Differences between capnography and pulse oximetry

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Waveform capnography monitors track end-tidal carbon dioxide (etCO2) with the use of circuits (nasal cannula type devices are typically used for breathing patients). This measured concentration of carbon dioxide in exhaled air creates a capnography waveform to immediately detect changes that could signal respiratory distress or failure. Pulse oximeters, which had been the standard of care in in many settings, take much longer to register respiratory distress. This is because oxygen levels in blood can remain normal for several minutes after a patient stops breathing.

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  • 1 While pulse oximetry measures oxygenation or the amount of arterial blood oxygen saturation and pulse rate, capnography provides a measure of ventilation – or concentration of CO2 exhaled air. This process is also known as end tidal CO2 or etCO2.
  • 2 Capnography, unlike pulse oximetry, is not affected by supplemental oxygen.
  • 3 A pulse oximeter may appear normal for several minutes even if the patient has stopped breathing, which is not the case with a capnograph.
  • 4 4. Apnea or any altered ventilation is detected immediately by capnography, while pulse oximetry takes time to detect such problems.

These differences are the reasons why capnography is considered superior to pulse oximetry. Factors like high incidence of respiratory failure in pediatric patients and pulse oximeter limitations have led to the increased use of capnography throughout the world. Major regulatory bodies are also endorsing the use of capnography.

Consider the following:

  • Capnography use is akin to an insurance policy – it can keep you out of trouble when used correctly
  • A lawsuit due to unrecognized hypoxia can cost thousands or millions of dollars
  • The PC900 handheld waveform capnography monitor is cost effective at less than $2,000.
  • Circuits for single patient use are around $10-12/each.