Lung Volumes And Capacities

Question 1

What is the alveolar capillary unit?

Answer 1

The physiologic unit of the lung

Question 2

What is tidal volume (VT)?

Answer 2

The amount of air inspired/expired in a single breath

Varies under circumstances (ex. During aerobic exercises)

Question 3

What is normal resting tidal volume?

Answer 3

500mL

Question 4

What is residual volume (RV)?

Answer 4

Volume of air that cannot be forced out no matter how hard one tries
Cannot be determined by spirometry

Question 5

What is inspiratory reserve volume (IRV)?

Answer 5

Additional volume that can be inhaled greater than tidal volume
Gap between inspiration during TV and max inspiration

Question 6

What is expiratory reserve volume (ERV)?

Answer 6

Additional volume that can be exhaled greater than tidal volume
Does not include RV

Question 7

What does ERV require?

Answer 7

Activation of expiratory muscles (i.e. active respiration)

Question 8

What is total lung capacity (TLC)?

Answer 8

Maximal volume to which lungs can be expanded with greatest effort
Cannot be measured by spirometry
IC + FRC = VC + RV = ERV + RV + IRV + VT

Question 9

What is functional residual capacity (FRC)?

Answer 9

Amount of air that remains in the lungs following a normal expiration
Cannot be determined by spirometry
ERV + RV

Question 10

What is the function of FRC?

Answer 10

Helps prevent collapse of lungs, reduces workload, dilutes toxic inhaled gases

Question 11

What is vital capacity (VC)?

Answer 11

Amount of air that can be maximally inspired following a maximal expiration
IRV + VT + ERV

Question 12

What is VC influenced by?

Answer 12

Posture, ability of diaphragm to contract/relax, strength of respiratory muscles, thoracic wall expansibility, resistance to air flow, elasticity and disease

Question 13

What is inspiratory capacity (IC)?

Answer 13

Capacity of air that can be maximally inspired following a normal exhalation
VT + IRV

Question 14

FVC (TLC and VC) are largely impacted by what?

Answer 14

Disease

Question 15

What are factors that can change pulmonary volumes and capacities?

Answer 15

Body size, age, posture, sex, ethnicity, obesity and pulmonary disease

Question 16

Which capacities and volumes increase with age?

Answer 16

FVC, FRC and RV

Question 17

Which capacity is reduced when supine?

Answer 17

FRC

Question 18

What does obesity cause?

Answer 18

A reduction in all static long volumes (except for TV) particularly expiratory reserve volume and FRC

Question 19

What are the main changes that occur when one ages?

Answer 19

TLC say similar
RV increases
VC goes down

Question 20

What are other changes that can occur with age?

Answer 20

ERV decreases but RV increases to a greater extent so FRC increases
IC decreases

Question 21

Both TLC and VC are greater in what position?

Answer 21

Seated (rather than supine)

Question 22

Which volume has equal quantities when either seated or supine?

Answer 22

RV

Question 23

Which other capacities are also greater when seated than when supine?

Answer 23

FRC and ERV

Question 24

IC is greater in which position?

Answer 24

Supine (slightly)

Question 25

What main changes occur with obesity?

Answer 25

Reduces TLC and VC RV stays similar Seated vs supine becomes very similar to one another

Question 26

What other changes occur with obesity?

Answer 26

ERV largely reduces, IC less largely impacted and FRC is lower

Question 27

What is emphysema?

Answer 27

Destruction of alveoli and capillaries Obstructive lung disease characterized by limitations of airflow due to partial or complete obstruction Hard to push air out often

Question 28

What changes occur with emphysema?

Answer 28

TLC and RV increases | VC decreases

Question 29

What is fibrosis?

Answer 29

A restrictive lung disease Thickening of tissue between alveoli Characterized by reduced expansion of lungs, hard to inflate or fill the lungs

Question 30

What changes occur with fibrosis?

Answer 30

RV, TC and VC decreased

Question 31

What are some techniques for measuring residual volume?

Answer 31

Helium (He) dilution, body plethysmography, nitrogen washout technique

Question 32

What is helium (He) dilution?

Answer 32

Inhalation of a known concentration of helium (C1; insoluble in blood) from a known volume (V1) Change in concentration (C2) allows for determination of V2 = FRC which allows you to calculate RV

Question 33

What is body plethysmography?

Answer 33

Enclosed rigid box Breath against shutter Pressure in lungs change and pressure in box changes proportionally in opposite direction Boyles Law (P1V1 = P2V2)

Question 34

What does nitrogen washout determine?

Answer 34

Dead space

Question 35

What is the nitrogen washout technique?

Answer 35

Individual breathes 100% oxygen through one way valve, all expired gas is collected and monitored until N2 reaches zero Total volume of all gas expired is determined and multiplied by % of N2 in mixed expired air (usually 80%)

Question 36

What is the basic model for pulmonary dead space?

Answer 36

VT = VA (volume that participates in gas exchange; alveolar) + VD (does not participate in gas exchange)

Question 37

How much is anatomical dead space usually?

Answer 37

1 mL per lb in BW