Decompression Sickness (The Bends): Diagnosis and Treatment
A diver with symptoms after a deep-sea dive should be diagnosed with decompression sickness based on the timing of symptom onset after ascent and clinical presentation, and must receive immediate hyperbaric oxygen therapy as definitive treatment, with supplemental oxygen administration as first aid during transport.
Pathophysiology and Clinical Diagnosis
Decompression sickness occurs when dissolved inert gas (nitrogen) comes out of solution during or after ascent, forming bubbles in tissues and blood vessels 1. The diagnosis is primarily clinical and based on:
- Timing: Symptoms typically develop within 24 hours of surfacing, though most cases present within the first few hours after the dive 2, 3
- Symptom pattern: The clinical presentation depends on where bubbles lodge in the systemic circulation 1
Clinical Manifestations by Severity
Mild to Moderate ("Type I DCS"):
Severe ("Type II DCS"):
- Neurological deficits including motor weakness, ataxia, altered mental status, paresthesias 2, 4
- Pulmonary decompression illness ("the chokes"): chest tightness, cough, dyspnea, hypotension 1
- Cardiovascular collapse, convulsions, or death in extreme cases 1
Immediate Management Algorithm
Step 1: First Aid at Scene
- Administer 100% oxygen immediately via non-rebreather mask to all suspected cases 2, 3
- Position patient supine (not Trendelenburg, which is outdated) 3
- Begin oral or intravenous isotonic, glucose-free fluids to treat hypovolemia 3
Step 2: Rapid Assessment
- Document the dive profile (depth, duration, ascent rate) and exact timing of symptom onset 2
- Perform focused neurological examination looking for asymmetric motor deficits, non-dermatomal paresthesias, altered mental status, ataxia, or visual changes 5
- Assess for pulmonary involvement: respiratory distress, cough, hemoptysis 1
Step 3: Definitive Treatment
Hyperbaric oxygen therapy is the definitive treatment and should be initiated as rapidly as possible 2, 3. The standard protocol is:
- U.S. Navy Treatment Table 6: 100% oxygen breathing at 2.82 atmospheres absolute (equivalent to 60 feet of seawater depth) 3
- Treatment should begin within hours of symptom onset when possible—delays worsen outcomes 5
- Most cases require 1-2 hyperbaric treatments; severe cases may require additional sessions until clinical stability is achieved 3
Critical Risk Factors to Identify
The British Thoracic Society guidelines emphasize that certain anatomical and physiological factors increase risk and severity 1, 6:
- Patent foramen ovale or other intracardiac shunts: Allow bubbles to bypass pulmonary filtration and enter systemic circulation directly, causing more severe neurological and cardiovascular manifestations 1, 6
- Obstructive airway disease: Identified as an independent risk factor for developing decompression sickness 1, 6
- Smoking and small airway disease: Associated with increased risk in divers who develop neurological symptoms after "safe" dives 1
Common Pitfalls to Avoid
- Do not delay transport for hyperbaric treatment: Continue 100% oxygen during transport; high-flow oxygen is beneficial despite theoretical concerns 2, 3
- Do not misinterpret symptoms as viral illness, hypoxia, or hyperventilation: The delayed onset (often 1-2 hours after surfacing) and progressive nature are characteristic of DCS 5
- Do not assume normal spirometry excludes risk: FEV1 and FVC within normal range do not exclude individuals from developing decompression illness 1
- Recognize that recurrent episodes tend to be more severe: Document any history of decompression sickness prominently, as recurrence carries worse prognosis 1
Prognosis and Follow-up
- Prognosis is variable but improved by rapid recompression therapy 1
- Most cases achieve good outcomes with appropriate hyperbaric treatment 2
- Severe cases may have residual neurological manifestations despite treatment 2, 3
- Consider echocardiography to evaluate for patent foramen ovale in divers with severe or recurrent episodes 6