces hyperperfusion by local heating of the skin • Measures partial pressure of oxygen and carbon dioxide electrochemically
Transcutaneous Monitoring: Target Population Neonates, infants, and small children • Measures partial pressure of oxygen and carbon dioxide electrochemically
Transcutaneous Monitoring: INDICATIONS • The need to monitor the adequacy of arterial oxygenation and/or ventilation • The need to quantitate the response to diagnostic and therapeutic interventions as evidenced by PtcO2 and/or PtcCO2 values
Transcutaneous Monitoring: CONTRAINDICATIONS • Poor skin integrity • Adhesive allergy
TCM Monitoring: HAZARDS/COMPLICATIONS False-negative and false-positive results may lead to inappropriate treatment of the patient • It is appropriate to correlate non-invasive values with arterialized blood values • Tissue injury may occur at the measuring site
TCM : DEVICE LIMITATIONS/VALIDATION OF RESULTS: TCM monitoring is an indirect measurement • Does not reflect oxygen delivery or oxygen content. • Complete assessment of oxygen delivery requires knowledge of hemoglobin, saturation, and cardiac output • PtcCO2 accuracy is proportional to several factors: • Site placement • Probe temperature • Perfusion • Body temperature
TCM : DEVICE LIMITATIONS/VALIDATION OF RESULTS: TCM monitoring is an indirect measurement • The following factors may increase the discrepancy between arterial and transcutaneous values-- • hyperoxemia (PaO2 > 100 torr) • a hypoperfused state (shock, acidosis) • Improper electrode placement or application • Vasoactive drugs • The nature of the patient's skin and subcutaneous tissue (skinfold thickness, edema)
TCM Monitoring: Validation • Arterial blood gas values should be compared to transcutaneous readings taken at the time of arterial sampling in order to validate the transcutaneous values. • Validation should be performed initially and periodically as dictated by the patient's clinical state.
TCM Monitoring: Validation • During validation studies in patients with functional shunts, electrode site and arterial sampling site should be on the same side of the shunt. • When disparity exists possible causes should be explored before results are reported.
TCM Monitoring: Reducing disparity • Monitoring at alternate sites • Recalibration • Re-membrane TCM probe • Increasing TCM probe temperature • (Usually obligates clinician to increase site change frequency) • Substitution of instrument
TCM ASSESSMENT OF NEED: • When direct measurement of arterial blood is not available/accessible • When lab turn-around time is excessive • PtcO2 and/or PtcCO2 measurements may temporarily suffice if the limitations of the data are appreciated
TCM ASSESSMENT OF NEED: • Appropriate for continuous and prolonged monitoring (eg, during mechanical ventilation, CPAP, and supplemental oxygen administration) • PtcO2 diagnostic values: • assessment of functional shunts (eg, persistent pulmonary hypertension of the newborn, PPHN, or persistent fetal circulation • Useful to determine the response to oxygen challenge in the assessment of congenital heart disease
TCM FREQUENCY: • Transcutaneous blood gas monitoring should be continuous for development of trending data. • Spot checks are not appropriate Reference: Adapted from AARC Clinical Practice Guideline Transcutaneous Blood Gas Monitoring for Neonatal & Pediatric Patients Respir Care 1994:39(12):1176-1179)