Respiratory - Lung Infections Flashcards
What is pneumonia?
An infection of the lung tissue, causing inflammation and inflammatory exudate formation within the airways and alveoli.
How is pneumonia classified?
Community acquired pneumonia: if the pneumonia developed outside of hospital, or within the first 48h of admission.
Hospital acquired pneumonia: if the pneumonia develops more than 48h after hospital admission.
Aspiration pneumonia: if the pneumonia develops after inhaling a foreign material such as food.
What are the common causes of community acquired pneumonia?
- Streptococcus pneumoniae (~50%)
- Haemophilus influenzae (~20%)
What are the common causes of hospital acquired pneumonia?
- Escherichia coli
- MRSA
- Pseudomonas aeruginosa
Presentation of pneumonia.
- SOB
- cough productive of sputum
- fever
- haemoptysis
- pleuritic chest pain
- delirium
- sepsis
Signs of pneumonia.
- bronchial breath sounds
- focal course crackles upon auscultation
- dullness to percussion
- tachypnoea
- tachycardia
- hypoxia
How does NICE suggest pneumonia severity is assessed?
CURB-65 score:
Confusion
Urea >7mmol/L
Respiratory rate ≥30/min
Blood pressure <90/60mmHg
65yrs in age (or over)
A 81 year old patient presents with a productive cough and fever. Upon auscultation of the chest, you hear bronchial breath sounds and course crackles in the left lower lobe.
You note the following observations from your clinical examination and investigations:
No new confusion;
Urea 6.3mmol/L
Respiratory rate 29/min
Blood pressure 110/80mmHg
In which setting should this patient be managed?
CURB-65 score 1: consider treatment at home
A 55 year old patient presents with a productive cough and fever. Upon auscultation of the chest, you hear bronchial breath sounds and course crackles in the left lower lobe.
You note the following observations from your clinical examination and investigations:
No new confusion;
Urea 7.2mmol/L
Respiratory rate 26/min
Blood pressure 88/62mmHg
In which setting should this patient be managed?
CURB-65 score ≥2: consider hospital admission
A 75 year old patient presents with a productive cough and fever. Upon auscultation of the chest, you hear bronchial breath sounds and course crackles in the left lower lobe.
His past medical history is significant for a diagnosis of Alzheimer’s.
You note the following observations from your clinical examination and investigations:
Patient is confused, but wife states no more than usual
Urea 7.8mmol/L
Respiratory rate 25/min
Blood pressure 96/57mmHg
How is should this patient be best managed?
CURB-65 score ≥3: consider intensive care assessment
How should mild pneumonia be investigated?
Patients in the community with CRB of 0 or 1 do not necessarily need investigations. If CRB warrants hospital admission:
- CXR
- FBC (raised white cells; infection)
- U&Es (urea)
- CRP (raised in inflammation and infection)
- ABG if SpO2 <94%
How should moderate / severe pneumonia be investigated?
- CXR
- FBC (raised white cells; infection)
- U&Es (urea)
- CRP (raised in inflammation and infection)
- ABG if SpO2 <94%
PLUS
- sputum cultures
- blood cultures
- serology and urine screen for atypical causes (e.g. Legionella)
How should low-severity community acquired pneumonia be managed (UHL, 2023)?
Amoxicillin 500mg TDS PO for 5 days.
Doxycycline 100mg OD PO for 4 days if penicillin allergic.
How should moderate-severity community acquired pneumonia be managed (UHL, 2023)?
Amoxicillin 500mg TDS + Doxycycline 100mg OD, PO for 5 days.
Clarithromycin 500mg BD + Doxycycline 100mg OD, PO for 5 days if penicillin allergic.
How should severe community acquired pneumonia be managed (UHL, 2023)?
Co-amoxiclav 1.2g TDS IV + Clarithromycin 500mg BD PO, for 5 days.
What are the most common causes of pneumonia in:
a) immunocompromised patients or those with chronic pulmonary disease
b) patients with cystic fibrosis or bronchiectasis
a) Moraxella catarrhalis
b) Pseudomonas aeruginosa or Staphylococcus aureus
What is atypical pneumonia?
Pneumonia caused by an organism that cannot be cultured in the normal way, or detected using a gram stain.
They tend to not respond to penicillins, however can be treated with macrolides (ie. clarithromycin), fluoroquinolones (ie. levofloxacin) or tetracyclines (ie. doxycycline).
What are the causes of atypical pneumonia?
- Legionella pneumophila
- Chlamydia psittaci
- Mycoplasma pneumoniae
- Chalmydophila pneumoniae
- Q fever (Coxiella burnetii)
“Legions of psittaci MCQs”
What is Legionnaire’s disease?
A form of pneumonia caused by Legionella pnuemophila, contracted from contaminated water supplies or air conditioning units.
It can cause SIADH, causing a dilutional hyponatraemia. This can cause dangerous electrolyte imbalanaces and subsequent arrhythmias.
The typical exam patient has recently had a cheap hotel holiday / travel history, and presents with hyponatraemia.
Which extra-respiratory signs are likely to be seen in pneumonia caused by Mycoplasma pneumoniae?
- erythema multiforme (pink rings with pale centres)
- neurological symptoms
What is the typical aetiology of fungal pneumonia, and in which patient population is it typically seen?
Pneumocystis jiroveci (PCP) pneumonia occurs in patients that are immunocompromised, in particular those with poorly controlled or new HIV and a low CD4 count.
It usually presents subtly with a dry cough, shortness of breath upon exertion and night sweats.
Treatment is with co-trimoxazole, which can also be prescribed prophylactically to patients with low CD4 counts.
What is the causative organism of Tuberculosis (TB)?
Give the microscopy findings of this organism.
Mycobacterium tuberculosis
Gram negative, acid-fast bacillus
Risk factors for tuberculosis.
- known contact with active TB
- immigrants from areas of high TB incidence
- foreign travel to areas of high TB incidence
- ## immunosuppression (e.g. HIV, corticosteroids, diabetes mellitus)
What is the Mantoux test?
Used to look for a previous immune response to TB, so will be positive if there is latent or active TB, or due to previous vaccination.
The Mantoux test involves injecting tuberculin into the forearm, and looking for >5mm skin induration.
After a positive result, a patient should be assessed for active disease.
What CXR findings are consistent with a diagnosis of primary tuberculosis?
- patchy consolidation
- pleural effusions
- hilar lymphadenopathy
What CXR findings are consistent with a diagnosis of reactivated tuberculosis?
- patchy consolidation with cavitation
- typically in upper zones
What CXR findings are consistent with a diagnosis of miliary tuberculosis?
- ‘millet seeds’ uniformly distributed throughout the lung fields
TOM TIP: Disseminated miliary TB gives quite a characteristic appearance on a chest xray. This makes it a popular spot diagnosis in exams so it is worth looking at some pictures and remembering this.
What is bronchiectasis?
Chronic dilatation of one or more bronchi, causing poor mucus clearance and predisposition to recurrent or chronic bacterial infection.
How should bronchiectasis be investigated?
High resolution CT is GOLD STANDARD
On CT, signet ring sign will be present.
