Self-contained underwater breathing apparatus (SCUBA) has become more accessible to the public, with more than five million Americans now diving. Opportunities to learn about diving can vary from a brief course at a hotel resort to a full certification course. Certification courses can be completed in as few as 3 d and also are offered online to divers as young as 12 yr old. Training courses focus on the dynamics of underwater physiology and the inherent risks of diving.
SCUBA medicine is a developing specialty, and physicians should be aware of the serious medical conditions that can occur. This article discusses the physiology behind various diving injuries and medical supplies that may come in handy. It is important that you, as a physician, can recognize a diving injury and be able to treat the patient whether on a tropical vacation or when a patient arrives in the clinic after a recent dive.
Case: While on vacation at the Bikini Atoll, an isolated SCUBA-haven in the Pacific Ocean, a tourist runs up and asks for medical help. As the only physician nearby, you run to the water's edge and discover a SCUBA diver lying on her back, appearing to have a seizure. What do you do?
After contacting an emergency hotline, you realize that the only medical intervention this SCUBA diver has in the next few hours is you. What do you think is affecting this diver? What can you do to stabilize her, and are there any tools at your disposal that can increase her chances of survival?
We will discuss this life-threatening scenario as well as other commonly seen diving injuries as we delve into SCUBA medicine from the perspective of a medical professional and discuss what items should be included in a medical dive bag.
History of Scuba
Since the time of renowned oceanographer Jacques Cousteau, SCUBA diving has become a pastime of millions of Americans. What began with ancient divers using hollow reeds to breath air while underwater later developed into others using metal helmets and bodysuits connected by tubing to oxygen (9).
Diving continued to evolve, battling high underwater pressures and oxygen toxicity, until 1942, when Cousteau and Emile Gagnan invented the modern demand regulator. Their open-circuit device allowed divers to inhale compressed air from a tank and exhale it into the water (9). SCUBA equipment has since become more fine-tuned and now is more readily accessible to the public (10).
Recreational SCUBA uses compressed, normal sea-level air for respiration with a composition of approximately 21% oxygen, 78% nitrogen, and 1% other gases. Pure oxygen is not used due to potential toxicity and safety issues (5).
Two important laws regarding gas principles assist the physician in diagnosis and treatment of SCUBA injuries, as well as determining fitness to pursue diving:
1. Henry's Law. The amount of gas that enters a solvent is directly proportional to the partial pressure of that gas. Significance: With increasing depth, the gases present in air dissolve in greater amounts into the tissues of the body. Gases that are easily metabolized (e.g., oxygen) do not cause problems, but gases that are slowly metabolized (e.g., nitrogen) will tend to collect in the tissues (14).
2. Boyle's Law. The volume of gas is inversely proportional to its pressure. This is significant because the SCUBA system delivers air at increasing pressure as the diver goes deeper underwater. If air that is delivered underwater becomes trapped and cannot be released, the air will expand as the diver rises toward the surface (14).
The examining physician must be on the lookout for medical conditions that can trap air, such as Eustachian tube dysfunction, sinus disease, and chronic obstructive pulmonary disease (COPD). If the diver surfaces too quickly, trapped air increases in pressure and/or expands, creating potential barotraumatic damage to the affected area. Also, ascent from depth can cause dissolved gases to vaporize, form bubbles, and expand in the soft tissues. This is the basis of decompression sickness, the symptoms of which depend upon the size and location of these bubbles (14).
Adipose tissue tends to collect nitrogen more, so divers who are overweight should be alerted to their increased risk and need for strict adherence to time and depth limits. Women also have a greater predisposition toward development of decompression sickness for reasons that are not entirely clear (14).
The examination and clearance of the recreational SCUBA diver is a controversial subject with many medico-legal implications. Because research in this area is limited, much of the information and recommendations are based on speculation. The physician must have a clear understanding of diving physiology and refer any uncertain situations to an appropriate specialist. An excellent expert-reviewed resource for information regarding the preparticipation examination of the recreational scuba diver is the Guidelines for Recreational Scuba Diver's Physical Examination, created by the Recreational SCUBA Training Council. This document is available for free download at http://WRSTC.com/downloads.php (13).
A vital rule to remember: SCUBA diving has potentially fatal risks, and a distressed diver creates a significant risk for rescuers. The safety of other divers is at stake, so deviation from recommendations must not be tolerated. Instructors and physicians should be thorough and separate in their decisions to allow an individual to pursue diving (6,11).
A thorough predive history and physical should be undertaken with divers of all abilities. In addition to obtaining general past medical and surgical history, the evaluation should focus on several critical physiologic systems (Table 1). Other general considerations include:
1. Ability to breath. A history of emphysema or bullae can lead to pulmonary overinflation on ascent, which can cause air embolus or alveolar rupture.
2. Exercise tolerance. Diving equipment can weigh up to 40 lb, and the ability to both lift this weight and swim with it are important factors to consider prior to diving.
3. Mental status. Panic is a common response underwater; however, abnormal panic or anxiety can impact the diver's response time and course of action.
4. Medications. If certain medications (e.g., antiseizure or antiemetics) are not at therapeutic levels, the diver may lose consciousness, vomit (causing choking), or suffer other dire consequences.
5. Recent health concerns. An upper respiratory infection can lead to a ruptured tympanic membrane due to an inability to equalize pressure in the ears.
Relative contraindications to diving include a history of coronary artery disease (a stress test should be done before clearance), pregnancy (because of the unknown risk of fetal emboli), prior decompression sickness or diving-related injuries, and divers with pacemakers (should be interrogated to ensure the device can withstand increased pressure) (6,11).
Absolute contraindications include cardiac pathology such as hypertrophic cardiomyopathy, seizures or history of stroke, history of spontaneous pneumothorax, gastric outlet obstruction, certain ear/nose/throat disorders, and psychiatric conditions including claustrophobia or untreated panic disorder. All of these can lead to either sudden loss of consciousness, risk to other divers because of a potentially inappropriate response, or increased risk of barotraumas or decompression sickness (6,11).
The most common diving injuries are a result of the pressure environment that divers are exposed to during their descent and ascent. Barotrauma occurs because of the compression or the expansion of air that results in several pathophysiologic changes. Specifically, damage occurs when tissue within a given space is unable to equalize to the pressure of the water (5). The most common barotrauma is related to the ears and sinuses, and the most serious is form is pulmonary barotrauma (8).
Barotrauma of Descent
Middle ear barotrauma, or "ear squeeze," occurs during descent when a diver fails to equalize the pressure between the air in the middle ear and the pressure of the water. As a diver descends, the pressure of the water increases and compresses the small spaces of the middle ear. The unequal pressures can cause pain, vertigo, tinnitus, and hearing loss, and severe cases can rupture the tympanic membrane. Predisposing factors for developing "ear squeeze" include mucosal congestion, mucosal polyps, or prior maxillofacial trauma. Divers should attempt to equalize the pressure on descent with a gentle Valsalva maneuver. Treatment for middle ear barotraumas includes decongestion and abstinence from diving until recovery. In cases of large tympanic membrane perforations, a referral to an ear, nose, and throat (ENT) specialist is appropriate, and antibiotics should be started if there is a rupture with purulent drainage (5,11).
Inner ear barotrauma is damage to the round or oval window, which is often caused by a too-vigorous Valsalva maneuver. This can cause permanent injury to the cochleovestibular system. Symptoms are similar to the "ear squeeze" with pain, vertigo, tinnitus, and hearing loss. The history usually is most helpful in diagnosing a middle ear barotrauma, which includes difficulty equalizing ears, use of forceful Valsalva, and symptoms that are noted immediately after the ascent. The treatment consists of bed rest with elevating head of bed, avoiding Valsalva maneuvers (nose blowing, using stool softeners), and referral to ENT. Early surgical intervention may be indicated for patients with severe hearing loss (5,11).
"Sinus squeeze" is barotrauma that commonly affects the maxillary and frontal sinuses. Patients may experience sinus pain, headache, and epistaxis. Sinus barotrauma is treated with decongestants and possibly antibiotics (5,11).
Barotrauma of Ascent
During a diver's ascent, the environmental pressure from the water is decreased; therefore, air inside the body expands, which causes the lungs to expand. Pulmonary barotrauma occurs when there is overinflation of the lung, which can lead to bursting of alveoli. A well-trained diver purposely exhales during their ascent to allow for the air in their lungs to escape. Patients with obstructive lung disease are at greater risk for lung barotrauma because air is exhaled slower. This type of barotrauma usually results in mediastinal or subcutaneous emphysema. A pneumomediastinum may be seen on chest x-ray but rarely requires specific treatment. Although uncommon, a pneumothorax also may develop, which may require a tube thoracostomy. Consider the diagnosis of a pneumothorax if a patient is complaining of shortness of breath or has diminished breath sounds or tracheal deviation (5,13).
An air embolism is the most severe and life-threatening form of pulmonary barotrauma. It often occurs during a rapid, uncontrolled ascent. In the event of an air embolism, arterial occlusion occurs when air bubbles leak through a ruptured pulmonary vein and enter into the systemic circulation. The brain is the most susceptible organ to an air embolism; therefore, neurological symptoms are the most common presenting sign. Signs of a cerebral arterial gas embolism develop very quickly upon surfacing from the dive (usually within 5 min). Possible symptoms include seizure, loss of consciousness, disorientation, or stroke-like symptoms with hemisensory or motor deficits. In about 4% of cases, immediate apnea and cardiac arrest occur (13).
The treatment for arterial gas embolism includes immediate recompression in a hyperbaric chamber. Outcomes are best if a patient is treated within 4 h of symptoms. Other measures include administering oxygen and intravenous fluids to increase tissue perfusion. If the diver is on a boat and waiting for an ambulance, he or she should be placed in a supine position or, if vomiting, placed in a left lateral decubitus to prevent aspiration. The Divers Alert Network (www.diversalertnetwork.org, 919-684-9111) can provide assistance to provide the location of the nearest decompression facility (4,13).
Decompression sickness, or "the bends," results from bubble formation in the blood and tissue. This occurs during ascent when normally dissolved nitrogen in the tissue forms bubbles. The symptoms can range from muscle aches and fatigue to spinal cord involvement, including weakness and paresthesia. Bubbles also may enter the arterial circulation, which will produce symptoms similar to an air embolism. Decompression sickness is classified into two categories. Type I is nonsystemic or musculoskeletal and usually develops within 6 h. In this type, divers will complain of throbbing and aching joint pain, skin rash, and pruritis. Type II is systemic, which affects the neurologic, vestibular, and pulmonary functions. Patients develop symptoms within 1 h and include dizziness, weakness, and gait abnormalities. Treatment requires recompression in a hyperbaric oxygen chamber in order to decrease the bubbles' size. Supplemental oxygen and IV fluids also should be administered (5,12).
The most common marine envenomation is from the organisms in the Cnidaria category. The Cnidaria are characterized by their stinging, venomous cells called nematocysts. Types include jellyfish, Portuguese man-of-war, box jellyfish, soft corals, and sea anemones. There are over 8,000 species, and about 100 are toxic to humans (1,3).
In the United States, true jellyfish are the most frequently encountered. The presentation is a painful, papular-urticarial eruption at the site of the sting. Treatment should focus on deactivating and removing the nematocysts. Vinegar is the treatment of choice, and the affected area should be immersed in vinegar and soaked for at least 10 min. Rubbing alcohol also has been shown effective, or irrigation with saltwater. Special care should be used when removing the nematocyst from the skin to avoid further venom release. Use a gloved hand to prevent further stings, and do not rub or scrape the area. To assist in nematocyst removal, tweezers and adhesive tape may be helpful. The anecdotal treatments, including alcohol, urine, and meat tenderizer, have not consistently shown success in treating symptoms. Freshwater rinsing is not recommended because it stimulates venomous release, and pressure bandages also are no longer recommended. Other treatment considerations should include basic first aid, pain control, tetanus prophylaxis protocol, and wound care. Prophylactic antibiotics are not required for most stings (1,2,7).
The Portuguese man-of-war is another frequently encountered envenomation. They tend to float at the surface of the ocean and reside in regions of the Pacific, Indian oceans, and the northern Atlantic Gulf stream. In the summer months of Australia, there are reported to be 10,000 human stings each year. The stings are very painful and create red welts on the skin that last for several days. In rare occasions, anaphylactic reaction can occur, which require immediate medical attention. For cutaneous cases, treatment should focus on carefully removing any remaining parts of the Portuguese man-of-war with gloved hands to avoid secondary stinging. Similarly to true jellyfish stings, fresh water can worsen the reaction and should be avoided. Salt water can be applied to the area, and vinegar is controversial in its effectiveness (2,7).
There are several toxic species in the Cnidaria group; however, the Cuboza or box jellyfish (Chironex fleckeri and Carukia barnesi) are some of the most deadly marine organisms. They are found in northern Australia waters but have not been reported in the North America region. The Chironex fleckeri is the most lethal jellyfish in the world, but many of the cases are limited to cutaneous symptoms because the toxin does not penetrate skin well. Skin findings include severe pain with dark reddish-brown whip-like areas. These areas can form blisters and become necrotic within 24 h and remain for over 2 wk. If systemic symptoms occur, they usually present within 20 min and include headache, fever, vomiting, muscle spasm, and respiratory distress (3,7).
The Carukia barnesi is another potentially fatal organism. The initial sting is described as moderate pain at the site of envenomation, but within 30 min, patients will develop systemic symptoms, referred to as the Irukandji Syndrome. This syndrome includes hypertension, tachycardia, agitation, abdominal cramping, nausea, vomiting, severe low-back pain, and possibly pulmonary edema (2).
Treatment for box jellyfish stings is similar to treatments for other Cnidaria, including basic first aid, careful removal of nematocysts, tetanus prophylaxis protocol, and wound care. However, when systemic symptoms occur, patients may require respiratory and cardiovascular support. There is an antivenom for Chironex fleckeri stings, and it is indicated in patients with cardiopulmonary arrest, hypotension, dysrhythmias, altered level of consciousness, difficulty swallowing, or speaking (2).
Another venomous creature a diver may encounter is a stingray. Humans are usually stung on their lower extremities because stingrays hide underneath the sand and will strike after humans accidentally step on them. Envenomation immediately causes severe pain. Rarely, the spine can break off into the wound and causes significant bleeding. Treatment involves irrigation and removal of any pieces of the spine. To help reverse the effects of the venom, the area should be placed in hot water for 30 to 90 min at temperatures as tolerated (up to 113°F). Basic first aid, pain control, tetanus prophylaxis protocol, and wound care also should be addressed (7).
While SCUBA diving remains a fascinating underwater adventure for most participants, physicians need to be aware of the risks of this potentially fatal endeavor. By discussing medical physiology, clearance issues, and common injuries, divers can be prepared for many possible scenarios.
In addition, most diving expeditions take place in exotic but small locales or on boats, far from any nearby advanced medical treatment centers. This quandary puts the onus of medical care on nearby physicians and other health care personnel.
Let's revisit the scenario that we presented in our introduction. You arrive at the edge of the water to discover a SCUBA diver lying down with apparent seizure activity. Your first step is standard first-aid - ABCs (Airway, Breathing, Circulation). While assessing the diver, her partner tells you that the afflicted diver had a rapid ascent from a deep underwater depth. You conclude that the diver is likely suffering from barotrauma causing a possible air embolism. You place the diver in the supine position and look into your medical dive bag (see Table 2 for a list of potentially beneficial supplies). You then administer oxygen and utilize your portable hyperbaric chamber while awaiting further medical help (4).