Patients decompensate in largely unpredictable ways on medical-surgical units (MSUs). Cardiac and respiratory monitoring of patients in MSUs is minimal, even though approximately 40 percent of medical-surgical patients experience an acute respiratory event.1 Generally, patients in MSUs are assumed to be less complex and more hemodynamically stable — not requiring additional or continuous monitoring,2 however, many patients receive opioids for pain control, increasing their risk of opioid-induced respiratory depression (OIRD). Patients that experience an incident of respiratory depression are at higher risk of longer hospital length of stay, readmission to the hospital within 30 days of their discharge, higher cost of care, and higher mortality rates.3
Any patient can be at risk for OIRD, defined as hypoventilation with or without oxygen desaturation.4 Risk factors for developing OIRD include increased age, gender, obstructive sleep apnea, chronic pulmonary or cardiac disease, diabetes, hypertension, neurologic disease, renal disease, and obesity.5
Vital signs are usually monitored every 4 to 8 hours on the MSU, which could lead to missed early signs of OIRD — especially if only intermittent monitoring occurs. Additionally, rousing the patient for spot check assessments may mask respiratory depression. One study found periodic patient monitoring missed more than 90 percent of prolonged hypoxemia in MSUs.6
The workload clinicians carry on the MSU should be mentioned as patient-to-nurse ratios are commonly one clinician per every four to six patients. This leaves less time per patient for assessments and documentation to be completed. This is unlike an intensive care unit (ICU) where clinicians generally have only one to two patients. The availability of monitoring tools to assist medical-surgical clinicians in identifying patients at risk for OIRD could decrease the risk of serious adverse events, reduce length of stay and improve patient outcomes as clinicians may be able to intervene earlier to prevent adverse outcomes.
A monitoring tool was developed to help support clinicians further in identifying OIRD signs in patients. Recently, the PRediction of Opioid-Induced Respiratory Depression in patients monitored by capnoGraphY (PRODIGY) trial was conducted to derive and validate a risk prediction tool for respiratory depression in patients receiving opioid analgesia in MSUs.7
The tool was created by monitoring continuous pulse oximetry and capnography results to identify patients experiencing respiratory depression. Capnography is a validated measurement of respiratory rate and end tidal CO2 that captures respiratory depression earlier than pulse oximetry, as CO2 levels increase before oxygen decreases in response to hypoventilation from OIRD.8
Monitoring capnography and utilizing a risk assessment tool such as PRODIGY may assist MSU clinicians in identifying at risk patients and assuring necessary resource allocation. A device that captures capnography, such as the Capnostream™ 20p bedside monitor or Capnostream™ 35 portable respiratory monitor, is designed for ease-of-use and collects CO2 measurements from a special nasal cannula with an oral scoop and O2 levels from a pulse oximeter placed on the patient’s finger.
Additionally, work is being done to integrate the PRODIGY tool into health system’s electronic health records to decrease the documentation burden on MSU clinicians. Once a patient is identified as high risk for OIRD and placed on a capnography monitor, an alarm notifies clinical staff when patients levels go above or below normal. Clinicians may use this knowledge to help determine whether to intervene to correct the patient’s breathing abnormality, administer medications to reverse sedation, or correct medication dosages as needed.
A clinician’s over-arching goal is to keep patients safe. Knowing which patients are at high risk for OIRD using the PRODIGY score may help provide information clinicians can use to determine the appropriate monitoring needed. Preventing respiratory depression events may decrease the burden on hospitals and health systems, but ultimately preventing these events helps to enhance patient safety.
Microstream™ capnography and Nellcor™ pulse oximetry monitoring systems should not be used as the sole basis for diagnosis or therapy and are intended only as adjuncts in patient assessment.
1. Anderson LW, Berg KM, Chase M, Cocchi MN, Massaro J, Donnino MW. American Heart Association’s Get With The Guidelines Resuscitation Investigators. Acute respiratory compromise on inpatient wards in the United States: Incidence, outcomes, and factors associated with in-hospital mortality. Resuscitation. 105:23-129:2016. https://doi.org/10. 1016/j.resuscitation.2016.05.014.
2. Khanna A K, Overdyk FJ, Greening C, Di Stefano P, Buhre WF. Respiratory depression in low acuity hospital settings-Seeking answers from the PRODIGY trial. Journal of Critical Care. 47:80-87:2018.. https://doi.org/10.1016/ j.jcrc.2018.06.014.
3. Jungquist CR, Chandola V, Spulecki C, Nguyen KV, Crescenzi P, Tekeste D, Sayapaneni PR. Identifying patients experiencing opioid-induced respiratory depression during recovery from anesthesia: The application of electronic monitoring devices. Worldviews on Evidence-Based Nursing.16(3):186-194:2019.
4. Dahan A, Aarts L, Smith TW. Incidence, reversal, and prevention of opioid-induced respiratory depression. Anesthesiology. 112:226-238:2010.
5. Gupta K, Prasad A, Nagappa M, Wong J, Abrahamyan L, Chung FF. Risk factors for opioid-induced respiratory depression and failure to rescue: A review. Current Opinion in Anaesthesiolgy. 31(1):110-119:2018. https://doi.org/ 10.1097/ACO.0000000000000541.
6. Sun Z, Sessler DI, Dalton JE, Devereaux PJ, Shahinyan A, Naylor A J, et al. Postoperative hypoxemia is common and persistent: A prospective blinded observational study. Anesthesia & Analgesia. 121(3):709-715:2015. https://doi. org/10.1213/ANE.0000000000000836.
7. Khanna AK, Bergese SD, Jungquist CR, Morimatsu H, Uezono S, Lee S, et al. Prediction of opioidinduced respiratory depression on inpatient wards using continuous capnography and oximetry: An international prospective, observational trial. Anesthesia & Analgesia. 131(4 ):1012-1024:2020. https://doi.org/10.1213/ANE.000 0000000004788.
8. Stites, M., Surprise, J., McNeil, J., Northrop, D., & DeRuyter, M. (2017). Continuous capnography reduces the incidence of opioid-induced respiratory rescue by hospital rapid resuscitation team. Journal of Patient Safety. https://doi.org/10. 1097/PTS. 0000000000000408.