A 32-year-old man comes to the emergency department due to joint pains that began about an hour after a scuba diving excursion and have been worsening over the past 12 hours. He describes significant pain in his shoulders and elbows that does not change with movement. The patient has no medical history and takes no medications. Blood pressure is 122/80 mm Hg, pulse is 104/min, and respirations are 20/min. Pulse oximetry is 97% on room air. The patient is alert and oriented but appears uncomfortable. Cardiopulmonary examination is normal. The joints are nontender with full range of motion. He has normal strength and sensation in the extremities. The patient is placed on 100% oxygen, and intravenous fluids are administered. Which of the following is the best next step in management?
Decompression sickness | |
Pathophysiology |
|
Risk factors |
|
Presentation |
|
Treatment |
|
This patient with worsening joint pain (shoulders and elbows) after scuba diving 12 hours ago most likely has decompression sickness, an environmental emergency that occurs when dissolved gases (mostly nitrogen) form bubbles within the body.
To keep divers' lung inflated during their dive, air from scuba tanks, consisting of a mixture of nitrogen and oxygen, is administered at high pressures. During the descent phase, increased ambient pressure causes a greater amount of the gases to be dissolved into the bloodstream, resulting in excess dissolved nitrogen accumulating within the bloodstream and tissues. Slow return to the lower ambient pressure at the surface allows time for the excess dissolved nitrogen to return to the lungs and be removed with exhalation. However, with rapid ascent, the more abrupt decrease in ambient pressure may cause much of the dissolved nitrogen to come out of solution and form gas bubbles throughout the tissues and bloodstream, leading to pain and obstruction of blood flow.
Symptoms usually start within an hour of ascent but can develop up to 24 hours later. Type 1 decompression sickness is relatively mild and includes:
Musculoskeletal involvement ("the bends") consists of painful joints that are nontender to palpation and have normal range of motion. The elbows and shoulders are most commonly affected.
Cutaneous involvement consists of pruritus and erythema.
Type 2 decompression sickness is severe and includes neurologic symptoms ("the staggers"), which consist of ataxia, dizziness, visual disturbance, and possibly spinal cord involvement (eg, weakness, paresthesia, loss of bladder control). Pulmonary involvement ("the chokes") is rare but can lead to obstructive shock due to venous gas embolism occluding the pulmonary vasculature.
To prevent decompression sickness, slow ascent and delay of flying (eg, for 12 hr) after diving are recommended. Initial treatment with intravenous fluids and 100% oxygen helps improve blood flow and increase oxygen delivery to the tissues. Hyperbaric oxygen therapy (eg, in a hyperbaric oxygen chamber) facilitates the resorption of gas bubbles and should be initiated as soon as possible. A delay in therapy is associated with poorer outcomes.
(Choices B, C, and E) Acetazolamide, dexamethasone, and nifedipine are used in the treatment of high-altitude illness (HAI) but have no role in the management of decompression sickness. Although HAI is associated with a change in pressure (due to a change of altitude), its pathophysiology is related mostly to responses to hypoxia (including edema) and it presents with symptoms similar to an alcohol hangover, encephalopathy, or noncardiogenic pulmonary edema.
(Choice D) Low-molecular-weight heparin is used in the treatment of pulmonary embolism, which is unlikely in the absence of hypoxia and does not typically cause joint pains.
Educational objective:
Decompression sickness in divers is caused by rapid ascent to the surface that leads to formation of nitrogen bubbles in the tissues and bloodstream. It is diagnosed clinically, and the definitive treatment is hyperbaric oxygen therapy.