The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

EVALUATION OF A NEW DIGITAL TRANSCUTANEOUS TCPCO2 & SpO2 COMBINATION SENSOR AND ITS COORELATION TO ABG PaCO2 MEASUREMENTS

Daniel D. Rowley, BS, RRT-NPS, RPFT, Brian K. Walsh, BS, RRT-NPS, RPFT Barry Young, BS, RRT, Frank J. Caruso, BS, RRT Pulmonary Diagnostics and Respiratory Therapy Services University of Virginia Health System, Charlottesville, Virginia

BACKGROUND: Obtaining ABGs for measuring PaCO2 can be painful for patients, time consuming and perilous for healthcare providers. In an attempt to improve patient satisfaction while reducing risks associated with percutaneous and invasive ABG sampling, we evaluated the CO2-O2XYS Digital Sensor made by SenTec AG (http://www.sentec.ch/) to determine if it would yield clinically accurate TCPCO2 measurements when compared to ABG PaCO2 samples.

METHOD:
25 patients ranging between 10 months to 79 years of age were randomly and prospectively identified as needing an ABG for clinical indications unrelated to the TCPCO2 device evaluation. Patient demographic and clinical data points were obtained and recorded while the SenTec sensor was self-calibrating. After sensor calibration was confirmed the sensor was attached to the tragus of each patient's ear per manufacture's guidelines. An ABG was obtained 15 minutes after sensor application and simultaneous TCPCO2 measurement were recorded. ABG samples were subsequently analyzed with a Rapidpoint® 405 analyzer and the measured PaCO2 levels were recorded next to the corresponding TCPCO2 values.

RESULTS: 20% of the patients required vasopressors at the time of analysis. We found a reliable correlation between the TCPCO2 and the PaCO2 (R2-0.61, p < 0.001). Neither age nor temperature appears to affect the accuracy. However, we observed clinically significant (> 5 torr) variation in 3 patients, 2 of which required vasopressors and were known to have peripheral vascular disease.

CONCLUSION: In our patient sampling the SenTec TCPCO2 monitor was proven to have a good correlation with PaCO2. This can reduce the need for ABG needle sticks in many patients and reduce the overall cost and patient discomfort associated with the procedure. The difference between the CO2 measurements could be related to the standard deviation of the two compared devices and/or the identified pre-existing medical condition. We find this device especially intriguing in the clinical settings of non-invasive positive pressure ventilation, adult high frequency oscillatory ventilation where end tidal CO2 measurement and clinical assessment can be difficult or impossible, and in the Emergency Department for trending CO2 levels in patients presenting with COPD exacerbation. Further studies will need to be done to determine if temperature and/or vascular disease plays a clinically significant roll in the overall accuracy of this TCPCO2 measuring device.

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