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Transcutaneous Blood Gas Monitoring

Clinician's Brief (Capsule)

Internal Medicine

|December 2014

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Blood gas monitoring is vital when assessing ventilation and oxygenation in critically ill patients. Decisions regarding oxygen supplementation or mechanical ventilation are aided by PO2 and PCO2 measurements, but frequent blood sampling can be difficult and may lead to iatrogenic anemia, bruising, and pain. Transcutaneous monitors can detect changes in respiratory status more quickly than blood gas analysis and are widely used in human medicine, enabling clinicians to monitor neonates or patients without arterial access. This study investigated a comparison between transcutaneous and arterial blood gas values in critically ill dogs to verify whether the transcutaneous system can be used reliably in dogs.

The transcutaneous monitoring system was calibrated and used according to manufacturer instructions for human patients, with probe location extrapolated from data in human neonates. Canine subjects (n = 23 critically ill client-owned dogs) had indwelling arterial catheters, allowing for blood gas measurements to
be taken concurrently with readings from the transcutaneous monitor. Agreement between transcutaneous and arterial PO2 and PCO2 was inferior to that found in comparable human studies. The transcutaneous system tended to overestimate PO2 and PCO2. Inaccuracies may have occurred for technical reasons (eg, inappropriate probe placement) or clinical reasons (eg, hypoperfusion, variations in tissue thickness). Other species-specific changes (eg, skin metabolism, local CO2 production) may have also influenced the measurement accuracy. Therefore, the transcutaneous monitoring system cannot currently be recommended as a sole device for blood gas monitoring in critically ill dogs.


The potential utility of transcutaneous blood gas measurements in veterinary patients cannot be overemphasized. Although this study indicated there is too much of a discrepancy between arterial blood gas and transcutaneous measurements in critically ill dogs, other veterinary studies have suggested that transcutaneous monitoring may be more accurate and useful in other clinical settings, such as assessing the viability of skin grafts. It is also yet unknown if transcutaneous blood gas monitoring would be applicable in other species, like cats or smaller mammals, from which arterial or venous blood gas measurements are more difficult to obtain.—Heather Troyer, DVM, DABVP, CVA


Evaluation of a transcutaneous blood gas monitoring system in critically ill dogs.  Holowaychuk MK, Fujita H, Bersenas AM. JVECC 24:545-553, 2014.

This capsule is part of the One Health Initiative.

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