Session 2: Some Disorders of Ventilation and Lung Mechanics Flashcards
(43 cards)
Give some common disorders of ventilation and lung mechanics.
Interstitial lung disease
Respiratory distress syndrome in the new born
Emphysema
Asthma
Pneumothorax
Hypoventilation
Explain the relationship between compliance and elastic recoil.
It’s an inverse relationship.

Bronchioles have no cartilage. How do they stay open in expiration?
Due to something called radial traction.
This is the outward tugging actiong of the surrounding alveolar walls on bronchioles.
Briefly explain what interstitial lung disease is.
Also give the cause.
This is the thickening of the pulmonary interstitium. A lot of collagen is layed down in the interstitium.
There are over 200 different types of the disease and causes.
However the common final pathway almost always result in the same thing: lung fibrosis.
Is interstitial lung disease reversible?
Sometimes, sometimes not.
It depends on what kind and how early it was detected/treated.
Give a some common causes of interstitial lung disease.
Asbestos
Coal workers pneumoconiosis
Radiation
Rheumatoid arthritis
Sarcoidosis
Exterernal alleric alveolitis
Fibrosing alveolitis
Which lung is healthy?

The left lung.
What does pulmonary interstitium contain?
Elastin fibres
Collagen fibres
Fibroblasts
Matrix substance
In interstitial lung disease there is a lot more collagen fibres.
Explain the pathophysiology of interstitial lung disease.
(Consequences of the disease)
The lungs become stiffer and harder to expand since the collagen fibres are less stretchy than elastin fibres.
Lung compliance is reduced.
Elastic recoil of the lungs is increased.
Smaller lungs
On examination chest expansion is reduced.
Also thicking of the alveolar walls increases the distance oxygen has to diffuse from alveolar air to the blood and vice versa. Less efficient gas exchange.

Why are the lungs smaller in interstitial lung disease?
Because of the increased elastic recoil creating a netforce inwards since the chest recoil of the muscles still stay the same.
Symptoms of interstitial lung disease.
Shortness of breath
Reduced exercise tolerance
Dry cough
Fatigue
Signs of interstitial lung disease.
Tachypnoea
Tachycardia
Reduced chest movement (bilaterally)
Coarse crackles
Pleural effusions
Finger clubbing
How can you examine the reduced chest movement of interstitial lung disease.
If you put your hands on their back with your thumbs touching. In a normal lung as they take a deep breath your thumbs should separate.
If they don’t, this is a sign.

What happens to compliance in interstitial lung disease?
It is greatly reduced.
Explain Respiratory distress syndrome in new born.
It comes down to insufficient amount of surfactant.
Surfactant is produced by type II pneumocytes in increasing quantities from 32 weeks’ gestation.
RDS is therefore caused by deficiency of surfactant in premature babies, particularly those less than 30 weeks old.
Pathophysiology of RDS in new born.
Without the surfactant the surface tension in the fluid lining of the alveoli will be high.
This makes the lungs harder to expand at birth. Since lung expansion is incomplete and due to the absence of surfactant some alveoi remain collapsed and some existing ones start to collapse. There is no gas exchange in these alveoli.
Lungs are stiffer and harder to expand which means compliance is low.
This means more effort is needed to breathe sufficiently.
Impaired ventilation.
Signs of RDS in new born.
Cyanosis
Grunting
Intercostal and subcostal recession.
Nasal flaring
Tachypnoea
Treatment of RDS of the new born.
Surfactant replacement via an endotracheal tube
Supportive treatment with oxygen and assisted ventilation.
Classic definition of COPD encompasses two medical conditions.
Which?
Chronic bronchitis
Emphysema
Which part of the airways/lungs is affected in COPD?
From bronchi to bronchioles.
Pathophysiology of chronic bronchitis.
There is mucus hypersecretion from goblet cells and submucus glands.
There is also reduced cilia which means that the mucus is not cleared effectively and can lead to mutliple infections.
Airflow is limited and obstructed.
Epithelial remodeling.
Parts of airways tend to collapse because of increased surface tension.
Clinical diagnosis of chronic bronchitis.
Cough productive sputum over three months of the year for over one year.
Common cause of emphysema (and COPD).
90% of cases of COPD and emphysema are due to smoking.
Inhaled cigarette smoke results in the breakdown of elastin fibres and alveolar walls.
Pathophysiology of emphysema.
Loss of elastin fibres due to the cigarette smoke.
Higher compliance since there is less elastin and less elatic recoil.
The reduction of elastic recoil disturbs the net balance between elastic recoil (inwards) and chest recoil (outwards).
This causes the lungs to be hyperinflated.
The small airways are narrowed.

