A Deep Dive into Decompression Sickness: Advancements in Hyperbaric Oxygen Therapy for Navy Divers

From locating and disarming Confederate mines during the Civil War to rescuing trapped sailors at Pearl Harbor during World War II, Navy divers have been regarded as crucial assets to the U.S. military for more than 150 years. Since the mid-19th century, Navy divers have accepted a variety of military assignments, including ship maintenance, construction, search and rescue missions, and other underwater operations.

While Navy diving is a vital facet of the U.S. military, it is also an inherently dangerous occupation with numerous associated health risks and complications. With the assistance of organizations, such as the Navy Experimental Diving Unit, the implementation of Haldane's decompression model, and advancements in diving technology, the U.S. Navy continues to develop new and improved safety measures for its divers.

During the early 20th century, most Navy divers served in the gunner's mate rating. They were responsible for operating and maintaining weapons systems, such as gun mounts and underwater explosives. Due to the nature of their assignments, gunner's mates typically received minimal training, as they were only tasked with completing dives of less than 60 feet, with a hand pump supplying air. By 1912, Chief Gunner George D. Stillson oversaw most naval diving activities and recognized the risks facing U.S. Navy divers.

The most pressing concern Stillson aimed to address was the health risk associated with deep diving known as decompression sickness, or caisson disease. It's more commonly referred to as "the bends." This condition can negatively impact a diver's health during their ascent from a deep dive. When divers breathe compressed air, primarily composed of nitrogen and oxygen, the concentration of these gases is much higher than at the surface. While the body continuously uses oxygen, nitrogen accumulates in the bloodstream. If a diver ascends too quickly, nitrogen can form bubbles that expand and can potentially block blood vessels. This blockage can cause a wealth of physiological reactions, including itching, redness, swelling, stiffness in the limbs, confusion, paralysis, difficulty breathing, vertigo, nausea, unconsciousness, and even structural damage in extreme cases.

To help mitigate the risk of decompression sickness in Navy divers, Stillson conducted experiments using Haldane's decompression model. Developed by John Scott Haldane in 1908, this model proposed that divers could ascend to the surface in stages, allowing nitrogen to escape naturally through the lungs. Haldane's decompression tables identified how long a diver needed to remain at each stated depth, or stage, to prevent decompression sickness.

In 1915, Stillson's team was sent to Honolulu to assist with the recovery of an F-4 submarine, which sunk to a depth of 304 feet. During the mission, many divers suffered from mental impairments, ultimately attributed to breathing compressed air. This recovery, along with the sinking of two additional submarines soon after, led to the establishment of the Navy Experimental Diving Unit. The new unit was tasked with researching, developing, testing, and evaluating diving equipment and procedures.

One significant advancement in treating decompression sickness was the introduction of hyperbaric oxygen therapy. Naval institutions began administering hyperbaric oxygen treatments in the 1930s. This treatment uses pressurized gas to treat divers affected by decompression sickness and arterial gas embolisms. After World War II, increased submarine activity sparked greater interest in hyperbaric oxygen therapy, leading to its acceptance as a standard treatment option. In the subsequent years, research and development further demonstrated its effectiveness in addressing a variety of ailments, including carbon monoxide poisoning and radiation injuries.

The U.S. Navy continues to use hyperbaric oxygen therapy to treat individuals suffering from decompression sickness. The National Museum of Health and Medicine houses a hyperbaric stretcher, a portable pressurized chamber designed to transport affected individuals to recompression treatment facilities. Although this model, the SOS Ltd. Hyperlite Emergency Evacuation Hyperbaric Stretcher (EEHS), is used by the U.S. Air Force, it features a pressure chamber sufficient to complete a full U.S. Navy Table 6 treatment, which is currently considered the 'standard of care' for treating decompression sickness. While this table is available for public use, it is often modified to meet the needs of commercial and recreational divers.

The U.S. Navy remains committed to innovating deep-sea diving technologies using pressurized air. In recent years, the Office of Naval Research sponsored the production and testing of the Deep Sea Expeditionary with No Decompression system. Essentially a wearable hyperbaric chamber, the DSEND system enables divers to maintain internal pressure while descending, eliminating the need for decompression during their ascent. This system allows for the exploration of greater depths in less time and reduces the risk of suffering caused by decompression sickness.

• U.S. Navy
• Historical Collections
• Navy Diving
• Navy Diver
• Decompression Sickness
• Caisson Disease
• The Bends
• John Scott Haldane
• George D. Stillson
• Hyperbaric Chamber
• Hyperbaric Stretcher
• History
• Innovation
• Technology