Pathology of Respiratory Tract Infections Flashcards
Name some examples of URTIs
Laryngitis Coryza (common cold) Sore throat symptoms Acute epiglottitis Sinusitis Acute larygotracheobronchitis (croup)
What is the respiratory tract defence?
Macrophage-mucociliary escalator system
General immune system
Resp. tract secretions
Upper resp. tract as ‘filter’
Failure in any of these increases risk of infection
What is the mechanism of the macrophage-mucociliary escalator system?
Clearance by:
Alveolar macrophage phagocytosis
Leave lung through ciliary escalator or cough reflex
Keeps lower tract sterile
What happens if escalator is damaged?
If surface is damaged then it is unable to remove mucous. Epithelium is damaged by bacteria
What are the possible outcomes of Pneumonia?
Pleurisy, pleural effusion or empyema - if spread to pleura
Organisation (fibrosis due to prolonged inflammation)
Lung abscess - due to necrosis
Bronchiectasis
Name some examples of LRTIs
Bronchiolitis
Bronchitis
Pneumonia
Pathology of bronchiectasis
Dilation of bronchi due to: Severe infective episode Recurrent infections Proximal bronchial obstruction Lung parenchyma destruction
Symptoms of Bronchiectasis
Cough Purulent foul sputum (contains pus) Haemoptysis Coarse crackles Clubbing
Normal PaO2 and PaCO2 levels
PaO2: 10.5-13.5 kPa
PaCO2: 4.8-6 kPa
Abnormal PaO2 and PaCO2 levels in respiratory failure
Type I: PaO2 < 8 kPa
Type II: PaCO2 > 6.5 kPa
What are 4 abnormal state associated with hypoxaemia?
V/Q mismatch
Diffusion impairment
Alveolar hypoventilation
Shunt
Pathology of Cor Pulmonale
Abnormal enlargement of the right side of the heart
Aetiology of Cor Pulmonale
Pulmonary vasoconstriction
Loss of capillary bed
Secondary polycythaemia
Treatment of hypoxaemia
Responds well to small increase in FlO2 (fraction of inspired air which is oxygen)
Explain shunt and treatment
Blood passing from R to L heart without contacting ventilated alveoli
Responds poorly to increase FlO2
What 3 factors that determine a microorganisms ability to cause infection?
Microorganism pathogenicity
Capacity to resist infection
Population at risk
What type of Microorganism pathogenicities are there?
Primary
Facultative (microorganism that requires some help to be able to grow)
Opportunistic
What determines an individual’s capacity to resist infection?
State of host defence mechanism
Age of patient
What are the two routes of exit in the lung?
Clearance via the much-ciliary escalator
Interstitial pathway via lymph to the lymph nodes
What is a cytopathic effect?
Structural changes in host cells that are caused by viruses i.e. influenza destroys normal respiratory epithelium
What are the etiological classifications of pneumonia?
Community Acquired Hospital Acquired (Nosocomial) In the Immunocompromised Atypical Aspiration Recurrent
What are 6 different anatomical patterns of pneumonia?
Bronchopneumonia Segmental Lobar Hypostatic Aspiration Obstructive, Retention, Endogenous Lipid
Describe the pattern go bronchopneumonia
Bilateral basal patchy opacification, relating to the focal nature of the consolidation
What is Cryptogenic organizing pneumonia (COP)?
Rare condition affecting the bronchioles and alveoli causing inflammation and stiffening of connective tissue
What 3 organisms can cause a lung abscess?
Staph aureus
Pneumococci
Klebsiella
What is pyaemia?
Blood poisoning (septicaemia) caused by the spread in the bloodstream of pus-forming bacteria released from an abscess
What investigations do you use for bronchiectasis?
Thin section CT
What is the treatment for bronchiectasis?
Postural drainage
Antibiotics
Surgery
What could a local bronchial obstruction be caused by?
Tumour
Foreign body
What could local pulmonary damage be caused by?
Bronchiectasis
What could general lung disease be caused by?
Cystic fibrosis
COPD
What are some non-respiratory disease?
Immunocompromised (i.e. HIV)
Aspiration
What are causes of aspiration pneumonia?
Vomiting Oesophageal lesion Obstetric anaesthesia Neuromuscular disorders Sedation
Describe the organisms that cause opportunistic infections
Organisms are not capable of producing disease in patients with intact lung defects - opportunistic pathogens
What does air flow depend on?
Pressure difference
What changes occur to pulmonary vasculature changes in hypoxia?
Pulmonary arteriolar constriction due to shunt
What pathological conditions can cause V/Q mismatch?
Bronchitis
Bronchopneumonia
Both cause inflammation causes decrease in ventilation
What pathological condition can cause shunt?
Severe bronchopneumonia - no ventilation
Lobar pattern with large areas of consolidation (less diffusion)
