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Respiratory: Physiology > Respiratory Mechanics 2 > Flashcards

Respiratory Mechanics 2 Flashcards

1
Q

What are the 2 major inspiratory muscles?

A
  • Diaphragm

* External intercostal muscles

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2
Q

What are the accessory muscles of inspiration?

A
  • Sternocleidomastoid
  • Scalenus
  • Pectoral
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3
Q

When do the accessory muscles of inspiration contract?

A

Contract only during forceful inspiration

Can be indication that something is wrong if contracting under resting conditions

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4
Q

What are the muscles of active expiration?

A
  • Abdominal muscles

* Internal intercostal muscles

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5
Q

What muscles contract during normal expiration?

A

None, normal expiration is a passive process

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6
Q

What is Tidal Volume (TV)?

A

Volume of air entering or leaving lungs during a single breath

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7
Q

What is the average value of TV?

A

0.5L

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8
Q

What is Inspiratory Reserve Volume (IRV)?

A

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume

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9
Q

What is the average value of IRV?

A

3.0L

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10
Q

What is the Expiratory Reserve Volume (ERV)?

A

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume

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11
Q

What is the average value of ERV?

A

1.0L

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12
Q

What is Residual Volume (RV)?

A

Minimum volume of air remaining in the lungs even after a maximal expiration

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13
Q

What is the average value of RV?

A

1.2L

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14
Q

What is Inspiratory Capacity?

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC = IRV + TV)

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15
Q

What is the average value of IC?

A

3.5L

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16
Q

What is Functional Residual Capacity (FRC)?

A

Volume of air in lungs at end of normal passive expiration
(FRC = ERV + RV)

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17
Q

What is the average value of FRC?

A

2.2L

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18
Q

What is Vital Capacity (VC)?

A

Maximum volume of air that can be moved out during a single breath following a maximal inspiration
(VC = IRV + TV + ERV)

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19
Q

What is the average volume of VC?

A

4.5L

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20
Q

What is Total Lung Capacity (TLC)?

A

Total volume of air the lungs can hold

TLC = VC + RV

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21
Q

What is the average value of TLC?

A

5.7L

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22
Q

Are the average values for lung volumes and capacities universal?

A

No, predicted normal values vary with age, height, male/female

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23
Q

Why is it not possible to measure the Total Lung Capacity by spirometry?

A

Residual volume cannot be measured by spirometry

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24
Q

When does residual volume increase?

A

When elastic recoil of the lungs is lost e.g. in emphysema

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25
Q

What does a volume time curve allow you to determine?

A
  • FVC - Forced vital Capacity

* FEV1 - Forced Expiratory Volume in one second

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26
Q

What is Forced Vital Capacity (FVC)?

A

Maximum volume that can be forcibly expelled from the lungs following a maximum inspiration

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27
Q

What is Forced Expiratory Volume (FEV1)?

A

Volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination

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28
Q

What is the FEV1/FVC ratio?

A

The proportion of the Forced Vital Capacity that can be expired in the first second = (FEV1/FVC) x 100%

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29
Q

What is the normal value for FEV1/FVC ratio?

A

Normally more than 70%

30
Q

How is a volume time curve produced?

A

Via spirometry

31
Q

What are Dynamic Lung Volumes measured via spirometry useful for?

A

Diagnosis of obstructive and restrictive lung disease

32
Q

The than FVC and FEV1, what is spirometry also used to determine?

A

How quickly patient can breathe air out of their lungs (patency of the airways)

33
Q

What is the FEV1/FVC ratio in a patient with obstructive lung disease?

A

<70%

34
Q

What are the features of the volume time curve in a patient with obstructive lung disease?

A

May reach same Forced Vital Capacity, but lower proportion of forced vital capacity in one second (FEV1)

35
Q

What are the features of the volume time curve in a patient with restrictive lung disease?

A

Lower FVC and FEV1 (FEV1/FVC ratio remains the same) - indicates problems with lung tissue rather than airways

36
Q

What are the features of the volume time curve in a patient with a combination of restrictive and obstructive lung disease?

A

FVC, FEV1 and FEV1/FVC ratio will be lower than normal

37
Q

What is the equation for airflow?

A

F = ΔP/R

F - flow
P - pressure
R - resistance

38
Q

Why is air able to move with a relatively small pressure gradient?

A

Resistance to flow is normally very low

39
Q

What is the primary determinant of airway resistance?

A

The radius of the conducting airway

40
Q

What does parasympathetic stimulation of airways cause?

A

Bronchoconstriction - increased resistance

41
Q

What does sympathetic stimulation of airways cause?

A

Bronchodilation (bronchodilators used to treat asthma, etc)

42
Q

What diseases can cause significant resistance to airflow?

A

COPD and asthma

43
Q

Why is expiration more difficult than inspiration in patients with diseases like asthma?

A

The airways are more narrow in expiration than inspiration

In inspiration, airways are pulled open by the expanding thorax

44
Q

What happens to intrapleural pressure during inspiration?

A

It falls

45
Q

What happens to intrapleural pressure during expiration?

A

It rises

46
Q

What does rising pleural pressure during ACTIVE expiration do?

(commonly seen in patients with respiratory disease)

A

Compresses the alveoli and the airway - Dynamic airway compression

47
Q

What is dynamic airway compression?

A

Pressure applied to airways and alveoli during active expiration, which compresses them

48
Q

In dynamic airway compression, what does pressure applied to the alveolus do?

A

Helps push air out of lungs

49
Q

In dynamic airway compression, what does pressure applied to the airway do?

A

Is not desirable - tends to compress it

50
Q

What is the effect of dynamic airway compression in normal people?

A

Causes no problems

51
Q

Why does dynamic airway compression cause no problems in normal people?

A

The increased airway resistance causes an increase in airway pressure upstream - this helps open the airways by increasing the the driving pressure between the alveolus and airway

52
Q

Why does dynamic airway compression cause problems in people with asthma or COPD?

A

If there is an obstruction (e.g. asthma or COPD), the driving pressure between the alveolus and airway is lost over the obstructed segment. This causes a fall in airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration

53
Q

When do the problems caused by dynamic airway compression become worse?

A

If the patient also has decreased elastic recoil of lungs (e.g. a patient with emphysema and obstructed airway caused by COPD)

54
Q

What is a peak flow meter used for?

A

Gives an estimate of peak flow rate

55
Q

What is peak flow rate used to assess?

A

Airway function

56
Q

When speak flow test useful?

A

With obstructive lung disease e.g. asthma, COPD

57
Q

How is it measured?

A

Patient gives a short, sharp blow into the peak flow meter - the best of 3 attempts is usually taken

58
Q

What is the peak flow rate in normal adults?

A

Varies with age and height

59
Q

What is pulmonary compliance?

A

The measure of effort that has to go into stretching or distending the lungs during inspiration

60
Q

What is the relationship between pulmonary compliance and the effort required for stretching?

A

The less compliant the lungs are, the more work is required to produce a given degree of inflation

61
Q

What factors decrease pulmonary compliance?

A
  • Pulmonary fibrosis
  • Pulmonary oedema
  • Lung collapse
  • Pneumonia
  • Absence of surfactant
62
Q

Why does decreased pulmonary compliance cause shortness of breath?

A

Decreased pulmonary compliance means greater change in pressure is needed to produce a given change in volume (i.e. lungs are stiffer)

63
Q

What volume time curve does decreased pulmonary compliance produce in spirometry?

A

Decrease pulmonary compliance may cause a restrictive pattern of lung volumes in spirometry

64
Q

When does pulmonary compliance become abnormally increased?

A

If elastic recoil of the lungs lost e.g. in emphysema

65
Q

What does emphysema cause?

A

Loss of elastic recoil of lungs, resulting in increased compliance

66
Q

What does increased compliance result in?

A

Hyperinflation of the lungs - patient has to work harder to get air out of the lungs

67
Q

What can aggravate dynamic airway compression in patients with an airway obstruction (asthma, etc)?

A

Emphysema caused by COPD

68
Q

What is the relationship between age and pulmonary compliance?

A

Pulmonary compliance increases with age

69
Q

How much energy does normal breathing require?

A

3% of total energy

70
Q

Do lungs normally fill completely?

A

Lungs normally operate at about “half full”

71
Q

What factors increase the work of breathing?

A
  • Decreased pulmonary compliance
  • Increased airway resistance
  • Decreased elastic recoil
  • When there is a need for increased ventilation

Respiratory: Physiology (6 decks)

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