The past 40 years have been rife with medical advancements. Treatments for cancer are now routinely targeted to the individual, stomach ulcers are no longer thought to result from a stressful lifestyle, and statins have proven effective in secondary prevention of acute cardiovascular events. In dive medicine, human experiments shaped the current flying-after-diving guidelines, we know more about the effects of diving on the endothelium than ever before, and technical divers are now almost routinely exceeding 100 meters (328 feet) on rebreathers. The results of recent research into the association between decompression sickness (DCS) and genetics are tantalizing, decompression time for extravehicular excursions in space has been halved, and breath-hold divers have exceeded what was thought to be the limit of human endurance.
We are amid a technological revolution. Many of the science-fiction gadgets that wowed us in the early days of Star Trek, such as cellphones and self-opening doors, are now everyday realities. Dive computers have kept pace with the times, and yet divers are keenly awaiting medical technology developments, such as real-time carbon-dioxide sensors for rebreather diving and blood-glucose monitors for divers with diabetes. What the future holds for waterproof wearable fitness trackers is anyone's guess.
We have asked two leading researchers in dive medicine for their opinions on the direction in which dive medicine is headed and what advances they think, or hope, we might see in the next 30 to 40 years.
What are the most important outstanding issues in dive medicine, and how could they be solved in the future?
Stephen Thom, M.D., Ph.D.: Establishing the etiology of diving stresses — in particular, that of DCS — is important. Clearly, bubbles are a central element to DCS, but that does not actually answer the question of etiology. We still do not clearly understand the source(s) of bubble nucleation or the physiological consequences that arise from bubbles.
Jean-Eric Blatteau, M.D., Ph.D.: The understanding of the origin of DCS and immersion pulmonary edema (IPE) must be improved to better prevent their occurrence and optimize treatment.
Reported incidents of IPE have been increasing in recent years. In some cases it can lead to heart failure. IPE can occur in many circumstances, including breath-hold, open-circuit and rebreather diving as well as while swimming at the surface. The origin of IPE is multifactorial; a good understanding of the different heart, lung and ventilatory components is essential to improve prevention. Additional work is necessary to understand the mechanisms and identify subjects at risk.
DCS is the most common type of serious dive injury. Its neurological forms are among the most common, and they occur despite the diver respecting established limits and procedures in most cases. Despite treatment in hyperbaric centers, DCS has a 20 to 30 percent rate of complications. Research to improve the treatment of these injuries remains a major objective.
In addition, it is essential to better identify factors of individual sensitivity. For example, why do some people form more decompression bubbles than others when the dive conditions are the same? Or why do some subjects, at equal bubble level, have a lower tolerance for bubbles in their body and develop DCS?
How do you envision science contributing to dive medicine over the next 30 to 40 years?
Thom: Biological sciences are gaining ground on answering the previous questions and offering measures to diminish health risks.
Blatteau: We will evolve toward more personalized medicine, which in dive medicine will mean better identification and prevention of individual risk factors for dive injuries. Fundamental research will make it possible to not only understand the mechanisms of bubble formation (from gaseous nuclei in the form of nanobubbles) or the effects of bubbles at the biochemical and cellular levels but also build large databases of dive injuries to highlight the factors involved.
What developments do you hope to see come true? Do you have any predictions that seem unlikely now but may one day prove correct? An example is doctors Barry Marshall and Robin Warren forecasting that stomach ulcers would become curable.
Thom: I truly believe we will generate sufficient knowledge to prevent DCS in virtually all divers, and for the rare cases that do arise, treatment will not involve hyperbaric chambers.
Blatteau: Medicine evolves very quickly with new perspectives, for example, on the development of stem cells that repair damaged neurological tissue. These technologies may someday be applicable to neurological consequences of DCS. Advancements in molecular biology and genetic editing may allow us to further act at a preventive level.
In addition, hyperbaric therapy is evolving. Research on therapeutic gases such as helium, xenon and argon should improve the management of many neurological diseases, including neurological DCS.
The association between genetics and DCS has sparked interest in recent years. What practical applications of this research do think a young diver today might see in 30 to 40 years?
Thom: In the short term, I suspect genetic screening will provide an assessment of relative risk to an individual — that is, genetic tests will identify those individuals at higher risk for developing DCS with provocative diving. With further work, I believe genetic studies will identify the physiological reasons that certain individuals have greater risk, and with this knowledge there will be interventions (possibly drugs) that abrogate the added risk.
Blatteau: The identification of genetic factors associated with the risk of DCS is an important area of research. It is likely that over time we will be able to detect immune or inflammatory functions that are abnormally activated in certain subjects in the presence of bubbles. The current evolution of genetic "scissors" techniques (cutting and fixing genes) will undoubtedly make it possible to propose corrective actions in these subjects. Comparative physiology studies of the genetic mechanisms of adaptation to decompression in marine mammals could lead to interesting proposals.
Another field of medicine in full expansion concerns the bacteria that colonize the digestive tract, which is defined by the term microbiota. This microbiota is fairly stable and specific to each individual and has recently been shown to act on our immune system and be involved in many diseases.
We now understand that the microbiota is involved in the occurrence of DCS. Some types of microbiota may be beneficial, and others may be deleterious to the risk of developing DCS. The identification of microbiota should develop in the coming years and bring the possibility of preventive actions.
In the past 30 to 40 years we have seen the development of dive computers, nitrox, technical diving and rebreathers. What technological advances do you think or hope we might see in the future?
Thom: I hope we will see real-time monitoring devices that calculate environmental parameters along with an individual diver's physiological status to provide a readout on when a diver should change his or her actions to achieve diving goals (such as a desired depth or extended time underwater) and still avoid injury.
Blatteau: In the coming years the use of rebreathers will develop and become more widespread in recreational diving. Thanks to the inhalation of optimized oxygen partial pressures, the major interest will be to reduce the occurrence of DCS. It will be necessary to be vigilant, however, because the use of rebreathers exposes divers to other forms of dive injuries such as biochemical insults and IPE.
Researchers will develop dive computers with physiological sensors, which will allow personalized decompression that identifies relevant risk factors. The development of sensors for the automatic measurement of circulating bubbles in the body will be an essential contribution to adjusting decompression procedures.
Flexible, easily transportable and affordable hyperbaric chambers should be developed to help improve dive safety in remote areas.
Predive treatments (preconditioning) are another topic of significant interest in recent years. What new practices might we see on dive boats in the future?
Thom: There is a growing list of preconditioning interventions that nullify or at least diminish DCS risk, but I do not see these treatments as being practical for day-to-day diving. I envision that when detailed physiological explanations establish why preconditioning works, scientists will develop more easily applied interventions — probably in the form of pharmaceuticals — that achieve the same results.
Blatteau: The main objective of the preconditioning methods is to remove the gaseous nuclei before the start of the dive and thus avoid the formation of decompression bubbles that develop from these gaseous nuclei. Several simple methods, including aerobic exercise, hydration, exposure to heat, oxygen inhalation and exposure to vibrations, are effective in reducing the formation of decompression bubbles.
Some communities of military divers perform moderate aerobic exercise followed by hydration, but this practice is difficult to apply in recreational diving. Physical exercise for typically sedentary subjects is not advisable without training and verification of their exercise tolerances.
We can systematically advise moderate hydration (500 milliliters before diving) in hot conditions. Inhaling oxygen during the 30 minutes before diving is an easy proposal for deep and/or successive dives. The use of a sauna or vibrating mattress is still marginal, but it may be useful in the future before specific at-risk dives.
Dive computers are becoming increasingly personalized. What developments will we see regarding the personalized prevention of DCS?
Thom: I expect we will see real-time monitoring devices that couple detection of environmental parameters (depth, dive time, breathing-gas mixture) as well as a diver's physiological status to provide a moment-to-moment readout of how a diver might need to change activities to safely achieve a particular goal.
Blatteau: Personalized decompression is an essential approach, but it is currently only empirical. The next step will be identifying at-risk individuals based on relevant scientific and medical criteria. In addition, we must independently study and verify the application of "secure" decompression protocols for at-risk subjects. The establishment of, composition of and access to independent databases of dive computers will be important issues in the coming years.
What role do you think pharmaceutical treatments might play in both preventing and treating DCS?
I anticipate pharmaceuticals will markedly diminish risk and provide treatment for DCS, completely removing the need for recompression therapy.
Blatteau: For diving as a leisure activity, we do not advise the general use of a drug. On the other hand, for certain risky subjects or those already suffering from a dive injury, a drug with preventive aims might be useful in the future. The use of probiotics that act on the microbiota is another consideration.
In the treatment of DCS, drugs are already used in addition to hyperbaric oxygen. In cases of neurological DCS, studies indicate some benefit of evaluating additional treatments in humans such as fluoxetine or therapeutic gases such as xenon.
Personal wearable fitness trackers are common today. Given that cardiovascular problems are a leading cause of death in divers and that fitness for diving is important to minimize risk, what fitness developments do you foresee?
Thom: I expect there will be much more accurate determinations of what it means to be "fit for diving" other than merely a general assessment of cardiovascular health or exercise tolerance.
Blatteau: The current development of physiological sensors will be transposed to the practice of diving. Sensors for cardiovascular and/or respiratory measurements will certainly be very useful for the prevention of IPE. The generalization of automatic sensors to quantify circulating bubbles will also optimize and improve decompression safety for individuals.
Jean-Eric Blatteau, M.D., Ph.D., is the director of the Department of Diving and Hyperbaric Medicine at Sainte Anne Military Teaching Hospital in Toulon, France. He is the research director of the team for underwater therapeutic and operational research at the French Armed Forces Biomedical Research Institute and a past president of the Société de physiologie et de médecine subaquatiques et hyperbares de langue française (French Language Society for Underwater and Hyperbaric Physiology and Medicine).
Stephen Thom, M.D., Ph.D., is the director of research in the Department of Emergency Medicine at the University of Maryland School of Medicine. Among his research interests are the biochemical and physiological responses to oxidative stress with a focus on the impact of high-pressure gases. He earned degrees in microbial biology from the University of Rochester and served for 27 years as professor of emergency medicine and chief of hyperbaric medicine at the University of Pennsylvania.