Physiology Lecture 1: Lung Statics

Question 1

Define tidal volume

Answer 1

Volume of air inspired and expired during regular breathing

Question 2

Define vital capacity

Answer 2

Maximum volume of air that you can inspire and forcibly expire

Question 3

Define residual volume

Answer 3

Volume in lungs that can never be expired (always there)

Question 4

Equations for FRC

Answer 4

FRC = RV + ERV

(ERV = Expiratory reserve volume)

Question 5

Equations for total lung capacity (TLC)

Answer 5

1. TLC = IC + FRC
   
   • (IC = Inspiratory capacity)
2. TLC = RV + ERV + VT + IRV

Question 6

Equations for vital capacity

Answer 6

1. VC = ERV + VT + IRV
   
   • IRV = inspiratory reserve volume
2. VC = ERV + IC

Question 7

Four major methods of volumes

Answer 7

1. Spirometry
2. Gas dilution
3. Plethysmography (body box)
4. Radiographic Techniques (x-ray; CT scan)

Question 8

Function of spirometer

Answer 8

• Measure the volume of gas entering or leaving the mouth (changes in lung volume)

Question 9

What divisions of lung volume can spirometry measure?

Answer 9

Subdivisions of vital capacity (VC, IRV, ERV, VT)

Question 10

4 uses of spirometry

Answer 10

• Diagnosis of lung disease in patients
• Determine severity of disease
• Evaluate the evolution of disease
• Evaluate treatment effect

Question 11

Define FEV1

Answer 11

Volume of air that can be forcibly expelled from maximum inspiration in the first second

Question 12

Define FVC

Answer 12

Volume of air that can be forcibly expelled from maximum inspiration to maximum expiration

Question 13

Define PEF

Answer 13

Maximum flow attained during a forced expiratory maneuver

Question 14

What is the important ratio in determining the health state of lungs using spirometry?

Answer 14

FEV1/FVC

Question 15

What is a normal FEV1/FVC ratio?

Answer 15

0.70

Question 16

Describe the changes in the flow volume curve and volume-time curve in obstructive lung disease

Answer 16

• FEV1 and PEF are decreased
• FVC is decreased or unchanged
• **FEV1/FVC is decreased

Question 17

Describe the changes in the flow volume curve and the volume-time curve of restrictive lung diseases

Answer 17

• FEV1 decreased
• Peak flow increases
• FVC decreases
• FEV1/FVC are normal or increased

Question 18

Equation used in gas dilution (explain components)

Answer 18

C1V1=C2V2

where V2 = V1 + FRC if measured at the end of usual breath

Question 19

Limitation of gas dilution

Answer 19

May underestimate lung volume of people with certain diseases (i.e. asthma) where air cannot accuss all parts of the lung

Question 20

Plethysmography equation

Answer 20

Boyle’s Law: P1V1 = k

Question 21

Why use plethysmograph?

Answer 21

Can measure trapped air volume not accessible by gas dilution

Question 22

3 determinants of lung volume

Answer 22

1. Pulmonary compliance
2. Chest wall compliance
3. Respiratory muscles

Question 23

Define transpulmonary pressure

Answer 23

P_tp = P_ao - P_pl

Question 24

Define transrespiratory pressure

Answer 24

P_RS = P_ao - P_atm

Question 25

Define transmural pressure

Answer 25

The pressure across the wall of a structure (i.e. chest wall, airway wall or alveolar wall)

Question 26

Define compliance (in general)

Answer 26

* A measure of stiffness * (Stiff = low; loose = high) * The slope of the P-V curve C_L = ΔV/ΔP

Question 27

How is pulmonary compliance obtained?

Answer 27

Using the transpulmonary pressure (Ptp)

Question 28

What is Ptp a measure of?

Answer 28

Elastic recoil pressure (Pel)

Question 29

When there is no flow, what is the Palv?

Answer 29

Pao = Palv

Question 30

2 determinants of compliance

Answer 30

* Tissue Forces * Surface tension

Question 31

Where do the tissue forces of the lung come from?

Answer 31

Elastin-collagen proteoglycan network of the lung tissue

Question 32

When are tissue forces reduced?

Answer 32

When the lung parenchymal architecture is destroyed (i.e. in emphysema)

Question 33

When are tissue forces increased?

Answer 33

When lung scarring occurs (i.e. fibrosis)

Question 34

2 vital properties of pulmonary surfactant

Answer 34

* Lowers surface tension to make it easier to inflate and delfate the lungs * Promotes alveolar stability, reducing the chance that alveoli will collapse

Question 35

Laplace's Law

Answer 35

P = 2T/r

Question 36

Airflow according to Laplace's law in the alveoli. How does this relate to pulmonary surfactant?

Answer 36

Decreased alveolus size = increase pressure = wair wants to go to bigger alveoli (P gradient) Therefore, without pulmonary surfactant, the smaller alveoli would all collapse

Question 37

Describe the Pressure-Volume curve

Answer 37

Question 38

Describe the pressure-volume curves in disease

Answer 38

Question 39

3 determinants of residual volume

Answer 39

* Limit of chest wall (i.e. youth) * Lung recoils inward * Chest wall reocils outward * Limit of emptying of the lung (i.e. elders) * Obstruction = more time to exhale (notion of closing volume) * Limit of expiratory force * Too weak = cannot blow

Question 40

Lung and chest recoil direction at TLC

Answer 40

Inward

Question 41

FRC lung and chest wall recoil

Answer 41

Lungs = inward Chest wall = ouitwards (Balance)

Question 42

RV lung and chest wall recoil direction

Answer 42

Lungs = inward Chest wall = outward + effect of age and muscle strength