If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
This month’s stumper
A 27-year-old scuba diver visits the emergency department for epistaxis following ascent from a 25-foot dive. During descent he experienced some pain in his right ear, but he continued to dive. He also notes decreased hearing in his right ear. The patient is otherwise healthy and has no significant medical history.
His vitals are: temperature of 36.6 °C (97.8 °F), blood pressure of 120/72 mm Hg, pulse of 74 beats per minute, respirations of 14 per minute, and oxygen saturation is 100% on room air.
Physical examination reveals the presence of blood behind an intact right tympanic membrane. The presence of blood in the nasal cavity is also noted. The remainder of the exam is unremarkable.
Which of the following is the most appropriate next step in management?
A. Arrange a transfer to the nearest hyperbaric chamber.
B. Consult a diving medicine specialist.
C. Order a CT scan of the head.
D. Provide oxygen therapy.
E. Reassurance and prescription of decongestants.
F. Refer the patient to an ENT physician.
The correct answer is E.
Kaplan Medical explains why
Reassurance and prescription of decongestants is appropriate treatment for mild middle ear barotrauma. During descent, water pressure on the external surface of the ear drum increases. To counterbalance this pressure, the air must be passed through the eustachian tube. When the eustachian tube is blocked (e.g., by mucus), it is impossible to equalize pressure between the internal and external surfaces of the tympanic membrane.
As the pressure increases with descent, the eardrum blows inward and initially equalizes the pressure by compressing the middle ear gas. There is a limit to this capability and soon the middle ear pressure becomes lower than the external water pressure, creating a relative vacuum in the middle ear space. This usually manifests as severe ear pain. Negative pressure in the middle ear cavity causes the blood vessels of the eardrum and the middle ear to expand, leak, and eventually burst. If descent continues, either the eardrum ruptures, allowing air or water to enter the middle ear and equalize the pressure, or blood vessels rupture and cause sufficient bleeding into the middle ear to equalize the pressure.
Interestingly, most cases of middle ear barotrauma occur at relatively shallow depths (15 to 25 feet). These events are attributed to Boyle's Law which describes the relationship between gas volume and pressure.
Upon reaching the surface, the diver may complain of pain, fullness in ear, hearing loss, or vertigo. Occasionally blood may be found in the nostrils. As air expands in the middle ear blood is forced through the eustachian tube. A slight ascent can result in immediate relief. Treatment of middle ear barotrauma consists of administration of decongestants and cessation of diving until symptoms improve.
Why the other answers are wrong
Choice A: Arranging transfer to the nearest hyperbaric chamber is not necessary, because hyperbaric oxygen is not used to treat middle ear barotraumas. Moreover, it may be harmful as pressure equalization is required.
Choice B and F: Consulting a diving medicine specialist or referring the patient to an ENT physician for a case of mild middle ear barotrauma is not necessary. Since the tympanic membrane is intact, the management of this patient is relatively simple.
Choice C: Ordering a CT scan of the head is not necessary because it would not provide any additional information.
Choice D: Providing oxygen therapy is not necessary because the patient does not have signs or symptoms of hypoxia.
Tips to remember
Reassurance and prescription of decongestants is appropriate treatment for mild middle ear barotraumas.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
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