Updated: Apr 5, 2020
The current pandemic brings to mind that last great pandemic (1918-1920) and the actions of one physician who became the first to employ a hyperbaric chamber specifically to drive additional oxygen into tissues. Today we call this process hyperbaric oxygen (HBO) therapy and its first patients were Spanish Influenza victims.
Early Hyperbaric Chamber Use
Until this period, the singular therapeutic basis for hyperbaric chamber use was that of the inverse relationship between pressure and volume, namely Boyle’s Law. Workers exposed to compressed air during bridge construction and mass transit tunneling projects were at risk for “caisson disease”, now referred to as decompression sickness. This condition resulted from formation of embolic gas secondary to inadequate decompression. Re-exposing injured workers to elevated air pressures within a hyperbaric chamber reduced/eliminated offending gas, frequently affecting cure. By the turn of the 20th century, "recompression" chambers were increasingly commonplace at civil engineering worksites incorporating compressed air. Naval and civilian divers, likewise at risk of decompression sickness, were soon to benefit in a similar manner.
Oxygen as Therapy
The discovery of oxygen occurred some 150 years earlier. However, it had remained more of a research curiosity until 1922 and the publication of Haldane’s seminal work “Respiration” before it finally entered mainstream medical therapeutics. Although Haldane proposed its clinical use several years earlier, “Respiration” clearly got everyone's attention. Unfortunately, the outbreak of Spanish Influenza pre-dated this advancement, leaving its victims struggling to breathe with nothing more forthcoming than the oxygen concentration in normal atmospheric air. For a great many this proved woefully inadequate.
HBO's First Patients
Enter Orval J. Cunningham, Associate Professor of Surgery and Chair of the Department of Anesthesia at the University of Kansas Medical Center. Cunningham was considered a remarkably keen clinical observer. In one example, he had noted that patients with lung diseases appeared to improve when traveling from Colorado to Kansas. Another example, and more critical at the time, was that the pandemic's morbidity and mortality was greater in areas of high elevation, such as Colorado, compared to coastal regions. As an anesthesiologist, Cunningham was understanding of Dalton's Law and its effect on gas pressures. He rightly considered that the only significant variable was an increase in oxygen pressure as altitude decreased. He sought to determine if further increases in ambient air pressure beyond normal atmospheric pressure could produce a clinically meaningful effect. To investigate this he borrowed a small hyperbaric chamber from a local diving contractor and arranged for its installation at the university medical center. In it, he treated several profoundly cyanotic and moribund influenza patients and met with "instant success". "Patients whose lips bore the blue-black livid stamp of the kiss of death and were deeply unconscious, but if not too far from the brink, in a matter of minutes were brought back to normal color and return to consciousness". Importantly, Cunningham had no access to oxygen. He had managed to accomplish these marked clinical improvements by the simple act of increasing chamber pressure with air, letting Dalton's Law do the rest. History should acknowledge, then, Dr. Orval J. Cunningham as the first hyperbaric oxygen practitioner. It would be another 15 years before oxygen breathing under hyperbaric conditions was introduced, thereby forming the basis for the modern practice of hyperbaric medicine.
By late 1918, the second and more deadly wave of the pandemic had started to subside, so too the number of its victims treated by Cunningham. With additional and much larger chambers under consideration and a diminishing influenza caseload, he sought out other conditions that he thought might benefit from increased oxygen delivery afforded by elevated air pressure. This journey eventually resulted in him condemned by the American Medical Association and his legacy forever tarnished.
Oxygenation of Today's Pandemic Victims
Fortunately, today's influenza sufferers have ready access to unlimited supplies of oxygen. Delivered at normal atmospheric pressure within the ED and ICU, it results in higher doses than those achievable within Cunningham's compressed air chamber. Mechanical ventilation, when indicated, further enhances oxygen’s therapeutic effect.
References available upon request.