Lower Respiratory Tract Infections Flashcards
What are the predisposing factors to LRTI?
- Loss or suppression of cough reflex / swallow
- e.g. stroke, coma, ventilation
- Ciliary defects e.g. PCD
- Mucus disorders e.g. CF
- Pulmonary oedema – fluid flooding alveoli
- Immunodeficiency: congenital or acquired (Multiple examples!)
- Macrophage function inhibition e.g. smoking
What are the different syndromes of LRTI?
- Bronchitis
- Bronchiolitis
- Pneumonia
What is acute bronchitis?
Inflammation & oedema of trachea and bronchi
What are the symptoms of acute bronchitis?
- Cough (typically dry), dyspnoea & tachypnoea
- Cough may be associated with retrosternal pain
What is the epidemiology of acute bronchitis?
Most frequent in winter, in children
What is the aetiology of acute bronchitis?
·Viruses are the usual cause (rhinovirus, coronavirus, adenovirus, influenza)
·Bacterial causes less common (H.influenzae, M.pneumoniae, B.pertussis)
How is the diagnosis of acute bronchitis performed?
–Diagnostic tests not indicated in mild presentations
–Vaccination & previous exposure history (e.g. influenza, B. pertussis) may exclude some organisms
–If needed, cultures of respiratory secretions may be helpful if looking for a specific cause, e.g. B. pertussis – but not routine
How is acute bronchitis treated?
–Supportive treatment for healthy patients
–Those with severe disease or co-morbidities may require oxygen therapy or respiratory support
–Antibiotics only if bacterial cause is suspected or found
What is the definition of chronic bronchitis?
Cough productive of sputum on most days during at least 3 months of 2 successive years (which cannot be attributed to an alternative cause).
What is the epidemiology of chronic bronchitis?
- Affects 10-25% of adult population
- Most common in men and >40yrs
- Associated with smoking, pollution, allergens
What are the features of chronic bronchitis?
- If airflow obstruction present on spirometry = COPD
- Inflammation & oedema of airways is mediated by exogenous irritants (rather than infective agents)
- Patients have acute exacerbations mediated by same infective pathogens as acute bronchitis
What is bronchiolitis?
Inflammation and oedema of bronchioles
What is the epidemiology of bronchiolitis?
- Primarily young children
- Peaks in winter and early spring, in infants 2-10 months
What are the symptoms of bronchiolitis?
Acute onset wheeze, cough, nasal discharge, respiratory distress (grunting, retractions, nasal flaring)
What is the aetiology of bronchiolitis?
•Most commonly caused by RSV (75% of cases)
- 80% children have evidence of previous RSV infection by 2yrs old
•Also caused by parainfluenza, adenovirus, influenza
How would you diagnose bronchiolitis?
- Chest x-ray
- Full blood count
- Microbiological diagnosis: usually nasopharyngeal aspirate of respiratory secretions sent for viral PCR
How would you treat bronchioltis
- Supportive: oxygen, feeding assistance
- No clear evidence to support steroids, bronchodilators, ribavirin
- Antibiotics only if complicated by bacterial infection
What is pneumonia?
Infection affecting the most distal airways and alveoli
What are the two types of pneumonia (according to distribution)?
- Bronchopneumonia
- Characteristic patchy distribution centred on inflamed bronchioles & bronchi then subsequent spread to surrounding alveoli
- Lobar pneumonia
- Affects a large part, or the entirety of a lobe
- 90% due to S.pneumoniae
What are the types of pneumonia according to acquisition?
- Community acquired pneumonia (CAP)
- Hospital acquired pneumonia (HAP)
- Pneumonia developing >48hrs after hospital admission
- Different causative organisms to CAP, especially if >5days after admission: enterobacteriaceae & Pseudomonas sp.
•Ventilator acquired pneumonia (VAP)
- Subgroup of HAP
- Pneumonia developing >48hrs after ET intubation & ventilation
•Aspiration pneumonia
- Subgroup of HAP
- Pneumonia resulting for the abnormal entry of fluids e.g. food, drinks, stomach contents, etc. into the lower respiratory tract
- Patient usually has impaired swallow mechanism
What is the epidemiology of CAP?
- Incidence of 1 per 100 people per year (common!)
- 20-40% cases require hospital admission
- Peak age 50-70 years
- Peak onset midwinter to early spring
- Acquisition of organisms:
- Person-to-person or from a person’s existing commensals (S.pneumoniae, H.influenzae)
- From the environment (L. pneumophilia)
- From animals (C.psittaci)
What organisms cause ‘typical’ pneumonia?
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Staphylococcus aureus
Klebsiella pneumoniae
What organisms cause ‘atypical’ pneumonia?
Mycoplasma pneumoniae
Legionella pneumophilia
Chlamydophila pneumoniae
Chlamydophila psittaci
Coxiella burnetii
What are the signs and symptoms of CAP?
•Symptoms
–Usually rapid onset
–Fever / chills
–Productive cough
–Mucopurulent sputum
–Pleuritic chest pain
–General malaise: fatigue, anorexia
•Signs
–Tachypnoea, tachycardia, hypotension
–Examination findings consistent with consolidation:
- Dull to percuss
- Reduced air entry, bronchial breathing
