Pathology of Rest Tract Infection Flashcards
what are the common organisms causing upper respiratory infection?
- strep pyogene bacteria
- viruses such as rhinoviruses, adenoviruses, parainfluenza, influenza and EB virus.
- type A beta haemolytic streptococci causes acute epiglottis.
Define the mechanisms of defence in the respiratory system.
- Macrophage-mucociliary escalator system (main mechanism)
- General immune system (humoral and cellular immunity)
- Respiratory tract secretions
- Upper respiratory tract which acts as a “filter” (nasal hair, mucus)
Describe the clinical features of acute bronchitis,
- Cough.
- Production of mucus, it may be streaked with blood.
- Fatigue.
- Shortness of breath.
Be aware of causes of recurrent pneumonia.
- Tumour, Foreign body? (Local Bronchial Obstruction)
- Bronchiectasis? (- Local Pulmonary Damage - )
- Cystic Fibrosis, COPD (generalised lung disease)
- Immunocompromised (HIV, other) Aspiration? (non respiratory disease related)
Understand the physiological changes to pulmonary gas exchange in respiratory tract infections.
• Normal PaO2 10.5– 13.5 kPa
• Normal PaCO2 4.8 – 6.0 kPa
•
Respiratory Failure:
• Type I PaO2 <8 kPa
- (PaCO2 normal or low)
• Generally occurs as a result of failure of gas exchange in a part or all of the lungs
• Type II PaCO2 >6.5 kPa
- (PaO2 usually low)
• Failure to get rid of CO2
• Failure of airin and out of lungs- a failure of ventilation, not gas exchange.
-describe what Macrophage-mucociliary escalator system (main mechanism) to defend against rep tract infections?
o ALVEOLAR MACROPHAGES
(monitor and digest foreign materials)
o MUCOCILIARY ESCALATOR
(moves carpet of mucus from lower region of lungs to the throat- failure of this mechanism leads to infection)
Failure is caused by cold air, no epithelium
Can be wiped out by viral infections
o COUGH REFLEX (expirate whatever we have coughed up or normally swallow it)
describe
lobar pneumonia.
-lower respiratory tract infection
It is one of the two anatomic classifications of pneumonia (the other being bronchopneumonia).
o Classic infection from primary pathogens in young fit patients and catch it outside in the community.
- vigorous inflammatory response. Aform of pneumonia characterized by inflammatory exudate within the intra-alveolar space resulting in consolidation that affects a large and continuous area of the lobe of a lung
o may fill the entire lobe of a lung until the infection can spread no further because it has reached the pleura of the lungs (hence the name lobar)
describe the pathogenesis of bronchopneumonia
o Bacterial infection which affects bronchioles and alveolated lung tissue around those bronchioles.
o Usually arises from COPD and the excess production of mucus.
o Often bilateral basal patchy opacfication, relating to the focal nature of the consolidation
the complications and consequences of lower respiratory tract infection.
Pneumonia… ->
- Pleurisy, pleural effusion, empyema
- Organisation
o Mass lesion
o COP (cryptogenic organising pneumonia)
o Constrictive bronchiolitis - Lung abscess
- Bronchiectasis
Complication- what is a lung abscess.
- Infection but also destruction and necrosis of the tissue which has been infected. Leads to the formation of cavities (more than 2 cm) containing necrotic debris or fluid.
- Staph aureus in particular is known to cause lung abscess
Caused by…
- Obstructed bronchus -> Tumour
- Aspiration
- Particular organisms (Staph aureus, some pneumococci, Klebsiella)
- Metastatic in Pyaemia
- Necrotic lung (2 degree infection)
Recurrent lung infection- why are the defences failing?
- Local Bronchial Obstruction - Tumour, Foreign body?
- Local Pulmonary Damage - Bronchiectasis?
- Generalised Lung Disease - Cystic Fibrosis?, COPD?
- Non-Respiratory Disease - Immunocompromised (HIV, other) Aspiration?
complication- what is empyema
collection of pus in the pleural cavity,
usually associated with pneumonia
complication- what is bronchiectasis?
the permanent dilation of bronchi due to the destruction of the elastic and muscular components of the bronchial wall
