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These 10 free UHM questions are organized by exam domain, so you can see how each part of the AOA Subspecialty Certification in Undersea and Hyperbaric Medicine blueprint is tested. Reveal the answer and explanation under each question.
Forty minutes after surfacing from a scuba dive, a diver develops bilateral leg weakness and difficulty urinating. The deficits persist despite surface oxygen. Recompression is begun using U.S. Navy Treatment Table 6, and the neurological examination becomes normal after six minutes at 60 feet of seawater. How should this early recovery affect the treatment plan?
Correct answer: B - Complete Treatment Table 6 despite the early neurological recovery.
Before an open-circuit working dive to 30 meters of seawater, two calibrated analyzers show that a cylinder labeled 32% oxygen actually contains 40% oxygen. The label is corrected. The team's working oxygen partial-pressure limit is 1.4 ATA, and the diver will use this cylinder. At sea level, take each 10 meters of seawater as adding 1 ATA. Which revised plan respects the working limit?
Correct answer: D - Limit depth to 24 meters, where the oxygen partial pressure will be 1.36 ATA.
Halfway through an oxygen-breathing period at 2.4 ATA, a patient in an air-filled multiplace chamber develops a generalized tonic-clonic seizure. An attendant can immediately remove the oxygen hood. A bedside glucose measurement is 122 mg/dL. During the active convulsions, what should the team do first?
Correct answer: C - Remove the oxygen hood, protect the airway and patient, and hold chamber pressure steady.
Three oxygen sensors on a closed-circuit rebreather agree at a partial pressure of 1.2 ATA. During sustained swimming at 24 meters, the diver develops a pounding headache, air hunger, and impaired concentration. Symptoms improve after switching to an independent open-circuit supply with similar oxygen and nitrogen partial pressures, without changing depth. Subsequent testing confirms that the oxygen sensors were accurate. Which breathing-gas problem was the oxygen display failing to exclude?
Correct answer: C - Hypercapnia from inadequate carbon dioxide removal
During the first dive of a trip, a 52-year-old diver with hypertension develops breathlessness while swimming against a current in cold water at 8 meters. Symptoms begin before any ascent. The regulator is functioning, and there has been no choking or water aspiration. On the boat, oxygen saturation is 86% on room air, diffuse crackles are audible, and the diver coughs blood-tinged froth. The diagnosis that best accounts for this sequence is:
Correct answer: A - Immersion pulmonary edema
An asymptomatic recreational diver requests a test for patent foramen ovale after a buddy is diagnosed with one. The diver has completed 200 dives without decompression illness and has no history of stroke, unexplained neurological events, or migraine with aura. The cardiovascular examination and exercise history are unremarkable. Under DAN/UHMS guidance, which screening approach is indicated by this history?
Correct answer: D - Routine PFO screening is not indicated by the clinical history.
A freediver takes repeated deep, rapid breaths before a single descent to 20 meters. The diver appears comfortable at depth but loses consciousness during the final few meters of ascent, before experiencing a strong urge to breathe. A safety diver provides immediate rescue. The breathing preparation and timing of the blackout are linked by the following mechanism:
Correct answer: B - Lower carbon dioxide delayed the breathing stimulus, while falling ambient pressure reduced alveolar oxygen pressure.
A 67-year-old man with diabetes has a plantar ulcer extending to exposed tendon, without clinical infection. There is no abscess, osteomyelitis, joint infection, or gangrene. Perfusion is adequate. Six weeks of comprehensive standard wound care, including offloading, debridement, dressings, and nutritional and glycemic optimization, have produced no measurable healing. A referral requests hyperbaric oxygen under Medicare's diabetic lower-extremity wound indication. Which assessment correctly applies CMS NCD 20.29?
Correct answer: C - This Wagner grade 2 ulcer does not meet the wound-severity requirement.
At 24 weeks' gestation, a patient is rescued from a home with a malfunctioning gas heater after briefly losing consciousness. After two hours of 100% oxygen, she is alert, her headache has resolved, conventional pulse oximetry reads 100%, and blood carboxyhemoglobin is 8%. Initial fetal assessment is reassuring. Which disposition addresses the remaining risk?
Correct answer: B - Continue 100% oxygen and arrange urgent hyperbaric and obstetric assessment despite the improved maternal findings.
The reconstructive surgeon calls four hours after a free-flap operation. The flap has become swollen and purple, with brisk capillary refill and dark bleeding on pinprick. An arterial Doppler signal remains present, but the previously audible venous signal is absent. Releasing the external dressing has not improved the findings. Both an operating room and a hyperbaric chamber are immediately available. What takes priority?
Correct answer: A - Urgent operative assessment for a correctable venous outflow obstruction.
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