LRTI I Flashcards
Bronchitis
Characterised by temporary (self limited) inflammation of the large and mid sized bronchial tubes
Epidemiology of bronchitis
Seasonal variation; peak incidence in winter and where influenza (outbreak?) is present in the community.
Risk factors include:
(1) Age (ie children <5 years and the elderly)
(2) Underlying disease (ie chronic obstructive pulmonary disease (COPD), asthma)
(3) Exposure to second-hand smoke
Microbiology of bronchitis
Viral
- Influenza virus
- Rhinovirus
- Adenovirus
- Respiratory synctial virus (RSV)
- Human metapneumovirus
Bacteria (approximately 10% of cases)
- Mycoplasma pneumoniae
- Chlamydophila pnumoniae
- Bordetella pertussis (rare cases)
Pathophysiology of bronchitis
A virus(es) replicating in the epithelial cells of the upper respirtaory tract can spread to the lower airways resulting in:
- Inflammation of the bronchial/bronchiolar epithelia (ie. infiltration of mononuclear cells)
- Necrotic epithelia sloughed off into the lumina of the airways, togetehr with inflammation and increased mucous production and oedema, can cause obstruction characterised by ‘wheezing’.
Bronchitis clinical manifestations
Symptoms usually begin with common cold syndrome
- nasal congestion, rhinitis, sore throat, and general malaise
- low grade fever (37.5-38)
- Cough (dry at first/ becomes productive [white; green; yellow sputum])
- Wheezing *
Symptoms and signs usually resolve over 7-10 days for otherwise healthy person
Diagnosis of bronchitis
Made on clinical presentation, suspected in any person with acute respiratory illness where cough is the dominant symptom.
Differential diagnosis of bronchitis
Pertussis (whooping cough)
Pneumonia (i.e. chest x-ray with signs of infiltrates/consolidation)
Chronic obstructive pulmonary disease (COPD); asthma.
Treatment of bronchitis
Supportive therapy: adequate hydration, cough suppressants, decongestants, antihistamines.
Bronchiolitis
Describes inflammation of the smaller air passages, bronchioles, of the lung.
Bronchiolitis epidemiology
Peak incidence is during winter to early spring; usually correlated with the prevalence of RSV in the community.
Most common during the first years of life:
- each uear 1-3% of infants <6 months of age
- more common in boys
- children with chronic underlying conditions (i.e. cardiopulmonary function decline)
Bronchiolitis risk factors
Young maternal age Lower cord blood antibody titres to RSV Lower socioeconomic status Crowded living conditions Bottle feeding Tobacco/smoke exposure
Bronchiolitis microbiology
Viruses (order of prevalence)
- RSV
- Rhinovirus
- Influenza
- Parainfluenza virus (1-3)
- Adenovirus
- Bocavirus
- Non-SARS coronaviruses
Bronchiolitis clinical manifestations
Prodrome (range 2-7 days) of signs of upper respiratory tract infection:
- Coryza
- Cough
- Fever (usually mild)
Followed by:
- Wheezing
- Dysponea
- Dehydrations (due to coughing spasm associated vomiting/ poor oral intake)
- Recovery usually over a period of 1-2 weeks.
Bronchiolitis diagnosis
Based on child’s history and physical examination
Usually suspected in children <2 years of age with:
- cough
- wheezing
- increased respiratory effort
Bronchiolitis differential diagnosis
Broad and usually includes:
- obstruction of an airways by foreign body.
- retropharyngeal abscess
- cystic fibrosis
- congestive heart failure
Bronchiolitis treatment
Supportive care for outpatient and inpatient
Maintain comfort and hydration
Treat for fever where necessary.
Factors that increase the risk of community-acquired pneumonia
Age over 50 years Alcoholism Asthma COPD Dementia HF Diabetes Immunosuppression Indigenous background Institutionalisation Seizure disorders Smoking Stroke
Factors that might perturb airway defence systems predisposing to pneumonia
(1) Cigarette smoke (disrupts mucociliary function and macrophage activity)
(2) Alteration in consciousness (stroke, seizures, anaesthesia, alcohol abuse, normal sleep)
(3) Iatrogenic manipulations (endotracheal tubes, nasogastric tubes, other respirtaory therapy machinery)
(4) Congenital defects in ciliary activity (immotile cilia syndrome)
(5) Underlying respiratory tract disorders (chronic obstructive pulmonary disease [COPD], bronchiecstasis, cystic fibrosis)
Common bacterial causes of pneumonia
Streptococcus pneumoniae* Staphylococcus aureus*
Haemophilus influenzae*
Anaerobes (Bacteriodes species; Fusobacterium species; Prevotella species) Escherichia coli
Klebsiella pneumoniae*
Enterobacter species
Serratia species
Pseudomonas aeruginosa*
Intracellular/atypical bacterial causes of pneumonia
Legionella pneumophila* Mycoplasma pneumoniae* Chlamydophila psittaci* Chlamydophila pneumoniae* Chlamydia trachomatis Mycobacterium tuberculosis Coxiella burnetii
Common viral causes of pneumonia in children
Respiratory syncytial virus (RSV) Parainfluenza virus types 1-3 Influenza A virus
Common viral causes of pneumonia in adults
Influenza A virus
Influenza B virus
RSV
Human metapneumovirus Adenovirus types 4 and 7 (ie., military staff)
Fungal causes of pneumonia
Histoplasma capsulatum Coccidiodes immitis Rhizopus species Absidia species
Mucor species Aspergillus species Candida species
What is important information to obtain when taking a history of a patient with suspected pneumonia?
(1) Clinical setting - community acquired/hospital acquired
(2) Predisposing/underlying disorders in patients
(3) Possible exposure to specific pathogens (travel to tropical areas, occupation, pets)
Clinical findings of patients with pneumonia
Fever * (elderly patients may present only with confusion)
Rigors
New onset cough
Cyanosis
Tachypnoea
Tachycardia
Sputum production (with changes in colour)
Chest discomfort/pain
Dyspnoea
Non-respiratory symptoms (fatigue; sweats; headache; nausea; myalgia)
Chest examination
- crackles
- consolidation (dullness on percussion)
CXR (required for diagnosis): need to differentiate if new lung infiltrate is caused by atelectasis, non-infective pneumonitis, haemorrhage, or cardiac failure.
Microscopic and culture of respiratory samples
Sputum
Induced sputum (40-60% of patients cannot expectorate)
Bronchial washing
Broncheoalveolar lavage
Endotracheal aspirated
Lung biopsy (usually reserved for cases of pneumonia in impaired hosts/paediatric populations)
Examination of sputum
May include observation of colour, amount, consistency and odour:
- mucopurulent: bacterial pneumonia
- scant/watery: viral mycoplasma/atypical pneumonias
- rusty: alveolar involvement with pneumococci
- dark red mucoid: current jelly-like (Klebsiella pneumoniae)
- foul smelling: mixed anaerobic infections
When is the diagnostic value high in sputum gram staining and culture?
Diagnostic value high when number of neutrophils >25, and epithelial cells <10 (under 100x magnification)
Sputum gram staining and culture
Before abx are administered, can aid in identifying the causative agent and guide choice of abx therapy.
Additional tests for pneumonia
PCR (on respiratory samples; nose and throat swabs for viruses like influenza A) - does not give abx sensitivity.
Antigen testing (i.e. urinary antigen tests).
Blood chemistry/full cell count; blood cultures; and serology (requires acute and convalescent serum samples; acute serum helpful for the serodiagnosis of M. pneumoniae and other ‘atypical’ bacteria)
How do you determine the severity of pneumonia?
Various tests have been developed to help assess the severity of pneumonia and the need for intensive respiratory and vasopressort support (IRVS) including:
(1) Pneumonia severity index (PSI)
(2) CURB-65
(3) CORB*
(4) SMART-COP*
CORB
Provides a relatively simple and quick assessment because it can be done in the absence of investigation results.
Confusion
Oxygen saturation 90% or less
Respiratory rate 30 breaths or more per minute
Blood pressure less than 90 mmHg or diastolic BP 60 mmHg or less
Severe community acquired pneumonia is diagnosed as having at least two of the above four features.
SMART-COP
Systolic BP less than 90mmHg (2pts) Multilobar CXR involvement (1 pt) Albumin less than 35 g/L (1 pt) Respiratory rate 25 bpm or greater if 50 (1 pt) Tachycardia 125bpm or more (1 pt) Confusion (acute) (1pt) Oxygen low (2 pts) - PaO2 50; or - O2 saturation 50; or - PaO2/FiO2 less than 333 if 50 pH less than 7.35 (2 pts)
0-2: low risk of needing IRVS
3-4: moderate (1-8) risk of needing IRVS
5-6: high (1 in 3) risk of needing IRVS
7 or more: very high (2 in 3) risk of needing IRVS
What factors does the choice of empiric abx and duration of therapy depend upon?
Child or adult Community of hospital acquired Complications (e.g. lung abscess) Severity score Geographical region (tropical vs non-tropical)
