Friday, June 28
DCI Theory & Mechanisms
CNS Oxygen toxicity: Where are we now?
Hyperbaric oxygen (HBO2) is breathed during hyperbaric oxygen therapy and during certain undersea pursuits in diving and submarine operations. What limits exposure to HBO2 in these situations is acute onset of central nervous system oxygen toxicity (CNS-OT) following a latent period of safe oxygen breathing. CNS-OT presents as various non-convulsive signs and symptoms (S/Sx), many of which appear to be of brainstem origin that involve cranial nerve nuclei, autonomic centers and cardiorespiratory centers, which ultimately spread to higher cortical centers and terminate in recurring bouts of generalized tonic-clonic seizures. The initial latent period makes breathing HBO2 practical in hyperbaric and undersea medicine; however, the safe latent period is highly variable between individuals and within the same individual on different days, making it difficult to predict onset of toxic indications. Consequently, currently accepted guidelines for safe HBO2 exposure in undersea medicine and HBO2 therapy are highly conservative. During this lecture, I will review the results of research on CNS-OT, focusing on work done during the past two decades on behalf of the Office of Naval Research (ONR) Undersea Medicine Program (one of four National Naval Responsibility Initiatives) and the Naval Sea Systems Command (NAVSEA). Topics that will be covered include the following: the pathophysiology of the S/Sx that define CNS-OT; conditions that increase the risk for developing acute toxic indications during exposure to HBO2; innovative animal (in vitro and in vivo) and human research methods adapted for use during HBO2 that have provided insight on the neural mechanisms underlying CNS-OT; brain regions that are thought to be involved in seizure genesis and propagation; and current strategies under investigation for predicting an impending seizure (“physiomarkers”) and delaying onset of CNS-OT (antiepileptic drug therapy, antiadrenergic drug therapy, ketone metabolic therapy and hyperbaric oxidative preconditioning) with the goal of longer and safer dives without impaired performance (author’s research funded by ONR Undersea Medicine).
|9:00-9:30:||Navy dive operations: Lessons learned about planning, DCS prevention and treatment
Pete Witucki, MD
Wearable diving technology
Altitude Decompression Sickness
|4:00-4:30:||Combating flier’s “bends” during unpressurized flight and explosive decompression in World War II
Jay Dean. PhD
The air war of 1939-45 was a “physiological war” because the Allies sought extreme altitudes in unpressurized warplanes to gain the tactical advantage in aerial combat. How high? In 1940, the Allies predicted the air war; thus WWII would be won by the side that waged combat operations at 40,000 feet. Altitude flying and fighting at 40,000 feet became the goal that would inspire America’s aeromedical research program for the war’s duration.
Accordingly, reducing the risk of decompression sickness (DCS) at altitudes above 30,000-35,000 feet in unpressurized aircraft became a major research challenge for the physiologists of the U.S. Army Air Forces (USAAF) and U.S. Navy (USN). In April 1944, America deployed its first pressurized bomber (Boeing B-29 Superfortress) in the Pacific theater of operations to alleviate the physiological problems caused by hypobaric pressure, anoxia and cold. Pressurized flight, however, created a new problem: Namely, it was unknown how aircrews would respond to explosive decompression at high altitude following structural failure of their ship’s pressure cabin (6.5 psig). Would the incidence of DCS increase compared to slower rates of decompression in unpressurized airplanes?
In this lecture, Dr. Dean will revisit the research and mitigation strategies for dealing with “flier’s bends” or “aeroembolism” during unpressurized flight and following explosive decompression during pressurized flight. Topics covered include the following:
Ultimately, the air war of 1939-1945 would be mostly fought and won below 40,000 feet; however, the equipment and procedures developed during the war years were immediately available for higher altitude flight during the post-war jet era.
About Dr. Dean: Dr. Jay B. Dean is a professor of Molecular Pharmacology & Physiology at the University of South Florida in Tampa. He currently teaches respiratory physiology in the Morsani College of Medicine and directs the USF Hyperbaric Biomedical Research Laboratory, which is funded by the ONR’s Undersea Medicine Program to study the pathophysiology of CNS oxygen toxicity. Dean is a devoted historian of aeromedical research during World War II, a topic he has researched extensively since his days as a PhD graduate student at Ohio State. Dean hails from Mason, Michigan, and received his training from Central Michigan University (BS 1979, Biology), Michigan Technological University (MS 1981, Biol. Sci.), The Ohio State University (PhD 1986, Physiology), and did his postdoctoral training in neurophysiology and respiratory control at the University of North Carolina-Chapel Hill (1986-91). Jay lives in Land O’Lakes, Florida with his wife, Janet, who teaches biology and oceanography at Pasco Hernando State College.
|4:30-5:00:||USAF hypobaric exposures experience
Marc Robins, DO
Dr. Robins will speak on DCS altitude current problems faced and U2 case reports recently collected.
About Dr. Robins: Dr. Robins started his career in medicine working for the Ski Patrol in Southern Oregon at age 19 which soon led to employment as a nurses aide then as a Registered Nurse. Prior to medical school he worked as an RN in the Emergency Department at a level 1 Trauma Center, graduating with his Doctorate in Osteopathy in 1988. Receiving a Health Professions Scholarship to pay for Medical School he did his first Residency in Family Practice at the David Grant USAF Regional Medical Center at Travis AFB, California, and then a second Residency in Aerospace Medicine with Fellowship in Occupational Medicine and a Masters in Public Health from Harvard University School of Public Health. He was awarded the Malcom Grow Air Force Outstanding Flight Surgeon of the Year Award in 1995, and completed a 20-year career as an Air Force Flight Surgeon. His assignments included European Aeromedical Evacuation Squadron, and command positions for Fighter Base Aeromedical Squadrons and the High Altitude U2 program in Beale, California, commanding medical services in six major deployments and one Humanitarian Mission. Dr. Robins culminated his career as the US Aerospace Medicine Consultant to the Australian Defence Force Medical Chief (US Surgeon General equivalent), retiring as a Colonel. He attended the NOAA Dive Medical course in 2010 and maintains an avid interest in recreational scuba diving, certifying in 2003. He is a pilot, enjoys skiing, mountain biking, motorcycle riding and rock climbing.