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Tools & Reference>Emergency Medicine

Decompression Sickness and Dysbarism Workup

Updated: Mar 10, 2026
  • Author: Stephen A Pulley, DO, MS, FACOEP; Chief Editor: Joe Alcock, MD, MS  more...
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Workup

Laboratory Studies

Decompression sickness and dysbarism (DCS) are clinical diagnoses for which a fair amount of clinical suspicion is necessary if cases are not to be missed. [39] No specific tests exist; most of the time, the "test" is improvement with hyperbaric oxygen (HBO) therapy. Whenever diving is involved, it is worthwhile to consider whether the patient has any pressure-related injuries. Baseline laboratory studies should be obtained, but these will have no bearing on initial management. They may, however, be useful in the differential diagnosis while the patient is undergoing HBO therapy or in expanding the knowledge base about this disorder.

HBO therapy (and, if necessary, transfer) must not be delayed. In individuals with altered mental status, prudence dictates obtaining studies to help further evaluation. If the individual is in extremis (ie, in shock), appropriate resuscitation studies should be obtained.

For changes in mental status, the following are warranted:

  • Blood glucose level
  • Complete blood count (CBC)
  • Sodium, magnesium, calcium, and phosphorus levels
  • Oxygen saturation
  • Ethanol level, drug screen
  • Carboxyhemoglobin (COHb) level

For shock, the following are warranted:

  • Blood glucose level
  • CBC 
  • Electrolytes
  • Blood urea nitrogen (BUN) level
  • Creatinine and lactic acid levels
  • Type and screen, crossmatch
  • Prothrombin time (PT)/international normalized ratio (INR), activated partial thromboplastin time (aPTT)
  • COHb level
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Radiography

Because dysbaric injuries involving the lungs and chest can occur concomitantly with DCS, chest radiography should be performed to screen for overpressurization injuries. Chest radiography can identify evidence of pneumothorax, pneumomediastinum, subcutaneous emphysema, pneumopericardium, alveolar hemorrhage, and decreased pulmonary blood flow caused by nitrogen pulmonary emboli.

Opacification of the sinuses on radiography confirms that pathology is present in this area, but it does not confirm that the pathology is related to diving.

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Computed Tomography

Computed tomography (CT) can readily identify barotraumatic injuries in the brain, sinuses and orbits, chest, abdomen, and pelvis and is a reasonable first-line approach when there is a concern for diving injuries. It differentiates pathology in areas of concern better than radiography does.

If mental status does not initially improve in response to hyperbaric repressurization, other etiologies should be considered. Part of that consideration is CT of the head to evaluate for structural issues.

Chest CT, especially spiral CT, is recommended for evaluation of the lungs after a pulmonary barotrauma event. It can show preexisting pathology (eg, small lung cysts). [111]

In a patient who experience persistent symptoms of dyspnea or discomfort in the thorax but whose conventional chest radiographs are normal, CT can identify subtle or early findings for pneumothorax or pneumomediastinum. Identification of these barotraumas before initiation of HBO therapy is useful, in that the pressure changes can exacerbate these conditions. Differentiating pneumoperitoneum from DCS as the cause for abdominal pain can be of similar importance. [112]  

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Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) can be useful in the management of neurologic DCS. The diagnosis is still a clinical one, however. The decision to pursue HBO referral should be based purely on the clinical presentation and should not be either guided by MRI or other diagnostic findings or delayed to await such findings.

MRI may reveal focal spinal lesions that correlate with symptoms and physical findings. It readily detects cerebral damage in arterial gas embolization (AGE), [113] but its sensitivity is low in DCS. MRI may prove useful in patients who do not show initial improvement to HBO therapy by localizing the area of DCS injury or excluding other causes of the clinical findings.

In an HBO center, MRI may be a useful diagnostic adjunct to help guide management after the first treatment or subsequent treatments. [40] A normal MRI correlates with better outcome. [114]  MRI is also useful for monitoring injured divers through successive HBO treatments.

Cerebral MRI has even identified abnormalities in the brain that correlated with hours of diving in the air-breathing range even when no clinical or historical signs of neurologic DCS were present. [115]  MRI abnormalities have also been correlated with neuropsychological deficits in older divers. [116]  It must be kept in mind that negative MRI findings do not exclude the possibility of AGE or DCS and that improvement in MRI findings does not necessarily correlate with clinical improvement. [117]

Diffusion tensor MRI (DTI) has been demonstrated to be useful for investigating DCS. [118]

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Other Tests

Other tests that may be considered include electrocardiography (ECG) and oxygen saturation evaluation.

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Procedures

When there is some question as to whether the patient's problem is dysbarism or DCS, repressurization in a hyperbaric chamber can be pursued for diagnostic and therapeutic reasons. (This may require patient transfer.)

Intubation delivers 100% oxygen when less-invasive delivery methods do not work or are inappropriate.

Needle decompression and thoracostomy can help in the treatment of tension pneumothorax, simple pneumothorax, tension pneumoperitoneum, and subcutaneous emphysema.

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