Capnography: A Missed Vital Sign in Post Anesthesia Care Units

Submitted by Cheyenne D. Bonja, RN

Tags: anesthesia nurse opiods PACU

Capnography: A Missed Vital Sign in Post Anesthesia Care Units

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As nurses, we are taught to assess airway, breathing, and circulation. We learn these basic principles and bring them to the critical care setting daily. Airway and breathing are the first vital signs assessed for patients entering the post-anesthesia care unit, as well as blood pressure, level of consciousness, pain, and temperature. An essential vital sign often overlooked is measuring end-tidal carbon dioxide (ETCO2), which can give nurses crucial data on your patient's respiratory status. 

Capnography is a valuable monitoring tool that can provide critical ventilatory data for patients who are still intubated or have an oral airway present, patients under deep sedation or receiving opioids, or patients with underlying conditions such as sleep apnea, asthma, or COPD. Capnography is a non-invasive method that uses a small nasal/nasal-oral cannula to measure gas concentration by aspiring a small sample from the exhaled breath through the cannula tubing sensor inside the monitor. ETCO2 values are measured by mmHg or millimeters of mercury, with a normal range between 35-45mm Hg. It provides early detection of adverse respiratory events in post-operative patients in PACU.

Patients in PACU have an increased risk of respiratory adverse events because of anesthesia, nurses administering opioids for post-operative pain relief, and patients with compromised respiratory status. Capnography determines if a patient has hypo or hyperventilation compromise regardless of what the oxygen saturation monitor shows due to slight delays in the monitor. A nurse can asses real-time ventilation status and intervene quickly, which can lead to short recovery times or transfer patients to a higher level of care if needed. Interventions for a compromised ventilatory status include applying a CPAP or BiPAP to patients or possibly needing a reversal agent such as Narcan for opioid overdosing.

Many PACU nurses do not use capnography as a standard practice and should start implementing this tool as it can give you much information about the patient's well-being. Not only should capnography be used for patients still intubated or sedated, but it should be used for patients who have a history or familial history of malignant hyperthermia. Early signs of malignant hyperthermia can show increased changes in ETCO2. 

An analysis of a blinded observational trial by Chung et al. was conducted to determine how well capnography in the PACU works to detect early respiratory events rather than just using oxygen saturation (SpO2) alone. The capnography detected respiratory adverse events 8.3 to 11 minutes earlier than standard monitoring in 75 percent of cases. Chung et al. concluded that adding capnography to standard monitoring would be valuable in the early detection of respiratory adverse events. Another quality improvement project by Oswald et al. article about implementing capnography in the PACU and beyond monitored high-risk patients and patients receiving opioids "identified that 44% of patients had high ETCO2 and 48% of patients had a low respiratory rate". Capnography identified respiratory depression earlier than pulse oximetry observations in 100% of patients. (Wilks & Foran, 2021)

Capnography is a tool that needs to be utilized to monitor and respond to any respiratory events in the PACU. It should be brought into standard practice for all high-risk patients or intubated upon arrival to the PACU. Capnography will provide nurses with a full real-time assessment and understanding of the patients in recovery and treatment. PACU nurses should advocate having capnography monitoring and nasal cannulas be placed in recovery to be applied and increase patient safety. 

References:

  • Baird, M. (n.d.). IMPLEMENTATION OF CAPNOGRAPHY IN THE PACU AND POST-OPERATIVE UNIT. https://www.aspan.org/Portals/88/Conference/2022/Handouts/Saturday/403_Capnography.pdf?ver=2JTOXX5kJrSidSGAcp8wxw%3D%3D#
  • Kas, D. P. (2019, April 27). Capnography | Emergency Medicine Education. Resus. https://resus.com.au/capnography/
  • McNeill, M. M., & Tabet, C. H. (2021). The Effectiveness of Capnography Versus Pulse Oximetry in Detecting Respiratory Adverse Events in the Post-anesthesia Care Unit (PACU): A
  • Narrative Review and Synthesis. Journal of PeriAnesthesia Nursing, 37(2). https://doi.org/10.1016/j.jopan.2021.03.013
    Wilks, C., & Foran, P. (2021). Capnography monitoring in the post Anaesthesia Care Unit (PACU). Journal of Perioperative Nursing, 34(2). https://doi.org/10.26550/2209-1092.112