Lower respiratory disease Flashcards
What are the 4 causes of pneumonia?
Community acquired
Hospital acquired
Ventilator acquired
Aspiration
What are some 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
Macrophage function inhibition e.g. smoking
What are some bacteria that cause LRTIs?
- Streptococcus pneumoniae
- Haemophilus influenzae
- Staphylococcus aureus
- Klebsiella pneumonia
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Legionella pneumophila
- Mycobacterium tuberculosis
What are some viruses that cause LRTIs?
- Influenza
- Parainfluenza
- Respiratory syncytial virus
- Adenovirus
What are some fungi that cause LRTIs?
- Aspergillus sp.
- Candida sp.
- Pneumocystitis jiroveci
What are the different syndromes of LRTI?
bronchitis, bronchiolitis, pneumonia
What is acute bronchitis?
Inflammation & oedema of trachea and bronchi
Cough (typically dry), dyspnoea & tachypnoea
Cough may be associated with retrosternal pain
What are the causes of bronchitis?
Viruses are the usual cause (rhinovirus, coronavirus, adenovirus, influenza)
Bacterial causes less common (H.influenzae, M.pneumoniae, B.pertussis)
How is acute bronchitis diagnosed?
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 chronic bronchitis and who does it generally affect?
Cough productive of sputum on most days during at least 3 months of 2 successive years (which cannot be attributed to an alternative cause)
Affects 10-25% of adult population
Most common in men and >40yrs
Associated with smoking, pollution, allergens
What is the pathology behind chronic bronchitis?
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
If airflow obstruction present on spirometry = COPD
What is bronchiolitis and hat are the symptoms?
Inflammation and oedema of bronchioles
Acute onset wheeze, cough, nasal discharge, respiratory distress (grunting, retractions, nasal flaring)
Who does bronchiolitis typically affect?
Peaks in winter and early spring, in infants 2-10 months
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 is bronchiolitis diagnosed?
Chest x-ray
Full blood count
Microbiological diagnosis: usually nasopharyngeal aspirate of respiratory secretions sent for viral PCR
How is bronchiolitis treated?
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
Formation of inflammatory exudate
What are the two anatomical patterns of pneumonia?
Bronchopneumonia and Lobar pneumonia
What are the features of bronchopneumonia?
Characteristic patchy distribution centred on inflamed bronchioles & bronchi then subsequent spread to surrounding alveoli
What are the features of lobar pneumonia?
Affects a large part, or the entirety of a lobe
90% due to S.pneumoniae
How do you define hospital acquired pneumonia (HAP)?
Pneumonia developing >48hrs after hospital admission
Different causative organisms to CAP, especially if >5days after admission: enterobacteriaceae & Pseudomonas sp.
How do you define ventilator acquired pneumonia (VAP)?
Subgroup of HAP
Pneumonia developing >48hrs after ET intubation & ventilation
How do you define 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)
How are the bacterial causes of CAP divided?
Bacterial causes often divided into ‘typical’ and ‘atypical’
‘Atypical pneumonia’ traditionally described cases which failed to respond to penicillin or sulpha drugs and no organism could be identified
Now this is recognised to be caused by ‘atypical’ organisms – still considered in a separate group as clinical presentation and treatment is slightly different
What are typical organisms that cause CAP?
Streptococcus pneumoniae Haemophilus influenzae Moraxella catarrhalis Staphylococcus aureus Klebsiella pneumoniae
What are atypical organisms that cause CAP?
Mycoplasma pneumoniae Legionella pneumophilia Chlamydophila pneumoniae Chlamydophila psittaci Coxiella burnetii
What are the symptoms of pneumonia?
Usually rapid onset Fever / chills Productive cough Mucopurulent sputum Pleuritic chest pain General malaise: fatigue, anorexia
What are the signs of pneumonia?
Tachypnoea, tachycardia, hypotension
Examination findings consistent with consolidation:
Dull to percuss
Reduced air entry, bronchial breathing
What is the clinical presentation of pneumonia caused by mycoplasma pneumoniae?
Autumn epidemics every 4-8 years
Commonest in children & young adults
Main symptom is cough
Diagnosis: serology (difficult to culture)
Rare complications: pericarditis, arthritis, Guillain-Barre, peripheral neuropathy
What is the clinical presentation of pneumonia caused by legionella pneumophilia?
Colonises water piping systems
Outbreaks associated with showers, air conditioning units, humidifiers
High fevers, rigors, cough: dry initially becoming productive, dyspnoea, vomiting, diarrhoea, confusion
Bloods: deranged LFTs, SIADH (low sodium)
What is the clinical presentation of pneumonia caused by chlamydophila pneumoniae?
3-10% of CAP cases in adults
Causes mild pneumonia or bronchitis in adolescents & young adults
Incidence highest in the elderly – may experience more severe disease
What is the clinical presentation of pneumonia caused by Chlamoydophila psittaci?
Associated with exposure to birds
Consider in those with pneumonia, splenomegaly & history of bird exposure
May also have rash, hepatitis, haemolytic anaemia, reactive arthritis
What is the clinical presentation of influenza?
Fever, headache, myalgia, dry cough, sore throat
Convalescence takes 2-3 weeks
What is the clinical presentation of primary viral pneumonia?
Primary viral pneumonia occurs more commonly in patients with pre-existing cardiac & lung disorders
Cough, breathlessness, cyanosis
Secondary bacterial pneumonia then may develop after initial period of improvement:
S.pneumoniae, H.influenzae, S.aureus
How is primary viral pneumonia diagnosed?
viral antigen detection in respiratory samples using PCR
What are some non-microbiological investigations for CAP?
Routine observations: BP / pulse / oximetry
Bloods: including FBC / U&E / CRP / LFTs
Chest X-ray
What are the microbiological investigations for inpatients with CAP?
Sputum Gram stain & culture
Blood culture
Pneumococcal urinary antigen
Legionella urinary antigen
PCR or serology for:
- viral pathogens e.g. influenza (PCR of respiratory samples)
- Mycoplasma pneumoniae (PCR of respiratory samples preferable, complement fixation: interpret with caution)
- Chlamydophila sp. (complement fixation test most widely available – on blood)
Why should we bother establishing a diagnosis?
Optimise antibiotic selection
Limit the use of broad spectrum agents
Identify organisms of epidemiological significance
Identify antibiotic resistance and monitor trends
Identify new or emerging pathogens
What schemes are in place for prevention of LRTIs?
Pneumococcal vaccination (S. pneumoniae)
- Patients with chronic heart, lung and kidney disease
- Patients with splenectomy
- May repeat after 5 years in certain populations
Influenza vaccination for vulnerable groups (annually)
- Over 65s
- Chronic disease, multiple co-morbidities
How is disease severity of CAP assessed?
CURB65 score for pneumonia
Confusion
Urea
Resp rate
BP
Age
(If 2 or more of these factors is a problem, admit to hospital)
