Treatment Options and Costs for Decompression Sickness - Diving Medicine

Dr. Lin Zhengyan reply Diving Medicine

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Introduction: In the early days, due to a lack of understanding of decompression sickness (DCS), various names were used based on observed conditions.
For example, workers in underwater caissons frequently exhibited symptoms, leading to the term "caisson disease." Additionally, due to the variability in clinical manifestations, it was also referred to as "the bends," "chokes," and "staggers." Decompression sickness is defined as a syndrome resulting from the rapid reduction of environmental pressure, causing inert gases (primarily nitrogen) dissolved in body tissues and blood to form bubbles that obstruct blood vessels and damage tissues.
The first report of DCS was by Frenchman Triger, who documented two cases of miners using compressed air; one experienced tingling in the left arm, while the other had pain in the knee and left shoulder after seven hours in a high-pressure environment.
In 1878, Paul Bert was the first to confirm through animal experiments that nitrogen bubble formation was the primary pathogenic cause of DCS.
In 1889, Moir was the first to apply hyperbaric chambers for the treatment of DCS.
Between 1945 and 1966, the U.S.
Navy's air pressure tables became the standard treatment protocol worldwide.
Due to high failure rates, it wasn't until 1967 that oxygen pressure tables were officially recognized for treating DCS.
The symptoms of DCS are diverse and can include joint pain, skin rashes, difficulty breathing, blurred vision, headaches, limb numbness and weakness, hearing loss, incontinence, lower body paralysis, and peripheral nerve dysfunction.
In severe cases, blood circulation obstruction and fluid loss within blood vessels can lead to decreased blood pressure, shock, and rapid death.
When DCS occurs, hyperbaric oxygen therapy is the only effective treatment.
Chronic injuries caused by DCS most commonly manifest as dysbaric osteonecrosis, which may require bone resection and joint replacement surgery.
Understanding the gas laws is essential for further comprehension of DCS.
(1) Dalton's Law: The total pressure of a mixed gas is equal to the sum of the partial pressures of its individual gases.
Air consists of 78% nitrogen, 21% oxygen, and 1% other gases.
For example, if a high-pressure gas cylinder has a pressure of 1000 pounds per square inch (lbs/in²), the partial pressure of nitrogen in the cylinder would be 780 lbs/in² (1000 lbs/in² × 78%).
(2) Henry's Law: At a constant temperature, the amount of gas that dissolves in a liquid is proportional to the partial pressure of that gas.
(3) Boyle's Law: At constant temperature, the pressure of a given mass of gas is inversely proportional to its volume, meaning pressure multiplied by volume equals a constant (P1V1 = P2V2).
This indicates that as the pressure of a given mass of gas increases, its volume decreases, and vice versa.
Pathophysiology of Decompression Sickness: When a diver descends to a depth of 20 meters, they must breathe high-pressure air at three atmospheres to counteract water pressure (every 10 meters of water depth increases pressure by approximately one atmosphere, plus one atmosphere at the surface, totaling three atmospheres pressing on the chest wall).
At this depth, the partial pressure of nitrogen is three times that at the surface (Dalton's Law), resulting in a threefold increase in the amount of nitrogen dissolved in body tissues (Henry's Law).
The deeper and longer the dive, the more nitrogen becomes supersaturated in the body.
This phenomenon is akin to carbon dioxide being pressurized in a soda bottle.
When ascending from the depths back to the surface, the water pressure gradually decreases (as pressure decreases, the amount of nitrogen that can be dissolved in body tissues also decreases).
Therefore, a specific decompression procedure must be followed to allow the supersaturated nitrogen to be released from the tissues at various depths and expelled through the lungs.
If a diver ascends too quickly or fails to follow the decompression procedure (similar to shaking a soda bottle and suddenly opening the cap, resulting in a rapid release of bubbles), nitrogen dissolved in body tissues can form bubbles.
As the diving depth decreases, the volume of these bubbles increases (Boyle's Law).
In mild cases, bubbles accumulate in the joints, causing pain; in severe cases, bubbles can enter blood vessels, obstruct circulation, or affect the brain and spinal cord, disrupting normal tissue function and leading to symptoms such as headaches, hearing loss, incontinence, lower body paralysis, hemiplegia, loss of consciousness, and coma, collectively referred to as decompression sickness.
Classification and Symptoms of Decompression Sickness: The clinical symptoms of DCS can be classified into two types based on severity: Type I (mild) and Type II (severe).
Symptoms can appear singularly or in combination.
Type I symptoms can evolve into Type II symptoms, and Type II symptoms often include Type I symptoms such as skin rashes.
Type I symptoms include fatigue, itching, skin rashes, localized swelling, and joint and muscle pain.
Joint pain is the most common symptom, which may be described as aching or sharp and can be intermittent.
Notably, the presence of multiple marbled skin rashes can also indicate severe DCS.
Type II refers to more severe symptoms that affect vital organs.
Symptoms affecting the brain may include headaches, blurred vision, loss of consciousness, and limb numbness and weakness; symptoms affecting the lungs may include coughing, chest pain, and difficulty breathing; symptoms affecting the inner ear may include dizziness, nausea, vomiting, and unsteady gait; and symptoms affecting the spinal cord may lead to numbness and weakness below the navel and difficulties with bowel and bladder control.
If bubbles affect the entire body, they can cause decreased blood pressure, shock, or even death.
Type II symptoms include: (1) Central Nervous System: headaches, dizziness, nausea, vomiting, facial droop, slurred speech, altered consciousness, personality changes, stupor, coma, seizures, and death; (2) Vision: blurred vision, double vision, hemianopsia, blindness, and dilated pupils; (3) Hearing and Balance: tinnitus, hearing loss, dizziness, vomiting, and nystagmus; (4) Sensory Nerves: numbness or tingling in the limbs, facial nerve paralysis; (5) Motor Nerves: weakness in the limbs, unsteady gait, hemiparesis, and coordination difficulties; (6) Spinal Nerves: back pain, abdominal pain, diarrhea, lower body paralysis, and incontinence; (7) Other neurological symptoms.
(2) Respiratory System: dry cough, shortness of breath, chest pain, rapid heartbeat, and hyperventilation.
(3) Cardiovascular System: chest tightness, chest pain, and shock due to myocardial hypoxia.
(4) Severe muscle and joint pain during ascent.
Diagnosis and Treatment of Decompression Sickness: The diagnosis of DCS is primarily based on the following points: 1.
The likelihood of DCS is low if the dive depth is less than 10 meters; most cases have a history of rapid ascent to the surface or failure to perform decompression stops.
2.
Any of the aforementioned clinical symptoms occurring within 48 hours post-dive, with approximately 85% of neurological symptoms appearing within one hour of surfacing.
3.
Experimental diagnostics are not absolute but can serve as auxiliary diagnostic tools beyond the above two points.
For example, ultrasound gas detectors can detect the presence of bubbles in the subclavian blood vessels.
Blood tests may reveal increased hematocrit and abnormalities in coagulation factors.
Before discussing the treatment of DCS, it is essential to review the pathophysiology: when decompression occurs, bubble formation can cause vascular occlusion or stimulate the release of vasodilators, increasing microvascular permeability and leading to tissue edema, ultimately resulting in ischemia and hypoxia.
Therefore, the principles of DCS treatment include three points: (1) Repeated compression of small bubbles to relieve vascular occlusion; (2) Hyperbaric oxygen can promote the dissipation of gases within bubbles; (3) Hyperbaric oxygen can improve ischemic and hypoxic conditions in tissues.
The equipment used for treating DCS is hyperbaric oxygen therapy chambers, which can be classified into multi-person and single-person chambers.
Multi-person chambers are commonly used as they can be pressurized to over six atmospheres, while single-person chambers are typically set at three atmospheres.
The treatment tables used for DCS include the U.S.
Navy Treatment Tables 5, 5A, 6, and 6A.
Tables 5A and 6A involve pressurizing air to 165 feet for 15 and 30 minutes, respectively, before ascending to 60 feet and 30 feet, using intermittent hyperbaric oxygen.
If residual symptoms persist after the first treatment, hyperbaric oxygen therapy at 50 feet for 120 minutes may be administered multiple times.
The method of hyperbaric oxygen therapy involves: (1) Rapidly pressurizing to six atmospheres to compress the bubbles to one-sixth of their original size, allowing previously obstructed blood vessels to regain patency and prevent ischemia and hypoxia; (2) Breathing hyperbaric oxygen to facilitate the gradual expulsion of residual bubbles from the body and nourish tissues that were previously hypoxic due to bubble obstruction.
Chronic Decompression Sickness - Dysbaric Osteonecrosis: Divers or underwater workers who frequently dive at significant depths and durations often fail to adhere to proper decompression procedures, leading to joint pain symptoms post-dive, indicating DCS.
Some divers may not receive hyperbaric oxygen treatment and instead rely on injections or painkillers to suppress joint pain, unaware that these medications may contain steroids and analgesics.
Injections only passively suppress joint pain symptoms without actively addressing the underlying issue of bubble-induced vascular occlusion in the bones.
Over time, bubble embolism can lead to ischemia and hypoxia in bone tissue, resulting in aseptic necrosis or avascular necrosis, which occurs without the invasion of pathogenic microorganisms, termed dysbaric osteonecrosis.
Thus, injections or painkillers not only fail to treat DCS but may also mask the problem, leading to more severe consequences.
Occupational injuries resulting from breathing high-pressure air can occur not only in underwater divers but also in workers engaged in underground transportation projects who must breathe high-pressure air in caissons, leading to DCS and dysbaric osteonecrosis.
The alarming aspect of dysbaric osteonecrosis is that early-stage symptoms may be absent, detectable only through X-rays revealing early lesions.
By the time joint pain is felt, it often indicates a more advanced stage requiring joint replacement surgery.
Risk Factors for Decompression Sickness: (1) Obesity: Particularly if exceeding ideal body weight by more than 20%, as a large amount of nitrogen can dissolve in fatty tissue.
(2) Gender: Reports indicate that women are more susceptible to DCS than men.
(3) Individuals with complement response sensitivity are more prone to DCS.
(4) High cholesterol, blood hyperviscosity, prolonged underwater exposure, rapid ascent, or engaging in strenuous underwater work increases the risk of DCS.
Occupations Prone to Decompression Sickness: (1) Commercial divers.
(2) Recreational divers.
(3) Cage net aquaculture divers.
(4) Underwater construction divers.
(5) Divers collecting stones underwater.
(6) Well-drilling personnel.
(7) Workers in underground metro construction under high-pressure conditions.
(8) Civilian pilots and cabin crew.
(9) Military divers, aviators, parachutists, and cabin crew training personnel.
Management of Decompression Sickness: In the event of DCS, immediate contact should be made with a hospital equipped with multi-person hyperbaric oxygen therapy chambers and trained medical professionals.
For severe cases, emergency management is divided into immediate emergency care and transport care.
(1) Immediate Emergency Care: 1.
The patient should lie down immediately.
2.
Check the mouth and maintain airway patency.
3.
If there is no breathing, perform mouth-to-mouth resuscitation immediately.
4.
If there is no heartbeat, initiate cardiopulmonary resuscitation immediately.
5.
Call emergency services and notify a hospital with multi-person hyperbaric chambers capable of reaching six absolute atmospheres, ensuring medical staff and chambers are prepared.
(2) Transport Care: 1.
Maintain a head-down, feet-up, left-side lying position.
2.
Administer 100% pure oxygen.
3.
Provide intravenous fluids.
4.
Ensure warmth to prevent shock.
5.
Comatose or lower limb-paralyzed patients require catheterization.
6.
Unstable patients must be monitored and treated for shock.
7.
Avoid transporting patients by airplane.
If air transport is unavoidable, it should be done at low altitude, maintaining cabin pressure at one atmosphere.
Preventive Measures for Decompression Sickness: (1) Personnel working under abnormal pressure should undergo regular physical examinations and oxygen tolerance tests at hospitals equipped with multi-person hyperbaric chambers, with only qualified individuals permitted to work in such environments.
(2) Personnel working under abnormal pressure must receive professional training before work, with only qualified individuals allowed to engage in such tasks.
(3) Before engaging in work under abnormal pressure, a work plan must be established, including work depth and duration, adhering to the work plan and following standard decompression tables for ascent.
(4) Avoid repeated exposure to abnormal pressure within 12 hours.
(5) Individuals engaging in abnormal pressure work should refrain from flying within 12 hours; those involved in multiple abnormal pressure tasks or recreational scuba diving should avoid flying within 24 hours.
(6) Personnel working under abnormal pressure should notify the nearest hospital with hyperbaric chamber facilities before work and immediately contact a hospital with multi-person hyperbaric chambers if any questions or clinical symptoms arise post-work.

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Reply Date: 2002/04/24