About 8:30 a.m. on the 29th of May, Chris Frost, was near the end of the “Run with the Alewives” 10K race.

A fit 68-year-old, Chris was feeling good as he entered the final stretch on the Mills Road in Damariscotta Mills. Looking ahead, he saw somebody wearing yellow shorts and picked up his pace to pass. It was his last memory until he awoke in the critical care unit of Maine Medical Center in Portland several days later.

At that same time, registered nurse Jennifer Carlson was driving home on the Mills Road after a 12-hour shift at Maine Medical Center. As she entered Damariscotta Mills, she noticed a group of runners ahead of her and slowed down. Just then, Chris took a faltering step and fell down.

For a second or two she hesitated, unclear whether Frost had just tripped or was in serious difficulty. “‘Please get up,’” Carlson remembered thinking.

When he didn’t, she pulled over, assessed him, and began to perform cardiopulmonary resuscitation. Somebody in a truck pulled alongside and asked if she needed help. “Dial 911,” she shouted.

Chris was a victim of sudden cardiac arrest, a condition caused by an electrical malfunction in the heart that causes an irregular heartbeat or arrhythmia. Starved of oxygen, the brain begins to die in minutes.

Often affecting otherwise healthy people, sudden cardiac arrest strikes more than 390,000 people outside of a hospital each year, according to a 2015 report from the Institute of Medicine. Less than 6 percent survive.

Of that group of survivors, many will live with significant loss of function because their brain was without oxygen too long.

Chris was lucky. He not only survived, he survived without lasting negative effects. His first piece of luck was that he lost consciousness a few feet from a registered nurse trained and experienced in cardiopulmonary resuscitation (CPR).

His second piece of luck was that an AED (automated external defibrillator), a device designed to shock a heart that is beating irregularly back into a normal rhythm, was less than a mile away.

Nancy Jackson, nurse manager of the LincolnHealth Emergency Department, said success stories like Frost’s are all too rare. Wider availability of AEDs could make them more common, particularly in rural counties where ambulance response times can be long.

“We want to ensure that those devices are anywhere and everywhere they can be to immediately assist bystanders in their role of resuscitating people,” said Jackson, RN.

When a person suffers sudden cardiac arrest, CPR, particularly good chest compressions, circulates oxygenated blood to the body and brain, lengthening the window of survivability.

AEDs are not effective against every type of arrhythmia that causes sudden cardiac arrest, but they are effective against the most common cause – ventricular fibrillation. If CPR is combined with the use of an AED, the chances of survival rise dramatically.

According to the American Heart Association, immediate CPR and use of an AED more than double a victim’s chance of survival. Some communities have achieved sudden cardiac arrest survival rates of 40 percent, according to the American Heart Association.

As an experienced nurse, Carlson understood the importance of AEDs.

When Lincoln County Sheriff Sgt. Alan Shea arrived, the first question Carlson asked was if he had an AED.

Shea didn’t, but he knew where one was. Lincoln County Sheriff’s Deputy First Class Brian Collamore, who was in the Lincoln County Publishing parking lot less than a mile away, had one in his cruiser.

Within a minute, Collamore was on scene. Carlson applied the electrode pads to Chris’s chest and the machine gave one shock, restoring Chris’ heart to a productive rhythm.

Soon Chris was breathing on his own. The whole sequence of events, from the first stumble to the arrival of the AED, was perhaps 5 minutes long, although it felt much longer to Carlson.

Chris’s breathes were uneven, “staggered,” said Carlson. Still, his heart was beating and he was breathing. It was an enormously positive sign considering he had been clinically dead moments earlier.

When Central Lincoln County Ambulance Advanced Emergency Medical Technicians Devan Clark and Emily Wells arrived a minute or so later, Shea and Carlson were elated.

Clark and Wells inserted a tube into Chris’s trachea to help him breathe, starting two saline IVs and called the LincolnHealth Emergency Department to let them know they were on their way.

Clark was impressed with the level of carbon dioxide in Chris’s blood. It was almost normal, an indicator that the CPR had been very good and Chris had suffered almost no down-time.

As Chris was on his way to the hospital, so was his wife, Anne.

Anne had arrived at the Mills just as the race was ending and had been rerouted around the ambulance. After she parked, a friend told her the ambulance was for Chris and she ran to the scene.

It was a terrifying experience, but by the time Anne learned that her husband had been stricken, his chances of survival were already much better than the vast majority of people who suffer sudden cardiac arrest.

At the LincolnHealth Emergency Department, Registered Nurse Amy Tucker said she could tell Chris’ prognosis was positive from the moment the ambulance rolled into the Emergency Department bay.

“It was exciting,” said Tucker, “They weren’t doing compressions.”

That meant that Chris’ heart was already beating on its own and it meant he might not only survive, but might survive with normal brain function.

When Chris was transferred to Maine Medical Center, Tucker rode with him in the ambulance.

Chris’ heart maintained a normal rhythm on the way down and he continued to breathe, although as a precaution, he remained connected to a ventilator that assisted his breathing.

During that first anxious day or so before Chris regained consciousness, the key question was not whether he would survive, but how well he would be able to function when he awoke.

“The one thing they kept asking me at Maine Medical Center was how long had he been without oxygen,” said Anne.

Months later, Frost has made a full recovery with no lasting effects and is living life fully.

“The outcome is absolutely amazing to me,” said Anne. “He is fine. At first I worried about him doing this or that but now I think it was one of those (very rare) things. I don’t think it will happen again.”

Chris, a retired school administrator who was an advocate for AEDs during his career, also feels reassured.

“I am just tremendously appreciative of all the resources that came together to make it possible for me to be here,” said Chris, who served as Headmaster of Lincoln Academy in the 1990s.

Those resources can be divided roughly into two categories: the trained people who provided CPR, including Jennifer Carlson, Sgt. Alan Shea and an unidentified woman who also assisted.

Chest compressions – given at a rate of roughly 100 to 120 beats a minute (think the Bee Gee’s “Staying Alive”) – are the single most important part of CPR for victims of sudden cardiac arrest.

The other critical component was the AED that shocked Chris’ heart back into a productive rhythm.

The effectiveness of AEDs , however, is largely dependent on response time. According to the Red Cross, for each minute defibrillation is delayed, the chance of survival is reduced 10 percent.

In a rural county like Lincoln County, the chances of surviving sudden cardiac arrest are slim in towns more than 20 minutes away from centrally located ambulance stations, unless AEDs and trained volunteers are already nearby.