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BLOCK B - RESPIRATION > Lung statics 1 > Flashcards

Lung statics 1 Flashcards

1
Q

Define lung statics

A

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

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2
Q

Define lung dynamics

A

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

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3
Q

Tidal volume

A

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

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4
Q

Vital capacity

A

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

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5
Q

Total lung capacity

A

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)

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6
Q

Residual volume

A

Amount of air remaining in the lungs after maximum exhalation

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7
Q

Functional residual capacity

A

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

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8
Q

Inspiratory capacity

A

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

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9
Q

Inspiratory reserve volume

A

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

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10
Q

Expiratory reserve volume

A

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

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11
Q

Functional residual capacity is equal to the sum of…

A

expiratory reserve volume + residual volume

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12
Q

Inspiratory capacity is equal to the sum of…

A

tidal volume + inspiratory reserve volume

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13
Q

What is the diaphragm?

A

Primary inspiratory muscle , dome-shaped

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14
Q

What innervates the diaphragm?

A

Phrenic nerve (C3,4,5)

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15
Q

What happens to the diaphragm when it contracts?

A

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

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16
Q

Name the inspiratory intercostal muscles

A
  • external intercostals
  • parasternal intercostals
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17
Q

Name accessory respiratory muscles (inspiration)

A
  • scalenes
  • sternocleidomastoids
  • trapezius
    (muscles of the neck)
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18
Q

Expiration is normally … and driven by

A

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

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19
Q

What aids expiration during exercise?

A
  • abdominal muscles (rectus abdominis, transverse abdominis, internal/external oblique muscles)
  • thoracic muscles (internal intercostal muscles)
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20
Q

What is the function of pulmonary function tests?

A

To measure how well your lungs are working.

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21
Q

Why do we have residual volume?

A

To prevent the alveoli and lungs from collapsing

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22
Q

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

A
  • 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)
23
Q

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

A
  • 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.

24
Q

Four major methods to measure lung volumes

A
  • spirometry
  • gas dilution
  • plethysmography (body box)
  • radiographic techniques (x-ray, CT scan)
25
Q

What is a spirometer

A

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

26
Q

A spirometer measures subdivisions of …

A

the vital capacity

27
Q

A spirometer DOES not measure…

A

residual volume

28
Q

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

A
  • to diagnose lung disease in patients
  • to determine the severity of the disease
  • to evaluate the evolution of the disease
  • to evaluate treatment effect
29
Q

FEV1

A

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

30
Q

What does it mean if the FEV1 is very low?

A

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

31
Q

FVC

A

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

32
Q

FEV1/FVC

A

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

33
Q

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

A

Characterized by obstruction or narrowing of the airways, making it difficult to exhale air out of the lungs.

Causes:
- inflammation
- bronchoconstriction
- structural changes

34
Q

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

A

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

35
Q

A very low FEV1/FVC ratio indicates…

A

obstructive lung disease

36
Q

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

A

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

37
Q

PEF

A

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

38
Q

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

A

within the first second

39
Q

Flow is the derivative of …

A

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

40
Q

The shape of the flow curve helps us determine…

A

the type of lung disease the patient may have

41
Q

What does the bottom part of the flow curve represent?

A

Inhalation

42
Q

When is flow the highest during exhalation?

A

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

43
Q

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

A

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.

44
Q

What are key characteristics of restrictive lung syndrome?

A

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.

45
Q

In obstructive diseases, the lung volumes are shifted ….
In restrictive diseases, the lung volumes are shifted ….

a) rightward
b) leftward

A

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

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

46
Q

Can a spirometer determine total lung capacity?

A

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

47
Q

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

A

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

48
Q

How can we measure FRC or TLC

A

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!
49
Q

Describe plethysmography

A
50
Q

Plethysmography takes advantage of…

A

Boyle’s Law (P1V1 = P2V2)

51
Q

Plethysmography looks at changes in…

A

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

52
Q

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

A

Plethysmography

53
Q

What is Boyle’s Law?

A

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

BLOCK B - RESPIRATION (32 decks)

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