2. Clinical Application In Ventilation And Lung Mechanics

Question 1

What is the conducting portion of the respiratory tract?

Answer 1

Nasal cavity
Pharynx
Larynx
Trachea
Primary bronchi
Secondary bronchi
Bronchioles
Terminal bronchioles

Question 2

What is the respiratory portion of the respiratory tract?

Answer 2

Respiratory bronchioles
Alveolar ducts
Alveoli

Question 3

What s compliance?

Answer 3

Measure of distensibility. Change in volume relative to change in pressure

Question 4

What is elastance?

Answer 4

Measure of elastic recoil - tendency of something that has been distended t return to its original size

Question 5

What is the relationship between compliance and elastic recoil?

Answer 5

Inversely proportional

Question 6

What is lung compliance also inversely related to?

Answer 6

Connective tissue surrounding alveoli - elastic fibres including collagen and other matrix elements within the lung parenchyma
Alveolar surface tension

Question 7

What is lung elastic recoil directly related to?

Answer 7

Connective tissue surrounding alveoli - elastic fibres including elastin and collagen and other matrix elements within the lung parenchyma
Alveolar fluid surface tension

Question 8

What determines airway resistance?

Answer 8

Surface tension within airways

Diameter of airways - mucus in airways, pulmonary pressure gradients, radial traction

Question 9

How do bronchioles stay open in expiration?

Answer 9

Radial traction (outward tugging action) of surrounding alveolar walls on bronchioles

Question 10

What is atelactasis?

Answer 10

Lung (alveoli) collapse - inadequate expansion of air spaces

Impaired pulmonary surfactant production or function collapse - alveoli collapse secondary to surface tension

Question 11

Why do alveoli become compressed and collapse in atelectasis?

Answer 11

Air in pleural cavity (pneumothorax)
Fluid in pleural cavity (pleural effusion)
Tumour

Question 12

What is resorption collapse in atelectasis?

Answer 12

Due to obstruction
Airway obstructed - air downstream of blockage slowly absorbed into blood stream
Alveoli collapse

Question 13

How does atelectasis cause impaired respiratory function?

Answer 13

Alveoli not ventilated so can participate in gas exchange

Also collapsed alveoli more suggestible to lung infection including pneumonia

Question 14

What happens in interstitial lung disease?

Answer 14

Thickening of pulmonary interstitium - sometimes reversible

Question 15

What does the interstitium contain?

Answer 15

Elastin fibres
Collagen fibres
Fibroblasts
Matrix substance

Question 16

Where is the interstitium?

Answer 16

Between alveoli and capillaries

Question 17

What can cause interstitial lung disease?

Answer 17

Specific exposure - asbestos, drugs, mouldy hay etc.
Autoimmune-mediated inflammation
Unknown injury - e.g. idiopathic pulmonary fibrosis

Question 18

What happens to the lungs in interstitial lung disease?

Answer 18

Lungs are stiff, harder to expand as lung compliance is reduced

Question 19

What are the symptoms of interstitial lung disease?

Answer 19

Dry cough
Dyspnea on exertion
Fatigue
Typically gradual, insidious progression

Question 20

What are the signs of interstitial lung disease?

Answer 20

Decreased lung excursion on palpitation
Bi-basal end inspiratory lung crackles
Finger clubbing
Small pleural effusions

Question 21

When is surfactant produced in foetuses?

Answer 21

Starts at 24-28 weeks gestation
Increasing amounts by 32 weeks
Usually sufficient y 35-36 weeks

Question 22

What happens in pre term babies to their lungs?

Answer 22

Insufficient surfactant - high surface tension
Lung expansion at birth is incomplete
Some alveoli remain collapsed
Lung is stiff
Increased effort is required to breathe
Impaired ventilation

Question 23

What are the signs of neonatal respiratory distress syndrome?

Answer 23

Grunting
Nasal flaring
Intercostal and subcostal retractions
Rapid respiratory rate
Cyanosis

Question 24

What are the similarities between neonatal respiratory distress syndrome and diffuse pulmonary fibrosis?

Answer 24

Both have stiff lungs

Both decreased compliance and increased elastic recoil

Question 25

What is COPD primarily caused by?

Answer 25

Smoking and/or inhaled pollutants interacting with genetic vulnerability

Question 26

What does COPD encompass?

Answer 26

Chronic bronchitis

Emphysema

Question 27

What is pre-COPD?

Answer 27

Air flow impaired but no clinical symptoms yet and normal spirometry

Question 28

What happens in chronic bronchitis?

Answer 28

Disease of airways
Mucous hypersecretion
Reduced cilia

Question 29

What does chronic bronchitis lead to?

Answer 29

Air flow limitation/obstruction by luminal obstruction of small airways
Epithelial remodelling
Alteration of airway surface tension predisposing to collapse

Question 30

What is the clinical diagnosis of chronic bronchitis?

Answer 30

Cough productive sputum, for three months of the year for more than a year

Question 31

What is emphysema?

Answer 31

Air sacs disease

Abnormal, permanent enlargement of the air space distal to terminal bronchiole, destruction of alveolar walls

Question 32

What happens to lungs in emphysema?

Answer 32

Inflammatory cells accumulate, release elastases and oxidants, destroy alveolar walls and elastin
Reduced elastic recoil
Large air spaces - reduced surface area for gas exchange

Question 33

What is barrel chest?

Answer 33

Sign of emphysema
Distance between anterior chest and posterior chest increased
Due to more air in lungs, imbalance of chest wall elastic recoil and lung elastic recoil

Question 34

What happens in pneumothorax?

Answer 34

Communication created between pleural space and atmosphere
Air flows from atmosphere into pleural cavity until pleural pressure = atmospheric pressure
Pleural seal is lost
Lung collapses to unstretched size

Question 35

What is hypoventilation?

Answer 35

Failure to breathe rapidly enough or deeply enough

Question 36

What can cause hypoventilation?

Answer 36

Brain stem injury
Spinal cord trauma
Phrenic and intercostal nerve damage
Neuromuscular junction damage
Muscles of respiration impaired 
Chest wall impaired
Pleural cavity damaged
Poor lung compliance
Upper airway obstruction
High airway resistance