Lung statics 1

Question 1

Define lung statics

Answer 1

Mechanical properties of the lungs and chest wall during periods of no airflow
- Lung volume constant with time

Question 2

Define lung dynamics

Answer 2

Mechanical properties of the lungs and chest wall during periods of airflow
- Lung volume changes with time

Question 3

Tidal volume

Answer 3

Amount of air inhaled or exhaled during a normal, relaxed breath

Question 4

Vital capacity

Answer 4

Maximum amount of air a person can exhale after a maximum inhalation

Question 5

Total lung capacity

Answer 5

Maximum volume of air the lungs can hold after a full inhalation. It includes all lung volumes (tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume)

Question 6

Residual volume

Answer 6

Amount of air remaining in the lungs after maximum exhalation

Question 7

Functional residual capacity

Answer 7

Volume of air remaining in the lungs after a normal, passive exhalation

Question 8

Inspiratory capacity

Answer 8

Maximum amount of air a person can inhale after a normal, passive exhalation

Question 9

Inspiratory reserve volume

Answer 9

Amount of air that can be inhaled after a normal, tidal inhalation

Question 10

Expiratory reserve volume

Answer 10

Amount of air that can be exhaled after a normal tidal exhalation

Question 11

Functional residual capacity is equal to the sum of…

Answer 11

expiratory reserve volume + residual volume

Question 12

Inspiratory capacity is equal to the sum of…

Answer 12

tidal volume + inspiratory reserve volume

Question 13

What is the diaphragm?

Answer 13

Primary inspiratory muscle , dome-shaped

Question 14

What innervates the diaphragm?

Answer 14

Phrenic nerve (C3,4,5)

Question 15

What happens to the diaphragm when it contracts?

Answer 15

It descends and flattens, resulting in an increased lung volume. It also lifts the lower chest wall.

Question 16

Name the inspiratory intercostal muscles

Answer 16

• external intercostals
• parasternal intercostals

Question 17

Name accessory respiratory muscles (inspiration)

Answer 17

• scalenes
• sternocleidomastoids
• trapezius
  (muscles of the neck)

Question 18

Expiration is normally … and driven by

Answer 18

Expiration is normally PASSIVE and driven by the ELASTIC RECOIL and pressure of the lung.

Question 19

What aids expiration during exercise?

Answer 19

• abdominal muscles (rectus abdominis, transverse abdominis, internal/external oblique muscles)
• thoracic muscles (internal intercostal muscles)

Question 20

What is the function of pulmonary function tests?

Answer 20

To measure how well your lungs are working.

Question 21

Why do we have residual volume?

Answer 21

To prevent the alveoli and lungs from collapsing

Question 22

During normal tidal inspiration, the respiratory muscles (esp. diaphragm) contract, which leads to…

Answer 22

• diaphragm contracts and lowers
• external & parasternal intercostals contract, raising the ribs and sternum
  This expands the thoracic cavity and pulls on the parietal pleura. Therefore, the intrapleural space also expands.
• expansion of the intrapleural space creates a relative vacuum (more negative pressure in the pleural space)
• visceral pleura pulls on the lungs (due to the negative pressure)
  This expands the lungs and increases the volume of the alveoli.
• increased alveolar volume creates a negative pressure in the alveoli
• alveolar pressure is lower than the atmospheric pressure
• air is drawn from the outside to the inside of the lungs (from high to low pressure)

Question 23

When the inspiratory muscles relax, the elastic recoil of the lungs and chest wall results in…

Answer 23

• decreased volume of the thoracic cavity and lungs
• increased alveolar pressure

Alveolar pressure becomes more positive with respect to the atmospheric pressure, driving air (gas) out of the lungs.

Question 24

Four major methods to measure lung volumes

Answer 24

• spirometry
• gas dilution
• plethysmography (body box)
• radiographic techniques (x-ray, CT scan)

Question 25

What is a spirometer

Answer 25

Instrument that measure gas volume moving in or out of the mouth (can only measure changes in lung volume).

Question 26

A spirometer measures subdivisions of ...

Answer 26

the vital capacity

Question 27

A spirometer DOES not measure...

Answer 27

residual volume

Question 28

Why are spirometers useful? What are they used for by clinicians?

Answer 28

- to diagnose lung disease in patients - to determine the severity of the disease - to evaluate the evolution of the disease - to evaluate treatment effect

Question 29

FEV1

Answer 29

Forced expiratory volume 1: Volume of air that someone can forcibly expel after a maximum inspiration in the first second of expiration.

Question 30

What does it mean if the FEV1 is very low?

Answer 30

The patient has difficulty expiring air from the lungs effectively. This could be due to an obstructive or restrictive lung disease.

Question 31

FVC

Answer 31

Forced vital capacity: volume of air that can be forcibly expelled after a max inhalation (max, forceful exhalation)

Question 32

FEV1/FVC

Answer 32

Ratio that helps distinguish between the 2 types of lung disease: obstructive or restrictive.

Question 33

What is an obstructive lung disease? What are common causes?

Answer 33

Characterized by obstruction or narrowing of the airways, making it difficult to exhale air out of the lungs. Causes: - inflammation - bronchoconstriction - structural changes

Question 34

What is a restrictive lung disease? What are common causes?

Answer 34

Characterized by a reduction in lung volume, which makes it difficult to fully expand the lungs. Causes: - stiffness in lung tissue - stiffness in chest wall - stiffness in respiratory muscles

Question 35

A very low FEV1/FVC ratio indicates...

Answer 35

obstructive lung disease

Question 36

In someone with normal lungs, is there a difference between FVC and VC?

Answer 36

Theoretically, there is no difference (except for some rare exceptions)

Question 37

PEF

Answer 37

Peak expiratory flow - maximum flow (L/sec) attained during a forced expiratory maneuver (maximum rate at which air is exhaled).

Question 38

Most of the air we exhale exits our mouth within the first...

Answer 38

within the first second

Question 39

Flow is the derivative of ...

Answer 39

Flow is the derivative (slope) of the volume-time curve (dV/dT)

Question 40

The shape of the flow curve helps us determine...

Answer 40

the type of lung disease the patient may have

Question 41

What does the bottom part of the flow curve represent?

Answer 41

Inhalation

Question 42

When is flow the highest during exhalation?

Answer 42

It peaks right within the first second (right at the start of exhalation)

Question 43

How does obstructive lung syndrome affect the FEV1, PEF, FVC and FEV1/FVC ratio?

Answer 43

FEV1 and PEF are decreased FVC is decreased or unchanged FEV1/FVC is decreased (lower than 0.7) Make sure you understand WHY these things happen! And how the diagrams look.

Question 44

What are key characteristics of restrictive lung syndrome?

Answer 44

FEV1 and FVC are proportionally decreased FEV1/FVC ratio is normal or elevated PEF can be normal or decreased Make sure you understand WHY these things happen! And how the diagrams look.

Question 45

In obstructive diseases, the lung volumes are shifted .... In restrictive diseases, the lung volumes are shifted .... a) rightward b) leftward

Answer 45

Obstructive diseases: leftward, towards higher lung volumes (higher RV) Restrictive diseases: rightward, towards lower lung volumes (lower RV)

Question 46

Can a spirometer determine total lung capacity?

Answer 46

No! Because it cannot measure residual volume, so we don't know how much air is left in the lungs at all times.

Question 47

Since a spirometer cannot measure the RV, what else can it not determine?

Answer 47

FRC (functional residual capacity) and TLC (total lung capacity)

Question 48

How can we measure FRC or TLC

Answer 48

We can measure the FRC and TLC by gas dilution using non-absorbable tracer gas like He or N2 (C1V1=C2V2) * Make sure you do practice problems!

Question 49

Describe plethysmography

Question 50

Plethysmography takes advantage of...

Answer 50

Boyle's Law (P1V1 = P2V2)

Question 51

Plethysmography looks at changes in...

Answer 51

changes in pressure inside the body box, which allows us to infer changes in lung volumes

Question 52

Which method is more accurate to measure lung volumes? He dilution or plethysmography?

Answer 52

Plethysmography

Question 53

What is Boyle's Law?

Answer 53

P1V1=P2V2 *Make sure you can apply this in problems!