The ESP Coordinating Center (ESP CC) developed this evidence brief on capnography for moderate sedation in response to a request from the VA National Gastroenterology Program Office and the GI Field Advisory Committee. Findings from this evidence brief will be used to inform the development of a Moderate Sedation Directive by the VA National Anesthesia Service.

Preface

The VA Evidence Synthesis Program (ESP) was established in 2007 to provide timely and accurate syntheses of targeted healthcare topics of importance to clinicians, managers, and policymakers as they work to improve the health and healthcare of Veterans. These reports help:

• Develop clinical policies informed by evidence;
• Implement effective services to improve patient outcomes and to support VA clinical practice guidelines and performance measures; and
• Set the direction for future research to address gaps in clinical knowledge.

The program is comprised of four ESP Centers across the US and a Coordinating Center located in Portland, Oregon. Center Directors are VA clinicians and recognized leaders in the field of evidence synthesis with close ties to the AHRQ Evidence-based Practice Center Program and Cochrane Collaboration. The Coordinating Center was created to manage program operations, ensure methodological consistency and quality of products, and interface with stakeholders. To ensure responsiveness to the needs of decision-makers, the program is governed by a Steering Committee comprised of health system leadership and researchers. The program solicits nominations for review topics several times a year via the program website.

Comments on this evidence report are welcome and can be sent to Nicole Floyd, Deputy Director, ESP Coordinating Center at vog.av@dyolF.elociN.

Executive Summary

Guidelines from professional societies disagree on the incremental value of adding capnography to routine monitoring during moderate sedation. Moderate sedation is a drug-induced (typically by an opioid and a benzodiazepine) depression of consciousness during which patients respond to verbal commands, either alone or accompanied by light touch, and have adequate spontaneous breathing without medical intervention. Moderate sedation is routinely used for common outpatient procedures performed by non-anesthesiologists. Capnography is a method of measuring CO₂ levels during exhaled breaths and can be used to detect hypoventilation, an earlier indicator of respiratory compromise than other indicators such as low oxygen levels detected by pulse oximetry. However, it is unclear whether detection of hypoventilation during moderate sedation via capnography has a clinically meaningful effect on patient outcomes, and whether there are any unintended negative effects of capnography (such as false alarms that may distract the clinician during a procedure).

We conducted a rapid evidence review evaluating studies that compare capnography to routine monitoring for procedures under moderate sedation. We identified 8 studies (4 RCTs, 3 prospective observational, and 1 retrospective observational). Both GI procedures (colonoscopy, esophagogastroduodenoscopy [EGD], endoscopic retrograde cholangiopancreatography [ERCP], endoscopic ultrasonography [EUS], and other endoscopic procedures) and non-GI procedures (minor oral surgery, flexible bronchoscopy, transesophageal echocardiography [TEE]) were represented in the literature.

Five studies (2 RCTs, 2 prospective observational, and 1 retrospective observational) evaluated capnography versus routine monitoring for GI procedures. Severe hypoxemia (SpO₂ <85%) was lower in the capnography group than routine monitoring group (5% vs 18%) during colonoscopy; however, there was no difference in severe hypoxemia between monitoring groups during EGD. There was no difference in hypoxemia (SpO2<90%) between capnography and routine monitoring for either EGD or colonoscopy. Those monitored by capnography for ERCP or EUS had a decreased risk of hypoxemia (SpO2<90%) (46% vs 69%), severe hypoxemia (15% vs 31%), apnea (41% vs 63%), and need for oxygen supplementation (52% vs 67%), but no difference in abnormal ventilation compared to routine monitoring. Complications (eg, abnormal vital signs and need for reversal agents) were rare but overall similar between capnography and routine monitoring groups. False alarms occurred in 13% of patients undergoing ERCP and EUS, and patients and nurses reported more discomfort with colonoscopy during capnography than during routine monitoring. The total cost of implementing capnography was variable depending on type of procedure, setting, and types of costs authors reported but was consistently higher for capnography than routine monitoring. In terms of subgroup differences, capnography was more beneficial at reducing hypoxemia during ERCP versus EUS procedures, and for obese patients versus non-obese patients. Overall, we have low confidence in these studies’ findings because of limitations in study design and execution – such as lack of outcome assessor blinding and greater loss of data in the capnography group – and because there was an inconsistent effect of capnography across studies.

Three studies (2 RCTs and 1 prospective observational study) examined capnography for non-GI procedures, including minor oral surgery, flexible bronchoscopy, and TEE. For minor oral surgery, there was no difference between capnography and routine monitoring on hypoxemia outcomes; but for bronchoscopy, capnography was associated with a reduced risk of hypoxemia (29% vs 46%) and severe hypoxemia (17% vs 32%), as well as shorter duration of hypoxemia (average of 20.4 vs 41.7 seconds) compared to routine monitoring. For TEE, respiratory depression developed in 45% of patients monitored by capnography, but no data comparing capnography to routine monitoring is available. Similar to GI procedures, complications in non-GI procedures were rare and generally similar between capnography and non-capnography groups. False apnea alarms occurred in 45% of bronchoscopy procedures. No studies reported subgroup differences between capnography and routine monitoring groups, nor did they report costs or other downstream outcomes. Overall, we have low confidence in these findings due to similar study limitations as were seen in the GI studies, as well as an inconsistent effect of capnography across studies.

There were limitations to our rapid review methods as well as limitations of primary studies. First reviewer inclusion of articles and extraction of data with second reviewer checking may have resulted in missing eligible studies or data, although we attempted to reduce this risk by establishing explicit inclusion criteria for studies and developing and using a piloted data abstraction tool. Most primary studies excluded those at highest risk of respiratory event (ASA category IV or V); therefore, findings from our review reflect lower-risk patients. The quality of the available literature was also mixed.

To weigh the added value of capnography monitoring during moderate sedation against potential trade-offs, more studies are needed that evaluate the role of timing and frequency of provider-delivered interventions to address respiratory distress on hypoxemia and clinical outcomes. More studies are also needed on downstream effects of implementing capnography (such as impact on wait times resulting from added procedural time or need for additional staffing or equipment that reduces the number of procedures that can be completed each day) as well as procedures not evaluated in any studies, such as tissue biopsies and cardiac procedures other than TEE.

Overall, the evidence does not support an effect of capnography on 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 for colonoscopy compared to routine monitoring. Capnography does not reduce hypoxemia, severe hypoxemia, or adverse events in other procedures including TEE, minor oral procedures, or EGD.

Introduction

Methods

Results

The literature flow diagram (Figure 1) summarizes the results of the search and study selection processes. Among 186 potentially relevant citations, 8 published studies^4,15,23–28 (4 RCTs^23–26 and 4 controlled observational studies^4,15,27,28) met our inclusion criteria. We did not receive any unpublished data from manufacturers of capnography devices.

The 8 included studies examined different types of procedures, including colonoscopy, esophagogastroduodenoscopy (EGD), complex GI procedures such as endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasonography (EUS), upper endoscopy with expandable metal stent placement, photodynamic therapy, and therapeutic push enteroscopy, transesophageal echocardiography (TEE), minor oral surgery, and flexible bronchoscopy. Most studies were conducted in an outpatient procedure unit, but settings also included a dental clinic, an emergency department, and a hospital. Sample size ranged from 49 to 5,466. Study follow-up periods were not reported but can be assumed to have ended after each procedure.

Detailed study-level data abstraction and quality assessment appear in the Supplementary Materials. The most relevant findings for each of these studies appear below, organized into 2 main categories: 1) GI procedures (colonoscopy, EGD, ERCP, EUS, and other complex GI procedures) and 2) other procedures (TEE, oral surgery, and flexible bronchoscopy).

Literature Flow

Figure 1

Literature Flowchart.

GI Procedures

Overview

Five studies (2 RCTs,^25,26 2 prospective observational,^15,27 and 1 retrospective observational)⁴ evaluated capnography versus routine monitoring for GI procedures including colonoscopy,^15,25 EGD,²⁵ ERCP,^26,27 EUS,^26,27 upper endoscopy with expandable metal stent placement,²⁷ photodynamic therapy,²⁷ and therapeutic push enteroscopy.²⁷ One study included a mix of procedures performed in an adult endoscopy suite but does not provide procedure details.⁴ Selected findings from these 5 studies are presented in Table 1.

Study design and limitations

Two RCTs^25,26 (total n=805) evaluated the effect of capnography versus routine monitoring on hypoxemia and risk of adverse events for patients undergoing EGD, colonoscopy, ERCP, or EUS. In both RCTs, patients were randomized to either an open or blinded capnography group, with the endoscopy team blinded to assignment throughout the procedure. In both studies, an independent observer monitored capnography and alerted the endoscopist of any respiratory abnormalities in the open capnography group, but only alerted the endoscopist of apnea >30 seconds in the blinded group. The main limitations of the RCT²⁵ examining EGD and colonoscopy were that baseline systolic blood pressure was higher in the EGD capnography blinded group versus open group, more patients’ data were excluded from the capnography group than the routine monitoring group (8 vs 1 patient), and outcome assessors were aware of what group patients were assigned to. The main limitation of the RCT²⁶ examining ERCP and EUS was that outcome assessors were aware of what group patients were assigned to.

Two prospective observational studies^15,27 (total n=1,015) provide data on additional outcomes and GI procedures not covered by these RCTs, including 1 hospital’s experience implementing capnography for all colonoscopy procedures. The first prospective observational study¹⁵ compared safety, patient satisfaction, and costs of colonoscopy procedures before and after hospital-wide implementation of capnography monitoring. Because data was collected from the 2 groups at different times, there is risk that other factors besides the implementation of capnography (such as hospital-wide quality improvement initiatives or secular trends) could have affected to the results. The second prospective observational study²⁷ compared capnography versus routine monitoring on hypoxemia outcomes for patients undergoing ERCP, EUS, and other complex procedures. In this study, the endoscopist was blinded to the capnography device and did not receive any information from the independent observer during the procedure, meaning they did not have the opportunity to act on the data collected by capnography. Additional limitations of the study were that outcome assessors were aware of what group patients were in, and there was no information on the number of patients who were approached for or were otherwise eligible for the study compared to the number who enrolled.

One additional retrospective observational study⁴ (n=5,446) evaluated sedation-related complications in a large series of patients undergoing endoscopic procedures either monitored by capnography or routine monitoring. However, because authors provided limited information on patient characteristics, types of procedures, sedation used, and reason why capnography was used in some procedures but not others, little meaningful information can be drawn from the study.

Hypoxemia outcomes

In the RCT²⁵ of EGD and colonoscopies, there was no difference between open and blinded capnography groups on hypoxemia (risk of hypoxemia [SpO2<90%] during EGD: 50% open vs 54% blinded; risk of hypoxemia during colonoscopy: 52% open vs 54% blinded). However, the risk of severe hypoxemia (SpO2<85%) during colonoscopy was lower in the open capnography group (5% vs 18%). In the RCT²⁶ of ERCP and EUS, the open capnography group had a decreased risk of hypoxemia (46% vs 69%), severe hypoxemia (15% vs 31%), apnea (flat line or no respiratory rate ≥15 s) (41% vs 63%), and need for oxygen supplementation (52% vs 67%), but no difference in abnormal ventilation (flat line for ≥5 seconds but <15 seconds, >75% reduction in amplitude of respiratory waves for ≥5 seconds) compared to the blinded group. Of patients receiving oxygen supplementation due to hypoxemia in this study, more people in the blinded arm than the open capnography arm had recurrent hypoxemia (38% vs 18%). In a prospective observational study²⁷ of ERCP, EUS, and other complex GI procedures, 54 episodes of apnea (no respiratory activity ≥30 seconds) and disordered respiration (45-second interval that contained ≥30 seconds of apneic activity) were detected in 49 patients, only 50% of which were caught by pulse oximetry, 5% of which were caught by hypercapnea, and none of which were caught by visual assessment.

The proportion of people who had obstructive sleep apnea – a potential driver of hypoxemia during moderate sedation – was reported in 3 studies. In the RCT²⁵ of EGD and colonoscopies, those with sleep apnea were excluded from enrollment. In the RCT²⁶ of ERCP and EUS, the percentages of people with sleep apnea were similar between open and blinded capnography groups (11.3% vs 13%). Finally, in the prospective observational study²⁷ of ERCP, EUS, and other complex GI procedures, the number of people with sleep apnea was not reported but one can infer they were included as a history of sleep apnea was found to be associated with increased propensity to desaturation.

Adverse events and interventions to address respiratory distress

Complications (eg, abnormal vital signs and need for reversal agents) were rare but overall similar between capnography and routine monitoring groups in these studies. In the RCT²⁵ of EGD and colonoscopies, 1 patient in the EGD open capnography group received naloxone after their procedure due to persistent hypoxemia, and 2 patients in the colonoscopy open capnography group had their procedure terminated early (no other details provided). Similar rates of hypotension and bradycardia were seen in both capnography and routine monitoring groups for both procedure types. In the RCT²⁶ of ERCP and EUS, there were no deaths in either capnography or routine monitoring groups. False alarms (defined as a flat line of respiratory activity for at least 50 seconds without an associated decrease in oxygen saturations or normal chest excursions) occurred in 35 out of 263 (13%) patients in this study. Authors hypothesized these false alarms were caused by diminution of air stream because of narrow oropharyngeal inlet or blockage of the connecting tube with moisture.

In a prospective observational study¹⁵ of colonoscopies, sedation events (defined as any of the following: oxygen saturation <90% or leading to an intervention; problematic changes in heart rate or blood pressure; any hemodynamic or respiratory condition that interrupted procedure; use of any reversal agent; hospitalization) were similar before and after implementation of capnography (8.2% vs 11.2%), and no patients were hospitalized or required reversal agents in either group. However, patients and nurses reported more discomfort with the colonoscopy procedure after capnography implementation (1.71 vs 1.00 for patients and 1.82 vs 1.33 for nurses on PROSAS survey) than before. In a retrospective observational study⁴ of endoscopic procedures, 14 (out of 4,846) procedures without capnography encountered an over-sedation complication that required either assisted bag-mask ventilation or reversal agents while 0 (out of 600) procedures with capnography resulted in an over-sedation complication, although the difference between groups was not statistically significant.

These studies report when patients required reversal agents or bag mask ventilation but do not report how often lesser interventions such as patient stimulation or repositioning occurred. The studies thereby leave gaps in our full understanding of the practical implications of adding capnography monitoring, such as staffing needs.

Costs and other system-level outcomes

The total cost of implementing capnography was variable depending on the type of procedure and setting, as well as what types of costs authors reported. Authors reported both fixed costs (eg, costs of procuring and maintaining hardware and software for procedure rooms) as well as variable costs (eg, costs of single-use capnograph lines and cannulas). Implementing capnography for colonoscopies in a single hospital was estimated to cost an additional $40,000 to upgrade procedure rooms and provide cannulas for patients.¹⁵ Capnography was more expensive than routine monitoring for endoscopic procedures in an adult endoscopic unit⁴ (costs were approximately $2,100-$12,900 for capnography vs $725-$3,075 for pulse oximetry). Finally, the addition of capnography was associated with additional costs for ERCP, EUS, and other complex procedures in another hospital (ie, a one-time software activation fee [$150], an in-line dehumidifying module that is changed weekly [$23)] and a disposable nasal cannula used for each patient [$4]).²⁷

Studies reported^25,26 that procedure times were generally similar between capnography and routine monitoring groups (EGD lasted 5.6 minutes in both groups; colonoscopy lasted 17.3 in capnography group vs 17.5 minutes in routine group; ERCP/EUS lasted 34.4 in capnography group vs 37.2 minutes in routine group), indicating that capnography does not add time to procedures. Studies did not report any other implementation-related outcomes (such as costs and time required to train staff and any differential staffing requirements during procedures) or any other downstream, system-level outcomes such as wait times.

Differences by subgroups

One RCT²⁶ found that capnography monitoring was more beneficial at reducing hypoxemia during ERCP versus EUS procedures, and for obese patients versus non-obese patients. RCTs^25,26 also reported that certain patient characteristics (older age, female sex, lower baseline oxygen saturation, higher BMI, higher baseline diastolic blood pressure) were associated with hypoxemia across monitoring groups. One RCT²⁵ also found that higher doses of fentanyl were associated with severe hypoxemia across monitoring groups. One prospective observational study²⁷ additionally found that patient comorbidities (ischemic heart disease, pack-year smoking history) were associated with apnea and disordered respiration across monitoring groups. A final retrospective observational study⁴ found that those who experienced sedation-related complications (all of whom were routinely monitored) had some common patient and procedural characteristics (longer duration of procedure, older age, and medical comorbidities such as previous stroke or COPD), although these weren’t compared to those who did not experience sedation-related complications.

Strength of evidence

We have low confidence in these studies’ findings given that outcome assessors and sometimes providers were aware of what group patients were assigned to, more people were excluded from analyses due to data loss in capnography compared to routine monitoring groups, and there was not a consistent effect of capnography seen across studies.

Table 1

Selected findings of studies of capnography versus routine monitoring for GI procedures.

Other Procedures

Overview

Three studies (2 RCTs and 1 prospective observational study) examined capnography for non-GI procedures, including minor oral surgery,²³ flexible bronchoscopy,²⁴ and TEE.²⁸

Study design and limitations

One RCT²³ (n=190) compared capnography to routine monitoring for patients undergoing minor oral surgery on hypoxemia outcomes. A major limitation of this study is that patients and providers were aware of their group assignment by the time of the surgery. An additional limitation was that more people in the capnography group than routine monitoring group were removed from analysis because of missing data (6 vs 2 people). A second RCT²⁴ (n=185) compared capnography to routine monitoring for patients undergoing flexible bronchoscopy on hypoxemia outcomes, false alarms, and risk of adverse events. Similar to the previous RCT, providers were aware of group assignment before the procedure. In addition, 21 total patients were excluded from analysis due to protocol deviations or incomplete data on vital signs (although rates of missing data were similar between capnography and routine monitoring groups). A third prospective observational study²⁸ (n=200) of patients undergoing transesophageal echocardiography (TEE) provides data on how many patients experienced respiratory depression as measured by capnography as well as overall rates of sedation reversal agents or advanced airway procedures. However, because all providers were blinded to the capnography monitor during the procedures and no comparative analyses were conducted afterwards, no comparative data is available on the effect of capnography compared to routine monitoring.

Hypoxemia outcomes

In the RCT²³ of minor oral surgeries, there was no difference between capnography and routine monitoring on any hypoxemia outcomes (including any hypoxemia [SpO2⩽94%], moderate hypoxemia [SpO2 90-92%] or severe hypoxemia [SpO2 <90%]). In the RCT²⁴ of flexible bronchoscopy, capnography was associated with reduced risk of hypoxemia (SpO2 <90%) (29% vs 46%) and severe hypoxemia (SpO2 <85%) (17% vs 32%), as well as reduced duration of hypoxemia (average of 20.4 vs 41.7 seconds) compared to routine monitoring. In the prospective observational study²⁸ of TEE, respiratory depression (defined as ETCO2 level of greater ≥50 mm Hg at any time during the procedure, an ETCO2 change from baseline greater than 10 mm Hg, or a loss of ETCO2 waveform ≥15 seconds) developed in 45% of patients monitored by capnography. This study’s abstract states that capnography identified respiratory depression earlier than pulse oximetry but does not provide data to support this statement.

The proportion of people who had obstructive sleep apnea was reported in 2 studies. In the RCT²⁴ of flexible bronchoscopy, those with severe sleep apnea were excluded. In the prospective observational study²⁸ of TEE, 15% of participants had obstructive sleep apnea and 7.5% used a CPAP or BiPAP machine.

Adverse events and interventions to address respiratory distress

Similar to GI procedures, complications in non-GI procedures were rare and generally similar between capnography and non-capnography groups. In the RCT²⁴ of flexible bronchoscopy, there were similar rates of adverse events (hypotension and bradycardia) in both capnography and routine monitoring groups. False apnea alarms (flat line >10 seconds determined to be false after physical assessment) occurred in 45% of these procedures. Of note, bronchoscopy is often performed by inserting a tube through the nose, which can interfere with capnography reading which is also measured through the nose. False alarms in this study were caused by continuous suction with bronchoscope, oral suction with suction catheter, or disconnection or obstruction of sample line, and authors noted the suction may have prevented the capnography device from sampling expired air. The prospective observational study²⁸ of TEE concluded that blinding providers to capnography data and not giving patients a subsequent intervention to address respiratory depression “was not harmful” but did not provide any data to support this.

The RCT²³ of minor oral surgeries reported that more people in the capnography group received verbal stimulation to take breaths than in the control group (54 vs 38 people), but the number of people requiring supplemental oxygen was the same (3 in each group). The RCT²⁴ of flexible bronchoscopy reported that interventions to address apnea or hypoxemia episodes were similar in capnography versus routine monitoring groups, with the most commonly received procedures being increased O₂ supply (45 vs 42 participants) and a chin-lift/jaw-thrust movement (14 vs 8). Timing of these interventions was not reported. The prospective observational study²⁸ of TEE blinded providers to capnography throughout the procedure.

Costs and other system-level outcomes

The RCT²⁴ of bronchoscopy reported procedure times were similar in capnography versus routing monitoring groups (28.3 vs 27.4 minutes), indicating the use of capnography did not increase procedure time. No studies reported on costs or any other downstream outcomes such as access.

Differences by subgroups

None of these studies reported subgroup differences in the effect of capnography versus routine monitoring. However, 1 prospective observational study²⁸ did report that those with lower baseline respiratory rates and those who received more hydromorphone were more likely to experience respiratory depression during TEE across monitoring groups.

Strength of evidence

We have low confidence in these studies’ findings, as providers were made aware of which group patients were assigned to assignment before the procedure, more data was missing from capnography than routine monitoring groups, and the effects of capnography were inconsistent across procedure types.

Table 2

Selected findings of studies of capnography versus routine monitoring for non-GI procedures.

Summary and Discussion

We conducted a rapid evidence review evaluating the benefits and harms of capnography monitoring for procedures involving moderate sedation with a benzodiazepine and an opioid. Previous systematic reviews on capnography for moderate sedation have either focused on a specific clinical specialty (such as emergency department²⁹) or a limited set of outcomes (such as hypoxemia, sedation-related adverse events, and patient satisfaction^30,31). Our review includes a broader range of specialty areas and outcomes to help health systems determine which patients and procedures might benefit from capnography monitoring, and when added value of capnography may not justify potential trade-offs.

We found 8 studies (4 RCTs and 4 observational) examining capnography for a variety of GI and non-GI procedures. In 4 of these studies^4,24–26 on ERCP, EUS, flexible bronchoscopy, colonoscopy, and EGD, both capnography and routine monitoring were associated with low rates of adverse events such as abnormal vital signs and use of reversal agents. Across studies, no patients died²⁶ or were hospitalized.¹⁵ Otherwise, we found no data indicating that capnography provides a clinical benefit to patients. In terms of system outcomes, 3 studies^24–26 found that procedure times were similar when capnography or routine monitoring were used, but no other implementation-related outcomes (such as training time or staffing requirements for procedures) were reported. Three studies found capnography added costs to systems, although the total amount was variable depending on what aspects of capnography were included in their calculations.^4,15,27 Our findings are consistent with a 2017 Cochrane review²⁹ which found “a lack of convincing evidence that the addition of capnography to standard monitoring in ED PSA [procedural sedation and anesthesia] reduces the rate of clinically significant adverse events.”

While studies suggested there are no clinical or system-level benefits of capnography, capnography can reduce the occurrence of hypoxemia for certain types of procedures. Two RCTs^24,26 of ERCP, EUS, and bronchoscopy indicated capnography is associated with a lower risk of hypoxemia and severe hypoxemia than routine monitoring. In addition, another RCT²⁵ found capnography is associated with lower risk of severe hypoxemia but no difference in hypoxemia when compared to routine monitoring. Otherwise, there were no effects of capnography compared to routine monitoring on hypoxemia for any other procedure. Harms of capnography included high rates of false alarms (13% and 45% depending on the procedure)^24,26 and more procedural discomfort as reported by patients and nurses.¹⁵ Our findings are consistent with 2 recent reviews^30,31 which found that capnography may reduce risk of hypoxemia. One of these reviews³⁰ found that capnography did not lead to additional harms related to assisted ventilation, patient satisfaction, recovery time, or the quality and duration of sedation, but did not consider false alarms to be a harm, and did not include the prospective observational study¹⁵ indicating patients experienced more discomfort with capnography than routine monitoring. The high rates of false alarms in these studies align with clinicians’ anecdotal accounts of their experiences using capnography monitoring^14,32 – specifically, that false alarms have the potential to lead to “needless disruption, prolongation, or abandonment of procedures that the sedation was intended to facilitate.”^14,32 Tellingly, the ASA revised its Standards for Basic Monitoring in 2005³³ to mandate that pulse oximeter and capnography not be turned off, indicating that many proceduralists find capnography alarms to be more harmful than helpful.

Subgroup analyses from a single RCT²⁶ indicated that capnography was more beneficial at reducing hypoxemia events during ERCP versus EUS procedures, and for obese patients versus non-obese patients. Other studies reported that certain patient and sedation characteristics were associated with increased risk of hypoxemia^25,26 (ie, lower baseline oxygen saturation, female sex, higher BMI, older age) and severe hypoxemia²⁵ or respiratory depression²⁵ (ie, higher doses of fentanyl or hydromorphone) across monitoring groups. Comorbidities such as ischemic heart disease and pack-year smoking history were also associated with apnea and disordered respiration²⁷ across monitoring groups. Consistent with standard practice,⁶ these findings suggest that clinicians should consider patient, procedure, and sedation characteristics when determining a monitoring plan, as some patients may be at higher risk of respiratory distress and other adverse outcomes than others undergoing the same procedure.

Conclusions

Overall, the evidence does not support an effect of capnography on 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 for colonoscopy compared to routine monitoring. Capnography is not associated with any difference in hypoxemia, severe hypoxemia, or adverse events in other types of procedures including TEE, minor oral procedures, or EGD. More detailed information is needed on how the timing of provider-delivered interventions affects hypoxemia, how the use of capnography affects downstream system outcomes such as wait times, as well as on the use of capnography for interventional radiology and cardiac procedures other than TEE.

Acknowledgments

This topic was developed in response to a nomination by the VA National Gastroenterology Program Office and the GI Field Advisory Committee for the purpose of informing a Moderate Sedation Directive by the VA National Anesthesia Service. The scope was further developed with input from the topic nominators (ie, Operational Partners), the ESP Coordinating Center, the review team and topic experts.

In designing the study questions and methodology at the outset of this report, the ESP consulted with technical and content experts. Broad expertise and perspectives were sought. Divergent and conflicting opinions are common and perceived as healthy scientific discourse that results in a thoughtful, relevant systematic review. Therefore, in the end, study questions, design, methodologic approaches, and/or conclusions do not necessarily represent the views of individual technical and content experts.

The authors gratefully acknowledge Payten Sonnen and Julia Haskin for their editorial review and the following individuals for their contributions to this project:

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Supplementary Materials

Suggested citation:

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. Posted final reports are located on the ESP search page.

This report is based on research conducted by the Evidence Synthesis Program (ESP) Coordinating Center located at the VA Portland Health Care System, Portland OR, funded by the Department of Veterans Affairs, Veterans Health Administration, Health Services Research and Development. The findings and conclusions in this document are those of the author(s) who are responsible for its contents; the findings and conclusions do not necessarily represent the views of the Department of Veterans Affairs or the United States government. Therefore, no statement in this article should be construed as an official position of the Department of Veterans Affairs. No investigators have any affiliations or financial involvement (eg, employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties) that conflict with material presented in the report.