The following exhibit tells the story of the Mayo Aero Medical Unit during World War II. Also highlighted is Dr. Edward J. Baldes’ work in postwar Germany with Operation Paperclip, a secret U.S. government program that recovered important research and recruited German scientists. This “Top Secret” exhibit features aeromedical artifacts, historical photographs, and newly translated archival documents.
In the 1930s, newly designed aircraft were able to fly higher than 10,000 feet. Pilots at this altitude were at increased risk of hypoxia, a condition in which the body’s tissues are starved of oxygen leading to fatigue and blackout. This was an increasingly significant factor in pilot error and plane crashes worldwide. Mayo Clinic and commercial airlines began researching solutions to this problem.
During World War II, Mayo Clinic created the Aero Medical Unit. They built pressure chambers, a centrifuge, and a cold chamber to study the effects of altitude and G-force on the human body. The Unit conducted research with Army and Navy pilots to develop the BLB oxygen mask, G-suit, and bail-out bottle that allowed pilots to fly faster, higher, and make more maneuvers in the air. These developments proved instrumental in the war effort.
One of Mayo Clinic’s high altitude pressure chambers, circa 1942.
Mayo Clinic researchers built a pressure chamber to simulate the high altitudes pilots endured. On March 26, 1939, Mayo Clinic’s pressure chamber, the first civilian high altitude chamber in North America, made its first “flight” to 15,500 feet. This gave Mayo Clinic researchers new understanding of the pathophysiology of hypoxia and decompression sickness at high altitude. The work produced a series of high-altitude oxygen masks (BLB masks) which were used during and after the war to protect pilots from oxygen deficiencies.
Dr. Earl H. Wood (right) and unidentified man in the centrifuge, 1946.
In 1942, Mayo Clinic built a human centrifuge in the basement of the Medical Sciences Building. The centrifuge was capable of simulating the high G-forces encountered in flight which led to pilot blackout and unconsciousness. The classified studies produced fundamental knowledge that led to the production of anti-gravity or “G”-suits for WWII fighter pilots. Drs. Charles F. Code, Edward H. Lambert, and Earl H. Wood repeatedly served as experimental subjects on the centrifuge.
Early prototype of the G-suit, 1941 (left) and improved design, 1945 (right).
With the help of David Clark of the David Clark Company, Mayo Clinic created the G-suit, a garment designed to combat the forces that kept blood from being pumped to the brain during high-speed maneuvers. As centrifugal forces on the pilot climbed above 1.5 G, bladders on the suit were automatically pumped full of air, restricting the flow of blood from the abdomen to the lower extremities thereby maintaining arterial pressure to the head. Its basic design is still in use today in modern fighter aircraft.
Patent drawing of an oxygen mask invented by J. D. Akerman, Dr. Boothby, and Dr. Bulbulian, circa 1940.
The BLB mask, named after its designers, Dr. Walter M. Boothby, Dr. W. Randolph Lovelace, and Dr. Arthur H. Bulbulian, was initially developed as part of Mayo Clinic’s response to an inquiry from Northwest Airlines regarding the efficacy of providing oxygen during regular passenger service at high altitudes. An increase in commercial airline crashes was attributed to “pilot error” due to newer airplanes flying above 10,000 feet. This altitude led to hypoxia, causing pilot fatigue. The first BLB mask was created at Mayo Clinic in February 1938.
At the solicitation of the U.S. Air Force in the early 1940s, the Mayo team modified the BLB mask and its oxygen equipment many times to meet the special needs of the military, resulting in the A-14 mask. This included making it frost-proof and equipped with a microphone for radio intercommunication. In the decades following WWII, the A-14 mask was a prototype for all subsequently developed military and medical oxygen masks.
This mold (left) for the A-14 came from Dr. Bulbulian’s personal collection of oxygen mask-related items. The mask displayed with it is a military surplus example.
Called a “benchmark” in oxygen mask development, the A-14 mask was modified by Dr. Arthur Bulbulian from earlier versions of the BLB mask. It made its combat debut in 1943 and was so well-designed that improved models remained in regular use well into the 1980s.
To stay conscious at high altitudes, aviators abandoning an aircraft needed an emergency supply of oxygen. Mayo Clinic designed a bailout bottle that could easily be attached to the pilot and activated upon leaving the plane. The end of the tube not connected to the bottle could be attached to the face mask. The bailout bottle was tested in numerous simulated parachute jumps in the altitude chambers in Rochester.
Aero Medical Unit personnel wearing the BLB mask and bail-out bottle, 1942.
The studies conducted in Mayo Clinic’s Aero Medical Unit were considered top secret and only individuals vetted by Mayo Clinic’s newly created Security Section were allowed access to the Unit. Specific Mayo staff members were issued photo identification cards that were required for admission. A number of women worked in the Unit, many of whom trained in Dr. Boothby’s Metabolic Lab, worked through the war, and continued to have long careers at Mayo Clinic.
The 2023 Heritage Days movie highlights the multi-faceted research done in Mayo Clinic’s Aero Medical Unit. It contains footage from newly transferred film reels held in the Mayo archives. The movie can be viewed on the Video Exchange and on Mayo Clinic’s History & Heritage external facing site.
The W. Bruce Fye Center for the History of Medicine has over 1,500 reel-to-reel films in its collections. Over the years, many have been transferred to digital format. The Center identified numerous films related to aeromedicine. With the help of Heritage Days, these films were then digitized at high resolution. Clips from many of these films can be seen in the new Heritage Days film described above.
Life at High G-Force: The Quest of Mayo Clinic Researcher Dr. Earl H. Wood by E. Andrew Wood, 2023
Dr. Earl Wood’s son, E. Andrew Wood, recently published a biography about his father that includes his experience in Mayo Clinic’s Aero Medical Unit. Published by Mayo Clinic Press, it can be purchased online at https://mcpress.mayoclinic.org.
At the end of 1945, Drs. Edward J. Baldes and Earl H. Wood joined Operation Paperclip, a secret U.S. government program aiming to salvage German scientific research. American advisors like Dr. Baldes traveled to Germany and met with scientists, examined facilities, and purchased necessary equipment and supplies for the continuation of vital projects. As part of the mission, thousands of German scientists and engineers—such as Wernher von Braun—were brought to the United States.
Born in 1898 to a German American family in Nebraska, Dr. Baldes joined Mayo Clinic’s Section of Biophysics and Biophysical Research in 1924. During World War II, Dr. Baldes’ work focused on the effects of acceleration, and he designed a human centrifuge to aid Mayo Clinic’s aeromedical research.
In September 1945, Dr. Baldes received orders to go to Germany, which he visited between October 1945 and May 1946. Based at the Army Air Forces (AAF) Aero Medical Center in Heidelberg, he met several German aeromedical experts and purchased scientific equipment for the continuation of their research. Dr. Baldes was struck by the state of postwar Europe, often noting the hardships the civilian population faced.
Operation Paperclip ran through the 1950s, but it is not clear whether Dr. Baldes participated beyond his 1945-46 visits to Germany. He served as special consultant to the USAF Aeromedical Laboratory at Wright-Patterson Air Force Base in Dayton, Ohio until 1954.
Back in Rochester, Dr. Baldes served as head of the Section of Biophysics and Biophysical Research from 1948 to 1958. During the 1955-56 school year, Dr. Baldes and his wife opened their home to Christa Bungener, a Lourdes High School exchange student from Olpe, Germany.
This exhibit was designed and curated by the staff of The W. Bruce Fye Center for the History of Medicine. All images and artifacts are from the Center unless otherwise stated.
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