USMLE Step 1 Respiratory Physiology Review 61 11 V/Q Mismatch

USMLE Step 1 Respiratory Physiology Review 61 11 V/Q Mismatch

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)

The idea is that you can review for the USMLE online by:

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

If you like what you here, you can purchase the entire Gold Standard Step 1 MP3 audio USMLE review for your iPhone, iPod, or computer here.

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

Play USMLE Audio MP3  61 11 V/Q Mismatch  Below

Begin 61 11 V/Q Mismatch  Transcription

Continuing with the ventilation perfusion mismatch. From the apex to the base of the lung, normal variations in VQ occur because both ventilation and perfusion vary from apex to base.

Where in the normal lung is the ventilation perfusion ratio equal to 3?

  • At the apex of the vertical lung, ventilation perfusion ratio is about 3

What does this greater than one ventilation perfusion value indicate about the apex of the lung?

  • The apex of the lung is under perfused compared to ventilation which means wasted ventilation.

What types of organisms tend to flourish in the apex of the lungs?

  • Organisms that thrive on high oxygen intake flourish in the apex of the lungs

What is an example of this?

  • Tuberculosis

In liters per minute, what is typical ventilation at the base of the lung?

  • Typical ventilation at the base of the lung is about .82 liters per minute.

In liters per minute, what is typical blood flow at the base of the lung?

  • About 1.29 liters per minute.

What does the ventilation perfusion ratio equal at the base of the normal vertical lung?
About .6

What does this value indicate about ventilation and blood flow at the base of the lung?

  • The base of the lung is over perfused compared to ventilation which means wasted blood flow

With exercise and increased cardiac output, what is the resulting ventilation perfusion ratio?

  • It approaches unity. In other words, it approaches 1

What happens in the lungs to allow the ventilation perfusion ratio to approach unity?

  • Vasodilation of apical capillaries

Student doctor, please pause the tape and summarize what we’ve discussed about ventilation perfusion ratios at the apex and base of the lungs.

  • From the apex to the base of the lung, normal variations in ventilation perfusion ratio occur because both ventilation and perfusion vary from apex to base. At the apex of the vertical lung, ventilation perfusion ratio is about 3. The apex of the lung is under perfused compared to ventilation which means wasted ventilation. Organisms that thrive on high oxygen intake flourish in the apex of the lungs. One example of this is tuberculosis. At the base of the lung, typical ventilation is about .82 liters per minute and typical blood flow is about 1.29 liters per minute. Ventilation perfusion ratio is about .6 at the base of the normal vertical lung. The base of the lung is over perfused compared to ventilation which means wasted blood flow. With exercise and increased cardiac output, vasodilation of the apical capillaries allows the ventilation perfusion ratio to approach unity. That is, the ventilation perfusion ratio approaches 1.

 

****END OF TRANSCRIPTION****

Want More USMLE Step 1 Review Facts?

boardprep.net

Leave a Reply