Respiratory Physiology Lecture 2 part 9: Ventilation

Question 1

Tidal volume

Answer 1

volume of inspired air at each breath

Question 2

Approximately how much air is inspired (in tidal volume)?

Answer 2

~0.5 L

Question 3

Total/minute ventilation

Answer 3

total amount of air moved into the respiratory system per minute

Question 4

Total/minute ventilation = ??

Answer 4

Total/minute ventilation = Tidal volume x respiratory frequency

= 0.5 L x 15 bpm (Breaths per minute)

= 7.5 L/min

Question 5

Alveolar ventilation

Answer 5

amount of air moved into the alveoli per minute

Question 6

What does alveolar ventilation depend on?

Answer 6

It depends on the anatomical dead space

Question 7

How much is anatomical dead space?

Answer 7

0.15 L

Question 8

Alveolar ventilation = ??

Answer 8

Alveolar ventilation = (TV - anatomical dead space) x frequency

V_A = (V_T - V_D) x frequency

= (0.5 - 0.15) L x 15 bpm

= 5.25 L/min

Question 9

Why is alveolar ventilation lower than total/min ventilation?

Answer 9

due to anatomical dead space consideration

Question 10

What zone is anatomical dead space in?

Answer 10

conductive zone

Question 11

How much of normal breath is not available for gas exchange?

Answer 11

~ ⅓ (1-2 L)

Question 12

V_A = (V_T - V_D) x frequency

Answer 12

Alveolar ventilation

Question 13

What happens to anatomical dead space with breath size?

Answer 13

anatomical dead space is constant regardless of breath size

Question 14

Effects of Breathing Pattern on Alveolar Ventilation

Answer 14

Normal quiet breathing → 4200 mL/min (V_A)

Shallow & fast → 0 mL/ min (V_A)

Deep & shallow → increase (V_A)

Question 15

How does breathing patter effect minute ventilation?

Answer 15

stays the same

Question 16

What breathing patter increases aveolar ventilation (V_A)?

Answer 16

Increased DEPTH of breathing is more effective in increasing alveolar ventilation than an equivalent increase in breathing RATE