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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
What does a volume time curve allow you to determine?
* FVC - Forced vital Capacity | * FEV1 - Forced Expiratory Volume in one second
26
What is Forced Vital Capacity (FVC)?
Maximum volume that can be forcibly expelled from the lungs following a maximum inspiration
27
What is Forced Expiratory Volume (FEV1)?
Volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination
28
What is the FEV1/FVC ratio?
The proportion of the Forced Vital Capacity that can be expired in the first second = (FEV1/FVC) x 100%
29
What is the normal value for FEV1/FVC ratio?
Normally more than 70%
30
How is a volume time curve produced?
Via spirometry
31
What are Dynamic Lung Volumes measured via spirometry useful for?
Diagnosis of obstructive and restrictive lung disease
32
The than FVC and FEV1, what is spirometry also used to determine?
How quickly patient can breathe air out of their lungs (patency of the airways)
33
What is the FEV1/FVC ratio in a patient with obstructive lung disease?
<70%
34
What are the features of the volume time curve in a patient with obstructive lung disease?
May reach same Forced Vital Capacity, but lower proportion of forced vital capacity in one second (FEV1)
35
What are the features of the volume time curve in a patient with restrictive lung disease?
Lower FVC and FEV1 (FEV1/FVC ratio remains the same) - indicates problems with lung tissue rather than airways
36
What are the features of the volume time curve in a patient with a combination of restrictive and obstructive lung disease?
FVC, FEV1 and FEV1/FVC ratio will be lower than normal
37
What is the equation for airflow?
F = ΔP/R F - flow P - pressure R - resistance
38
Why is air able to move with a relatively small pressure gradient?
Resistance to flow is normally very low
39
What is the primary determinant of airway resistance?
The radius of the conducting airway
40
What does parasympathetic stimulation of airways cause?
Bronchoconstriction - increased resistance
41
What does sympathetic stimulation of airways cause?
Bronchodilation (bronchodilators used to treat asthma, etc)
42
What diseases can cause significant resistance to airflow?
COPD and asthma
43
Why is expiration more difficult than inspiration in patients with diseases like asthma?
The airways are more narrow in expiration than inspiration In inspiration, airways are pulled open by the expanding thorax
44
What happens to intrapleural pressure during inspiration?
It falls
45
What happens to intrapleural pressure during expiration?
It rises
46
What does rising pleural pressure during ACTIVE expiration do? (commonly seen in patients with respiratory disease)
Compresses the alveoli and the airway - Dynamic airway compression
47
What is dynamic airway compression?
Pressure applied to airways and alveoli during active expiration, which compresses them
48
In dynamic airway compression, what does pressure applied to the alveolus do?
Helps push air out of lungs
49
In dynamic airway compression, what does pressure applied to the airway do?
Is not desirable - tends to compress it
50
What is the effect of dynamic airway compression in normal people?
Causes no problems
51
Why does dynamic airway compression cause no problems in normal people?
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
Why does dynamic airway compression cause problems in people with asthma or COPD?
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
When do the problems caused by dynamic airway compression become worse?
If the patient also has decreased elastic recoil of lungs (e.g. a patient with emphysema and obstructed airway caused by COPD)
54
What is a peak flow meter used for?
Gives an estimate of peak flow rate
55
What is peak flow rate used to assess?
Airway function
56
When speak flow test useful?
With obstructive lung disease e.g. asthma, COPD
57
How is it measured?
Patient gives a short, sharp blow into the peak flow meter - the best of 3 attempts is usually taken
58
What is the peak flow rate in normal adults?
Varies with age and height
59
What is pulmonary compliance?
The measure of effort that has to go into stretching or distending the lungs during inspiration
60
What is the relationship between pulmonary compliance and the effort required for stretching?
The less compliant the lungs are, the more work is required to produce a given degree of inflation
61
What factors decrease pulmonary compliance?
* Pulmonary fibrosis * Pulmonary oedema * Lung collapse * Pneumonia * Absence of surfactant
62
Why does decreased pulmonary compliance cause shortness of breath?
Decreased pulmonary compliance means greater change in pressure is needed to produce a given change in volume (i.e. lungs are stiffer)
63
What volume time curve does decreased pulmonary compliance produce in spirometry?
Decrease pulmonary compliance may cause a restrictive pattern of lung volumes in spirometry
64
When does pulmonary compliance become abnormally increased?
If elastic recoil of the lungs lost e.g. in emphysema
65
What does emphysema cause?
Loss of elastic recoil of lungs, resulting in increased compliance
66
What does increased compliance result in?
Hyperinflation of the lungs - patient has to work harder to get air out of the lungs
67
What can aggravate dynamic airway compression in patients with an airway obstruction (asthma, etc)?
Emphysema caused by COPD
68
What is the relationship between age and pulmonary compliance?
Pulmonary compliance increases with age
69
How much energy does normal breathing require?
3% of total energy
70
Do lungs normally fill completely?
Lungs normally operate at about "half full"
71
What factors increase the work of breathing?
* 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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