Disorders of Ventilation and Lung Mechanics Flashcards
In terms of cartilage and glands, what is the difference between small bronchus and bronchioles?
Small Bronchus: small islands of cartilage and glands in submucosa
Bronchioles: no cartilage or glands
How are bronchioles kept open if they have no cartilage?
Bronchioles are attached to intact surrounding alveolar walls
positive outward pressure on exhilation keeps bronchioles open
Known as radial traction
What is the interstitium?
A potential space between alveolar cells and the capillary basement membrane
What is interstitial lung disease?
A group of diseases characterised by thickening of pulmonary interstitium causing ‘stiffer’ lungs
What is contained within the interstitial space?
- Elastin Fibres
- Collagen Fibres
- Fibroblasts
- Matrix Substance
Describe the pathophysiology of interstitial lung diease?
Deposition of fibrous tissue in the interstitium
- Lungs are stiffer and harder to expand
- Lung compliance is reduced
- Eleastic recoil of lungs is increased
- Due to elastic recoil lungs are smaller than normal
Give some of the causes of interstitial lung disease
What are some of the symptoms of interstitial lung disease?
- dry cough
- shortness of breath
- dyspnea on exertion
- fatigue
- gradual progression
What are some of the signs of interstital lung disease?
- decreased lung excursion on palpation (thumbs not pushed apart)
- lung crackles
- increased resp rate (tachypnoea)
- finger clubbing
- pleural effusions
Why is gas exchange impared in interstitial lung disease?
- alveolar walls thickened = increased diffusion distance
- effect great for O2 than CO2
Describe the pathophysiology of Respiratory Distress Syndrome
- Premature babies <25 weeks are deficient in surfactant
- Without surfactant surface tension is high; lungs have reduced compliance and some alveoli are collapsed (no gas exhange here)
- Increased effort is needed to breathe
- Ventilation is impaired
What are some of the symptoms of neonatal respiratory distress syndrome?
- Grunting
- Nasal Flaring
- Intercostal and subcostal retractions
- Rapid resp rate
- Cyanosis
How can a baby with respiratory distress syndrome be treated?
- replace surfactant via endotracheal tube
- supportive O2 treatment and assisted ventilation
- Give steroids to mum in prem labour → causes baby to make surfactant
What is COPD?
Chronic Obstructive Pumlmonary Disease encompasses 2 medical conditions
- Chronic Bronchitis
- Emphysema
What is Pre-COPD?
A patient with impared airflow but no clinical symptoms and normal spirometry
But at high risk of developing COPD in next 5 years
What is chronic bronchitis?
A disease of the airways from bronchi to bronchioles characterised by mucus hypersecretion
Clinical diagnosis: cough productive of sputum for >3 months of the year for >1 year
Why is mucus hypersecretion in chronic bronchitis problematic?
- Reduced cilia, mucus not cleared effectively
- airways occluded
- epithelial remodelling
- alterns airways surface tension predisposing to collapse
What are some of the causes of increased mucus production?
Why is airway obstruction worse on expiration than inspiration?
Inspiration: negative pressure in pleural space helps keep airway open
Expiration: Postive intra pulmonary pressure exacerbates the narrowing of thoracic airways
Define Emphysema
The abnormal, permanent enlargement of the air spaces distal to the terminal bronchioles, with destruction of alveolar walls
What are 90% of cases of COPD caused by? What is the hosts response?
Smoking
host responds by breakdown of elastin and alveolar walls
What effects does loss of elastin fibres have on the lung?
- The lung is easier to expand (loss of elastic recoil)
- lungs become hyperinflated → barrel chest appearance
- loss of radial traction on small bronchioles narrows the small airways
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What are some of the symptoms on emphysema?
- Shortness of breath
- Reduced exercise tolerance
What is a much rarer form of emphysema?
Alpha-1-antitrypsin deficiency
(alpha 1 antitrypsin is an anti-protease, deficiency causes destruction of elastin)
