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Respiratory > Physiology - Respiratory Mechanics > Flashcards

Physiology - Respiratory Mechanics Flashcards

1
Q

Define Internal Respiration?

A

The intracellular mechanisms which consume O2 and produce CO2.

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2
Q

Define External Respiration?

A

The sequence of events that lead to the exchange of O2 and CO2 between the external environment and alveolar sacs.

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3
Q

What are the 4 stages of external respiration?

A

Ventilation
Gas exchange between alveoli and blood
Gas transport in blood
Gas exchange at tissue level.

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4
Q

Describe Ventilation.

A

The mechanical process of moving air between atmosphere and alveolar sacs.

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5
Q

Gas exchange between alveoli and blood?

A

The exchange of O2 and CO2 between the air of the alveoli and the blood in the pulmonary capillaries.

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6
Q

Gas transport in blood?

A

The binding and transport of O2 and CO2 in the circulating blood.

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7
Q

Gas exchange at tissue level?

A

The exchange of O2 and CO2 between the blood in the systemic capillaries and body cells.

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8
Q

Body systems involved in external respiration?

A

Nervous
Respiratory
Cardiovascular
Haematology

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9
Q

In what direction does air flow?

A

Down concentration gradient from high pressure region to low pressure region.

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10
Q

Intra-alveolar and atmospheric pressure before inspiration?

A

Equivalent.

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11
Q

Boyle’s Law?

A

Pressure exerted by a gas varies inversely with volume of gas.

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12
Q

What must occur for air to flow into lungs?

A

Intra-alveolar pressure must be less than the atmospheric pressure.

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13
Q

Volume of gas increases, what happens to the pressure exerted by the gas?
What is this an example of?

A

Decreases.

Boyle’s Law.

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14
Q

When do the thorax and lung expand?

A

In response to contraction of inspiratory muscles.

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15
Q

Describe the 2 forces that hold the thoracic wall and lungs in close opposition.

A

Intrapleural fluid cohesiveness; Water molecules in Intrapleural fluid are attracted to each other and stick together. Hence pleural membranes stick together.

Negative Intrapleural pressure; Sun-atmospheric Intrapleural pressure create a transmural pressure gradient across the lung and chest wall.

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16
Q

What happens to the lungs when the chest is squeezed inwards?

A

Expands.

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17
Q

General atmospheric pressure? Give units.

A

760 mm Hg.

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18
Q

What are the 3 pressures important in ventilation?

A

Atmospheric
Intra-alveolar
Intrapleural

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19
Q

Inspiration and expiration, passive or active? Why?

A

Inspiration - active, requires contraction of diaphragm and external intercostal muscle.

Expiration - passive, involves relaxation of inspiratory muscles.

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20
Q

Describe Expiration.

A

Chest wall and lungs recoil which causes intra-alveolar pressure to rise due to air being contained in smaller volume, air then leaves lungs down pressure gradient until intra-alveolar pressure = atmospheric.

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21
Q

Describe Inspiration.

A

Chest wall and lungs stretched, increased size of lungs therefore intra-alveolar pressure falls causing air to enter lungs down pressure gradient until intra-alveolar pressure = atmospheric.

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22
Q

What is pneumothorax?

3 causes?

A

Air in pleural space.

Iatrogenic, Spontaneous, traumatic.

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23
Q

What can pneumothorax result in?

A

Air entering pleural space can abolish transmural pressure gradient leading to lung collapse.

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24
Q

Forces that keep alveoli open.

A

Transmural Pressure Gradient

Pulmonary Surfactant

Alveolar Interdependence

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25
Q

Forces promoting lung collapse/recoil.

A

Elasticity of stretched lung connective tissue.

Alveolar surface tension.

26
Q

Contraction of external intercostal muscle?

A

Lifts ribs and moves sternum out.

27
Q

What causes lung recoil during expiration?

A

Elastic connective tissue in lungs.

Alveolar surface tension.

28
Q

What is pulmonary surfactant?Purpose?

A

A complex mixture of lipids and proteins secreted by type II alveoli.

Lowers alveolar surface tension by interspersing between water molecules lining the alveoli.

29
Q

LaPlace’s Law Equation

A

p = 2T/r
p - inward collapsing pressure
T - Surface Tension
r - Radius of alveoli

30
Q

Respiratory Distress Syndrome?

A

Foetal lungs unable to synthesize surfactant until late in pregnancy - lack of this causes RDS which results In strenuous inspiratory efforts to overcome high surface tension and inflate lungs.

31
Q

What is alveolar interdependence?

A

If an alveolus start to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces on the collapsing alveolus to open it.

32
Q

Major and accessory inspiratory muscles?

A

Major -Diaphragm and external intercostal muscles.

Accessory - Pectoral, sternocleidomastoid, scalenus.

33
Q

Muscles of active expiration?

A

Abdominals, internal intercostal muscles.

34
Q

TV? Average value?

A

Tidal Volume - Vol of air entering/leaving lungs during a single breath. (0.5L)

35
Q

IRV? Average value?

A

Inspiratory reserve volume - Extra vol of air that can be maximally inspired over and above typical resting TV. (3L)

36
Q

ERV? Average value?

A

Expiratory reserve volume - Extra vol of air that can be actively expired. (1L)

37
Q

RV? Average value?

A

Residual Volume - Min vol of air remaining in lungs after a maximal expiration. (1.2L)

38
Q

What are the 4 lung volumes?

A

Tidal
Inspiratory reserve
Expiratory reserve
Residual

39
Q

What are the 4 lung capacities?

A

Inspiratory
Functional residual
Vital
Total lung

40
Q

IC? Average value?

A

Inspiratory Capacity - Max volume of air that can be inspired after normal expiration. IC = IRV + TV. (3.5L)

41
Q

FRC? Average Value?

A

Functional residual capacity - Volume of air in lungs at end of normal passive expiration. FRC = ERV + RV. (2.2L)

42
Q

VC? Average value?

A

Vital Capacity - Max vol of air moved out during a single breath following a maximal inspiration. VC = IRV + TV + ERV. (4.5L)

43
Q

TLC? Average Value?

A

Total lung capacity - Total vol of air the lungs can hold. TLC = VC + RV. (5.7L)

44
Q

Why isn’t it possible to measure TLC by spirometry?

A

TLC = VC + RV but RV cannot be measured by spirometry.

45
Q

When does RV increase?

A

When elastic recoil of lungs is lost (emphysema).

46
Q

FVC and FEV1?

A

Forced vital capacity - Max vol forcibly expelled from lungs after max inspiration.

Forced expiratory vol in 1 sec - vol of air expired during first second of expiration.

47
Q

FEV1/FVC ratio?

A

Proportion of forced vital capacity that can be expired in 1 second. FEV1/FVC * 100%
usually >70%.

48
Q

FEV/FVC ration <70%

A

Obstructive lung disease.

49
Q

Obstructive lung disease and examples.

A

Difficulty exhaling air because of narrowing of airways. E.g. Asthma and COPD.

50
Q

Restrictive lung disease and examples.

A

Difficulty fully expanding lungs with air, usually caused by stiffness n the lungs. E.g. Lung Fibrosis, cystic fibrosis.

51
Q

Obstructive lung disease spirometry results?

A

Normal/low FVC
Low FEV1
Low FEV1/FVC

52
Q

Restrictive lung disease spirometry results?

A

Low FVC
Low FEV1
Noemal FEV1/FVC

53
Q

Normal airway resistance?

Primary determinant of AR?

A

Very low with small pressure gradient.

Radius of airway.

54
Q

Airway resistance equation?

A

F = change in pressure/ resistance

55
Q

when is peak flow useful?

A

Useful test for patients with obstructive lung disease.

56
Q

What is pulmonary compliance?

A

The measure of effort that is required to stretch the lungs during inspiration.

Vol change per unit of pressure change.

57
Q

What causes decreased pulmonary compliance?

A

Pulmonary fibrosis, oedema, lung collapse, pneumonia, absence of surfactant.

58
Q

What causes abnormally increased pulmonary compliance?

A

Loss of elastic recoil in lungs (Occurs in emphysema).

Age.

59
Q

What causes hyperinflation of lungs?

A

Emphysema (Increased compliance) where patients must work harder to expel air from lungs.

60
Q

Normal work of breathing?

A

3% total energy.

61
Q

When is work of breathing increased?

A

Pulmonary compliance is decreased

Airway resistance is increased

Elastic recoil is decreased

Need for increased ventilation.

Respiratory (7 decks)

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