Pathology of Respiratory Tract Infection Flashcards
RTIs can be primary, facultative or opportunistic. What is meant by these terms?
Primary: patient well but has interacted with the right organism to make them unwell
Facultative: relatively healthy patient but with a risk factor to RTI
Opportunistic: only really infects immunocompromised indivdiuals
Give e.g.s of upper RTIs
Coryza (common cold) Sore throat syndromes Acute laryngotracheobronchitis (croup) Laryngitis Sinusitis Acute epiglottitis
What causes acute epiglottitis?
Hib
Who does epiglottitis primarily affect?
Was seen as a disease of childhood, but now more common in adults due to immunisation
What are features of acute epiglottitis?
Rapid onset
High temperature, generally unwell
Stridor
Drooling
What sign can be seen on CXR in acute epiglottitis?
A lateral view may show swelling of epiglottis - thumb sign
Give e.g.s of LRTIs
Bronchitis
Bronchiolitis
Pneumonia
What defense mechanisms does the respiratory tract have against infections?
Mucociliary escalator + macrophages
Humoural and cellular immunity - antibac secretions
URT acts as a filter (e.g. nose filters out large particles, complex space + large SA –> tuberulent flow = more particles trapped)
Nasal hair
What is the mucociliary escalator?
Macrophages can’t always digest debris so they move to the escalator to be cleared
What happens when the mucociliary escalator fails?
Secretions/FBs are retained in the lung –> secondary bacterial infection
When does the mucociliary escalator fail?
Tends to happen in a viral LRTI (viruses destroy the resp epithelial layer = deficient cilia)
What are 5 classifications of pneumonia based on aetiology?
Community acquired Hospital acquired/nosocomial (more aggressive + more likely to be resistant to antibiotics) Atypical Aspiration Recurrent
What causes an aspiration pneumonia?
Aspiration of gastric contents in the context of abnormal vomiting
What does aspiration pneumonia often result from?
Incompetent swallowing mechanism, e.g. in neurological disease/injury, like stroke or intoxication
What are iatrogenic causes of aspiration penumonia?
Intubation
What are RFs for developing an aspiration pneumonia?
Poor dental hygiene Swallowing difficulties Prolonged hospitalisation/surgical procedures Impaired consciousness Impaired mucociliary clearance
What bacteria most commonly are implicated in an aspiration pneumonia?
Streptococcus pneumoniae
Staphylococcus aureus
Haemophilus influenzae
Pseudomonas aeruginosa
What are different patterns of pneumonia?
Bronchopneumonia (diffuse)
Segmental
Lobar
Hypostatic (accumulation of secretions/fluid in lower bits of lungs –> increased risk of infection) - usually due to cardiac failure
Where does bronchial pneumonia affect?
Patches throughout both lungs (bronchioles + adjacent areas of lung)
What things commonly cause a bronchopneumonia?
AECOPD
Bacterial pneumonia etc.