THE USMLE TIMES - #84
Highlights for the week of July 15, 2024
Welcome to issue #84 of The USMLE Times… We’ve now posted our USMLE TIMES newsletter eighty-four weeks in a row! Welcome to the 243 new members of the community 👋
Here’s what’s on tap for issue #84 of the USMLE Times:
Question of the Week (Pulmonary Physiology)
This week’s video training (5 Step 1 Mistakes To Avoid)
Tweet thread of the week
Links to recent training
Question deep-dive & breakdown
Let’s dive in!
A 22-year-old male walks into the emergency room because of a recent onset of nausea and dizziness. The patient lives in Miami and has been visiting a ski resort in Switzerland for the past seven days. He has been unable to enjoy the trip due to his symptoms. His medical history is unremarkable and he has no family history of significance. He denies any recent use of medication, alcohol, or illicit drugs. Physical examination reveals a heart rate of 110 beats/min and a temperature of 101.1°F. If a blood gas analysis is performed, which of the following changes is most likely to be present?
A. Decreased 02 saturation, decreased erythropoietin level
B. Increased 02 saturation, increased erythropoietin level
C. Decreased 02 saturation, increased erythropoietin level
D. Increased 02 saturation, decreased erythropoietin level
E. Decreased 02 saturation, unchanged erythropoietin level
F. Unchanged 02 saturation, decreased erythropoietin level
G. Unchanged 02 saturation, increased erythropoietin level
H. Increased 02 saturation, unchanged erythropoietin level
I. Unchanged 02 saturation, unchanged erythropoietin level
The answer & question breakdown is at the bottom of the post.
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🔗 LINKS TO RECENT POSTS
USMLE Times Issue #83 - READ HERE
USMLE Step 1 Question (Pulmonary) - TRY IT HERE
USMLE Times Issue #82 - READ HERE
The King of Bulls**it USMLE Qbank Advice - READ HERE
ANSWER + QUESTION BREAKDOWN
The Mental Model for this week’s question:
Step 1. Identify the question’s goal (Pick the correct blood gas).
Step 2. Identify the patient’s problem.
Step 3. Ask yourself what abnormalities this would cause.
Step 4. Look for your hypothesized answer in the answer choices.
GENERAL ANALYSIS
The patient’s signs and symptoms are a likely response to elevated altitudes.
ANSWER CHOICES:
ANSWER CHOICE A: Decreased 02 saturation, decreased erythropoietin level
Decreased oxygen saturation would be expected at high altitudes due to lower oxygen pressure. However, erythropoietin (EPO) levels would increase in response to hypoxia to stimulate red blood cell production.
ANSWER CHOICE B: Increased 02 saturation, increased erythropoietin level
Increased oxygen saturation would not occur at high altitudes due to lower oxygen pressure. EPO levels would increase in response to hypoxia.
ANSWER CHOICE C: Decreased 02 saturation, increased erythropoietin level
At high altitudes, the partial pressure of oxygen is lower, leading to decreased oxygen saturation. The body responds to hypoxia by increasing EPO levels to stimulate red blood cell production.
ANSWER CHOICE D: Increased 02 saturation, decreased erythropoietin level
Increased oxygen saturation would not occur at high altitudes due to lower oxygen pressure. EPO levels would increase in response to hypoxia.
ANSWER CHOICE E: Decreased 02 saturation, unchanged erythropoietin level
Decreased oxygen saturation would occur at high altitudes due to lower oxygen pressure. However, EPO levels would increase in response to hypoxia.
ANSWER CHOICE F: Unchanged 02 saturation, decreased erythropoietin level
Oxygen saturation would decrease at high altitudes due to lower oxygen pressure. EPO levels would increase in response to hypoxia.
ANSWER CHOICE G: Unchanged 02 saturation, increased erythropoietin level
Oxygen saturation would decrease at high altitudes due to lower oxygen pressure. EPO levels would increase in response to hypoxia.
ANSWER CHOICE H: Increased 02 saturation, unchanged erythropoietin level
Increased oxygen saturation would not occur at high altitudes due to lower oxygen pressure. EPO levels would increase in response to hypoxia.
ANSWER CHOICE I: Unchanged 02 saturation, unchanged erythropoietin level
Oxygen saturation would decrease at high altitudes due to lower oxygen pressure. EPO levels would increase in response to hypoxia.
FINAL VERDICT…
When an individual ascends to high altitudes, the partial pressure of oxygen in the atmosphere decreases, leading to lower oxygen availability. This results in decreased arterial oxygen saturation (SaO2). In response to hypoxemia, the body increases the production of erythropoietin (EPO) by the kidneys.
EPO stimulates the production of red blood cells to enhance the oxygen-carrying capacity of the blood, which is a compensatory mechanism to counteract the reduced oxygen availability at high altitudes.
In this scenario, the patient's symptoms of nausea and dizziness, along with the recent travel to a high-altitude location, suggest altitude sickness. The physiological response to high altitude includes decreased oxygen saturation and increased erythropoietin levels.
FINAL ANSWER: C: Decreased 02 saturation, increased erythropoietin level
That’s it for issue #84 of The USMLE Times!
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