Tracey Barron

Academic Research

By Tracey Barron

Research to test the ability of a layperson-caller to detect a carotid pulse and accurately determine the pulse rate in a conscious person using the EMD-provided pulse check instructions shows precisely the reason behind the reliability, sustainability, and growing international reputation of the Medical Priority Dispatch System (MPDS).

The study conducted over six months (Sept. 2010–March 2011) gave us answers to what we had yet to discover and indications to what we could improve.

From long-standing research, we know that the pulse rate of a patient in a medical emergency can help to determine patient acuity and the level of medical care required. It is a key vital sign that can help an EMD determine a patient’s status, the type of response needed, and how quickly.

Drawing on previous research evidence and dispatch expertise, the International Academies of Emergency Dispatch (“Academy”) developed the MPDS Pulse Check Tool. The Pulse Check Tool can classify a patient into one of two clinical categories: patients with a pulse rate of 50–129 beats per minute, and those who fall outside this range. Protocol 19: Heart Problems/Automatic Implanted Cardiac Defibrillator (A.I.C.D.) directs the caller to take the patient’s pulse yet, prior to the study, little evidence existed regarding the ability of the caller to accurately determine a conscious patient’s pulse rate.

The Academy was eager to collect the empirical evidence necessary to test the tool’s effectiveness. Could the EMD-provided pulse check instructions provide the guidance a 9-1-1 layperson-caller needed to accurately determine a conscious patient’s pulse rate?

To test the question, electrocardiogram (ECG) monitors were set up to obtain a healthy mock patient’s pulse rate during the study conducted at three separate public places in Salt Lake City, Utah, USA.

The ECG reading was the control for investigators to determine the accuracy of layperson-callers performing a carotid pulse check on the same mock patient and obtaining a pulse rate following EMD scripted information in the Pulse Check Tool. A stopwatch tracked the time the layperson-caller took to detect a pulse. After 15 seconds, the investigator stopped the clock and the EMD instructed the layperson-caller to report the number of beats counted. The rate was recorded.

Results were encouraging.

Of the 268 layperson-callers participating, 246 (91.8%) found the patient’s pulse by following the EMD-provided pulse check instructions, and of those, 50% obtained a pulse rate within an eight-beat margin of error (allowing plus or minus one beat for each of four 15-second periods). The average time to detect a pulse was 15 seconds and there was an overall 94.6% correlation between pulse rates obtained using the ECG monitor and the rate by layperson-callers.

The study demonstrated that layperson-callers could find a carotid pulse and accurately determine the pulse rate of a conscious person, when given specific instructions over the phone.

Somewhat less reliable was the ability of some of the layperson-callers to count each of the pulses for the entire 15-second interval. Minor problems included the layperson-caller’s inability to find the pulse, losing the pulse while counting, and withdrawing fingers from the site of the carotid pulse when advised “not to press too hard,” which is a complication we will discuss later.

What does this mean for the evolution of the Pulse Check Tool?

Based on the findings, investigators recommended restructuring two of the instructions: pressure when applying fingers to check carotid pulse, and initiating the count once finding a pulse.

Pressure application: At times, the research team observed layperson-callers repositioning or removing their pulse-checking fingers from the patient’s neck as soon as the EMD stated the instruction “Be careful not to push too hard,” although none of the test patients reported that the layperson-callers were pressing too hard. This resulted in delays in finding a pulse (again) and, in some cases, counting the beats.

Consequently, it was recommended to remove this particular instruction from the MPDS script or merge it with the first instruction to read, “Without pushing too hard, find the Adam’s apple on her/his neck.”

Initiating count: Layperson-callers did not always inform the EMD when they had found a pulse, a necessary signal to the EMD to start the 15-second timer.

In this case, it was recommended that the pulse script could be improved by adding the following statements: “Tell me when you have found her/his pulse,” and “Count the beats out loud so I can time you, starting now.”

The Academy Medical Council of Standards subsequently reviewed the suggested changes to the Pulse Check Tool and, based on the research, made protocol changes that will be included in the next major protocol release.

It will be interesting to discover the effect of the modified instructions on layperson-callers’ ability to accurately take a pulse using this tool.

Note: The column was based on a study published in 2012: Scott, G., Clawson, J., Rector, M., Massengale, M., Thompson, M., Patterson, B., Olola, C. The accuracy of Emergency Medical Dispatcher Assisted Layperson-Caller Pulse Check Using the Medical Priority Dispatch System Protocol. Prehosp Disaster Med. 2012 June;27(3):1-8. (accessed Jan. 29, 2013)