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HUBS192 > Lecture 17 resp physiology work of breathing / lung volumes > Flashcards

Lecture 17 resp physiology work of breathing / lung volumes Flashcards

1
Q

Work of Breathing

A
  1. Expand chest / lungs

2. Overcome airways resistance

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2
Q

what do you need to overcome to expand chest / lungs?

A

Stiffness / elasticity of lung/chest wall - Compliance

AND

Surface tension
(How hard is it to expand lungs?)

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3
Q

what is compliance lung stiffness?

A

measure of how easy it is to change lung volume

increase pressure = increase lung volume

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4
Q

Fibrosis

A

Low compliance = “stiff lungs”

Need to do more work to expand

increase pressure

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5
Q

Fluid lining alveoli

A

exerts surface tension which causes them to contract / resist expansion
-> need to overcome this force to expand lung

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6
Q

Surface tension reduced by

A

SURFACTANT

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7
Q

Surfactant

A

reduces surface tension in alveoli

i.e makes them easier to expand

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8
Q

Lack of surfactant/failure

A

results in stiff lungs

fibrosis

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9
Q

Surfactant

where produced?

A

by alveolar type II pneumocytes.

Major constituent is phospholipids

Lowers surface tension.

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10
Q

surfactant

why do you lower surface tension?

A

Reduces attractive forces between fluid molecules lining alveoli.

Easier to increase lung size i.e. increased compliance

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11
Q

what does Lack of surfactant/failure to produce

adequate surfactant result in?

A

stiff lungs

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12
Q

Surfactant is absent in premature infants what syndrome does it result in?

A

development of respiratory distress syndrome (RDS)

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13
Q

what air flow is during quiet breathing?

A

laminar flow

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14
Q

what determines resistance to flow?

A

Poiseuille’s Law

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15
Q

Poiseuille’s Law

A

R = 8nl / πr4

R=resistance;
n = viscosity;
l = length;
r = radius

R inversely proportional to r4

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16
Q

R inversely proportional to r4

what does 1/2 r =?
what does 2r =?

A

16 x R

1 / 16 x R

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17
Q

what are some important elements in airways resistance (e.g. asthma)?

A

Bronchoconstriction /Bronchodilation

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18
Q

Bronchi

A

Main area airway resistance

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19
Q

where does most of the resistance to airflow rise?

A

in upper airways and the first 6 generations of the lower airway

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20
Q

do small airways contribute a lot or very little to airway resistance and why?

A

Very little

due to high CSA

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21
Q

Ventilation → Pressure gradient →

A

Airflow

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22
Q

Need to do work to generate a big enough pressure gradient to:

(also = work of breathing?

A

Expand lung - overcome lung stiffness

Move air - overcome airways resistance

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23
Q

How big a breath can you take?

A

Measurement of Lung Function

Spirometry

24
Q

what are some Measurement of Lung Function tests?

A

Pulmonary Function tests, Lung Function tests

25
Q

Spirometry

A
  1. Lung volumes – How much?

2. Air flow rates – How fast?

26
Q

Pulmonary Function Tests (Spirometry)

A

Mechanical / Digital
Common, simple test
Can measure how much and how fast
Test response to therapy

27
Q

Explain what Pulmonary Function Tests (Spirometry) Mechanical / Digital is?

A

Breathe into/out of a hollow bell inverted over water – measures volume inspired / exhaled

28
Q

Spirometry: How Much?

Divide the air in lungs into four volumes: what are they?

A

Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume

29
Q

whats Tidal volume?

A 
500 ml (VT). 
Volume of air moved in and out during normal quiet breath
30
Q

whats Inspiratory reserve volume?

A

3300ml (IRV).

Extra volume that can be inspired with maximal inhalation - external intercostal muscles

31
Q

whats Expiratory reserve volume?

A

1000ml (ERV).

Extra volume that can be exhaled with maximal effort - internal intercostal and ab muscles

32
Q

whats Residual volume?

A

1200ml (RV).

Volume remaining in lungs after maximal exhalation.

33
Q

Lung capacities
These volumes can then be grouped into capacities:
what are they?

A

Vital capacity
Total lung capacity
Inspiratory capacity
Functional residual capacity

34
Q

whats Vital capacity?

A

~4800ml.

Maximal breath in to maximal out – volume of air you can shift in/out of lungs

35
Q

whats Total lung capacity?

A

~6000ml.

Total volume in lungs when maximally full = VC + RV

36
Q

whats Inspiratory capacity?

A

Tidal volume + IRV

37
Q

whats Functional residual capacity?

A

~2200ml.
Volume at end of normal breath out
(Equilibrium point for thorax / lungs)

38
Q

Spirometry: how fast?

Forced measurements give info about flow.
what are they?

A

Forced Vital capacity (FVC)

Forced expiratory volume in one second FEV1

39
Q

whats Forced Vital capacity (FVC)?

A

maximum breath into maximum breath out (VC) - forced out as hard as possible

40
Q

whats Forced expiratory volume in one second FEV1?

A

How much of FVC comes out in first second

Reduced with diseases causing resistance to airflow
(airways obstruction e.g. asthma) or small lungs

41
Q

what diseases causes resistance to airflow?

A

airways obstruction e.g. asthma or small lungs

reduce FEV1

42
Q

whats FEV1/FVC ratio?

A

Normal ~ 80%

< 0.70 indicates airways obstruction

43
Q

what can Spirometry identify?

A

Obstruction and restriction airflow diseases

44
Q

whats an Obstructive disease?

A

Increase Resistance to airflow

Asthma
Chronic obstructive lung disease (Chronic bronchitis and Emphysema)

45
Q

whats a restrictive disease?

A

decrease lung volume (reduced lung capacity)

Fibrosis (reduced lung compliance)
Chest wall abnormalities
Respiratory muscle disease

46
Q

how much do we breathe in / out?

A

Volume of single breath = Tidal Volume = VT = 500 ml (0.5L)

Respiratory rate =
Frequency (f) = 10 – 12 / minute

Total (mouth) ventilation (Respiratory minute volume - VE) = Frequency x Tidal volume

47
Q

Respiratory minute volume (VE)

A

= frequency (f) x Tidal Volume (VT)

48
Q

VE = Frequency (f) x VT units

A 
VE = ml / min
f = breaths / min
VT = ml / breath
49
Q

whats DEAD SPACE (VD)?

A

150ml

Some of the inhaled air never gets to the alveoli so cannot gas exchange

About 150 ml of each breath just fills upper airways and is of no use for gas exchange

50
Q

What’s really important is the amount of air that gets into the alveoli. whats this called?

A

….Alveolar Ventilation VA

51
Q

whats Alveolar Ventilation VA?

A

measures the flow of
fresh gases into and out of the alveoli–

VA = f x (VT - VD)

52
Q

Hypoventilation

A

Low VA

53
Q

Hyperventilation

A

High VA

54
Q

whats the equation for pulmonary ventilation?

A

Pulmonary ventilation VE = frequency x tidal volume

55
Q

whats the equation for Alveolar Ventilation?

A

Alveolar ventilation VA = frequency x (tidal volume – dead space)

HUBS192 (36 decks)

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