Introduction
Classification
The majority of patients develop pneumonia within the community, i.e. outside of hospital and these patients are said to have community-acquired pneumonia (CAP). Patients who develop pneumonia within hospitals are said to have hospital-acquired pneumonia. The distinction is important as the causative organisms vary and hence first-line antibiotic guidelines are also different.
Atypical pneumonia
Some type of infections give rise to atypical pneumonias. These are termed atypical and may have the following features:
- symptoms may be subacute or less severe hence the term 'walking pneumonia'
- absence of lobar consolidation on chest x-ray
- not detectable on Gram stain
- lack of response to penicillin antibiotics
Examples of atypical pneumonias include:
- Legionella pneumonia
- Mycoplasma pneumonia
- Q fever secondary to Coxiella burnetii
- psittacosis secondary to Chlamydophila psittaci
Epidemiology
- Incidence: 500.00 cases per 100,000 person-years
- Peak incidence: 70+ years
- Sex ratio: 1:1
Condition | Relative incidence |
---|---|
Viral upper respiratory tract infections | 60.00 |
Acute bronchitis | 8.80 |
Musculoskeletal chest pain | 2.00 |
Acute exacerbation of COPD | 1.50 |
Pneumonia | 1 |
<1 | 1-5 | 6+ | 16+ | 30+ | 40+ | 50+ | 60+ | 70+ | 80+ |
Aetiology
- Aged under 5 or over 65-years-old
- Smoking cigarettes
- Recent viral respiratory tract infection
- Chronic respiratory diseases: e.g. cystic fibrosis and COPD
- Immunosuppression: e.g. cytotoxic drug therapy and HIV
- Patients at risk of aspiration: e.g. those with neurological diseases such as Parkinson's disease or those with oesophageal obstruction
- IV drug users
- Other non-respiratory co-morbidities: e.g. diabetes and cardiovascular disease
Pathophysiology
- viral
- fungal (e.g. Pneumocystis jiroveci)
Once a pathogen has entered the lower respiratory tract an inflammatory cascade begins. Neutrophils migrate to the infected alveoli and release cytokines which activate an immune response and induce fever. This process leads to an accumulation of fluid and pus within the alveoli that impairs gaseous exchange, leading to a hypoxic state which is characteristic of pneumonia.
Clinical features
Symptoms:
- A cough with purulent sputum (rust coloured/bloodstained)
- Dyspnoea
- Chest pain (may be pleuritic in nature)
- Fever
- Malaise
Signs:
- Signs of systemic infection: High temperature, tachycardia, hypotension, confusion
- Tachypnoea
- Low oxygen saturation (below 95% or below 88% in patients with COPD)
- On auscultation, there may be reduced breath sounds, bronchial breathing, and crepitations/crackles
- Dullness on percussion (fluid)
Management
NICE recommends that patients should initially be assessed in primary care using the CRB65 criteria:
Criterion | Marker |
---|---|
C | Confusion (abbreviated mental test score <= 8/10) |
R | Respiration rate >= 30/min |
B | Blood pressure: systolic <= 90 mmHg and/or diastolic <= 60 mmHg |
65 | Aged >= 65 years |
Patients are stratified for risk of death as follows:
- 0: low risk (less than 1% mortality risk)
- 1 or 2: intermediate risk (1-10% mortality risk)
- 3 or 4: high risk (more than 10% mortality risk).
NICE recommend, in conjunction with clinical judgement:
- home-based care for patients with a CRB65 score of 0
- hospital assessment for all other patients, particularly those with a CRB65 score of 2 or more.
NICE also mention point-of-care CRP test. This is currently not widely available but they make the following recommendation with reference to the use of antibiotic therapy:
- CRP < 20 mg/L - do not routinely offer antibiotic therapy
- CRP 20 - 100 mg/L - consider a delayed antibiotic prescription
- CRP > 100 mg/L - offer antibiotic therapy
Secondary care setting
Note that in hospital, once blood tests are available the CURB65, rather than the CRB65, can be used. This adds an extra criterion of urea > 7 mmol/L:
Criterion | Marker |
---|---|
C | Confusion (abbreviated mental test score <= 8/10) |
U | urea > 7 mmol/L |
R | Respiration rate >= 30/min |
B | Blood pressure: systolic <= 90 mmHg and/or diastolic <= 60 mmHg |
65 | Aged >= 65 years |
NICE recommend, in conjunction with clinical judgement:
- consider home-based care for patients with a CURB65 score of 0 or 1 - low risk (less than 3% mortality risk)
- consider hospital-based care for patients with a CURB65 score of 2 or more - intermediate risk (3-15% mortality risk)
- consider intensive care assessment for patients with a CURB65 score of 3 or more - high risk (more than 15% mortality risk)
Investigations
- chest x-ray
- in intermediate or high-risk patients NICE recommend blood and sputum cultures, pneumococcal and legionella urinary antigen tests
- CRP monitoring is recommend for admitted patients to help determine response to treatment
Management of low-severity community acquired pneumonia
- amoxicillin is first-line
- if penicillin allergic then use a macrolide or tetracycline
- NICE now recommend a 5 day course of antibiotics for patients with low severity community acquired pneumonia
Management of moderate and high-severity community acquired pneumonia
- dual antibiotic therapy is recommended with amoxicillin and a macrolide
- a 7-10 day course is recommended
- NICE recommend considering a beta-lactamase stable penicillin such as co-amoxiclav, ceftriaxone or piperacillin with tazobactam and a macrolide in high-severity community acquired pneumonia
Complications
- sepsis
- lung abscesses
- pleural effusion
- parapneumonic
- empyema
- acute respiratory distress syndrome
Prognosis
NICE recommend that patients are not routinely discharged if in the past 24 hours they have had 2 or more of the following findings:
- temperature higher than 37.5°C
- respiratory rate 24 breaths per minute or more
- heart rate over 100 beats per minute
- systolic blood pressure 90 mmHg or less
- oxygen saturation under 90% on room air
- abnormal mental status
- inability to eat without assistance.
They also recommend delaying discharge if the temperature is higher than 37.5°C.
NICE recommend that the following information is given to patients with pneumonia in terms of how quickly their symptoms should symptoms should resolve:
Time | Progress |
---|---|
1 week | Fever should have resolved |
4 weeks | Chest pain and sputum production should have substantially reduced |
6 weeks | Cough and breathlessness should have substantially reduced |
3 months | Most symptoms should have resolved but fatigue may still be present |
6 months | Most people will feel back to normal. |
TYPES
Legionella pneumoniaMycoplasma pneumonia
Psittacosis
Q fever