The following is an excerpt from “Life at High G-Force,” a new Mayo Clinic Press biography of Dr. Earl H. Wood, one of Mayo Clinic’s most prominent researchers, best known for his ground-breaking work on the G-suit during World War II as well as his role in the creation of several innovative medical technologies.
Tensions were high in the Aero Medical Laboratory at Mayo Clinic in the fall of 1959.
The space race with the Soviet Union to send a human into outer space and eventually to the moon was in full gear. Laboratory personnel were busy preparing the human centrifuge and a human subject for an experiment to evaluate physiological responses to prolonged g-forces. The newly formed National Aeronautics and Space Administration (NASA) had funded Mayo Clinic’s Aero Medical Laboratory, directed by Dr. Earl Wood, to study the effects of prolonged g-forces on the human body during blastoff and reentry into the Earth’s atmosphere from space.
During World War II, Earl Wood and a team of doctors, scientists, and technicians developed the instrumentation to record physiological data from human subjects on a centrifuge experiencing the high gravitational forces pilots experienced in combat aircraft. Now they were being asked to study the effects of gravitational forces on astronauts going into outer space.
That day, Dr. Hiram “Hi” W. Marshall sat strapped into the cockpit at the end of the centrifuge, in the same position as an astronaut in a Mercury space capsule. A research fellow at Mayo Clinic, Dr. Marshall had been chosen as the subject for this study — and he was a little nervous as his coworker went through checklists; he could feel the vibration of two twenty-ton flywheels rotating underneath the superstructure of the centrifuge.
A catheter was placed in his arm and ran up to his heart to measure heart pressures while he was subject to the g-forces. An infrared sensor was placed on his ear to monitor his pulse at head level and blood-oxygen saturation. All of this, of course, was being closely monitored by Dr. Wood, his fellow medical researchers, and technical staff to assure Dr. Marshall’s safety and get data for the research they were conducting.
In the center seat at the center shaft of the centrifuge, Dr. Earl Wood monitored the physiological responses of the subject plus the functioning of the centrifuge. In a room next to the centrifuge, Lucy Cronin monitored the safety procedures of the centrifuge runs. In a room above Lucy, Bill Sutterer ran the centrifuge’s clutch and braking system. Across the hall was Don Hegland, who ran all the analog data-recording equipment.
With the two twenty-ton flywheels spinning freely at a prescribed speed for a 4G run, Dr. Wood spoke over the intercom: “OK, Donnie, start your recording.” This was to get baseline data on the subject at 1G.
Once the data was reviewed, Lucy began the ten-second countdown for a centrifuge run. On ten, the subject was A-OK. On nine, the flywheels were spinning at the correct rpm; on eight, all tools had been removed from the centrifuge, the doors to the centrifuge room were locked, and so on. When she got to three, the countdown was handed over to Dr. Wood.
“Two, Donnie, start your recording; one, Bill, start the run.”
Bill Sutterer released the brakes on the centrifuge and engaged the clutch on the flywheels, and the centrifuge started to spin, reaching the prescribed G in one and a quarter rotations!
After one minute at 4G, Dr. Marshall indicated he was having severe chest pain. Dr. Wood signaled to hit the brakes on the centrifuge, which came to a grinding halt.
Frightened, he and the team rushed to the cockpit. They could see only one side of Dr. Marshall’s chest rising when he took a breath, and they could hear a gurgling sound with each breath.
Dr. Marshall was suffering from a pneumothorax. He was rushed to Saint Marys Hospital, where he recovered, and he was back to work the next day. Although very concerned and worried, Dr. Wood and the team were relieved Dr. Marshall did not sustain any long-lasting injury.
The human centrifuge experiments posed some risks that the scientists were willing to take to increase the biological knowledge of aviation, space travel, and clinical medicine.
