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1. Respiratory > Physiology of Ventilation > Flashcards

Physiology of Ventilation Flashcards

1
Q

What is internal respiration?

A

the intracellular mechanisms which consumes O2 and produces CO2

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2
Q

What is external respiration?

A

sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body

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3
Q

What are the 4 steps of external respiration?

A

Ventilation - the mechanical process of moving gas in and out of the lungs

Gas exchange between alveoli and blood - exchange of O2 and CO2 between the air in the alveoli and the blood in the pulmonary capillaries

Gas transport in the blood - binding and transport of O2 and CO2 in the circulating blood

Gas exchange at the tissue level - exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells

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4
Q

What is Boyles Law?

A

At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas

i.e. air flows down pressure gradient from a region of high pressure to a region of low pressure

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5
Q

How are the intra-alveolar pressure and atmospheric pressure before inspiration? and how must they become for air to reach the lungs?

A

before = equal

for air = intra-alveolar pressure less than atmospheric pressure

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6
Q

What two forces hold the lungs and thoracic wall in close opposition?

A

The intrapleural fluid cohesiveness

The negative intrapleural pressure

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7
Q

Describe the intrapleural fluid cohesiveness?

A

The water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Hence the pleural membranes tend to stick together.

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8
Q

Describe the negative intrapleural pressure?

A

the sub-atmospheric intrapleural pressure create a transmural pressure gradient across the lung wall and across the chest wall. So, the lungs are forced to expand outwards while the chest is forced to squeeze inwards.

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9
Q

Describe the transmural pressure gradient?

A

Across the lung wall, the intra-alveolar pressure of 760 mm Hg pushes outward, while the intrapleural pressure of 756 mm Hg pushes inward. This 4 mm Hg difference in pressure constitutes a transmural pressure gradient that pushes out on the lungs, stretching them to fill the larger thoracic cavity.

Opposite for lung collapse

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10
Q

What 3 forces are important in ventilation?

A

Atmospheric pressure
Intra-alveolar pressure
Intrapleural pressure

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11
Q

What gives lungs their elastic behaviour?

A

alveolar surface tension

- attraction between water molecules at liquid air interface

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12
Q

What is the Law of La Place?

A

the smaller alveoli (with smaller radius - r) have a higher tendency to collapse

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13
Q

Is Inspiration an active or passive process?

A

ACTIVE

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14
Q

What is pulmonary surfactant? What is its role?

A

complex mixture of lipids and proteins secreted by type II alveoli
It lowers alveolar surface tension by interspersing between the water molecules lining the alveoli (acts more on small alveoli than large)

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15
Q

What 3 forces keep the alveoli open?

A

transmural pressure gradient
pulmonary surfactant
alveolar interdependence

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16
Q

What 2 forces promote alveoli collapse?

A

elasticity of stretched lung connective tissue

alveolar surface tension

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17
Q

Describe the alveolar interdependence?

A

If an alveolus starts to collapse, the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it

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18
Q

What are the major inspiratory muscles?

A

Diaphragm

external intercostal muscles

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19
Q

What are the muscles used during forceful inspiration? (accessory)

A

Sternocleidomastoid
scalenus
pectoral

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20
Q

What muscles are used duing active (forced) expiration?

A

Abdominal muscles

internal intercostal muscles

21
Q

What is the tidal volume (TV)? what is its average value?

A

Volume of air entering or leaving lungs during a single breath
0.5 L

22
Q

What is the inspiratory reserve volume (IRV)? what is its average value?

A

Extra volume of air that can be maximally inspired
over and above the typical resting tidal volume
3L

23
Q

What is the expiratory resrve volume (ERV)? what is its average value?

A

Extra volume of air that can be actively expired by maximal contraction
beyond the normal volume of air after a resting tidal volume
1L

24
Q

What is residual volume? What is its average value?

A

Minimum volume of air remaining in the lungs even after a maximal expiration
1.2L

25
Q

What does Total lung capacity=? What is its averge volume?

A 
Vital Capacity + Residual volume
5700 ml (4500 + 1200 ml)
26
Q

What is the Inpiratory capacity?

A

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

27
Q

What is the functional residual capacity?

A

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

28
Q

What is the vital capacity?

A

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

29
Q

What is the total lung capacity?

A

Total volume of air the lungs can hold

30
Q

In Spirometry, what is FVC?

A

Forced Vital Capacity - maximum volume that can be forcibly expelled from the lungs following a maximum inspiration

31
Q

In Spirometry, what is FEV1?

A

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

32
Q

What is a normal FEV1/FVC ratio?

A

Above 70%

33
Q

How does dynamic airway compression cause problems in patients with obstructive lung diseases?

A

makes active expiration to be more difficult in patients with airway obstruction

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

34
Q

What is pulmonary compliance? What causes it and what can it cause?

A

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

decreased by: pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant

causes: breathlessness on exertion

35
Q

When is work of breathing increased?

A
  • When pulmonary compliance is decreased
  • When airway resistance is increased
  • When elastic recoil is decreased
  • When there is a need for increased ventilation
36
Q

What does Pulmonary Ventilation =?

A

tidal volume x respiratory rate

37
Q

What does Alveolar Ventilation =?

A

tidal volume - dead space volume

38
Q

Why is alveolar ventilation less than pulmonary?

A

presence of anatomical dead space

39
Q

What is ventilation perfusion?

A

The transfer of gases between the body and atmosphere

depends upon:
Ventilation: the rate at which gas is passing through the lungs
Perfusion: the rate at which blood is passing through the lungs

40
Q

What is ventilation perfusion matching?

A

Accumulation of CO2 in alveoli as a result of increased perfusion decreases airway resistance leading to increased airflow

  • reverse for increased O2 = increased blood flow
41
Q

What is alveolar ventilation?

A

volume of air exchanged between the atmosphere and alveoli per minute

42
Q

What is pulmonary ventilation?

A

the volume of air breathed in and out per minute

43
Q

What 4 factors affect the rate of gas exchange across the alveolar membrane?

A
  1. Partial Pressure Gradient of O2 and CO2
  2. Diffusion Coefficient for O2 and CO2
  3. Surface Area of Alveolar Membrane
  4. Thickness of Alveolar Membrane
44
Q

What is Daltons law of partial pressure?

A

The Total Pressure exerted by a gaseous mixture = The sum of the partial pressures of each individual component in the gas mixture

45
Q

How do gasses move?

A

Partial pressure gradient

46
Q 
What do:
PAO2
PiO2
PaCO2 
mean?
A 
PAO2 = Partial Pressure of O2 in alveolar air
PiO2 = Partial pressure of O2 in inspired air
PaCO2 = Partial pressure of CO2 in arterial blood
47
Q

What does PAO2 = ?

A

PiO2 - (PaCO2/0.8)

48
Q

What would a big gradient between PAO2 and PaO2 indicate?

A

problems with gas exchange in the lungs or a right to left shunt in the heart.

1. Respiratory (29 decks)

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