SM_155a: Ventilation

Question 1

What is pulmonary (minute) ventilation?

Answer 1

Volume inspired/expired per minute (V·_I, V·_E)

Goal is to maintain optimal levels of P_aO₂ and P_aCO₂

V·_E = V_T * f

Question 2

What is anatomical dead space (V_D)?

Answer 2

Airways without gas exchange: conducting airways (nose/mouth to terminal bronchioles)

Question 3

Inspired air must pass through _____ to reach alveoli

Answer 3

Inspired air must pass through anatomical dead space (V_D) to reach alveoli

(150 mL, which is 1/3 of tidal volume, in a 70 kg individual)

Question 4

What is alveolar ventilation (V·_A)?

Answer 4

Minute ventilation minus dead space ventilation: V·_A = f * (V_T - V_D)

(dead space is 1/3 of tidal volume)

Question 5

Breathing pattern affects _______

Answer 5

Breathing pattern affects alveolar ventilation

Decreasing V_T at a constant V·_E decreases V·_a

Question 6

Decreasing V_T at a constant V·_E ________ V·_a

Answer 6

Decreasing V_T at a constant V·_E decreases V·_a

Question 7

Knowing only breathing frequency or tidal volume is ______ to determine whether a person has adequate V·_a

Answer 7

Knowing only breathing frequency or tidal volume is not sufficient to determine whether a person has adequate V·_a​

Question 8

An increase in V·_E can be produced by _______, _______, or _______

Answer 8

An increase in V·_E can be produced by increasing V_T, increasing breathing frequency, or increasing both V_T and breathing frequency

Question 9

For a given increase in minute ventilation, the increase in alveolar ventilation will be larger if V·_E is increased via an increase in _______ rather than _______

Answer 9

For a given increase in minute ventilation, the increase in alveolar ventilation will be larger if V·_E​ is increased via an increase in V_T rather than breathing frequency

Question 10

What is alveolar dead space?

Answer 10

Ventilation not participating in gas exchange

Question 11

What can cause alveolar dead space?

Answer 11

• Pulmonary hypotension: ventilation but no blood flow
• Embolus: ventilation but no blood flow
• Unperfused space
• Precapillary vasoconstriction: limits blood flow to a rgion in the lung

Question 12

Physiologic dead space = ________ + ________

Answer 12

Physiologic dead space = anatomic dead space + alveolar dead space

Question 13

What is the respiratory quotient?

Answer 13

Ratio CO₂​ production to O₂ consumption

RQ = V·_CO2 / V·_O2

Question 14

What is the relationship between V·_I and V·_E in normal resting steady-state ventilation?

Answer 14

V·_I > V·_E

Question 15

What is a normal respiratory quotient?

Answer 15

RQ = 0.8

Question 16

Order from least to highest the respiratory quotient caused by carbohydrate, lipid, protein, and normal RQ

Answer 16

Carbohydrate > protein > normal > lipid

(1.00 > 0.83 > 0.80 > 0.71)

Question 17

Why is N₂ not included in the alveolar gas (air) equation?

Answer 17

There is no net exchange of N₂

Question 18

What is the approximation of the alveolar gas (air) equation?

Answer 18

P_AO₂ = P_IO₂ - (P_ACO₂/RQ)

Question 19

What is the alveolar gas equation?

Answer 19

P_AO₂ = P_IO₂ - (P_ACO₂ / RQ)

Question 20

In alveolar air, normal values are

P_AO₂:

P_ACO₂:

Answer 20

In alveolar air, normal values are

P_AO₂: 80-100 mmHg

P_ACO₂: 35-45 mmHg

Question 21

What is the alveolar ventilation equation for CO₂?

Answer 21

V·_A = (RT * V·_CO2) / P_ACO₂

Relates ventilation, metabolism, and alveolar gas pressures

Question 22

What is the formula relating V·_A and P_ACO₂?

Answer 22

V·_A = (863 * V·_CO2) / P_ACO₂

At constant V·_CO2, V·_A is proportional to 1 / P_ACO₂

Question 23

1 mol of gas at STP is ___ L

Answer 23

1 mol of gas at STP is 22.4 L

Question 24

What does the hyperbola shape of the P_ACO₂ vs ventilation indicate?

Answer 24

• At beginning, very small increases in alveolar ventilation cause large changes in P_ACO₂
• At the end, large changes in alveolar ventilation are required to produce a small change in P_ACO₂

Question 25

Increasing ventilation (hyperventilation) ______ P_ACO₂

Answer 25

Increasing ventilation (hyperventilation) decreases P_ACO₂​

Question 26

Decreasing ventilation (hypoventilation) ______ P_ACO_2​

Answer 26

Decreasing ventilation (hypoventilation) increases P_ACO_2​

Question 27

At normal rest, P_ACO₂ is ____ mmHg

Answer 27

At normal rest, P_ACO₂ is 39 mmHg

Question 28

If a person exercises without increasing V·_A, P_ACO₂ ________

Answer 28

If a person exercises without increasing V·_A, P_ACO₂ increases

Question 29

In a normal response to submaximal exercise, V·_A _______ to match the increase in V·_CO2, so P_ACO₂ ______

Answer 29

In a normal response to submaximal exercise, V·_A increases to match the increase in V·_CO2, so P_ACO₂ stays constant

Question 30

Normally, P_aCO₂ _____ P_ACO₂

Answer 30

Normally, P_aCO₂ = P_ACO₂​

Question 31

Alveolar ventilation changes in proportion to ________, so P_aCO₂ ________

Answer 31

Alveolar ventilation changes in proportion to changes in metabolism, so P_aCO₂ remains nearly constant

Question 32

When P_aO₂ is more than a few mmHg below P_AO₂, O₂ gas exchange ________

Answer 32

When P_aO₂ is more than a few mmHg below P_AO₂, O₂ gas exchange is compromised