Respiratory Flashcards
What is transmural pressure in the lungs?
Pressure across a structure e.g. the pressure difference between inside the alveoli and the pleural space
For air-filled lungs what are the two main factors that determine the compliance of the lungs?
Intrinsic compliance of the lungs (mainly related to its elasticity) and the surface tension at the liquid-air surface
How does the intra-pleural pressure compare to the pressure of the atmosphere?
Negative i.e. pressure in the intrapleural space is less than atmospheric pressure
What creates the negative pressure in the lungs?
Negative pressure reflects the effects of two opposing forces: lungs elastic properties tending to collapse and the chest wall elastic properties tend to spring out. These two opposing forces create a vacuum in the intra-pleural space, which then opposes the forces producing it
What is a pneumothorax?
Presence of air in the intra pleural space
What effect does a pneumothorax have on the intra pleural pressure?
Intra-pleural pressure will increase (become less negative) and will eventually approach zero or even become positive
What effect does the change in intra pleural pressure in a pneumothorax have on the lungs?
Lack of negative intra-pleural pressure means the lungs collapse (natural tendency is to collapse but they are held open by the negative intra-pleural pressure)
What effect does the change in intra pleural pressure in a pneumothorax have on the chest wall?
Lack of negative intra-pleural pressure means that the chest wall tends to spring out (natural tendency of the chest wall is for it to spring out, but it is held in by the negative intra-pleural pressure)
What are the common causes of pneumothorax?
Spontaneous, idiopathic, secondary to an underlying lung disease e.g. COPD, TB, asthma, lung abscess, cystic lung disease, lung cancer or traumatic i.e. following injury to the chest wall
What are the common symptoms associated with pneumothorax?
Sudden onset, unilateral chest pain, which is pleuritic with acute dyspnoea
What clinical findings would you expect to see in a patient with a pneumothorax?
Reduced chest expansion of the affected side
Resonance or hyper-resonance on percussion over affected side
Absent breath sounds
Tracheal deviation
What are the 3 types of pneumothorax and what are common causes?
Closed: spontaneous
Open: Bronchopleural fistula or ruptured bulla or abscess
Tension: Bullae or following a penetrating injury
What can be a serious consequence of an open pneumothorax?
Risk of infection
What can be a serious consequence of a tension pneumothorax?
Acute cardiovascular compromise
What additional clinical signs are you more likely to see in a patient with a tension pneumothorax versus non-tension pneumothorax?
Tension pneumothorax will often have deviation of the trachea, tachycardia and hypotension
What changes would you see on an X-ray of a patient with pneumothorax? Why?
Collapsed lung edges can usually be identified very clearly
In the area of the pneumothorax there is complete translucency i.e. complete blackness with an absence of any lung markings. If it is tension type pneumothorax you could also see evidence of mediastinal shift. There may also be evidence of underlying lung disease e.g. COPD giving clues as to the likely underlying aetiology
What effect would fibrosis have on the lung tissue? Why?
Fibrosis is the replacement of normal tissue with scar tissue, this typically contains a high amount of collagen fibres and scanty elastic fibres. The lack of elastic fibres would decreased the compliance of the lungs
What features on examination would support a diagnosis of pulmonary fibrosis?
Digital clubbing can be seen and late, often fine, inspiratory crackles can be heard on auscultation of the lungs
What changes would you expect to see on chest x-ray in a patient with pulmonary fibrosis?
This disease is one of the interstitium and so evidence of involvement of the supporting tissue of the lung parenchyma resulting in fine or coarse reticular opacities or small nodules
What pattern of changes would you expect to see on lung function testing in a patient with a fibrotic lung disease?
Restrictive pattern of changes on lung function testing as in fibrotic tissue for a given change in pressure there will be smaller increase in volume compared to healthy lung tissue
What is the diagnostic golden standard criteria for diagnosis of bronchiectasis?
High-resolution CT (HRCT) scanning
What abnormalities would you expect to see on a CT scan of a patient with bronchiectasis?
Parallel tram track lines, or signet-ring appearance composed of a dilated bronchus cut in a horizontal section with an adjacent pulmonary artery representing the stone
Diameter of bronchus lumen is normally 1-1.5 times that of the adjacent vessel; a diameter greater than 1.5 times that of the adjacent vessel is suggestive of bronchiectasis
Varicose bronchiectasis has irregular or beaded bronchi, with alternating areas of dilatation and constriction
Cystic bronchiectasis has large cystic spaces and a honeycomb appearance; this contrasts with the blebs of emphysema, which have thinner walls and are not accompanied by proximal airway abnormalities
What two components of the respiratory system principally determine its compliance?
Lungs and chest wall
65 y/o M comes in complaining of SOB when walking up hill. Given a salbutamol inhaler last week but it hasn’t helped. Been breathless getting up stairs for last 2 years. Advised to give up smoking but doesn’t want to. Has been smoking 20 cigarettes a day for last 40 years. Coughs every day, usually in mornings and always produces yellow sputum. This has been going on for years and is no worse this week than at any other time. He has no fever or chest pain. What is the likely diagnosis?
Chronic obstructive pulmonary disease
