Lower Respiratory Tract infections Flashcards
What are the 4 main categories of LRTIs and where do they affect?
1) Tracheitis (trachea)
2) Bronchitis (Bronchi or bronchioles)
3) Pneumonia (lung)
4) Abscesses (lung)
What are the 3 main types of bronchitis?
1) Acute bronchitis
2) Chronic bronchitis
3) Bronchiolitis
What are the 4 main types of pneumonia?
1) Community aquired (CAP)
2) Hospital aquired (HAP)
3) Ventilator aquired (VAP)
4) Aspiration pneumonia
Give the 6 main predisposing factors for LRTIs?
1) Loss or suppression of cough reflex/swallow eg. stroke, coma ventilation
2) Ciliary defects eg. primary ciliary dyskinesia
3) Mucous disorders eg. CF
4) Pulmonary oedema - fluid flooding alveoli, provides good environment for infection eg. congestive HF
5) Immunodeficiency: congenital or aquired
6) Macrophage function inhibition eg. Smoking
What 2 main types of organisms cause LRTIs?
Bacteria and Viruses
Do fungi commonly cause LRTIs?
Not in healthy people
Fungi only tend to cause LRTIs in immunosuppressed patients
Which 8 bacteria commonly cause LRTIs?
1) Strep pneumoniae
2) Haemophilus influenxa
3) Staph aureus
4) Klebsiella pneumoniae
5) Mycoplasma pneumoniae
6) Chlamydophilia pneumoniae
7) Legionella pneumophilia
8) Mycobacterium TB
Which 4 viruses commonly cause LRTIs?
1) Influenza
2) Parainfluenza
3) Respiratory syncitial virus
4) Adenovirus
What 3 fungi can cause LRTIs, normally in immunocomprimised patients?
1) Aspergillus sp.
2) Candida sp.
3) Pneumocystitis jiroveci
What is acute bronchitis?
Inflammation and oedema of trachea and bronchi - mediated by an infective cause
What are the 4 common symptoms of acute bronchitis?
1) Cough (typically dry)
2) Dyspnoea
3) Tachypnoea
4) Cough may be associated with retrosternal pain (due to inflammation)
When does acute bronchitis most commonly occur and in who?
Most frequent in winter, commonly in children
What are the usual cause of acute bronchitis?
Viruses - bacterial causes are less common (h. influenza, m. pneumoniae and B. pertussis)
What procedures are usually involved in the diagnosis of acute bronchitis?
- Diagnostic tests are not indicated in mild presentations
- Vaccination and previous infection history can help determine the organism causing the infection
- If needed can do cultures of respiratory secretions to look for specific cause although this is uncommon
What is the treatment for acute bronchitis?
- Supportive for healthy patients
- People with severe disease or co-morbidities may need O2 therapy or even ventilation
- Abx would only be used if bacterial cause is found
What is the definition of chronic bronchitis?
Cough production of sputum on most days for 3 months if 2 successive years, which cannot be attributed to an alternative cause
In what group is chronic bronchitis most common?
Males >40
What are the main 3 risk factors for chronic bronchitis?
1) Smoking
2) Pollution
3) Antigens
Other than the length of symptoms what is the main difference in pathology between chronic and acute bronchitis?
The inflammation and oedema in chronic bronchitis is mediated by exogenous irritants rather than infective agents
But patients with chronic bronchitis can have exacerbations mediated by the same pathogens which cause acute bronchitis
Bronchiolitis commonly occurs in which group of patients?
Infants 2-10 months
What is bronchiolitis?
Inflammation and oedema of the bronchioles
What is the most common cause of bronchiolitis?
Respiratory syncitial virus (75% of cases) but can also be caused by parainfluenza, adenovirus and influenza
What are the 4 main symptoms of bronchiolitis?
1) Acute onset wheeze
2) Cough
3) Nasal discharge
4) Respiratory distress (grunting, retractions, nasal flaring)
What 3 procedures would be involved in a diagnosis of bronchiolitis?
1) Chest x-ray
2) Full blood count
3) Microbiological diagnosis - Viral PCR of nasopharyngeal aspirate
What is the treatment for bronchiolitis?
Supportive: O2, feeding assistance
No clear evidence to support steroids or other bronchodilators
Only use Abx if complicated by bacterial infection
What is pneumonia?
Infection affecting the most distal airways and alveoli with the formation of inflammatory exudate (which fills the alveoli)
What are the 2 anatomical patterns of pneumonia, how is each characterised?
1) Bronchopneumonia - patchy distribution centred on inflamed bronchioles and bronchi the subsequent spreading to surrounding alveoli (nb. may be bilateral)
2) Lobar pneumonia - affects large part or all of lobe, clear, ‘straight line’ demarkation on x-ray with homogenous appearance
90% of lobar pneumonias are caused by what bacteria?
Strep Pneumoniae
How is hospital aquired pneumonia defined, what are the 2 common causative organisms?
Pneumonia developing 48 hours after hospital admission
Different causative organisms to CAP - enterobacteriacae and pseudomonas
What are the 2 sub-groups of HAP?
1) Ventilator acquired pneumonia
2) Aspiration pneumonia (although this could happen in the community)
What is ventilator acquired pneumonia?
Pneumonia developing >48 hours after ET intubation and ventilation
What is aspiration pneumonia?
Pneumonia resulting from the abnormal entry of fluids eg. food, drink, stomach contents etc. into the lower respiratory tract - patient usually has impaired swallow mechanism
What percentage of CAP require hospital admission, how common is it?
1 in 100 people
20-40% require hospital admission
What is the peak age of CAP?
50-70 years
In what 3 ways can the pneumonia causing organism sin CAP be acquired - give examples of organisms?
1) Person to person or from person existing commensals - S. pneumonia and h. influenza
2) From the environment (Legionella. pneumonia)
3) From animals (C. psittaci)
What does atypical pneumonia traditionally refer to?
Traditionally described cases which failed to respond to penicillin or sulpha drugs and no organism could be identified, now recognised to be caused by atypical organisms
Name 5 typical pneumonia causing organisms?
1) Strep pneumonia
2) H influenza
3) Moraxella catarrhalis
4) Staph aureus
5) Klebsiella pneumonia
Name 5 atypical pneumonia causing organisms?
1) Mycoplasma pneumonia
2) Legionella pneumonia
3) Chlamydia psittaci
4) Chlamydia pneumonia
5) Coxiella burnetii
What are the 6 main symptoms of bacterial pneumonia?
1) Usually rapid onset
2) Fever/chills
3) Productive cough (blood or sputum)
4) Mucopurulent sputum
5) Pleuritic chest pain
6) General malaise: fatigue, anorexia
What are the 4 main clinical signs of bacterial pneumonia?
1) Tachypnoea
2) Tachycardia
3) Hypotension
4) Examination findings consistent with consolidation: dull to percuss, reduced air entry and bronchial breathing
The atypical pneumonia mycoplasma pneumonia is commonest at what time of year and in who?
When: autumn epidemics every 4-8 years
Who: children and young adults
What is the main symptom, method of microbial diagnosis and 4 rare complications of the atypical organism mycoplasma pneumonia?
Main symptom: cough
Diagnosis: Serology (looking for IgG in serum) as difficult to culture
Rare complications: pericarditis, arthritis, Guillain-Barre, peripheral neuropathy
What are outbreaks of the atypical pneumonia legionella pneumophilia associated with?
Colonises water systems so outbreaks associated with showers, air conditioner, humidifiers
What are the 7 main symptoms of legionella pneumonia and what would bloods show?
1) Vomiting
2) Diarrhoea
3) Confusion
4) High fevers
5) Rigors
6) Cough: dry initially becoming productive
7) Dyspnoea
Bloods: deranged LFTs, SIADH (low sodium)
What percentage of CAP in adults is attributable to the atypical pneumonia chlamydophilia pneumonia and who is the incidence highest in?
3-10%
Incidence highest in the elderly who may experience more severe disease
What does the atypical pneumonia chlamydia pneumonia cause in adolescents and young adults?
Mild pneumonia or bronchitis in adolescents and young adults
What risk factor is the atypical pneumonia chlamydophilia psittaci associated with?
Exposure to birds
You would consider the atypical pneumonia chlamydophilia psittaci in patients with what 3 things?
1) Pneumonia
2) Splenomegaly
3) History of bird exposure
Other than symptoms of pneumonia what 4 other symptoms/conditions is chlamydophilia psittaci associated with?
1) Rash
2) Hepatitis
3) Haemolytic anaemia
4) Reactive arthritis
In which patients does primary viral pneumonia occur more commonly in?
Patients with pre-existing cardiac and lung disease
How does influenza typically present? 5
Uncomplicated disease
1) Fever
2) Headache
3) Myalgia
4) Dry cough
5) Sore throat
What are the 3 main symptoms of primary viral pneumonia?
1) Cough
2) Breathlessness
3) Cyanosis
Primary viral pneumonia could lead to what other infection?
Secondary bacterial pneumonia after and initial period of improvement, likely caused by s. pneumonia, h. influenza, staph aureus
How is primary viral pneumonia diagnosed?
Viral antigen detection in respiratory samples using PCR
What 3 non-microbial investigations may be carried out in CAP?
1) Routine obs: BP, pulse, oximetry
2) Bloods: including FBC/U&E/CRP/LFTs
3) CXR
What microbiological investigations are recommended by BTS for all cases of moderate-severe CAP?
1) Sputum gram stain and culture
2) Blood culture
3) Pneumococcal urinary antigen
4) Legionella urinary antigen
5) PCR or serology for viral pathogens, mycoplasma pneumonia, chalmydophilia sp.
For what 5 reasons is it useful to establish a microbiological diagnosis?
1) Optimise Abx selection
2) Limit the use of broad spectrum Abx
3) Identify organisms of epidemiological significance
4) Identify antibiotic resistance and monitor trends
5) Identify new or emerging pathogens
What 5 parameters is a CURB score based on and what does it tell you?
1) Confusion
2) Urea >7mmol/L
3) Resp rate >30
4) BP 65
Get a score of 1 for each that applies
Tells you the severity and where to treat (home, hospital, ITU)
How is CAP managed?
In the same way as a septic patient
Airways - make sure patent
Breathing - give O2 if needed
Circulation - BP and rate, gain IV access and give fluids if needed, catheter to monitor urinary output
Then prompt empirical Abx therapy - if indicated at all
In what 2 ways do we aim to prevent LRTIs?
1) Pneumococcal vaccination (s. pneumonia)
Those with chronic heart, lung and kidney disease and splenectomy
2) Influenza vaccine for vulnerable groups (elderly and co-morbidities)
