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Respiratory Infection26
https://t.me/med1917
4. PATHOPHYSIOLOGY
Inflammation of the bronchi may occur in response to a viral or bacterial
•
infective trigger, or an environmental irritant.
is is associated with increased mucus production within the bronchi.
•
• is is responsible for the characteristic productive cough.
5. CLINICAL FEATURES
Symptoms:
•
• Cough: initially unproductive, later productive of yellow/green sputum.
• Discomfort behind sternum.
• Chest tightness.
• Wheeze.
• Shortness of breath.
Signs:
•
• On auscultation: wheeze.
6. INVESTIGATIONS
Sputum: culture and microscopy.
•
Chest X-ray: consider to exclude pneumonia.
•
7. DIFFERENTIAL DIAGNOSIS
Influenza
•
Pharyngitis
•
Sinusitis.
•
8. MANAGEMENT
Often resolves with rest and increased fluid intake.
•
Symptomatic treatment: analgesia, antipyretics.
•
Antibiotics such as amoxicillin may be prescribed in those with increased
•
risk of developing subsequent pneumonia.
9. COMPLICATIONS
neicid MeyrotarpiseR
Pneumonia may occur if the infection spreads distally through the airways.
•
10. PROGNOSIS
In healthy individuals, resolution within 4–8 days.
•
Risk of complications or a longer duration of illness is increased in those with
•
pre-existing lung disease and in smokers.
2.4 Community-Acquired Pneumonia (CAP)
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2.4 COMMUNITY-ACQUIRED PNEUMONIA
(CAP)
1. DEFINITION
Pneumonia is a disease that leads to consolidation of the lung parenchyma.
•
• It is characterised by acute inflammation in alveoli, as well as the respi-
ratory and terminal bronchioles, with an infiltration of neutrophils.
e consolidation is either in bronchopulmonary segments (bronchopneu-
•
monia) or involves an entire lobe (lobar pneumonia; see Figures 2.1
and 2.2).
ere are also non-infectious idiopathic pneumonias (such as usual interstitial
•
pneumonia [UIP] and cryptogenic organising pneumonia [COP]), which are
considered in
Chapter 12.
27
Figure 2.1 Chest X-ray of patient with right-sided upper lobe pneumonia; opacity is
seen in the right upper lobe, indicating lobar consolidation.
Respiratory Medicine
Respiratory Infection28
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Figure 2.2 CT chest of a patient with right-sided upper lobe pneumonia.
2. EPIDEMIOLOGY
Community-acquired pneumonia has an incidence of 5–11 per 1,000
•
in the UK.
neicid MeyrotarpiseR
e rate of hospital admission is approximately 1 per 1,000 /year.
•
Pneumonia is the fifth leading cause of death in the UK.
•
3. AETIOLOGY AND RISK FACTORS
Pneumonia can be caused by a variety of organisms: bacterial, viral, fungal,
•
protozoal.
• Community-acquired pneumonia is most commonly caused by S. pneu-
moniae (see Table 2.1 for important causative pathogens).
Risk factors:
•
• Female (3:1 predominance).
• Young or elderly (<16 yrs or >65 yrs).
• Chronic heart or lung disease (e.g. COPD, CF, bronchiectasis).
2.4 Community-Acquired Pneumonia (CAP)
https://t.me/med1917
Table 2.1 Common pathogens causing community-acquired pneumonia.
COMMON
PATHOGENS FEATURES CASES (%)
Streptococcus pneumoniae High susceptibility to penicillin. 30–54%
Haemophilus influenzae Causative pathogen in young children 6–15%
and those with underlying lung
disease or immunodeficiency.
Mycoplasma pneumonia Cyclical epidemics in young adults 18%
every few years.
Legionella pneumophilia Found in stagnant humidified water. 2–7%
Sporadic outbreaks. High mortality
(30%). Associated with high fever,
rigors, myalgia, headache and ataxia.
Staphylococcus aureus Common in IV drug users, alcoholics 2%
and those with mitral valve disease.
Causes cavitating pneumonia.
• Smoking and environmental pollutants.
• Compromised immune system (e.g. HIV/AIDS, malignancy, splenectomy,
diabetes mellitus).
• Alcohol and drug abuse.
29
MICRO-facts
Atypical pneumonia is caused by less common organisms that are harder to
identify through standard microbiological tests (i.e. not Streptococcus pneu-
moniae, Haemophilus influenza or Moraxella catarrhalis). Examples include:
Mycoplasma pneumoniae
•
Legionella pneumophilia
•
Chlamydophilia pneumoniae
•
Chlamydophilia psittaci.
•
Atypical organisms are considered more likely to cause an unusual or
systemic presentation. An atypical organism is suggested if:
The pneumonia does not respond to penicillin.
•
There is no lobar consolidation.
•
There are extra-pulmonary symptoms.
•
There is absence of leucocytosis.
•
There is moderate or no sputum production.
•
There are few physical signs, compared to symptom profile.
•
Identifying an atypical cause can be important, as it may not respond to
standard first-line therapy.
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Respiratory Infection30
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4. PATHOPHYSIOLOGY
Majority of serious CAP are bacterial:
•
• Colonisation of upper airway by pathogen.
• Translocation of pathogen into lower airway.
• Infiltration of neutrophils: cytokine release.
• Inflammation and oedema.
• Consolidation.
• Resolution (+/− chronic damage and scarring) or death.
5. CLINICAL FEATURES
Symptoms:
•
• Cough, sometimes with haemoptysis.
• Sputum which is usually discoloured, although cough may be dry.
• Dyspnoea.
• Pleuritic chest pain.
• Referred abdominal pain.
• Vomiting.
• Confusion (cause of acute confusional state in elderly).
• Myalgia + arthralgia.
• Malaise.
Signs:
•
• Fever
• Tachycardia
• Tachypnoea
• Cyanosis
• Chest signs:
– ↓ Chest expansion
– Dullness on percussion
– ↑ Vocal/tactile fremitus
– Bronchial breathing
– Crepitations/crackles
– Whispering pectoriloquy/bronchophony
– ↓ Air entry.
6. INVESTIGATIONS
Full blood count (FBC) (with white cell differential).
•
U+Es (performed to assess CURB-65 score; see Table 2.2).
•
Chest X-ray.
•
Pulse oximetry (arterial blood gas may be required).
•
Sputum culture and Gram stain.
•
Point-of-care PCR for respiratory viruses (COVID-19/influenza).
•
Respiratory Medicine
Special tests: urinary legionella and pneumococcal antigen testing.
•
HIV testing: pneumonia often initial presentation.
•
2.4 Community-Acquired Pneumonia (CAP)
https://t.me/med1917
7. DIFFERENTIAL DIAGNOSIS
Tuberculosis.
•
Acute bronchitis.
•
Lung malignancy.
•
Aspiration of upper airway secretions, vomitus, or foreign body.
•
Bronchiectasis.
•
8. MANAGEMENT
Decision on whether to admit based on clinical judgment and by using the
•
CURB-65 score (see Table 2.2). Note that this score is only validated for
community-acquired pneumonia, not for other respiratory infections. It is a
predictor of mortality, with the higher the score, the higher the risk of death.
Table 2.2 CURB-65 community-acquired pneumonia prognostic score.
CURB65 PNEUMONIA TREATMENT SCORE
Confusion 1
Urea ≥7 mmol/L 1
Respiratory rate >30 1
Blood Pressure ≤ 90/60 mmHg 1
≥65 years old 1
Management algorithm
Manage as an outpatient 0–1
Admit to hospital (short-stay) 2
Admit to hospital + consider level 2 or 3 care setting 3+
Points
31
Antibiotic therapy: antibiotic therapy generally follows local treatment
•
guidelines and are often based on CURB-65 score. Typical oral regimes
(NICE and BTS guidance) are:
• Amoxicillin 500 mg TDS + clarithromycin 500 mg BD for 5 days.
• Suspected penicillin resistance: macrolide or doxycycline 100 mg BD
for 5 days.
• Aspiration pneumonia: co-amoxiclav.
If CURB-65 ≥3:
•
• Co-amoxiclav 1.2 g IV TDS with IV/oral clarithromycin 500 mg BD.
IV fluid replacement: if patient is hypotensive or dehydrated.
•
romboprophylaxis: if appropriate after risk assessment.
•
Analgesia: e.g. paracetamol.
•
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9. COMPLICATIONS
Respiratory failure.
•
Parapneumonic effusion.
•
Empyema (see Chapter 2 section 5).
•
Lung abscess.
•
Bronchiectasis.
•
10. PROGNOSIS
Most bacterial pneumonias with appropriate antibiotic treatment will
•
improve within a week.
X-ray changes should resolve within:
•
• 6 weeks in patients <60 yrs.
• 6 weeks + a week per decade past 60 in patients >60 yrs.
Mortality is about 1% , but rises to between 5.7 and 14% in the subpopula-
•
tion that are hospitalised with CAP.
Prevention:
•
• Smoking cessation
• Appropriate antibiotic prescribing
• Pneumococcal + influenza vaccinations.
MICRO-references
For more detail on the investigation and management of an adult
patient with community-acquired pneumonia, including use of the
CURB-65 score, the reader should access the British Thoracic Society
guidance:
www.brit-thoracic.org.uk/Portals/0/Clinical%20Information/Pneumonia/
Guidelines/CAPQuickRefGuide-web.pdf
MICRO-case
You are an SHO working in A&E. Ayoung woman brings in her grandfather, Alfred, a 72-year-old pensioner. She says that he has had a cough for
the last few days and has been generally unwell. However, she tells you
that over the last few hours he seems to have had problems breathing.
When you go to see him he is confused and is not orientated to place
or person. When you take his vital signs, he has a RR 29, BP
temperature 39°C and a pulse of 82. On examination of the chest you
note dullness on percussion at the left base, and on auscultation you hear
coarse crackles. When his blood results come back from the lab, his WCC
and CRP are raised, but his urea and glucose are normal. Achest X-ray
shows consolidation at the left lung base. You calculate
Respiratory Medicine
that his CURB-65 score is 2 and so decide that he should
115/ 65,
continued…
2.5 Hospital-Acquired Pneumonia (HAP)
https://t.me/med1917
33
continued…
cal antibiotics and send blood cultures and sputum cultures to the lab. He
is kept under close observation for any change in his clinical condition. He
deteriorates and his blood pressure drops to
35, at which point you ask for senior review and a decision is made that
he should be transferred to the critical care unit. His CURB-65 score at this
point is 4.
Key Points
Always try to get a collateral history e.g. from family/carer.
•
This is especially important if the patient is confused or has reduced
•
levels of consciousness.
Always calculate a CURB-65 score for a patient with suspected pneu-
•
monia: it can be used to guide management decisions.
Initially, this gentleman had a “moderate severity” score and would
•
need managing as an inpatient.
However, he deteriorates and now has a “high severity” score (4), so
•
senior review and transfer to ITU is indicated.
CURB-65 is also useful as a prognostic index (e.g. a score of 4 has
•
approximately a
Always frequently re-assess acutely ill patients.
•
Management decisions may need to be adjusted in line with the
•
patient’s clinical condition.
Always obtain a baseline CRP and WCC, as repeat measurements will
•
then allow assessment of the patient’s response to treatment.
Treatment failure or atypical changes on chest X-ray (e.g. cavitation)
•
may indicate an atypical organism.
Start empirical antibiotic therapy as soon as possible.
•
Always try to send blood and sputum cultures for MC&S.
•
This allows tailoring of future antibiotic therapy.
•
If possible, take samples before initiation of empirical antibiotic therapy.
•
be admitted as an inpatient. You start IV fluids and empiri-
88 / 50 and his RR is now
40% risk of mortality).
2.5 HOSPITAL-ACQUIRED PNEUMONIA (HAP)
1. DEFINITION
Hospital-acquired (nosocomial) pneumonia (HAP) refers to new consolidation.
•
• Onset is at least 48 hours after admission to hospital or within 6 weeks
of discharge.
• Higher morbidity and mortality than CAP.
2. EPIDEMIOLOGY
HAP occurs in 5–15 patients per 1,000 hospital admissions.
•
In the important subgroup of patients on mechanical ventilation this rises to
•
10- 25 episodes per 1,000 ventilator days.
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3. AETIOLOGY AND RISK FACTORS
Gram-negatives are the predominant organisms in hospital-acquired
•
pneumonia:
• Escherichia coli.
• Klebsiella pneumonia.
• Pseudomonas aeruginosa.
Antibiotic-resistant strains are more prevalent in the hospital setting.
•
• Pneumonias are associated with a higher rate of treatment failure.
Aetiology: Likely infective organisms are dependent on the period of onset
•
(relative to the patients admission) of the illness (atypical organisms are
described in the MICRO-Facts box below):
• Early onset (<4 days): S. pneumoniae, Haemophilus influenzae,
Moraxella catarrhalis.
• Late onset (>4 days): gram-negative organisms, S. aureus, Legionella
pneumophilia.
• It is also important to consider hospital-acquired viral infection such as
COVID-19 or influenza, especially during pandemics.
Risk factors: are the same as those for CAP but also include:
•
• Use of invasive devices: intubation, nasogastric tube, nasotracheal tube.
• Prior antibiotic use.
• Hyperglycaemia.
• Obesity.
• Decreased consciousness.
• Suppressed cough reflex (e.g. post-surgery and use of sedatives, narcot-
ics or neuromuscular blockade).
4. PATHOPHYSIOLOGY
Aspiration from the digestive tract is the most common route of infection in
•
hospital-acquired pneumonia.
Due to this, there are high rates of mixed organism infections.
•
Local trauma and inflammation from mechanical ventilation aid colonisation.
•
5. CLINICAL FEATURES
Presentation is usually the same as CAP and should always be considered
•
when a patient in hospital shows new respiratory symptoms or a non-specific
deterioration in their condition.
6. INVESTIGATIONS
Same as for a patient with CAP.
•
Bronchoscopy + broncho-alveolar lavage (BAL) if there is diagnostic
•
uncertainty.
Respiratory Medicine
2.5 Hospital-Acquired Pneumonia (HAP)
https://t.me/med1917
Consider chest CT: aids in the diagnosis of complications such as empyema +
•
lung abscess.
7. DIFFERENTIAL DIAGNOSIS
Same differential diagnosis to CAP, but also consider:
•
• Pulmonary embolus.
• Pneumothorax.
• Pulmonary oedema.
• Acute respiratory distress syndrome (ARDS).
• Congestive heart failure.
8. MANAGEMENT
IV antibiotics: typical regimes in HAP (taken from NICE guidelines, please
•
check local guidelines) are:
• Piperacillin/tazobactam 4.5 g IV TDS.
• If penicillin allergic: meropenem 2 g IV TDS (discuss with micro-
biology; meropenem is not always appropriate if penicillin causes
anaphylaxis).
• Early antibiotic therapy improves outcomes, so empirical coverage
should be started and then streamlined once sensitivities are known.
• Antibiotic treatment should be guided by culture and sensitivity.
Analgesia (use WHO analgesia ladder as a guide for effective analgesia).
•
romboprophylaxis.
•
IV fluid replacement.
•
Chest physiotherapy.
•
Prevention:
•
• Handwashing + proper infection control strategies.
• Early identification and mitigation of swallowing problems (common in
elderly or patients with dementia).
• Removal of invasive devices as soon as possible.
• Nursing in semi-upright position.
• Limited use of sedatives.
• Early weaning from ventilation.
35
Respiratory Medicine
9. COMPLICATIONS
Hospital-acquired pneumonia has the same complications as CAP.
•
10. PROGNOSIS
Pneumonia treated in hospital has a mortality rate of 61- 2% (majority of
•
which are CAP).
HAP has a mortality rate of approximately 30% .
•
Mortality approximately 50% for pneumonia requiring treatment in ITU.
•
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