Physiology - Respiratory Mechanics

Question 1

Define Internal Respiration?

Answer 1

The intracellular mechanisms which consume O2 and produce CO2.

Question 2

Define External Respiration?

Answer 2

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

Question 3

What are the 4 stages of external respiration?

Answer 3

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

Question 4

Describe Ventilation.

Answer 4

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

Question 5

Gas exchange between alveoli and blood?

Answer 5

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

Question 6

Gas transport in blood?

Answer 6

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

Question 7

Gas exchange at tissue level?

Answer 7

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

Question 8

Body systems involved in external respiration?

Answer 8

Nervous
Respiratory
Cardiovascular
Haematology

Question 9

In what direction does air flow?

Answer 9

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

Question 10

Intra-alveolar and atmospheric pressure before inspiration?

Answer 10

Equivalent.

Question 11

Boyle’s Law?

Answer 11

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

Question 12

What must occur for air to flow into lungs?

Answer 12

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

Question 13

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

Answer 13

Decreases.

Boyle’s Law.

Question 14

When do the thorax and lung expand?

Answer 14

In response to contraction of inspiratory muscles.

Question 15

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

Answer 15

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.

Question 16

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

Answer 16

Expands.

Question 17

General atmospheric pressure? Give units.

Answer 17

760 mm Hg.

Question 18

What are the 3 pressures important in ventilation?

Answer 18

Atmospheric
Intra-alveolar
Intrapleural

Question 19

Inspiration and expiration, passive or active? Why?

Answer 19

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

Expiration - passive, involves relaxation of inspiratory muscles.

Question 20

Describe Expiration.

Answer 20

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.

Question 21

Describe Inspiration.

Answer 21

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.

Question 22

What is pneumothorax?

3 causes?

Answer 22

Air in pleural space.

Iatrogenic, Spontaneous, traumatic.

Question 23

What can pneumothorax result in?

Answer 23

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

Question 24

Forces that keep alveoli open.

Answer 24

Transmural Pressure Gradient

Pulmonary Surfactant

Alveolar Interdependence

Question 25

Forces promoting lung collapse/recoil.

Answer 25

Elasticity of stretched lung connective tissue. Alveolar surface tension.

Question 26

Contraction of external intercostal muscle?

Answer 26

Lifts ribs and moves sternum out.

Question 27

What causes lung recoil during expiration?

Answer 27

Elastic connective tissue in lungs. Alveolar surface tension.

Question 28

What is pulmonary surfactant?Purpose?

Answer 28

A complex mixture of lipids and proteins secreted by type II alveoli. Lowers alveolar surface tension by interspersing between water molecules lining the alveoli.

Question 29

LaPlace's Law Equation

Answer 29

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

Question 30

Respiratory Distress Syndrome?

Answer 30

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.

Question 31

What is alveolar interdependence?

Answer 31

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

Question 32

Major and accessory inspiratory muscles?

Answer 32

Major -Diaphragm and external intercostal muscles. Accessory - Pectoral, sternocleidomastoid, scalenus.

Question 33

Muscles of active expiration?

Answer 33

Abdominals, internal intercostal muscles.

Question 34

TV? Average value?

Answer 34

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

Question 35

IRV? Average value?

Answer 35

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

Question 36

ERV? Average value?

Answer 36

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

Question 37

RV? Average value?

Answer 37

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

Question 38

What are the 4 lung volumes?

Answer 38

Tidal Inspiratory reserve Expiratory reserve Residual

Question 39

What are the 4 lung capacities?

Answer 39

Inspiratory Functional residual Vital Total lung

Question 40

IC? Average value?

Answer 40

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

Question 41

FRC? Average Value?

Answer 41

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

Question 42

VC? Average value?

Answer 42

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

Question 43

TLC? Average Value?

Answer 43

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

Question 44

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

Answer 44

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

Question 45

When does RV increase?

Answer 45

When elastic recoil of lungs is lost (emphysema).

Question 46

FVC and FEV1?

Answer 46

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.

Question 47

FEV1/FVC ratio?

Answer 47

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

Question 48

FEV/FVC ration <70%

Answer 48

Obstructive lung disease.

Question 49

Obstructive lung disease and examples.

Answer 49

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

Question 50

Restrictive lung disease and examples.

Answer 50

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

Question 51

Obstructive lung disease spirometry results?

Answer 51

Normal/low FVC Low FEV1 Low FEV1/FVC

Question 52

Restrictive lung disease spirometry results?

Answer 52

Low FVC Low FEV1 Noemal FEV1/FVC

Question 53

Normal airway resistance? Primary determinant of AR?

Answer 53

Very low with small pressure gradient. Radius of airway.

Question 54

Airway resistance equation?

Answer 54

F = change in pressure/ resistance

Question 55

when is peak flow useful?

Answer 55

Useful test for patients with obstructive lung disease.

Question 56

What is pulmonary compliance?

Answer 56

The measure of effort that is required to stretch the lungs during inspiration. Vol change per unit of pressure change.

Question 57

What causes decreased pulmonary compliance?

Answer 57

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

Question 58

What causes abnormally increased pulmonary compliance?

Answer 58

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

Question 59

What causes hyperinflation of lungs?

Answer 59

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

Question 60

Normal work of breathing?

Answer 60

3% total energy.

Question 61

When is work of breathing increased?

Answer 61

Pulmonary compliance is decreased Airway resistance is increased Elastic recoil is decreased Need for increased ventilation.