In 1950, Kouwenhoven began his research on a closed-chest defibrillator.
Alfred Blalock, the Chief of Surgery at the time, was dubious at first regarding Kouwenhoven's ideas.
However, he soon agreed to provide laboratory space and equipment for Kouwenhoven's studies.
At first, Kouwenhoven and his team monitored the effect of electrodes on the opposite sides of the chest.
 They noted that a brief AC current of 20 amperes was able to jolt a heart from ventricular fibrillation back into a normal sinus rhythm.
Samuel Talbot, a surgeon who was studying heart arrhythmias in dogs at the time, asked Kouwenhoven to merge his research on a defibrillator with Talbot's studies.
Afterwards, Kouwenhoven observed that the current flowed best vertically instead of horizontally when passed through a dog's heart.
By noticing this, he was able to decrease the shock's intensity by 50 percent.

By 1957, Kouwenhoven and his team had designed a prototype specifically to work on humans.
This novel device weighed approximately 200 pounds and consisted of a small box with two insulated cables with copper electrodes, which administered an AC current.
One electrode was to be placed over the suprasternal notch, and the other electrode was to be placed over the apex of the heart.
In 1961, Kouwenhoven and his team were able to launch the first truly portable defibrillator with the help and support of Mine Safety Appliance Company of Pittsburg.
This new portable device weighed 45 pounds, and it could fit in a small plastic suitcase.

Guy Knickerbocker, an electrical engineer working at Kouwenhoven's laboratory, discovered that the copper electrodes caused a rise in blood pressure in the rest of the body when they were pressed down onto a dog's chest even before the current was passed through them.
He hypothesized that massaging the chest in a rhythmical manner causes the blood to circulate.
This observation paved the path for the third major discovery by Kouwenhoven's team: cardiopulmonary resuscitation also known as CPR.
In 1950, Kouwenhoven began his research on a closed-chest defibrillator. Alfred Blalock, the Chief of Surgery at the time, was dubious at first regarding Kouwenhoven's ideas. However, he soon agreed to provide laboratory space and equipment for Kouwenhoven's studies. At first, Kouwenhoven and his team monitored the effect of electrodes on the opposite sides of the chest.  They noted that a brief AC current of 20 amperes was able to jolt a heart from ventricular fibrillation back into a normal sinus rhythm. Samuel Talbot, a surgeon who was studying heart arrhythmias in dogs at the time, asked Kouwenhoven to merge his research on a defibrillator with Talbot's studies. Afterwards, Kouwenhoven observed that the current flowed best vertically instead of horizontally when passed through a dog's heart. By noticing this, he was able to decrease the shock's intensity by 50 percent.
By 1957, Kouwenhoven and his team had designed a prototype specifically to work on humans. This novel device weighed approximately 200 pounds and consisted of a small box with two insulated cables with copper electrodes, which administered an AC current. One electrode was to be placed over the suprasternal notch, and the other electrode was to be placed over the apex of the heart. In 1961, Kouwenhoven and his team were able to launch the first truly portable defibrillator with the help and support of Mine Safety Appliance Company of Pittsburg. This new portable device weighed 45 pounds, and it could fit in a small plastic suitcase.
Guy Knickerbocker, an electrical engineer working at Kouwenhoven's laboratory, discovered that the copper electrodes caused a rise in blood pressure in the rest of the body when they were pressed down onto a dog's chest even before the current was passed through them. He hypothesized that massaging the chest in a rhythmical manner causes the blood to circulate. This observation paved the path for the third major discovery by Kouwenhoven's team: cardiopulmonary resuscitation also known as CPR.
William B. Kouwenhoven