Capnography is the noninvasive measurement of the partial pressure of carbon dioxide (CO2) in exhaled breath, expressed as the CO2 concentration over time and graphically represented by the CO2 waveform, or capnogram; it also measures end-tidal CO2 (etCO2).1
Capnography is part of the standard of care for all patients receiving general anesthesia and is an emerging standard of care in intensive care and other non-OR hospital locations, including the post-anesthesia care unit (PACU)2 and during procedural sedation and analgesia (PSA).3
The results of studies reported in 2015 support the expanded use of capnography in these clinical settings.4-9
Capnography Monitoring in the PACU
Continuous capnography monitoring is recommended in the PACU for patients with tracheal intubation or whose airways are maintained with a supraglottic or similar airway device.2 Capnography also may be used following surgery to monitor patients who are receiving patient-controlled narcotic analgesia or who may be at significant risk for respiratory compromise.10
In a prospective observational study of 162 obese (body mass index >28) or elderly (age >75 years) patients considered to be at high risk for respiratory compromise in the PACU following general surgery, monitoring by capnography and the Integrated Pulmonary Index predicted the onset of respiratory adverse events (defined as a respiratory event associated with prolonged
PACU stay or transfer to intensive care units due to airway narrowing, hypoxemia, wheezing, or apnea) with greater sensitivity and specificity than pulse oximetry alone.4 The results suggest the need to measure etCO2 in addition to pulse oximetry in high-risk PACU patients.
It is usually the responsibility of nurses to recognize respiratory compromise which consists of respiratory insufficiency, failure and arrest, and dramatically increases the likelihood of adverse outcomes and cost of patient care in the PACU.11
In a study to assess the usefulness of capnography for 51 PACU patients at high risk for respiratory compromise, monitoring by nurses identified the need for stimulation in 30% of patients, increased oxygen delivery in 14%, and further decrease of pain medication in 12%.5 The authors concluded that capnography monitoring serves as an adjunct non-invasive tool that is not harmful to the patient and can identify early signs of respiratory compromise.
SEE ALSO: Essential Capnography
Another study measured the impact of capnography monitoring by nurses in 21 PACU patients at risk for sleep apnea and found that 95% had abnormal etCO2 values with normal oxygen saturation, 81% required some intervention.6 The authors concluded that capnography monitoring of PACU patients at risk for respiratory compromise provides an opportunity for early intervention to mitigate adverse patient outcomes. In a third study, capnography monitoring identified patients in a hypercarbic state earlier in the postoperative recovery period than previously with no ventilation monitoring, supporting its use to ensure adequate ventilation is being measured in the PACU.
Capnography During PSA
Because PSA is associated with the same or even greater risk of sedation-related adverse events as general anesthesia, including respiratory compromise as a result of central nervous system depression, frequent monitoring, including capnography, is recommended.3 However, adding capnography to procedural sedation guidelines currently is being discussed by the medical community due to an absence of standardized endpoint definitions of adverse events and limited evidence demonstrating clinical utility.8 A study that, for the first time, systematically reviews clinical trials of capnography during PSA is planned to examine the current state of evidence on the benefits to patient safety in hospital settings.3
Although synthesis of clinical trial data is pending, the results of two safety benefit and cost-effectiveness studies of capnography in PSA were reported in 2015. In a modeling study to determine the potential cost-effectiveness during PSA for endoscopy, capnography monitoring reduced the proportion of patients experiencing one or more adverse events including respiratory compromise by 26.8%.8 Based on a cost-efficacy model assuming 8,000 patients in 1 year and a capnography cost of $4,000 per monitor, capnography resulted in a saving of $123 per procedure due to the reduction in adverse events. These results suggest that capnography monitoring during endoscopy is likely to be cost effective.
The same investigators reported the results of a second modeling study of capnography in patients receiving moderate sedation during gastrointestinal endoscopy.9 Results showed that the proportion experiencing one or more adverse events was reduced by 18% with capnography monitoring, which translated to a savings of $55 per procedure. The authors concluded that the use of capnography monitoring for PSA increases patient safety, does not significantly increase the cost of the procedure, and in the majority of cases is actually cost saving.
Barriers to Continuously Monitoring Patients on Opioids
The Association for the Advancement of Medical Instrumentation (AAMI) is a nonprofit organization with one mission: the development, management, and use of safe and effective healthcare technology. On November 14, 2014, the AAMI Foundation convened an Opioid Safety and Patient Monitoring Conference sponsored by the National Coalition to Promote Continuous Monitoring of Patients on Opioids, the Compendium of which was published in 2015.12 The vision statement emerging from the conference recommended improved safety for patients receiving parenteral opioids by supplementing ongoing assessments of sedation level and respiratory status with continuous electronic respiratory monitoring for timely detection of respiratory compromise. The conference also identified a number of potential financial barriers to adopting and implementing this recommendation including:
- What is the financial justification for continuously monitoring patients on opioids?
- How can clinical, quality, and safety directors best approach decision makers so that policy allows for continuous monitoring of patients on opioids?
- Will the new payment models (e.g., bundled payments, value-based purchasing) promote the business case for continuously monitoring patients on opioids?
These questions provide the basis for future economic studies and healthcare policy discussions that will determine the role of patient monitoring for patients on opioids in the era of value-based healthcare.
Summary and Conclusions
Capnography offers accurate monitoring of respiratory status and earlier warning of impending respiratory compromise, providing an increased level of patient safety and potentially better outcomes in the PACU and during PSA. Recently reported studies show the clinical and economic benefits of capnography monitoring when used in these settings. However, some financial barriers to implementation still exist and need to be further explored.
Sam Ajizian is Vice President, Medical Affairs, Medical Director and Safety Officer, Patient Monitoring and Recovery, Medtronic.
1. Krauss B, Silvestri S, Falk JL. Carbon dioxide monitoring (capnography). Up to Date. 2015. Available at: http://www.uptodate.com/contents/carbon-dioxide-monitoring-capnography
2. Whitaker DK, Booth H, Clyburn P, et al. AAGBI Safety Guideline. Immediate post-anaesthesia recovery 2013. London, UK. The Association of Anaesthetists of Great Britain and Ireland. 1-20.
3. Conway A, Douglas C, Sutherland J. Capnography monitoring during procedural sedation and analgesia: a systematic review protocol. Systematic Rev. 2015;4:92.
4. Okahara S, Ishii K, Morimatsu H. Integrated pulmonary index can predict respiratory adverse events in postoperative high-risk hypoventilation patients at post-anesthesia care unit. American Society of Anesthesiologists Annual Meeting. October 24-28, 2015. San Diego, CA. Abstract #A3024.
5. Guiterrez M, Dinh L, Graves S, Hernandez G. A healthy way to vent: capnography monitoring in the PACU. J PeriAnesth Nurs. 2015;30:e18. Available at: http://www.aspan.org/Portals/6/docs/ClinicalPractice/2015CSPpdfs/142_Poster.pdf
6. Taylor H, Antin N, Grandstrand J, et al. ETCO2 monitoring in high risk patients in the PACU: a quality improvement project. American Society of PeriAnesthesia Nurses (ASPAN) 34th National Conference. April 26-30, 2015. San Antonio, Texas. Available at: http://www.aspan.org/Portals/6/docs/ClinicalPractice/2015CSPpdfs/141_Poster.pdf
7. Wolf L, Coughlin K, Devaux D. Capnography for the perioperative nurse. American Society of PeriAnesthesia Nurses (ASPAN) 34th National Conference. April 26-30, 2015. San Antonio, Texas.Available at: http://www.aspan.org/Portals/6/docs/ClinicalPractice/2015CSPpdfs/143_Poster.pdf
8. Saunders R, Erslon M, Vargo J. Modeling the cost-effectiveness of capnography monitoring during procedural sedation for endoscopy. American Society of Anesthesiologists Annual Meeting. October 24-28, 2015. San Diego, CA. Abstract #A4163.
9. Saunders RJK, Erslon MG, Vargo JJ. Cost effectiveness of capnography monitoring during gastrointestinal endoscopy targeting moderate sedation. International Society for Pharmacoeconomics and Outcomes Research (ISPOR) 18th Annual European Congress. November 9, 2015. Milan, Italy. PMD63.
10. Spiegel J. End-tidal carbon dioxide: the most vital of vital signs. Anesth News. October 2013:21-27. Medtronic focuses on a preventable patient safety issue: respiratory compromise. Press Release. October 28, 2015. Available at: http://newsroom.medtronic.com/phoenix.zhtml?c=251324&p=irol-newsArticle&ID=2103395
11. AAMI Foundation. Summary of break groups: barriers to continuously monitoring patients on opioids. In: Opioid Safety and Patient Monitoring Conference Compendium. November 14, 2014. Chicago, Illinois. 2015:1-68. Available at: http://s3.amazonaws.com/rdcmsðaami/files/production/public/FileDownloads/HTSI/Opioids/2015_Opioid_Compendium.pdf