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- Bloc B - Respiration > Normal Physiology - Lung Statics 1&2 > Flashcards

Normal Physiology - Lung Statics 1&2 Flashcards

1
Q

How can we determine if someone has lung disease, broadly?

A

We need to compare it with what is expected, we need to be able to measure the lungs = Pulmonary Function Test

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2
Q

Explain Vt

A

Tidal volume (Vt) the volume of air that goes in and out in a normal breathing pattern

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3
Q

Explain VC

A

VC = vital capacity = the volume that you are able to get by forcing the exhalation at max and inhalation at max

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4
Q

explain RV

A

Residual volume = the volume of air that stays in your lung after you have exhale the more you can (the air that stays there so that you lungs dont collapse!)

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5
Q

Explain IC

A

Inspiratory capacity, so from base line of Vt and until the upper limit of TLC

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6
Q

Explain FRC

A

Functional residual capacity = the volume that stays in the lung after a normal exhale (so Vt baseline)

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7
Q

Explain IRV and ERV

A

IRV = Inspiratory Reserve Volume

ERV = Expiratory reserve volume

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8
Q

By what is innervated the diaphragm

A

by the phrenic nerve, that have root at C3-4-5

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9
Q

primary function of the diaphragm

A

primary inspiratory muscle

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10
Q

What are the normal inspiratory muscles used ?

A

External intercostals and parasternal intercostals

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11
Q

Accessory muscles

A

Scalenes,
Sternocleidomastoids
Trapezius

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12
Q

Why would someone use their accessory muscles when breathing?

A

If very big effort, like sport, or if respiratory distress

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13
Q

By what is mostly driven Expiration ?

A

normally quite passive, driven by the elastic recoil pressure of the lung (like inflating a balloon and letting it go)

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14
Q

What are the expiratory muscles used during exercise?

A

Abdominal muscles:
rectus abdominis, transverse abdominis, internal/external oblique muscles

Thoracic muscles:
internal intercostal muscles

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15
Q

What happens with the diaphragm during the normal tidal inspiration

A

it contracts/flattens and creates a relative vacuum (negative pressure) in the pleural space

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16
Q

What happens with the alveolar pressure during inspiration

A

the alveolar pressure is less than atmospheric pressure (more negative) and creates the driving pressure for gas to move into the lungs

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17
Q

What two forces drive the normal expiration

A

elastic recoil of the lungs and chest wall

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18
Q

what happens during inspiration with chest wall and lungs?

A

The alveolar pressure is positive with respect to atmospheric so this driving pressure moves gas out of the lungs

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19
Q

4 ways of measuring lung volumes

A
  • spirometry
  • gas dilution
  • plethysmography (body box)
  • Radiographic techniques (x ray, CT scan)
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20
Q

What measures the spirometer ?

A

Changes in lung volume - it measures subdivisions of vital capacity. it does NOT measure RV

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21
Q

Usefulness of spirometry

A

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

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22
Q

what is FEV1 and FVC with spinometry

A

FEV1 = volume (liters) of air that can forcibly expelled from maximum inspiration in the first second (the main parameter)

FVC = volume (liters) of air that can be forcibly expelled from maximum inspiration to maximum expiration

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23
Q

What information does the ratio FEV1/FVC gives?

A

Can detect disease, usually the ratio is almost 1

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24
Q

What is the PEF in spirometry

A

Maximum flow (liters/second) attained during forced expiratory maneuver

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25
Q

why is air flow (derivative of the volume-time curve) for expiration higher?

A

because during inhalation the diaphragm need to be assisted by other muscle

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26
Q

What would happened to FEV, PEF, FVC and FEV1/FVC in case of a pulmonary obstruction ?

A

↓ FEV1 and PEF are decreased
↓ FVC is decreased or unchanged
↓ FEV1/FVC is decreased (lower than 0.7)

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27
Q

What would happened to FEV, PEF, FVC and FEV1/FVC in case of a restrictive lung syndrome ?

A

FEV1 and FVC are proportionally decreased

FEV1/FVC normal or elevated

PEF can be normal or decreased

28
Q

Can we measure TLC with spirometry

A

Nop, because you can’t measure RV

29
Q

Formula to measure FRC or TLC by gas dilution

A

C1V1 = C2V2

30
Q

what gas is usually use for the gas dilution method?

A

helium

31
Q

difference between gas dilution and the body box

A

the body box (plethysmography) measures the atmospheric pressure according to Boyle’s Law - P1V1 = P2V2. more acurate than he dilution (not supposed to know calculation of plethysmography for exam)

32
Q

Define Pao, Pbs, Palv, Ppl, Pab

A

Pressure in ->
Pao : airway opening
Pbs: Body surface
Palv: alveolar
Ppl: intrapleural
Pab : abdominal

33
Q

What guides the movement of air (pressure wise)

A

a differential in pressure (Pao, Pbs, Palv, Ppl, Pab)

34
Q

trans-pulmonary pressure =

A

Pao-Ppl

35
Q

Trans-lung pressure =

A

Palv-Ppl

36
Q

Trans-chest wall pressure =

A

Ppl - Pbs

37
Q

Trans-respiratory system pressure =

A

Pao-Pbs

38
Q

What is compliance

A

The relationship between pressure and volume - its a measure of stiffness

39
Q

Stiff lungs have ___ compliance

A

Low

40
Q

Un-stiff lungs have ____ compliance

A

high

41
Q

Explain why with high compliance the lungs are “loose”

A

With high compliance you only need a small amount of pressure to exert a big amount in the lung volume

C = deltaV/deltaP, if pressure decreases (loose lung) compliance increases

42
Q

What really measure the transpulmonary pressure (Ptp)

A

The elastic recoil of the lungs and airways

43
Q

define hysteresis

A

the difference between the transpulmonary pressure of inhalation (increasing volume) and the pressure of exhalation (decreasing volume).

44
Q

What’s the logic behind hyteresis

A

You need less pressure to exhale than to inhale

45
Q

Why inspiration needs more energy/pressure than expiration?

A

alveoli are recruited during inspiration (which needs energy) and collapsed during expiration

So almost flat curve at the beginning of the inspiration on the graph - need a lot of pressure and no chance in volume for the first few moments

46
Q

According to this graph, what is the compliance of the lungs with emphysema?

A

Increased compliance

47
Q

whats the technique to calculate de P-V curve (so the compliance)?

A

Insert an Esophageal balloon in the esophagus adjacent to pleura

48
Q

3 determinants of compliance

A
  1. Tissue forces (lung)
  2. Surface tension
  3. Chest wall
49
Q

What (histologically) gives rise to lung elasticity/force ?

A

the elastin-collagen-proteoglycan network of the lung tissue

50
Q

whats the natural tendency of the lung?

A

to deflate

51
Q

what happened to the tissue with emphysema?

A

the parenchymal architecture is destroyed so the elastic recoil provided by the elastin-collagen-proteoglycan network reduces

52
Q

What happens to the tissue force histologically with fibrosis

A

tissue forces are increased, less elastic, more stiff, more tight

53
Q

What is the surface tension?

A

Occurs at air-liquid interface in alveoli and it arises from the tendency of liquid molecules to stick together rather than associate with air molecules

54
Q

How is the surface tension decreased in the alveoli (so that they dont colapse)

A

presence of pulmonary surfactant - small layer of phospholipid in the alveoli which decreases surface tension

55
Q

What happens to compliance if you loose surface tension?

A

loss of compliance

56
Q

What’s the law from which surface tension is derived?

A

Laplace’s law : P = 2T/r

The smaller your radius, the higher the pressure. The higher the tension, the higher the pression.

57
Q

How to explain alveolar instability (in terms of surface tension)

A

If you compare 2 alveoli, for the same surface tension, the smaller alveolus (smaller radius) will have a higher intraalveolar pressure -> tendency of smaller alveolus to empty itself in the larger alveolus -> leading to collapse of the smaller alveolus

58
Q

How can alveolar instabililty be resolved?

A

Pulmonary surfactant decreases surface tension -> decreases tendency of smaller alveoli to collapse -> improves alveolar stability and increases compliance

59
Q

2 vital properties of pulmonary surfactant

A
  1. Lowers surface tension to make it easier to inflate and deflate the lungs with each breath (increases compliance of lung)
  2. Promotes alveolar stability, reducing the chance that smaller alveoli will collapse
60
Q

What happens to the elastic recoil of the chest wall AND the elastic recoil of th pulmonary tissue at FRC

A

Perfect equilibrium: the outward elastic recoil of the chest wall is equal to the inward elastic recoil of the pulmonary tissue

61
Q

What happens to the elastic recoil of the chest wall AND the elastic recoil of th pulmonary tissue at RV

A

the respiratory system wants to reinflate: the outward elastic recoil of the chest wall is stronger than the inward elastic recoil of the pulmonary tissue

62
Q

What happens to the elastic recoil of the chest wall AND the elastic recoil of th pulmonary tissue at TLC

A

the respiratory system wants to deflate : both the chest wall and the pulmonary tissue present inward elastic recoil

63
Q

What happens to 2 regions of the lungs (upper region and lower region) at FRC

A

you will need more pressure to increase lung volume in the upper part, and the lower zone will need less pressure to increase volume, so it will be ventilated before.

64
Q

Determinants of RV

A
  • limit of chest wall in youth
  • premature airway closure in older adults
  • limit of expiratory force (if your too weak, you can’t blow)
65
Q

What happens to 2 regions of the lungs (upper region and lower region) at TLC

A

both lower and upper zones of lungs have large volumes, but they are at the flat part of the P/V curve -> low compliance, not easily ventilated

66
Q

What happens to 2 regions of the lungs (upper region and lower region) at RV

A

both upper and lower zones have smaller volumes, they are at the steep part of the P/V curve (increased compliance) and are more easily ventilated

- Bloc B - Respiration (9 decks)

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