Is capnography mandatory during sedation for endoscopy?

Sedation during endoscopic procedures needs to ensure adequate tissue oxygenation, which depends on good cardiovascular and respiratory function. These parameters need to be monitored non-invasively as it is difficult to predict how a certain patient will respond to sedation. Tissue oxygenation is monitored using oximetry. Cardiovascular function is monitored by measuring blood pressure and pulse. Finally, respiratory function is monitored by assessing airway patency and respiratory rate in cases of spontaneous ventilation and with capnography when a patient is intubated and mechanically ventilated. A capnograph monitor measures the partial pressure of end tidal CO2 (PETCO2) in the expired air at any given moment and expresses it as a graph usually depending on time (capnography). The absolute values of PETCO2 and the curve shape offer information on metabolic, respiratory, and cardiovascular function [1]: ▶ PETCO2 increases as a result of metabolic causes (malignant hyperthermia, severe sepsis), cardiovascular causes (CO2 insufflation, treatment of acidosis), and respiratory causes (hypoventilation, chronic obstructive pulmonary disease (COPD), asthma). ▶ PETCO2 decreases as a result of metabolic causes (hypothermia, metabolic acidosis), cardiovascular causes (profound hypovolemia), and respiratory causes (hyperventilation, pulmonary edema). In intubated and ventilated patients PETCO2 values and curve shape also offer information when technical malfunction occurs. ▶ For a sedated patient in spontaneous ventilation, hypoventilation (by airway obstruction or central respiratory depression) will likely precede hypoxemia. Hence, if the patient is monitored using a capnograph machine, when hypoventilation occurs, PETCO2 increases and the shape of the capnography curve is modified. This may trigger an adequate response from the person monitoring the anesthesia (chin thrust, sedative dose modification, oxygen supplementation) so as to prevent hypoxemia. As hypoxemia is an adverse reaction to sedation in endoscopy, are we doing enough for respiratory (as well as metabolic and cardiovascular) monitoring for patients under spontaneous respiration? Do we need capnography for these patients? If the answer is yes, then the subsequent questions will be: ▶ Should we use it for moderate (midazolam) sedation, deep (propofol) sedation or both? ▶ Should we use it for anesthesiologist, for nonanesthesiologist (nurse) administered sedation or both? ▶ Should we use it for some “high risk” procedures or for all? ▶ Should we use it for some “high risk” patients or for all? ▶ What should the precise trigger be for intervention in capnography monitoring? What should the exact intervention be to prevent hypoxemia? ▶ And finally, (when) is it cost efficacious? The American Society of Gastrointestinal Endoscopy (ASGE) does not endorse the use of capnography for moderate sedation, or for moderate risk procedures (routine endoscopy and colonoscopies), but only for endoscopic retrograde cholangiopancreatography (ERCP) or endoscopic ultrasound procedures [1–3]. Even so, the utility of capnography monitoring for ERCP procedures has recently been questioned by Klare et al. [4]. In their comparative prospective study on 242 patients with propofol-based sedation, hypoxemia incidence was not significantly reduced in the additional capnography arm compared with standard monitoring in intent to treat analysis (38.0% vs. 44.4%, P=0.314). Additional capnographic monitoring only resulted in improved detection of apnea compared to standard monitoring (64.5% vs. 6.0%, P<0.001). However, one pa-