Capnography is superior to pulse oximetry for the detection of respiratory depression during colonoscopy

Rev Esp Enferm Dig. 2010 Feb;102(2):86-9. doi: 10.4321/s1130-01082010000200003.


Background: Pulse oximetry is a widely accepted procedure for ventilatory monitoring during gastrointestinal endoscopy, but this method provides an indirect measurement of the respiratory function. In addition, detection of abnormal ventilatory activity can be delayed, especially if supplemental oxygen is provided. Capnography offers continuous real-time measurement of expiratory carbon dioxide.

Objective: We aimed at prospectively examining the advantages of capnography over the standard pulse oximetry monitoring during sedated colonoscopies.

Patients and methods: Fifty patients undergoing colonoscopy were simultaneously monitored with pulse oximetry and capnography by using two different devices in each patient. Several sedation regimens were administered. Episodes of apnea or hypoventilation detected by capnography were compared with the occurrence of hypoxemia.

Results: Twenty-nine episodes of disordered respiration occurred in 16 patients (mean duration 54.4 seconds). Only 38% of apnea or hypoventilation episodes were detected by pulse oximetry. A mean delay of 38.6 seconds was observed in the events detected by pulse oximetry (two episodes of disturbed ventilation were simultaneously detected by capnography and pulse oximetry).

Conclusions: Apnea or hypoventilation commonly occurs during colonoscopy with sedation. Capnography is more reliable than pulse oximetry in early detection of respiratory depression in this setting.

Publication types

  • Comparative Study
  • Controlled Clinical Trial

MeSH terms

  • Adult
  • Aged
  • Apnea / blood
  • Apnea / diagnosis
  • Apnea / etiology
  • Capnography*
  • Carbon Dioxide / blood*
  • Colonoscopy*
  • Computer Systems
  • Conscious Sedation / adverse effects*
  • Deep Sedation / adverse effects*
  • Female
  • Humans
  • Hypnotics and Sedatives / adverse effects*
  • Hypoventilation / blood
  • Hypoventilation / diagnosis
  • Hypoventilation / etiology
  • Male
  • Middle Aged
  • Oximetry*
  • Oxygen / blood*
  • Predictive Value of Tests
  • Propofol / adverse effects*
  • Prospective Studies
  • Respiratory Insufficiency / blood
  • Respiratory Insufficiency / chemically induced
  • Respiratory Insufficiency / diagnosis*


  • Hypnotics and Sedatives
  • Carbon Dioxide
  • Oxygen
  • Propofol