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

Abstract

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.

Sedation-related complications in gastrointestinal endoscopy

“…Supplementary nasal oxygen at 3 L/min in sedated patients abolishes desaturation and hypoxia. Upper airway obstruction may be attributed to anatomical structures or a foreign body [29] . Independent predictors of airway modifications include male sex, ASA class of Ⅲ or higher, and increased body mass index [1] .…”

Developing a Respiratory Depression Scorecard for Capnography Monitoring

“…Capnography is more sensitive than pulse oximetry in detecting respiratory abnormalities, and it can more rapidly detect acute changes in respiratory status 5 . Unlike a pulse oximeter, capnography monitoring involves wearing a nasal cannula.…”

“…The term capnography refers to the monitoring of the partial pressure of carbon dioxide during exhalation, and it has been shown to be a more reliable way of detecting respiratory depression 1,5 . Capnography is more sensitive than pulse oximetry in detecting respiratory abnormalities, and it can more rapidly detect acute changes in respiratory status 5 .…”

“…Additionally, pulse oximetry is unable to detect important early indicators of respiratory depression such as changes in respiratory rate, pauses in breathing, or decreases in exhaled carbon dioxide levels 1 . Also, pulse oximeters may give deceptive results under certain situations, such as when a patient is receiving supplemental oxygen, has weak pulses, has poor perfusion, or has a dyshemoglobinemia [1][2][3]5 .…”

“…A major disadvantage of pulse oximetry is that it only measures oxygenation of the arterial blood and therefore can only detect hypoxemia [1][2][3][4][5] . It does not have the capability to measure ventilation status or the adequacy of carbon dioxide elimination; therefore it is not an all-encompassing tool to measure respiratory function 4 .…”