4 - Disorder of Ventilation Flashcards
What is the relationship between compliance and elasticity of the lungs?
- One up, other down
- Compliance to do with expansion and elasticity with rest
How does lung elastic recoil affect functional residual capacity?
How do bronchioles stay open if they have no cartilage?
Radial traction - surrounding alveoli pull outward and prevent bronchiole collapse on expiration
What is interstitial lung disease?
- Deposition of fibrous tissue in the interstitium, so it gets thicker.
Interstitium is the space between alveoli and capillaries
- Group of diseases with a variety of causes but similar clinical features.
- Usually caught too late and irreversible
What effects does intersitial lung disease have on the lungs and why?
- Lower lung compliance due to stiff lungs as collagen fibres less stretchy than elastin
- Elastic recoil increased so lungs are smaller than normal
- Chest expansion reduced
- Inspiratory capacity and vital capacity is reduced
- Less O2 diffusion and more CO2 absorption due to thickening of alveolar walls
This increased distance reduces the efficiency of gas exchange, as oxygen and carbon dioxide molecules must travel a greater distance to diffuse across the alveolar wall.
What are some signs and symptoms of interstitial lung disease?
Symptoms: shortness of breath, reduced exercise tolerance, dry cough, tachypneoa, tachycardia,
Signs: clubbing, pleural effusions,
reduced bilateral chest movement, coarse crackles
Restrictive type of ventilatory defect on spirometry
What are some examples of causes of interstitial lung disease?
Can all lead to diffuse lung fibrosis
How can you treat someone with pulmonary fibrosis?
- Supervised structured exercise therapy
- May increase lung compliance by stretching, strengthen accessory muscles and teach people to tolerate dyspnoea
Interstitial lung disease refers to a group of about 100 chronic lung disorders characterized by inflammation and scarring that make it hard for the lungs to get enough oxygen. The scarring is called pulmonary fibrosis.
What effect does respiratory distress syndrome have on lung compliance and elasticity?
- Reduces compliance as lack of surfactant so high surface tension
- Collapsed alveoli
- Increase effort to breath so impaired ventilation
What happens to the diameter of the bronchioles in pulmonary fibrosis?
Not narrowed due to outward pull of fibrous tissue keeping bronchioles open
What is emphysema and what effect does it have on the compliance and elasticity of the lungs?
How does it present?
- Increased lung compliance as lungs easier to expand due to less elastin
- Elastic recoil decreased
- Narrowing of airways that is irreversible due to loss of elastic fibres exerting radial traction
- Lungs hyperinflated at rest as loss of elastic recoil (barrel chest)
- Obstructive ventilatory defect on spirometry
What are some symptoms and signs of emphysema?
- Barrel chest due to hyper inflated lungs
- Shortness of breath
- Reduced exercise tolerance
What is the main difference between emphysema due to smoking and emphysema due to A1 anti-trypsin deficiency.
Genetic defect presents at earlier age
Both asthma and emphysema are an example of airway obstructions, which can be reversed?
- Asthma is reversible but emphysema isn’t
- Pulmonary fibrosis and RDS are ventilatory obstructions
Describe the mechanism of airway obstruction in asthma?
- Asthma is a chronic inflammatory process which can be triggered by allergic/non-allergic stimuli.
- Inflammation causes the things in red
Chronic inflammatory process triggered by stimuli
Inflammation causes bronchoconstriction, hypertrophy (which leads to thicker and narrow airways)
What is the mechanism of airway obstruction in the three most common obstructive lung diseases?
Why does a pneumothorax lead to lung collapse?
- Presence of air in pleural space
- Air flows in from atmosphere
- Elastic recoil of lung causes it to collapse towards hilum as negative pleural pressure and outward recoil of chest can no longer counteract it
What are the two types of atelectasis?
Incomplete expansion of the lungs (neonatal) or collapse of previously inflate lung so areas of airless pulmonary parenchyma
Compression: when significant volumes of air or fluid, e.g pneumo/haemothorax, accumulate in pleural cavity
Resorption (Lung collapse) complete obstruction of an airway. air is resorbed from the alveoli and collapse, cause could be bronchial carcinoma
What causes hypoventilation?
When there is an inability to expand the chest, e.g DMD. Any respiratory muscle weakness or severe throacic wall deformity.
Stiff lungs or a severe airway obstruction can also cause poor ventilation
Why does chronic bronchitis lead to airway obstruction?
- Mucus hypersecretion so increased resistance due to narrowed lumen
- Reduced cilia so mucus is not cleared effectivley
What is the telltale sign of hyperinflation of the lungs?
Flattened diaphragm on lateral chest x-ray. Shows a barrelled chest
Compare and contrast diffuse lung fibrosis and emphysema.
How would you treat a pneumothorax?
What is the steps of the cough reflex?
- Coordinated by cough center in the medulla oblongata
- Initiated by irritation of mechano and chemoreceptors in respiratory epithelium
- Use the word glottis not just vocal cords
Why is there intercostal recession in a baby with RDS and what would a compliance curve look like in this baby?
- Baby has stiff lungs due to less surfactant so force from inward elastic recoil greater than from the outward force of the chest wall
In emphysema what happens to the elastic recoil and compliance of the chest wall and the lung?
- Compliance increases as stretched but reduced chest expansion
- Barrel Chest: transverse diameter becomes equal to anteroposterior diameter
Draw a compliance curve for a patient with COPD.
