[Non-invasive patient monitoring in veterinary medicine: pulse oximetry and capnography. II. Capnography].

The article examines the utility of capnography, a non-invasive technique of measuring carbon dioxide concentrations in the respiratory gas, in veterinary medicine, particularly in monitoring ventilation and metabolic functions. It concludes that while pulse oximetry complements capnography well, capnography has the upper hand in detecting critical events during anaesthesia.

Capnography Applications

• Capnography provides metrics such as carbon dioxide concentration or partial pressure, contributing to an understanding of a patient’s respiratory health. The end-tidal value, which roughly corresponds to the arterial value, has strong diagnostic significance. Discrepancies may occur in cases of ventilation-perfusion mismatching, shunting, or increased dead-space-ventilation.
• It primarily serves to monitor spontaneous and artificial ventilation, offering a dependable method for detecting hypo- and hyperventilation. This functionality is critical, especially during anaesthesia where securing a patient’s ventilation is of prime concern.

Monitoring Metabolic and Circulatory Functions

• The amount of carbon dioxide eliminated in the lung is influenced by metabolism and circulation, due to which, capnography also offers a measure of these functions.
• Plotting carbon dioxide concentration against time brings attention to any equipment malfunction, thereby enhancing the safety and reliability of the monitoring process.

Technical Challenges

• Technical challenges encountered with capnography depend on the design of the capnograph used (either main-stream or side-stream) and also on the patient’s weight.
• Despite the challenges, its utility in detecting critical events during anaesthesia is greater than that of pulse oximetry.

Value of Pulse Oximetry and Capnography

• The article discusses the relative merits of pulse oximetry and capnography in detecting critical events during anaesthesia.
• While capnography possesses a superior capability to detect such events, pulse oximetry seamlessly complements capnography, aiding a comprehensive understanding of the patient’s health condition.

Conclusion

• The combination of pulse oximetry and capnography ensures the reliable monitoring of a patient’s vital parameters, significantly enhancing the safety and efficiency of anaesthesia procedures in veterinary medicine.