USMLE Step 1 Respiratory Physiology Review 60 19 P50

USMLE Step 1 Respiratory Physiology Review 60 19 P50

 

On these “Gold Standard Step 1 Facts” pages you will find Free:

  • USMLE Audio Review files from our “Gold Standard USMLE Reviews”
  • Transcriptions of those files
  • And videos (as they become available)

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  • Following along with the transcription
  • Or by watching the video (if available)

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Let’s start our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.

Play USMLE Audio MP3 60 19 P50 Below

Begin 60 19 P50 Transcription

 

Shifts in the oxygen dissociation curve can also be described by talking about changes in P50. What is meant by the term P50?                                          

 

  • P50 is the oxygen tension that produces a 50% hemoglobin saturation with oxygen.

 

 What is the normal P50 for arterial blood?                

 

  • Normal arterial P50 is about 27 mm Hg.

 

 When the oxygen dissociation curve is shifted to the right, does this mean an increase or a decrease in P50?                                                    

 

  • A right shift means increased P50.

 

How are P50 and hemoglobin’s affinity for oxygen related?                                                   

 

  • They are inversely related.

 

What does an increase in P50 mean in terms of hemoglobin’s affinity for oxygen?         

 

  • An increase in P50 indicates a decrease in hemoglobin’s affinity for oxygen.

 

What does an increase in P50 indicate about hemoglobin saturation?                     

 

  • As hemoglobin saturation decreases, P50 increases.

 

 

When P50 is increased, what happens to the ease of unloading oxygen from arterial blood into the tissues?                                                                 

 

  • Unloading oxygen at the tissues becomes easier.

 

What happens to P50 when hemoglobin’s affinity for oxygen is increased? As with hemoglobin F, for example.

 

  • P50 is decreased.

 

When the P50 is decreased, what happens to the ease of unloading oxygen from arterial blood into the tissues?        

 

  • Unloading oxygen from arterial blood into the tissues becomes more difficult when P50 decreases.

 

Student doctor, please pause the tape and summarize what we’ve discussed about P50. 

  • Shifts in the oxygen dissociation curve can also be described by talking about changes in P50. P50 is the oxygen tension that produces a 50% hemoglobin saturation with oxygen. Normal arterial P50 is about 27 mm Hg. A right shifted oxygen dissociation curve means increased P50. P50 and hemoglobin’s affinity for oxygen are inversely related. An increase in P50 indicates a decrease in hemoglobin affinity for oxygen, and as hemoglobin’s saturation decreases, P50 increases. When P50 is increased, unloading oxygen at the tissues becomes easier. When hemoglobin’s affinity for oxygen is increased, as with hemoglobin F for example, P50 is decreased, which makes unloading of oxygen from arterial blood into the tissues more difficult.

 

****END OF TRANSCRIPTION****

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60-19 P50

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