The report is a product of the VA/HSR&D Evidence Synthesis Program.
Capnography for Moderate Sedation in Non-Anesthesia Settings
Professional societies disagree on the incremental value of adding capnography to routine monitoring during moderate sedation. Moderate sedation, a depression of consciousness during which patients are able to maintain spontaneous breathing without medical intervention, is routinely used for outpatient procedures performed by non-anesthesiologists, including colonoscopies. However, it is unclear whether detection of hypoventilation, a type of respiratory disturbance, through capnography has a clinically meaningful effect on patient outcomes, and whether there are any unintended negative effects (i.e., false alarms that may distract the clinician during a procedure).
Capnography is a method of measuring CO2 levels during exhaled breaths and is used to detect hypoventilation – an earlier indication of respiratory compromise than other signs such as low oxygen levels detected by pulse oximetry.
This rapid evidence review evaluated the benefits and harms of capnography monitoring for procedures involving moderate sedation with a benzodiazepine and an opioid. Investigators with VA’s Evidence Synthesis Program (ESP) Coordinating Center in Portland, OR searched the literature, including MEDLINE, CINAHL, and the Cochrane Central Register of Controlled Trials from inception through January 2020. After reviewing 186 articles, they included 8 studies (4 randomized controlled trials and 4 observational studies) in their analysis. Both GI procedures (i.e., colonoscopy, esophagogastroduodenoscopy [EGD], endoscopic retrograde cholangiopancreatography [ERCP], endoscopic ultrasonography [EUS]), and other endoscopic procedures and non-GI procedures (i.e., minor oral surgery, flexible bronchoscopy, transesophageal echocardiography [TEE]) were represented in the literature.
Summary of Findings
Overall, the evidence does not support an effect of capnography on any clinical outcomes compared to routine monitoring for any procedure type. However, capnography may improve intermediate outcomes such as risk of hypoxemia and severe hypoxemia during ERCP, EUS, bronchoscopy, and severe hypoxemia during colonoscopy compared to routine monitoring. Capnography does not reduce the risk of hypoxemia, severe hypoxemia, or adverse events in other procedures including TEE, minor oral procedures, or EGD. Additional findings include:
- Adverse events rarely occurred and were similar between capnography and routine monitoring groups;
- False alarm rates were 13% and 45% in two studies; and
- Capnography was consistently more costly than routine monitoring due to the need for additional equipment.
Subgroup analyses indicated that capnography is more beneficial at reducing hypoxemia during ERCP versus EUS procedures, and for obese patients versus non-obese patients. Across monitoring groups, certain patient characteristics (i.e., lower baseline oxygen saturation, female sex, higher BMI, older age) were associated with higher risk of hypoxemia and certain sedation characteristics (i.e., higher doses of fentanyl or hydromorphone) were associated with higher risk of severe hypoxemia or respiratory depression. Comorbidities such as ischemic heart disease and pack-year smoking history also were associated with apnea and disordered respiration across monitoring groups. Consistent with standard practice, these findings suggest that clinicians should consider patient, procedure, and sedation characteristics when determining a monitoring plan.
Implications for VA
Findings from this evidence brief will be used to inform the development of a Moderate Sedation Directive by VA’s National Anesthesia Service.
Research Gaps/Future Research
More studies are needed that evaluate the full scope of outcomes when capnography monitoring is added to moderate sedation, including the specific actions providers take when alerted to hypoventilation via capnography. Despite a reduction in hypoxemia, delivery of earlier or more frequent interventions to address respiratory distress could also have downsides – such as patient discomfort – so studies should include an evaluation of patients’ experiences during the procedure as well as their clinical outcomes.
Further, more studies are needed on the effects of capnography on downstream health system outcomes (i.e., costs of training/staffing, and wait times). While capnography adds costs to systems due to the use of additional equipment, studies did not report costs of any additional training of providers or staffing of procedures. Measurement of the downstream effects of capnography – such as longer wait times for a procedure due to limited access to equipment or staff – could indicate whether there are any access-related downsides of the use of capnography.
Veazie S, Vela K, Mackey K. Evidence Brief: Capnography for Moderate Sedation in Non-Anesthesia Settings. Washington, DC: Evidence Synthesis Program, Health Services Research and Development Service, Office of Research and Development, Department of Veterans Affairs. VA ESP Project #09-199; 2020.
To view the full report, go to on the intranet only at http://www.hsrd.research.va.gov/publications/esp/capnography-brief.cfm
ESP is currently soliciting review topics from the broader VA community. Nominations will be accepted electronically using the online Topic Submission Form. If your topic is selected for a synthesis, you will be contacted by an ESP Center to refine the questions and determine a timeline for the report.
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