By Kaitlin Mogentale
Originally published at ScientificAmerican.com
On one of our multiple dive training trips to California’s beautiful Santa Catalina Island, we were fortunate enough to receive a tour of the hyperbaric chamber stationed on the island. Inside the chamber, one of the volunteers runs through a quick explanation of typical treatment for a bent diver. The process of re-compression in the chamber complicated, and chambers must be fully staffed and well maintained to be of benefit to an injured diver. The experience left me wondering… Is there any other way to treat a bent diver?
Although the existence of an alternate form of treatment may not exist today, the future of diving medicine is advancing–and the possibility of medicinal decompression sickness protection is a topic of research interest. Research at the United States’ Naval Medical Research Center suggests new approaches to decompression sickness risk reduction. The scientists at the center are researching means of active elimination of the inert gas load in the body through two methods: immune system interactions and biochemical decompression.
When a diver is surfacing, the nitrogen pressure in some tissues may exceed the ambient pressure. To reach equilibrium, our body tissues off-gas and release the excess nitrogen. Problems occur when a diver ascends too quickly. If the ambient pressure drops to a specific point (as decided by the over-saturation limit of nitrogen in a specific tissue compartment), the nitrogen solution comes out of the body tissues, forming bubbles. As the bubbles course through our body, an inflammatory signal is activated, and the nitrogen bubbles are easily trapped in the pathways through which they travel.
The result is that blood flow is blocked–potentially harming vital organs such as the spinal cord and the brain. One possibility of decompression sickness risk reduction, as explored by the NMRC, involves blocking the immune system’s inflammatory response to intravascular bubbles with the use of anti-inflammatory drugs. This technique is regarded as one of the safest and most effective ways of avoiding decompression sickness.
Another potential approach to DCS risk reduction is biochemical decompression. Through biochemical decompression, the human body is provided with the mechanisms needed to metabolize inert gas, such as nitrogen or hydrogen. Research thus far favors the insertion of bacteria with a natural ability to metabolize inert gases into the large intestine of human divers, by means of digestion of a bacteria-containing capsule, as the method for biochemical decompression. Experimental results show that the insertion of bacteria with the ability to metabolize hydrogen gas is very successful in removing a substantial amount of inert gas in rat and pig test subjects–substantial enough that the test subjects had lower occurrences of decompression sickness than their control counterparts.
Hydrogen gas is not typically used in diving gas mixtures; nitrogen has much greater application as a breathing gas. The NMRC’s research with nitrogen-metabolizing bacteria shows that there are many issues preventing its widespread use for decompression sickness reduction. For one, most bacteria will only fix atmospheric nitrogen in an environment that contains no previously fixed nitrogen. If the bacteria were to be used in diving situations, it would need to be able to fix nitrogen in an environment where N2 has already built up in a diver’s tissues due to compression under water.
Additionally, nitrogen fixation occurs at a much slower rate than hydrogen metabolism, making nitrogen-fixing bacteria less effective at reducing the inert gas load in the human body. To account for the loss in efficiency of nitrogen-fixing bacteria, an exceptionally large volume of bacteria would need to be inserted into the intestine–a volume much too large for practical use. In the future, genetic engineering could alter nitrogen-fixing bacteria so that the rate of nitrogen absorption is increased to a degree large enough for application in the diving world.
Decompression is a tedious, but essential part of technical diving. With the mechanisms of decompression sickness risk reduction discussed above, as well as ongoing research on numerous other methods, decompression times would be reduced. In the future, these mechanisms may become widely available to not only the Navy, but also divers like me. I would be thankful for a little peace of mind when it comes to my common-held fear of developing a case of decompression sickness.
Author Bio: Kaitlin Mogentale is a freshman (rising sophomore) at USC pursuing a B.A. in Environmental Studies. She also looks to complete minors in Urban Policy & Planning and Spanish. She plans to use her interest and knowledge in the field of environmental science to serve as an advocate for businesses and developers, focusing on the importance of environmentally sound practices.
Dromsky, David M., Kayar, Sarah R. “Decompression Sickness Research: New Directions.” Naval Medical Research Center. 2000.
Lang, MA; Brubakk, AO. “The future of diving: 100 years of Haldane and beyond.” 2009.
Navy & Marine Corps Medical News: May 28, 1999.
Author’s note: A special thanks to Karl Huggins, director of the Catalina Hyperbaric Chamber, for sharing with me his time and expertise in decompression theory.
Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.
Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.