Clinical application of ventilation and lung mechanics Flashcards
What is hypoventilation?
Inspiratory muscles not working
What is a pneumothorax?
Pleural seal lost, lungs collapse
What is diffuse lung fibrosis?
Increased collagen in alveolar walls, lungs stiff so difficult for lungs to expand.
What is respiratory distress syndrome?
decreased surfactant - increased surface tension so difficult for lungs to expand.
What is emphysema
Destruction of elastic fibres, decreased elastic recoils of lungs so difficulty with quiet expiration.
What is asthma and COPD?
Increased airway resistance so difficulty with quiet expiration.
What epithelial cells are present in the conducting portion of the respiratory system?
Pseudostratified epithelium with cilia and goblet cells line the airways from the nasal cavity to the largest bronchioles.
How are small particles removed from the respiratory tract?
Carried down to alveoli then
engulfed by macrophages and removed by lymphatics and via airways (much-cilary)
What is the difference between bronchus and bronchioles?
Bronchus = cartilage Bronchioles = no cartilage or glands
What is radial traction?
Term used for the outward tugging action of the alveolar walls on bronchioles.
It prevents the collapse of bronchioles during expiration.
What is interstitium?
The microscopic space between the alveolar epithelium and capillary endothelium.
It contains: Elastin fibres, Collagen fibres and fibroblasts.
What causes interstitial lung fibrosis?
- Specific exposure e.g. asbestos, drugs, mouldy hay ect..
- Autoimmune-mediated inflammation
- Connective tissue disease
- Unknown injury (idiopathic pulmonary fibrosis)
What happens to the lungs in interstitial lung disease (diffuse lung fibrosis)?
Lungs are stiff and harder to expand. Therefore, lung compliance is low.
Elastic recoils of the lungs is high and so the lung volume is less than normal.
It has a ‘restrictive type of ventilatory defect.
What are the signs and symptoms of Interstitial lung disease?
Breathlessness
Dry cough
Relevant previous history: occupation, drug history ect
Chest expansion is reduced.
What is emphysema?
Abnormal, permanent enlargement of the air spaces distal to the terminal bronchiole with destruction of the alveolar walls (but no fibrosis)
Why does emphysema occur?
Protease mediated destruction of elastin is an important feature.
Reduced elasticity is a key problem.
This means there are larger air spaces for reduced surface area for gas exchange.
Why does smoking give rise to emphysema?
Smoking and inhaled pollutants cause inflammatory cells to accumulate which release elastase and oxidants This destroys the alveolar walls and elastin.
Other than emphysema, what other disease do most have?
Chronic bronchitis.
COPD = Emphysema + chronic bronchitis
What is chronic bronchitis?
This is in the larger airways
Mucus hyper secretion (from goblet cells and sub mucous glands)
Reduced cilia - mucus not cleared effectively
Why is airway obstruction is worse in expiration than inspiration?
Because positive intrapulmonary press during expiration exacerbates narrowing of intra thoracic airways.
What is a barrel chest?
When the chest is hyperinflated due to air trapped. This occurs in COPD.
What happens in a pneumothorax?
When the chest wall or the lung is breached.
A communication is created between pleural space and atmosphere so the air flows from the atmosphere (higher pressure) into the pleural cavity (lower pressure).
This occurs until pleural pressure = atmospheric pressure.
This results in the pleural seal being lost.
The lung elastic recoils is not counter balanced by negative pleural press so this results in the lung collapse to the unstretched size.
How do you treat a pneumothorax?
Insert a chest drain with an underwater seal to prevent fluid or air from entering the pleural cavity.
What is another word for a lung collapse?
Atelectasis - means inadequate expansion of air spaces
What could causes atelectasis?
- In birth failure of alveoli to expand
- Compression collapse due to pneumothorax or pleural effusion
- Resorption collapse due to obstruction -airway obstructed so air downstream of blockage slowly absorbed into blood stream. (eg tumour to mucus plug)
What are the symptoms of respiratory distress syndrome?
Respiratory difficulties from birth:
- Grunting
- Nasal flaring
- Intercostal and subcostal retractions
- Repid respiratory rate
- Cyanosis
How do you treat respiratory distress syndrome?
Give mum steroids before both
Suportive treatment with oxygen and assisted ventilation.
What type of epithelia is present in the bronchioles and terminal bronchioles?
Simple columnar epithelium with cilia and Clara cells but no goblet cells.
What type of epithelia is present in the respiratory bronchioles and the alveolar ducts?
Simple cuboidal epithelium with a few sparse scattered cilia and Clara cells
What type of epithelia is present in the alveoli?
Simple squamous (type 1 and type 2 pneumocytes).
How are large particles removed from the respiratory tract?
Filtered in nose and deposited on mucus layer in nose and nasopharynx then swept by cilia to the oropharynx where they are swallowed.
How are medium sized particles removed from the respiratory tract?
Deposited on mucus lining the trachea, bronchi and larger bronchioles then wafter up to pharynx by cilia (muco-cilary escalatory) then swallowed.
What physiological changes occur in interstitial lung disease?
- Alveolar capillary membrane is thickened
- Increases diffusion distance for oxygen and carbon dioxide
- This impairs gas exchange.
What is respiratory distress syndrome?
This is when babies are born prematurely so there is not enough surfactant for lung expansion (not sufficient until 35-36 weeks). This means there is high surface tension so lung expansion is incomplete at birth so some of the alveoli remain collapsed (airless) meaning that gas exchange cannot occur here.
What can cause hypoventilation?
Opiates Head injury Guillain-Barre syndrome Myasthenia graves Inherited muscle disease Severe obesity Pneumothorax Large pleural effusion Respiratory distress syndrome Laryngeal oedema Foreign body Severe, acute asthma
