Alaris® EtCO2 module
Topic 1: Overview of End Tidal CO2 Monitoring

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Comparing EtCO2 and Pulse Oximetry (SpO2)

The Respiratory Cycle has two separate, but related physiologic processes: Ventilation and Oxygenation.1

EtCO2 Monitoring Measures Ventilation

  • Measures carbon dioxide
  • Reflects breath-to-breath ventilation
  • Detects hypoventilation
  • Can be used with pulse oximetry

SpO2 Monitoring Measures Oxygenation

  • Measures oxygen saturation (O2 attached to hemoglobin)
  • Reflects oxygenation
  • Detects hypoxia
  • Can be used with capnography

The assessment of oxygenation by pulse oximeter is not a substitute for monitoring ventilatory function. Pulse oximetery measurement is a late detector of respiratory depression.1

1American Society of Anesthesiologists task force on Sedation and Analgesia by non-anesthesiologists. Practice guidelines for sedation and analgesia by non-anesthesiologists. (2002). Anesthesiology 96:1004-1017.