2004 OPEN FORUM Abstracts
COMPARISON OF CUTANEOUS CARBON DIOXIDE TENSION AND OXYGEN SATURATION MEASUREMENTS USING A NEW COMBINED DIGITAL SENSOR WITH ARTERIAL BLOOD GAS VALUES
Prashant
N Chhajed, MD, FCCP 1, Ludwig Heuss, MD 2,
Michael Tamm, MD 1Divisions of Respiratory
Medicine1 and Gastroenterology2, University
Hospital Basel, Switzerland
Background:
Various medical procedures are commonly performed using conscious
sedation. Oxygen saturation measured with a pulse oximeter does not
completely reflect hypoventilation and carbon dioxide monitoring is
desirable. Recently, a new digital device which measures both
oximetry and cutaneous carbon dioxide tension (PcCO2) has
been developed. Having the possibility to measure a reliable non
invasive surrogate marker of arterial carbon dioxide tension along
with pulse oximetry might improve patient safety during medical
procedures such as bronchoscopy and thoracoscopy carried out under
conscious sedation. The other areas where this might have potential
application is the intensive care unit to monitor non invasive
ventilation, weaning from mechanical ventilation or post extubation,
in the sleep laboratory to titrate non invasive ventilation pressures
using continuous carbon dioxide tension monitoring as opposed to only
diurnal blood gas measurements to check the arterial carbon dioxide
tension.
Aim:
Assess the accuracy of a newly developed combined PcCO2
and oximeter (SpO2) monitor.
Method:
A new combined digital earlobe sensor (Sentec
AG, Therwil, Switzerland) measuring SpO2 (%) and PcCO2
(mm Hg) was used. This device measures the PcCO2 using a
Severinghaus-type electrochemical sensor and the SpO2
using conventional optical pulse oximetry sensors. The sensor is
heated to a constant surface temperature of 42 degrees Celsius. It
undergoes regular automatic calibration when it is placed on the
docking station in between procedures. The calibration and
equilibration time are about five minutes each.
Results:
Accuracy of the combined SpO2/PcCO2 earlobe
sensor was compared in 86 patients with 106 PaCO2 and
SaO2 blood gas values obtained by arterial puncture. In
the lung function laboratory (90 samples) an average of two blood-gas
analyzers (ABL 500 and ABL 725, Radiometer, Copenhagen, Denmark) was
used and in the intensive care unit (16 samples) values were
available from one blood gas analyzer (ABL 735, Radiometer,
Copenhagen, Denmark). The correlation coefficient for carbon dioxide
tension and oxygen saturation comparing measurements of the combined
earlobe sensor and arterial blood gas analysis were r = 0·95
and r = 0·91 respectively.
Conclusion:
This combined SpO2/PcCO2 sensor
showed good correlation with measurements obtained with arterial
blood gas analysis. This novel approach to detect and monitor both
hypoxemia and hypoventilation has potential applications in patient
management in the ICU, in the sleep laboratory to quantify
hypoventilation and to enhance patient safety during procedures
performed under conscious sedation such as bronchoscopy and medical
thoracoscopy.