CP18 - Lower Respiratory Tract Infections Flashcards
what factors would predispose a patient to LRTIs?
- loss or suppression of cough reflex/ swallowing - risk of aspirating food, drinks etc.
- ciliary defects - increased risk of infections
- mucous disorders - increased risk of infections, CF
- pulmonary oedema
- immunodeficiency
- macrophage function reduction, eg. due to smoking
which bacteria cause LRTIs?
strep pneumoniae h influenzae staph aureus Klebsiella pneumonia mycoplasma pneumoniae chlamydophilla pneumoniae legiononella pneumophila mycobacterium tuberculosis
which viruses cause LRTIs?
influenza
parainfluenza
RSV
adenovirus
which fungi cause LRTIs?
aspergillus
candida
pneumocystitis jiroveci
define LRTIs
anything affecting the respiratory system below the larynx
what is bronchitis?
inflammation of the large airways (bronchi)
what is bronchiolitis?
inflammation of the bronchioles
what is acute bronchitis?
inflammation and oedema of the trachea and bronchi, generally a mild illness
what is the presentation of acute bronchitis?
dry cough, dyspnoea and tachypnoea, cough may be associated with retrosternal pain
most frequent in winter, and children under the age of 5
which organisms are responsible for acute bronchitis?
most commonly rhinovirus, coronavirus, adenovirus, influenza bacteria less common H. influenza Mycoplasma pneumoniae B. pertussis
what investigations are needed to confirm the diagnosis of acute bronchitis?
none in mild presentations, vaccination and past medical history may exclude some organisms.
resp cultures may be useful to single out a cause, but this is uncommon
how is acute bronchitis managed?
supportive treatment in healthy patients
oxygen therapy or respiratory support in patients with severe disease or co-morbidities
antibiotics if bacterial cause is suspected/found
what is chronic bronchitis?
cough, productive of sputum on most days during at least 3 months of 2 successive years, which cannot be attributed to an alternative cause
what are the risk factors for chronic bronchitis?
men, over 40s, smoking, pollution, allergens
mediate inflammation and oedema, but acute exacerbations are mediated by same infective pathogens as acute
how does bronchiolitis present?
primarily in paeds, 2-10 months
acute onset wheeze, cough, nasal discharge, respiratory distress
peaks in winter and early spring
what are the symptoms of respiratory distress?
grunting, retractions, nasal flaring
what are the causes of bronchiolitis?
RSV most common
others - parainfluenza, adenovirus, influenza
how is bronchiolitis diagnosed?
chest xray
FBC
nasopharyngeal aspirate of respiratory secretions sent for viral PCR
how is bronchiolitis treated?
supportive treatment - oxygen, feeding assistance.
antibiotics only given if complicated by a bacterial infection
no evidence for use of steroids, bronchodilators, ribavirin
what is pneumonia?
formation of inflammatory exudate in the most distal airways and alveoli
what is the presentation of community acquired pneumonia?
very common
usually rapid onset symptoms - fever/chills, productive cough, mucopurulent sputum, pleuritic chest pain, general malaise, fatigue, anorexia
what are the signs of CAP?
tachypnoea, tachycardia, hypotension, dull to percuss, reduced air entry and bronchial breathing
what is mucopurulent sputum?
sputum containing pus with WBCs, cellular debris, dead tissue, serous fluid and viscous liquid
what organisms are responsible for a typical CAP?
s. pneumoniae H. influenza M. catarrhalis S. aureus Klebsiella pneumoniae
what non microbiological investigations need to be undertaken to diagnose pneumonia?
BP, pulse, oximetry, bloods - FBC, U&E, CRP, LFT; CXR to locate consolidation and differentiate which type of pneumonia it is
what microbiological investigations need to be done if CAP is suspected and when?
moderate-severe CAP based on score>2 on CURB65
sputum gram stain and culture, blood culture, PCR or serology for viral antigens, m. pneumonia, Chlamoydophila sp.
how is CAP treated?
low severity - amoxicillin
moderate - amoxicillin and clarythromycin
high - co-amoxiclav and clarithromycin asap
choice of antibiotic depends on the CURB65 score
what are the 2 anatomical patterns of pneumonia?
- bronchopneumonia - characteristic patch distribution centred on inflamed bronchioles and bronchi then subsequent spread to surrounding alveoli
- lobar pneumonia - affects a large part or the entirety of a lobe, clear line of demarcation seen on CXR. almost always S. pneumoniae
why is it important to know where the pneumonia was acquired from?
it informs the course of treatment
what are the various types of pneumonia?
CAP
hospital acquired pneumonia
ventilator acquired pneumonia
aspiration pneumonia
when does hospital acquired pneumonia develop?
> 48 hours post hospital admission, divided into early onset (2-5 days) and late onset (5+ days)
late onset causative organisms - enterobacteriae and pseudomonas
what is ventilator acquired pneumonia?
a subgroup of HAP, develops >48h post ET intubation and ventilation
ET = endotracheal
what is aspiration pneumonia?
pneumonia that is caused by the abnormal entry of fluids - food, drinks, stomach contents into the LRT
usually due to an underlying impairment in the swallowing mechanism
what are the atypical organisms causing CAP?
dont respond to penicillin or sulpha drug treatment mycoplasma pneumoniae Legionella pneumophila chlamoydophila pneumoniae chlamoydophila psitacchi coxiella burnetti
how does M. pneumoniae present?
commonest in children and young adults
main symptom - cough
diagnosis through serology
complications - pericaridits, arthritis, guillain barre, peripheral neuropathy, all rare
legionella pneumophila
colonises water piping systems, outbreaks associated with showers, AC units, humidifiers.
high fevers, cough dry initially productive later, riggers, dyspnoea, D&V, confusion
bloods - deranged LFTs, SIADH
chlamoydophila pneumoniae
mild pneumonia or bronchitis in adolescence and young adults. incidence highest in the elderly. they may experience more severe disease
chlamoydophila psittaci
associated with exposure to birds, consider splenomegaly and history of bird exposure in patients with pneumonia. may also have a rash, hepatitis, haemolytic anaemia, reactive arthritis
influenza
usually produces uncomplicated disease - fever, headache, myalgia, dry cough, sore throat.
primary viral pneumonia occurs more commonly in patients with pre-existing cardiac and lung disorders or are immunocompromised
observe cough, breathlessness and cyanosis in these patients
secondary bacterial pneumonia may develop after initial improvement.
diagnosis - viral antigen detection in resp samples using PCR
why is it important to establish a diagnosis in pneumonia?
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 is Guillain-Barre syndrome?
acute disorder of the peripheral nerves, often preceded by a respiratory infection, causing weakness and often paralysis of the limbs
what is peripheral neuropathy?
damage of peripheral nerves
what are rigors?
a sudden feeling of cold with shivering accompanied by a rise in temperature, often with copious sweating
what is SIADH?
syndrome of inappropriate antidiuretic hormone secretion - too much ADH
CURB65 scoring
1 point each for
- confusion
- urea >7mmol/L
- resp rate >=30
- BP =65
how is CURB65 scoring used?
0-1 - low
2 - moderate
3-5 - high severity
how can LRTIs be prevented?
- pneumococcal vaccination for patients with a chronic heart, lung and kidney disease, and those with splenectomy
- annual influenza vaccination for those over 65 and those with chronic diseases or co-morbidities
