Continuing Education Activity

After an episode of decompression illness or other diving-related injuries, many divers want to go diving again, either for recreation, work, or military service. A thorough understanding of the factors that led to the injury and a careful clinical exam will help the clinician and diving medicine specialist decide if additional tests are indicated and advise the diver of his future risk with a return to diving.

This course covers returning to diving after decompression illness. This activity examines the critical considerations surrounding the resumption of diving post-decompression illness or other diving-related injuries, focusing on recreational divers, dive masters, and dive instructors. Participants can expect an in-depth exploration of the causative factors of decompression illness, emphasizing the absence of specific U.S. guidelines and the crucial role of diving medicine specialists. The course thoroughly examines decompression sickness types, arterial gas embolism, and the primary treatment of recompression in a hyperbaric chamber. Early intervention is underscored, emphasizing its effectiveness in minimizing residual effects and facilitating complete recovery. The course also sheds light on the complexities of bubble formation and the potential spectrum of effects, from mild symptoms to severe consequences such as paralysis or death.

A key highlight of this course lies in recognizing the pivotal role of the interprofessional team in minimizing the recurrence of decompression illness. By participating in this activity, learners gain insights into the nuanced considerations of returning to diving, ensuring a comprehensive and collaborative approach to decision-making.

Objectives:

• Identify the issues associated with return to diving after decompression illness.

• Determine the clearance protocol of a patient who wants to return to diving after decompression illness.

• Differentiate between decompression illness types and arterial gas embolism, ensuring accurate diagnosis and appropriate treatment selection.

• Identify interprofessional team strategies for improving care coordination and outcomes in divers who want to return to diving after decompression illness.

Introduction

Decompression illness is caused by bubbles that appear in the bloodstream or other tissues in the body by ascending too fast from underwater depth to the surface or from the surface to an altitude, such as in high-altitude fighter pilots. When ambient pressure increases, such as during diving, so will the pressure of any gas the person is breathing. This gas is distributed throughout the body at different speeds, where highly vascularized tissues equilibrate faster. Bubbles are formed when the ambient pressure is reduced faster than the ability of the blood or tissue to transport the gas, which is in solution (usually nitrogen), to the lungs to get exhaled. These bubbles can have various complex effects on the body, from blood and lymph flow obstruction to nerve injury by direct irritation or inflammatory mediators. These effects can be mild, resulting in pain or paresthesias, or severe, leading to paralysis and death.

The most widely used classifications of decompression illness include decompression sickness type 1 (DCS1) with mild pain or mild skin symptoms, decompression sickness type 2 (DCS2) with neurological involvement, and arterial gas embolism, resulting from pulmonary barotrauma.[1] The primary treatment of decompression illness is recompression in a hyperbaric chamber, which will increase the ambient pressure again, reduce the speed of new bubble formation and existing bubble size, and create a large diffusion gradient for the offending gas by breathing 100% oxygen. The appropriate treatment of decompression illness is usually very effective, especially if began early after the injury, leaving either minimal or no residual effects. As the body tries to heal, most residual effects will improve even further with time. However, some residual effects may be permanent. In addition, a diver may also suffer from barotrauma to air-filled spaces such as ears, sinuses, and lungs during a dive.

After an episode of decompression illness or other diving-related injuries, many divers want to go diving again, either for recreation, work, or military service. A thorough understanding of the factors that led to the injury and a careful clinical exam will help the diving medicine specialist decide if additional tests are indicated and advise the diver of his future risk with a return to diving. Guidelines do exist for military, government, scientific, and commercial divers. However, no guidelines have been published in the United States for recreational divers, dive masters, or dive instructors.

Issues of Concern

Divers who have had decompression illness, especially those without any physiologic explanation, are at higher risk of experiencing decompression illness again—and possibly aggravating any pre-existing residual injury. The odds ratio of experiencing neurologic decompression sickness (DCS) has been reported to be as high as 8.4 in divers who have suffered previously from DCS, have a sizeable right-to-left shunt, and have not modified their diving practice.[2] There are 2 general concerns for a diver who may be at higher risk of developing decompression illness. One is the risk of reinjury, but the other is the risk incurred by fellow divers coming to rescue an injured diver in an environment challenging for the human body.

Clinical Significance

In general, returning to diving after an episode of decompression illness should only occur after a specific time has elapsed, which depends on the severity of symptoms and any residual injury. Recommendations as to the time delay vary a bit according to the different diving organizations, and it should be remembered that those are recommendations that are specific to their diving populations and may include special rules and conditions such as supervised dives, full face masks, a recompression chamber on site, and specified evacuation plans. Applying those recommendations to the recreational scuba diver may not be possible nor in the patient's best interest, and an individual approach tailored to their health and anticipated diving conditions should be used.

Only a few tests are indicated in determining the etiology or risk of future damage to the central nervous system. An echocardiogram can determine the presence or absence of a patent foramen ovale (PFO); this is indicated after episodes (usually more than 1) of decompression illness after non-provocative dive profiles or severe neurological or skin symptoms. Divers with PFO have been reported to have a higher incidence of decompression illness.[3] However, PFOs are very prevalent in the normal population of nearly 30%, so many divers without decompression illness will have PFOs. If a PFO is discovered after episodes of decompression illness, the reported (low) risk of closure attempts in divers [4] should be weighed carefully against the risk of decompression illness with risk modification such as shallow dives or diving with a higher oxygen-enriched gas mix.[5] After the closure of a PFO, the diver should undergo a repeat echocardiogram with a Valsalva maneuver to demonstrate closure of the PFO. 

Magnetic resonance imaging (MRI) helps assess damage to the central nervous system in severe neurologic decompression illness; however, MRI is usually not helpful during acute events other than possibly ruling out other reasons for the diver's symptoms when they do not fit or do not respond to treatment as expected. The MRI may discover unanticipated significant brain or spinal cord lesions, providing information about future diving fitness. A subject of current medical debate is the appearance of hyperintense white matter lesions on MRI in divers with cerebral decompression illness. While there is insufficient scientific evidence as to the etiology or prognosis of those lesions in divers, caution with a return to diving may be recommended by some organizations as they represent abnormal MRI findings.

Return to diving after decompression illness of the inner ear deserves special consideration and specialized testing, as divers can become asymptomatic after some time, which may not be related to healing of the injured inner ear but rather due to compensation of the other inner ear.[6][7][8] A subsequent insult to the uninjured ear may lead to severe disability of the diver. A consultation with an otolaryngologist knowledgeable in diving medicine who can perform cochlear and vestibular testing is indicated to accurately assess the potential risk of returning to diving.

For an organization to permit a diver to return to diving, the implications and liabilities are different than for an individual who takes responsibility for their actions (and can mitigate the dive risk), ideally after a thorough discussion with a provider specialized in diving medicine.[9][10][11] The United States Navy will permit a diver with mild DCS1 symptoms resolved on initial treatment to return to diving after 7 days. Whereas after a DCS2 episode with symptoms resolved on initial treatment, a 30-day delay is mandated. Suppose there are persistent neurologic symptoms beyond the initial treatment. In that case, the diver is disqualified from further diving unless a medical waiver is granted after a thorough medical evaluation, including an MRI, a repeat MRI after 1 month, and a consultation with a neurologist. Again, these are recommendations for their otherwise young, healthy, fit divers performing US Navy dives.

The Association of Diving Contractors International (ADCI) has also published return-to-diving guidelines after decompression illness, where they do not recommend diving with residual symptoms or in divers with an abnormal brain MRI after an episode of DCS2. They permit a return to diving depending on the severity of the initial symptoms and the resolution speed after single or serial treatments. This speed can range from 72 hours for pain-only resolved after one treatment to 7 days after serial treatments. If neurological sensory symptoms resolve after one treatment, divers should delay for 7 days, whereas for any motor symptoms resolved with one treatment, the time delay extends to 4 weeks. DCS2 symptoms requiring serial treatments to resolve should be delayed 4 to 6 months and reevaluated. Any vestibular symptoms should also wait 4 to 6 months after treatment. Afterward, an examination that includes caloric and rotational or tilt table evaluation by an otolaryngologist has to confirm an intact vestibular system, as the patient can compensate with one side after the loss of function of the other. Any subsequent injury to the functioning side may leave the diver without balance for life.

In Europe, the Diving Medical Advisory Committee (DMAC) has issued its guidance for returning to diving after decompression illness, similar to the US Navy and ADCI. After limb pain or nonspecific symptoms with uncomplicated recovery, divers should delay diving for 7 days; this is extended to 14 days for a relapse that requires further treatment. They differ in their recommendations regarding skin or lymphatic manifestations without neurological signs, which others may treat as milder DCS1, and also recommend a 4-week lapse of diving activities. They further recommend a delay of 3 months for more severe neurologic manifestations or pulmonary barotrauma. A diving medicine specialist should review any diving deferral of greater than 2 weeks before the commercial diver can return to diving. Divers who had pulmonary barotrauma or arterial gas embolism should undergo a high-resolution computed tomography scan (HRCT) to assess the structural lung integrity. According to DMAC, any diver with residual symptoms "should be considered unfit for occupational diving."

As previously mentioned, companies and organizations can make and enforce rules and regulations for their divers, protecting them and limiting the organization's liabilities. However, for recreational divers, who in most jurisdictions are not subject to the same regulations, buy-in from the diver is needed to optimize their safety and those who dive with them. The waiting periods mentioned above for uncomplicated decompression illness episodes with complete resolution of symptoms are reasonable to most recreational divers. 

The issue of returning to diving with residual symptoms comes up frequently and is more controversial. Ideally, a diving medicine specialist should guide these decisions because they are familiar not only with various forms of decompression illness but also with the various stresses on the body during diving and possible mitigation strategies, such as shallow dives, using oxygen-enriched air, prolonging safety stops and adding extra conservative factors into their dive computers. Consultations from other specialties and medical imaging, such as MRI, HRCT, echocardiography, and vestibular testing, can help advise the diver on future risks.

Another population to consider is the numerous dive masters and dive instructors compensated for their diving and taking students who depend on them underwater. While they really should be considered occupational divers, many do not have occupational diver insurance and safety net covering health and disability benefits and do see the need to continue to make a living. They are often independent contractors or working for small businesses. Since these divers are often not employed by large corporations, they are not protected by the conservative strategies used in commercial diving that protect the companies from liability while protecting the divers from injury. They may not be able to modify their risk profile, other than modifying their breathing gas, to the same extent as a recreational scuba diver can. The diver-provider relationship and an understanding that the goal is to get them back to what they love to do goes a long way in maximizing their safety and that of their potential students.

Apart from decompression illness, other diving-related injuries usually relate to the pressure changes that occur during a dive, such as problems with the ears and sinuses and barotrauma to the lung. Patients with previous lung trauma should refrain from diving for at least 6 months and have a normal lung computed tomography scan. Existing literature does provide some guidance for other pressure-related issues and injuries to ears and sinuses.[12]

Other Issues

Most recommendations to return to diving after decompression illness are based on expert opinion and knowledge of injury and healing of various tissues rather than on randomized controlled trials or rigorous clinical research. Risks are observed or modeled in comprehensive surveys conducted by diving research organizations, including the Divers Alert Network, Diving Diseases Research Center, various navies, commercial entities, and others. However, quantifying the individual risk of a specific dive on a particular day for a diver who may have undertaken similar dives numerous times remains elusive.[13]

Significant pulmonary infections, such as COVID-19, can cause pulmonary fibrosis with minimal abnormality on spirometry. However, even minor issues such as pleural adhesions, scarring, or minor blebs have been associated with the risk of pulmonary barotrauma from air trapping, as they can lead to cerebral gas embolism and stroke. Therefore, chest imaging is considered mandatory in the post-COVID-19 assessment of fitness to dive; this includes subjects with mild symptoms during COVID-19 infection.[14] The British have developed a risk stratification guide to evaluate divers post-COVID.[15]

Enhancing Healthcare Team Outcomes

The diving medicine specialist should be the coordinating provider and lead the discussions on the individual risk and the risk for the organization of returning to dive after a diving-related injury. However, these specialists often need input from other specialties, such as cardiologists, neurologists, radiologists, and otolaryngologists. In addition, on an organizational level, information from the dive supervisor on what will be expected on working dives will help determine the future of an occupational diver. Unfortunately, for the dive masters and dive instructors in the recreational dive industry, no dive supervisor can predict the dive conditions, dive location, and workload, which will make recommendations to the divers who want to return to diving after an incident.