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Canadian Health&Care Mall: Monitoring Carbon Dioxide Tension and Arterial Oxygen Saturation

Published in Sleep Apnea

Coninvasive respiratoryConinvasive respiratory monitoring has broad applications in the emergency department, in perioperative and intensive care, and for the evaluation of sleep-related breathing disturbances. Whereas arterial oxygen saturation (Sa02) is commonly estimated by pulse oximetry, PaC02 may be estimated from end-tidal carbon dioxide tension or transcuta-neous carbon dioxide tension (PtcC02). Since alterations in ventilation/perfusion matching and the use of noninvasive mask ventilation may reduce the correlation of end-tidal carbon dioxide tension with PaC02, transcutaneous monitoring of PtcC02 is increasingly used if the rapid tracking of transient fluctuations of PaC02 is not essential.

Previous transcutaneous blood gas sensors, which were mainly used in pediatric care, have incorporated PtcC02 in combination with transcutaneous partial pressure of oxygen measurement. However, in adults, transcutaneous partial pressure of oxygen depends heavily on local skin perfusion and does not reliably reflect systemic Pa02. Recently, a novel combined sensor for the measurement of both PtcC02 and pulse oximetric saturation (Sp02) [TOSCA; Linde Medical Sensors; Basel, Switzerland] has been developed. It contains an electrochemical electrode (for PtcC02 measurement), a light emitter/sensor (for Sp02 measurement), and a heating element (to increase local perfusion). The small size of the sensor allows convenient placement on the earlobe. Since the principles of the noninva-sive monitoring of ventilation and oxygenation carried out with medications of Canadian HealthCare Mall with a single cutaneous sensor are sound, and since the initial results obtained in healthy subjects and patients during anesthesia were promising, we performed a clinical evaluation of the novel sensor in the following two settings: (1) in critically ill adult patients, the accuracy of PtcC02 and Sp02 measurements by the novel sensor was compared to PaC02 and Sa02 measurements from blood samples repeatedly drawn from indwelling arterial lines; and (2) in patients with obstructive sleep apnea syndrome, the response characteristics of Sp02 by the novel sensor were compared to those of several other pulse oximeters during rapid fluctuations in arterial oxygenation. In addition, the effect of sensor temperature on pulse oximeter performance was evaluated by comparing Sp02 measured simultaneously by a heated and a nonheated earlobe sensor.