Decompression Sickness

Original Editor - Stacy Lawrence
Top Contributors - Stacy Lawrence, Khloud Shreif, Ewa Jaraczewska, Rana Muhammad Tahir Aslam, Vidya Acharya and Mohamed A Hassanin

Overview

Decompression sickness (DCS), also known as “the bends,” “Caisson disease,” or “diver’s disease,” occurs due to rapid reduction in highly pressurized environment, typically after diving, high-altitude flights, or unpressurised aerospace activities. DCS results from gas bubbles forming in the blood and tissues due to rapid ascent, which disrupts normal physiological function. Symptoms vary widely, commonly including arthralgias, myalgias, paresthesias, and numbness.

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  Inside Caisson decompression.jpeg
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Etiology

Decompression sickness is rare among recreational divers adhering to safe ascent practices, though cases increase with depth and duration of dives. Divers who skip decompression stops or ascend too quickly are at elevated risk, as are those with specific health conditions like patent foramen ovale (PFO), which increases susceptibility to nitrogen bubbles.

Mechanism of Injury

Decompression sickness occurs when nitrogen absorbed into the bloodstream and tissues under high pressure (during a dive) forms gas bubbles as pressure decreases too rapidly during ascent. This can disrupt blood flow and damage surrounding tissues, particularly in high-fat areas such as the brain, spinal cord, and joints. There are two types of DCS:

• Type I (milder): Affects joints, skin, and lymphatics.
• Type II (severe): Affects central nervous, respiratory, and circulatory systems.

Clinical Presentation

DCS primarily impacts joints and the central nervous system due to nitrogen’s solubility in fat-rich tissues. Key structures at risk include the spinal cord, brain, lungs, and musculoskeletal system, as these areas are especially vulnerable to bubble formation during pressure changes. Symptoms of DCS can vary widely, influenced by the depth, duration, and rate of ascent.

Nerve damage at cellular level - Neuropraxia

Symptoms of DCS can vary by severity:

• Type I DCS: Presents with joint pain, itching, skin rashes, and fatigue.
• Type II DCS: Includes neurological symptoms like numbness, muscle weakness, confusion, and difficulty breathing. Spinal cord involvement can lead to paralysis if not managed promptly. Additionally, severe cases may cause "the chokes," where lung bubbles induce chest pain and breathing difficulties.
• Type III DCS: presents with potentially fatal pulmonary complications.

Symptoms usually appear within hours after ascent, although delayed onset up to 24 hours is possible.

Diagnostic Procedures

Lumbar Spine MRi

Diagnosis is based on medical history, symptoms following ascent, and often requires confirmation through imaging like MRI for severe cases.

Outcome Measures

Initial assessments involve symptom monitoring post-dive. Imaging (MRI or CT) is generally unnecessary for initial DCS diagnosis but may assist in identifying long-term damage like dysbaric osteonecrosis (bone damage). Neurological exams and functional assessments may track recovery and any residual disability.

Management / Interventions

The primary treatment for DCS is Hyperbaric Oxygen Therapy (HBOT), which helps dissolve nitrogen bubbles and re-oxygenate affected tissues. Rest, hydration, and gradual acclimatization are also critical for managing symptoms and preventing further complications.

Hyperbaric Chamber

• Immediate First Aid: 100% oxygen administration can reduce symptoms by enhancing nitrogen elimination.
• Hyperbaric Oxygen Therapy (HBOT): Recompression in a hyperbaric chamber remains the standard treatment. It restores proper blood flow and re-dissolves nitrogen bubbles to facilitate safe elimination.
• Supportive Care: Pain management and hydration are essential; fluids assist in bubble dissolution.

Timely HBOT is most effective, especially within hours of symptom onset. Repeated sessions may be necessary depending on symptom severity and residual effects.

Prevention

Key prevention strategies include:

• Gradual ascent with decompression stops
• Avoiding flights immediately after diving. Waiting 12-24 hours before flights after diving to reduce pressure-related risks.
• Hydration and avoidance of alcohol
• Adherence to dive tables and personal limits

This structured understanding of DCS helps guide effective diagnosis, treatment, and preventative measures, particularly for divers, high-altitude climbers, and astronauts, where the risks of decompression are more prevalent.

Other preventative strategies include maintaining adequate hydration, avoiding excessive alcohol intake post-dive, and conducting thorough medical evaluations, particularly for divers with predisposing conditions like PFO.

Risk Factors

Risk factors for DCS include prolonged dives, rapid ascents, dehydration, and physical exhaustion. Cold water, older age, obesity, and recent illnesses or injuries also increase susceptibility to DCS.

Differential Diagnosis

Conditions that may mimic DCS include:

• Air embolism: Gas bubbles in the bloodstream, usually following trauma.
• Musculoskeletal injuries: Joint and muscle pains from physical exertion.
• Heat stroke or exhaustion: Due to exertion and environmental exposure.

Accurate diagnosis often requires a history of recent diving and rapid symptom onset post-dive.

More specifically the following conditions may be confused with DCS Type I in patients presenting with musculoskeletal pain, skin rashes, and lymph node swelling:

• Systemic viral illness
• Systemic lupus erythematosus
• Acute leukemia
• Bacterial illnesses such as gonorrhea and syphilis
• Lymphoma
• Lyme disease
• Dehydration

On the other hand, DCS Type II may be confused with the following:

• Inner ear barotrauma
• Stroke
• Drowning
• Thermal stress
• Nitrogen narcosis
• Meningococcemia
• Intracranial and intraspinal masses
• Multiple sclerosis
• Hypoglycaemia
• Acute coronary syndrome
• Marine life toxin exposure
• Oxygen toxicity

Rehabilitation Care

Rehabilitation following DCS is essential to address physical deficits and prevent long-term complications. Rehabilitation focuses on restoring function, especially in cases with neurological impacts.

1. Physical Therapy (PT): PT interventions aim to improve strength, mobility, and balance. Early management will help with limb mobility. Exercise programs are adapted to individual needs and may include:
   • Range of Motion (ROM) exercises for joint flexibility.
   • Strengthening exercises to support the musculoskeletal system.
   • Balance and coordination activities to aid recovery from vestibular impairments due to DCS.
2. Occupational Therapy (OT): OT assists patients in regaining functional independence, focusing on:
   • Adaptive strategies for activities of daily living (ADLs).
   • Tools and aids to manage symptoms and accommodate any long-term impairments.
3. Vestibular Rehabilitation: For individuals experiencing vertigo or balance issues, vestibular rehabilitation helps retrain the inner ear and brain. This can include:
   • Gaze-stabilisation exercises to improve visual focus during head movements.
   • Balance training to prevent falls and improve stability.
4. Psychological Support: Chronic cases can lead to anxiety or depression, particularly for professional divers facing career impacts. Counseling or support groups may provide necessary emotional support.

It is important to note that "most of the research focuses on acute care and recompression therapies; however, information regarding outcomes of patients with SCDCS undergoing inpatient rehabilitation is lacking."