Supporters of IWR point out that early treatment and breathing of 100 percent oxygen under increased pressure can remove inert gas and gas bubbles before they cause permanent damage. They bring up positive experiences of occupational divers who used IWR, though they acknowledge a few known cases that resulted in complications. They also admit there are technical considerations not likely available in many recreational dive settings, including provider training and the fact that not all cases of DCS are appropriately managed with IWR.
In 1998, Divers Alert Network® (DAN®) and the Undersea and Hyperbaric Medical Society (UHMS) co-sponsored a workshop on IWR; the workshop prompted so much debate, it failed to produce a position paper. In 2000, the South Pacific Underwater Medicine Society (SPUMS) hosted a second public debate; this time the arguments of experts opposing IWR seemed to prevail.
Opponents argue that potential complications outweigh benefits. The data concerning IWR are anecdotal, and the reporting of outcomes may be prone to bias, with positive results being preferentially presented. Most cases of DCI in recreational diving are mild in nature and resolve even with delayed treatment. On the other hand, cases that could benefit from treatment are the most severe and require additional medical treatment such as critical life support, fluid resuscitation and other medical interventions not feasible underwater. In the most severe DCI cases, injury may occur before IWR can realistically be started in recreational diving conditions. In extreme cases, providing surface oxygen with additional treatment measures and medical assistance may be more beneficial than recompression and oxygen without additional treatment.
Ten years after the SPUMS debate, the opinions on IWR remain diverse.
Do you think in-water recompression should be used in recreational diving?
Dr. Edmond Kay: Victor Hugo once said, “There is nothing more powerful than an idea whose time has come.” In-water recompression is one of those captivating ideas I thought would have gained traction by now, given the number of experts who have embraced it.
IWR is indeed a compelling idea, and its use should be considered when diving in remote areas of the world, as long as adequate precautions are in place to ensure diver safety. IWR is not for everyone, however. It is most appropriate for the advanced diver, technical or commercial professional, or the military diver. Training requirements, equipment and support personnel make IWR inappropriate for casual recreational diving.
Dr. Alessandro Marroni: I believe there is no sufficient evidence to support this technique for general use in place of definitely safer methods, such as oxygen first aid and fluid administration, for which there is growing scientific evidence.
What are the most important considerations if IWR is attempted?
Kay: The requirements for safe IWR are well known. That said, there are serious consequences for the untrained and poorly prepared diver who tries to improvise. If strict procedures are not followed, the outcome could be tragic; fatalities are already a matter of record.
A good starting point for safe, controlled IWR is a full-face mask or hardhat with communications gear for the injured diver, a mandatory diver’s attendant and a surface tender. An ample supply of oxygen is also a requirement, along with a means of switching between air and oxygen.
In the unlikely event of oxygen toxicity, an in-water bailout to air (via a manifold or switching block) is easily accomplished by the attendant. The in-water attendant can then continuously monitor the condition of the injured diver and resume oxygen when the toxic effect has resolved.
Specialized equipment such as a dedicated underwater video camera and lighting for direct observation of both patient and attendant is optional but nice features for an advanced setup. Manpower needs include both surface support and rotating shifts of in-water attendants.
Marroni: The prerequisites [of IWR] are difficult to achieve, particularly in the recreational diving environment, and since the clinical evolution of DCI is often unpredictable, being underwater would imply additional danger in case of any complication.
What are some of the risks of performing IWR?
Kay: Hypothermia may not be a problem in warmer climates, but the shortest oxygen IWR treatment table is 2.5 to 3.5 hours and can extend to last for days. With that length of treatment, everyone needs thermal protection of some sort. A drysuit or dry “tube suit” with adequate undergarments, or perhaps even conductive polyamide electrically heated underwear, would do the trick in colder water. IWR treatment tables abound; the Australian and Hawaiian tables are cited most often.
Marroni: IWR can appear as an appealing, simple and quick remedy, especially to “expert” divers in denial of their symptoms, leading divers to ignore the potential for medical or logistic complications.
The downside of IWR is definitely more important than any potential benefit. It should not be considered unless it is extremely well preplanned with the necessary equipment ready at hand, underwater assistance by buddy divers ensured, and sheltered, warm waters in which the operations can take place with good surface-diver communication.
Another negative aspect of IWR is that it impairs the possibility for rehydration of the diver (fluids play an essential role, together with oxygen, in DCI first aid), potentially contributing to further dehydration.
Lastly, considering the current international guidelines for DCI first aid that recommend oxygen, fluid administration and timely evacuation to treatment facilities, one should not ignore the potential legal implications when suggesting or assisting in an IWR procedure.
When, if ever, should IWR be considered?
Kay: I firmly believe that we need to begin teaching the technique of IWR for remote area diving. Everyone seems to agree if a recompression chamber is available within a reasonable amount of time, it certainly should be used to treat DCI. The definition of “reasonable time to recompression” varies considerably with the concerns and biases of the expert commentator. A 12-hour delay in treatment is often cited as sufficient to consider IWR, but in truth, no one really knows how long a wait would make IWR appropriate. The sickest individuals need the most rapid recompression, but severity of DCI is often cited as a reason not to perform in-water recompression. In some of the remote regions of the world with no access to hyperbaric facilities, travel time to get to a chamber exceeds 24 hours, and transport is extremely expensive.
The amount of preparation and training that goes into IWR is considerable, but no more so than deep technical diving. The earlier DCI is treated, the greater the chance for complete resolution of symptoms. In many remote areas of the world, these techniques are put in use immediately upon recognition of DCI.
Marroni: In my many years of activity as a diving medical officer, I have witnessed many cases where IWR was attempted, and my personal experience is that in the majority of cases it did not produce significant improvements; in fact, in a good number of cases the procedure had to be aborted for logistical problems or medical complications.
Dr. Edmond Kay is the director of hyperbaric medicine at HealthForce Partners. He is a clinical assistant professor and diving medical officer for the University of Washington and is also medical director of Divers Institute of Technology. He is the project physician for a number of hyperbaric tunnels in Washington state and an advisor on the Nevada Lake Mead tunnel. He is a diving and hyperbaric physician trained by the National Oceanic and Atmospheric Administration and has been a diving medical examiner for UHMS, Health and Safety Executive, WorkSafeBC and the Diver Certification Board of Canada. He is board certified in both undersea and hyperbaric medicine and family medicine. In 1998, Kay co-chaired and edited the IWR workshop co-sponsored by DAN and UHMS.
Dr. Alessandro Marroni is the founder and president of DAN Europe as well as a member of the board of directors and president of International DAN. He serves as vice president of the European Committee for Hyperbaric Medicine (ECHM), president of the European Foundation for Education in Baromedicine, and secretary general of the European College of Baromedicine.
Marroni obtained post-graduate specialization degrees in occupational medicine, underwater and hyperbaric medicine, and anesthesiology and intensive care.
Marroni has academic teaching appointments at several universities and post-graduate programs. He has published more than 180 scientific papers, mainly in the area of underwater medicine research, with particular interest in the prevention of DCI in recreational diving.