Decompression Sickness Workup

Updated: Mar 05, 2019
  • Author: Stephen A Pulley, DO, MS, FACOEP; Chief Editor: Joe Alcock, MD, MS  more...
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Workup

Laboratory Studies

Acute decompression sickness (DCS) is a purely clinical diagnosis that requires a fair amount of clinical suspicion to avoid missing cases. [34] Most of the time, the "test" is improvement with hyperbaric oxygen (HBO) therapy. No specific tests exist for DCS. When diving is involved, consider determining whether the patient has any pressure-related injuries. Obtain baseline laboratory studies, but these will have no bearing on initial management. They may be useful in the differential diagnosis while undergoing HBO therapy. They may also be useful in expanding the knowledge base about this disorder.

Do not delay HBO therapy (and transfer, if necessary). In individuals with change in mental status, prudence dictates obtaining studies to help further evaluation. If the individual is in extremis (ie, shock), obtain appropriate resuscitation studies.

For changes in mental status, evaluate the following:

  • Blood glucose level, CBC count
  • Sodium, magnesium, calcium, and phosphorous levels
  • Oxygen saturation
  • Ethanol level and drug screen
  • Carboxyhemoglobin level

For shock, evaluate the following:

  • Blood glucose level, CBC count
  • Electrolytes and BUN level
  • Creatinine levels, lactic acid
  • Type and screen/cross
  • Prothrombin time/international normalized ratio, activated partial thromboplastin time
  • Carboxyhemoglobin level
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Imaging Studies

Chest radiography

Because dysbaric injuries involving the lungs and chest can occur concomitantly with decompression sickness (DCS), obtain a chest radiograph to screen for overpressurization injuries. Chest radiography reveals evidence of pneumothorax, pneumomediastinum, subcutaneous emphysema, pneumopericardium, alveolar hemorrhage, and decreased pulmonary blood flow caused by nitrogen pulmonary emboli.

Head CT scanning

If mental status does not initially improve in response to hyperbaric repressurization, consider other etiologies. Pursuing a noncontrast CT scan of the head to evaluate for structural issues is part of that consideration.

Chest or abdominal/pelvis CT scanning

In a patient with persistent symptoms of dyspnea or discomfort in the thorax that have normal conventional chest radiographs, CT scanning can identify subtle or early findings for pneumothorax or pneumomediastinum. If available, noncontrasted CT does not take long to accomplish. Identification of these barotraumas before doing HBO therapy is useful as the pressure changes can exacerbate these conditions.

Differentiating pneumoperitoneum from DCS as the cause for abdominal pain can be of similar importance. A unique gas pattern has been documented in the venous systems related to DCS. [129] Gas appeared in the portal venous system, omental veins, and peripheral veins in the pelvis.

See Dysbarism for more information.

MRI

MRI has been found useful in the management of neurologic DCS. [130, 131, 132, 133] The diagnosis is still clinical, and the patient's transfer to an HBO facility should not be delayed. MRI has revealed focal spinal lesions that correlated with the patient's symptoms and examination. MRI readily detects cerebral damage in arterial gas embolization (AGE), [134] but iy yields low sensitivity in DCS. MRI may prove useful in patients who do not show initial improvement to HBO therapy. In these individuals, the MRI may localize the area of DCS injury or exclude other etiologies for the patient's symptoms.

Spinal MRI found lesions more commonly in divers with severe spinal DCS and none at all in those that ultimately had a favorable outcome. Therefore, in an HBO center, it may be a useful diagnostic adjunct to help guide management after the first, or subsequent, treatment. [35] A normal MRI correlates with better outcome. [135] Do not delay HBO treatment to obtain an MRI.

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. [136]

Note that negative MRI findings do not exclude the possibility of AGE or DCS. Also, improvement in MRI findings does not necessarily correlate with clinical improvement. [137] It has also been correlated with neuropsychological deficits in older divers. [138]

Diffusion Tensor MRI (DTI) has been demonstrated to be useful for investigating DCS. [139]

MRI in a guinea pig model was able to identify small bubbles and blood in the inner ear. It may have future utility in management of inner-ear DCS. [140]

The decision to pursue HBO referral should be based on the purely clinical presentation and not be guided, or delayed, by obtaining MRI or other diagnostic findings.

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Other Tests

Other tests may include ECG and/or oxygen saturation evaluation.

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Procedures

Diagnostic repressurization

If diagnosis of decompression sickness (DCS) versus dysbarism or some other entity is unclear, order repressurization in a hyperbaric chamber (transfer if necessary) for diagnostic and therapeutic reasons.

Intubation

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

Needle decompression and thoracostomy

These procedures help in the treatment of tension pneumothorax, simple pneumothorax, tension pneumoperitoneum, and subcutaneous emphysema.

See Dysbarism for more information.

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