USMLE Step 1 Respiratory Physiology Review 62 02 Hypoxia

USMLE Step 1 Respiratory Physiology Review 62 02 Hypoxia

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Play USMLE Audio MP3 62 02 Hypoxia Below

Begin 62 02 Hypoxia Transcription

Now let’s talk about hypoxia.

Define hypoxia.

  • Hypoxia is inadequate levels of oxygen in tissues, the blood, or alveolar air

There are three reflex responses to low arterial PO2, all of which are signs of hypoxia. First we will just list them. I’ll cue you with the first letter of each.

First, H

  • hyperpnea     

Second, T

  • tachycardia       

And Third, T

  • tachypnea

What is tachycardia?

  • Rapid Heart rate

And what is tachypnea?

  • Rapid breathing

And what is hyperpnea?

  • Deep breathing

A less reliable sign of hypoxia is when tissues take on a bluish color because of too much deoxyhemoglobin in the capillary blood. What is this called? It starts with a C.

  • A less reliable sign of hypoxia is cyanosis which is when body tissues take on a bluish tinge caused by too much deoxyhemoglobin in the capillary blood.

What are these symptoms of? Lack of coordination, slurred speech, slower reflexes, and over confidence. The answer starts with AH

  • Acute hypoxia

If the body is unable to compensate, what does acute hypoxia lead to?

  • Uncompensated acute hypoxia results in first coma and then death

How long does it take for this to occur?

  • Anywhere from minutes to hours.

What causes fulminant hypoxia?

  • Sudden exposure to oxygen tension of less than 20 mm Hg causes fulminant hypoxia

Name one thing that would result in fulminant hypoxia?

  • Rapid depressurization of an airplane at very high altitude with no supplemental source of oxygen

What are the results of fulminant hypoxia?

  • Unconsciousness after 15 to 20 seconds, possible brain death after 4 to 5 minutes, and then death.

Different types of hypoxia are caused by different insufficiencies in the body. For the next three questions, I’ll describe the cause. Please respond with the type of hypoxia.

First, inadequate blood flow.

  • Hypokinetic hypoxia. or ischemic hypoxia.

Second, insufficient amounts of functional hemoglobin

  • Anemic hypoxia

Third, inactivation of metabolic enzymes

  • Histotoxic hypoxia

Student doctor, please pause the tape and summarize what we’ve discussed about the definition, signs, symptoms, and causes of hypoxia.

  • Hypoxia is inadequate levels of oxygen in the tissues, the blood, or alveolar air. There are three reflex responses to low arterial PO2, all of which are signs of hypoxia. They are hyperpnea, deep breathing; tachycardia, rapid heart rate; and, tachypnea, rapid breathing. A less reliable sign of hypoxia is when tissues take on a bluish color because of too much deoxyhemoglobin in the capillary blood. This is called cyanosis. Symptoms of acute hypoxia are lack of coordination, slurred speech, slower reflexes, and overconfidence. Sudden exposure to oxygen tension of less than 20 mm Hg, causes fulminant hypoxia. For example, rapid depressurization of an airplane at very high altitudes with no supplemental source of oxygen would result in fulminant hypoxia. This could lead to unconsciousness after 15 to 20 seconds, possibly brain death after 4 to 5 minutes, and of course death. Uncompensated acute hypoxia results in first coma and then death. This happens in anywhere from minutes to hours. Different types of hypoxia are caused by different insufficiencies in the body. Inadequate blood flow causes hypokinetic or ischemic hypoxia. Insufficient amountof functional hemoglobin will cause anemic hypoxia. Histotoxic hypoxia is caused by inactivation of metabolic enzymes.

 

****END OF TRANSCRIPTION****

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