Capnography, Patient Monitoring

Monitoring for Respiratory Compromise to Detect Cardiac Arrest

In his op-ed, Lakshmipathi Chelluri, MD, MPH (Professor, Department of Critical Care Medicine, Co-chair, P&T Committee, UPMC Presbyterian, University of Pittsburgh School of Medicine), asks a great question “Preventable In-Hospital Cardiac Arrests―Are We Monitoring the Wrong Organ?[1]

To help prevent the onset of cardiac arrest, Dr. Chelluri suggests that clinicians should be monitoring for respiratory compromise as a key trigger or potential alert for cardiac arrest.

To understand this proposition better, I asked Dr. Chelluri a number of questions. I hope that you will find this discussion to have high clinical value and interest. The actual implementation of them could significantly save patients’ lives:

Q: To detect cardiac arrest, isn’t electrocardiography (ECG) monitoring the accepted practice?

A: ECG monitoring is used extensively outside of ICU. However, recent research has looked at cardiac arrest outcome and continuous ECG monitoring, and found that many patients are receiving ECG monitoring unnecessarily.[2] Cardiac monitoring has been shown to be ineffective in identifying patients at risk for respiratory deterioration and cardiac arrest as result of respiratory arrest. With this knowledge, we need to be asking ourselves what monitoring might be better at detecting the onset respiratory deterioration. I would suggest that that monitoring should be respiratory monitoring.

Q: Why do you think that respiratory monitoring might detect and possibly prevent cardiac?

A: Many cardiac arrests have a respiratory origin. To do understand this better, we need to consider the etiology of cardiac arrest. Primary etiologies consist of a cardiac disease, such as ischemia or failure, causing ventricular fibrillation/ventricular tachycardia. Secondary etiologies consist of non-cardiac events, hypoxia and respiratory failure.1 These non-cardiac events are respiratory in nature, may cause asystole (commonly known as an incident when the patient ”flatlines”) or pulseless electrical activity (in which electrical activity is detected in the heart, but the heart does not contract to generate a pulse). Secondary cardiac arrest is often related to hypoxia or fatigue/hypercarbia, which may lead to respiratory compromise followed by tachycardia, bradycardia and cardiac arrest. Distinguishing between these two etiologies may therefore help us to increase focus on respiratory monitoring and prevent cardiac arrest in some patients.

Q: To help detect secondary cardiac arrest due to respiratory compromise, what respiratory monitoring would you currently recommend?

A: Current respiratory monitoring systems available for prevention of secondary cardiac are pulse oximetry and capnography monitoring. Pulse oximetry measures the oxygenation of blood and is widely use. However, pulse oximetry is a lagging indicator to detect fatigue and respiratory compromise. Capnography measures the amount of carbon dioxide in exhaled breath and is a better indicator of the adequacy of ventilation of the patient. However, capnography monitoring does have its own limitations. Most particularly, making sure that the nose cannula actually stays on the patient, as measurement depends on accurately sensing the flow. Improving capnography technology and multimodal monitoring (respiratory rate, pulse oximetry and capnography) could identify patients at risk of respiratory deterioration and progression to cardiac arrest.

References

Chelluri, L. (2014) Preventable In-Hospital Cardiac Arrests―Are We Monitoring the Wrong Organ? Open Journal of Emergency Medicine, 2, 43-45. http://dx.doi.org/10.4236/ojem.2014.23007

[1] http://www.scirp.org/journal/PaperInformation.aspx?paperID=49206#.VBdZGktpnzQ

[2] Henriques-Forsythe, M.N., Ivonye, C.C., Jamched, U., Kamuguisha, L.S.K., Olejme, K.A. and Onwuanyi, A.E. (2009) Is Telemetry Overused? Is It as Helpful as Thought? Cleveland Clinic Journal of Medicine, 76, 368-372. http://dx.doi.org/10.3949/ccjm.76a.07260

Schull, M.J. and Redelmeier, D.A. (2000) Continuous Electrocardiographic Monitoring and Cardiac Arrest Outcomes in 8,932 Telemetry Ward Patients. Academic Emergency

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