County first-responders to study cardiac arrest interventions

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King County emergency medical technicians (EMTs) will use two approved CPR approaches and researchers from UW Medicine will compare the outcomes to learn more about which CPR methods best support people to survive cardiac arrest. 

Study background

In a three-year study to begin this fall, King County emergency medical responders from area fire departments will alternately deliver two CPR interventions to people who experience an out-of-hospital cardiac arrest. Researchers will evaluate patients’ responses to the two approved approaches — both involving rescue breathing and chest compressions — to understand whether there is an optimal approach to improve cardiac-arrest survival.

Importantly, since people in this life-threatening circumstance are unconscious and unable to give informed consent to be involved, the UW Medicine researchers leading the trial have acquired a federal exception that allows people to be enrolled without their consent. People can, however, opt out of the study in advance or withdraw consent after they recover. See below for more information on how to opt-out of the study in advance.

CPR techniques to be studied

During cardiac arrest, a person’s heart suddenly stops pumping blood to the brain and body, which halts breathing, as well. Someone who experiences cardiac arrest will become unconscious and die in minutes unless chest compressions and rescue breathing are quickly provided. In some cases, an automated external defibrillator (AED) must also be applied to deliver a shock that restores the heartbeat.

The first CPR intervention being studied is rescue breathing. In one technique, a professional first responder places a bag mask over the patient’s mouth and nose, squeezing the bag to push air into the lungs. A second technique involves a curved plastic tube, which is inserted into the patient’s mouth. With this device, air from a squeezed bag is delivered more directly to the lungs.

“Both treatments are considered appropriate strategies for airway management, but it is unclear whether one approach has additional lifesaving benefit,” said Dr. Thomas Rea, an investigator and physician with UW Medicine and King County.

The second CPR intervention being studied is chest compressions, which help circulate blood. Current medical guidance is for first-responders to apply compressions to the unconscious person’s breastbone at a rate of 100 to 120 per minute.  However, this variable rate of compressions can yield different and dynamic blood flows. 

“We don’t know whether 100 compressions or 110 or 120 is better, in terms of the person’s regaining a working heartbeat,” said Dr. Rea. “So we’re comparing patients’ outcomes to see if one compression rate provides the most benefit.”

During the study, EMTs will deliver an assigned breathing strategy and compression rate. With each rescue attempt, the prescribed compression rate will follow the beats of an electronic metronome that EMTs will carry.

The study is expected to take three years and include 4,000 EMT responses to sudden cardiac arrest. Each King County fire department will be assigned one rescue approach for several months and then transition to the alternative approach, and EMTs will receive training with each transition. Researchers will review notes of each rescue attempt to determine that the first responders applied the assigned study treatment. 

For more information or to opt-out of the study

Patients who are rescued will be notified of their study enrollment when they are awake and alert. At that point, they can opt out of the study and decline future follow-ups associated with the clinical trial.

People can also opt out of trial participation in advance. To do so, email the FACT study’s administrators at To learn more about the study, including the emergency research exception, please visit or call 206-263-8577.

For more information, including videos about the study, see UW Medicine’s media release.

Originally published November 14, 2023.