L5 Alveolar Ventilation & Ventilation / Perfusion Ratio

Question 1

What does minute ventilation depends on ?

Answer 1

1. Ventilation rate ( how many breath in one min/ normal is 12 to 20 )
2. Tidal volume (normally it is 0.5-0.6, however it can increase during exercise in expense IRV and ERV )

Question 2

What is the Partial pressures of oxygen in the respiratory system ?

Answer 2

1. In the air (dry ) —

Question 3

What is types of dead space and what they mean ?

Answer 3

1. Anatomical dead space :
   - 100- 200 ml of air within the conducting airways
2. Functional ( alveolar ) dead space :
   - when there is ventilation but no perfusion as when there is blood clot that stop blood flow

Question 4

How you can measure anatomical dead space ?

Answer 4

By Fowler’s method (single-breath nitrogen test)

1. patient breath normal mixed air
2. Patient take deep pure oxygen air
3. Patient exhale in nitrogen analyzer device

Normally:
Upper airways ( dead space ) are filled with pure oxygen air
Alveoli are filled with mixed air ( oxygen and nitrogen )

Question 5

When the V/Q is zero and when it is infinite?

Answer 5

1. Zero —> when ventilation is zero —

Question 6

What are the types of shunts ?

Answer 6

1. Anatomical shunts : new path for blood not being oxygenated ( so V/Q=0)
2. Functional (alveolar/physiological ) shunts: normal perfusion but not ventilation so the blood bypass the unit without being oxygenated ( so V/Q=0)

Question 7

What is happening in asthma ?

Answer 7

1. Immune reactions
2. Release of cytokines
3. Starting asthma:
   A. Neural effects- nts breakdown and hyper-responsiveness
   B. Mucous hyper-secretion
   C. Fibrosis —> basement membrane thickening
   D. SM hyperplasia
   E. Epithelium shedding—

Question 8

What are the main types of emphysema?

Answer 8

1. Centriacinar emphysema :
   * affecting the centre of the acinus of terminal bronchioles
   * affecting upper lobes
   * caused by smoking
2. Panacinar emphysema :
   * affecting the whole acinus of distal to terminal bronchioles
   * affecting lower lobes
   * caused by anti-trypsin deficiency

Question 9

Why emphysema is considered as obstructive ?

Answer 9

As the affected alveoli are destroyed and hyper-inflated they will compress other airways leading to obstruction