Respiratory: Bronchiolitis, Bronchiectasis & TB Flashcards
What is bronchiolitis?
Viral infection of the bronchioles (the smallest air passages in the lungs).
What is the main pathogen causing bronchiolitis?
Respiratory syncytial virus (RSV) –> 75-80% cases
What time of year does bronchiolitis usually occur?
Winter & spring months
What age does bronchiolitis typically affect?
Children <2 y/o.
It is most common in children under 6 months.
Pathophysiology of bronchiolitis?
Response to infection:
1) Proliferation of goblet cells causing excess mucus production
2) IgE-mediated type 1 allergic reaction causing inflammation
3) Bronchiolar constriction
Infiltration of lymphocytes causing submucosal oedema
4) Infiltration of cytokines and chemokines
The airways of infants are very small to begin with, and when there is even the smallest amount of inflammation and mucus in the airway it has a significant effect on the infants ability to circulate air to the alveoli and back out. This causes the harsh breath sounds, wheeze and crackles heard on auscultation when listening to a bronchiolitic baby’s chest.
Risk factors for bronchiolitis?
1) Being breast fed for less than 2 months
2) Smoke exposure (eg. parents’ smoke)
3) Having siblings who attend nursery or school (increased risk of exposure to viruses)
4) Chronic lung disease due to prematurity
Clinical features of bronchiolitis?
1) coryzal symptoms (including mild fever, runny nose, sneezing etc) precede:
2) dry cough
3) increasing breathlessness & signs of respiratory distress
4) wheezing, fine inspiratory crackles on auscultation (not always present)
5) feeding difficulties associated with increasing dyspnoea are often the reason for hospital admission
Signs of respiratory distress in infants?
1) Raised RR
2) Use of accessory muscles of breathing, such as the sternocleidomastoid, abdominal and intercostal muscles
3) Intercostal and subcostal recessions
4) Nasal flaring
5) Head bobbing
6) Tracheal tugging
7) Cyanosis (due to low oxygen saturation)
8) Abnormal airway noises
Typical history in bronchiolitis?
The typical history is one of increasing symptoms over 2-5 days, usually consisting of:
- Low-grade fever
- Nasal congestion
- Rhinorrhoea
- Cough
- Feeding difficulty
What are some referral criteria for admission for children with bronchiolitis?
1) apnoea (observed or reported)
2) child looks seriously unwell
3) severe respiratory distress, for example grunting, marked chest recession, or a respiratory rate of over 70 breaths/minute
4) central cyanosis
5) persistent O2 sats <92% when breathing air.
Differentials for bronchiolitis?
1) pneumonia
2) croup
3) cystic fibrosis
4) HF - VERY IMPORTANT not to miss this, and it can be difficult to diagnose
5) bronchitis
1st line investigation in bronchiolitis?
Nasopharyngeal aspirate or throat swab –> RSV rapid testing and viral cultures.
Investigations in bronchiolitis?
1) Nasopharyngeal aspirate or throat swab
2) Blood and urine culture if child is pyrexic
3) FBC
4) ABG if severely unwell – this may detect respiratory failure and the need for respiratory support, but should not be done routinely
5) CXR (only if diagnostic uncertainty or atypical course)
Management of bronchiolitis?
It is worth noting that there is no role for antibiotics, steroids or bronchodilators in the treatment of bronchiolitis.
Bronchiolitis is largely managed supportively and can involve:
1) Nasal suction
2) Oxygen:
- Administer if oxygen saturations consistently fall below 92% in air.
- High-flow nasal cannula or nasal continuous positive airway pressure (nCPAP) can be used
3) Hydration
What is the role of nasal suction in bronchiolitis?
Saline nasal drops followed by bulb suction can clear nasal secretions, especially before feeding.
Complications of bronchiolitis?
1) Hypoxia
2) Dehydration
3) Fatigue
4) Respiratory failure
5) Persistent cough or wheeze (very common and parents should be counselled that their child may cough for several weeks)
6) Bronchiolitis obliterans – Airways become permanently damaged due to inflammation and fibrosis
What is bronchiolitis obliterans?
Airways become permanently damaged due to inflammation and fibrosis
How long does bronchiolitis typically last?
Bronchiolitis usually lasts 7-10 days.
Most children who require hospital admission can cough for up to 6 weeks, whereas those cared for at home will have a more minor ‘common cold’.
What is ‘grunting’?
Grunting is caused by exhaling with the glottis partially closed to increase positive end-expiratory pressure.
What is the stepwise approach to ventilatory support in infants?
1) High-flow humidified oxygen via tight nasal cannula (i.e. “Airvo” or “Optiflow”)
2) Continuous positive airway pressure (CPAP)
3) Intubation & ventilation
What does ‘high flow humidified oxygen’ involve?
Delivered via a tight nasal cannula.
This delivers air and oxygen continuously with some added pressure, helping to oxygenate the lungs and prevent the airways from collapsing.
It adds “positive end-expiratory pressure” (PEEP) to maintain the airway at the end of expiration.
What are 2 key signs of poor ventilation on an ABG?
1) Rising pCO2 –> showing that the airways have collapsed and can’t clear waste carbon dioxide.
2) Falling pH –> showing that CO2 is building up and they are not able to buffer the acidosis this creates (respiratory acidosis)
What drug may be indicated in the prevention of bronchiolitis?
Palivizumab (monoclonal antibody).
Role of Palivizumab in bronchiolitis?
This monoclonal antibody targets the respiratory syncytial virus (RSV).
A monthly injection is given as prevention against bronchiolitis caused by RSV.
Which babies is the Palivizumab injection given to?
It is given to high risk babies, such as ex-premature and those with congenital heart disease.
How does the Palivizumab work against RSV?
It is not a true vaccine as it does not stimulate the infant’s immune system. It provides passive protection by circulating the body until the virus is encountered, as which point it works as an antibody against the virus, activating the immune system to fight the virus. The levels of circulating antibodies decrease over time, which is why a monthly injection is required.
What is bronchiectasis?
Abnormal dilatation of the airways with associated destruction of bronchial tissue.
What does bronchiectasis commonly occur as a result of in children?
Cystic fibrosis
Pathophysiology of bronchiectasis?
Inflammatory response to a severe infection leads to structural damage within the bronchial walls, which cause dilatation.
Scarring then reduces the number of cilia within the bronchi.
This predisposes to further infection.
Give some categories of causes of bronchiectasis in children
1) CF
2) Post-infectious
3) Immunodeficiency
4) Primary ciliary dyskinesia (PCD)
5) Post-obstructive i.e. foreign body aspiration
6) Congenital syndromes:
- yellow nail syndrome
- Young’s syndrome
What are the most typical organisms causing post-infectious bronchiectasis? (7)
1) Strep. pneumoniae
2) Staph. aureus
3) Adenovirus
4) Measles
5) Influenza virus
6) Bordetella pertussis
7) Mycobacterium tuberculosis
What are 3 immunodeficiencies that can cause bronchiectasis in children?
1) Antibody defects e.g. agammaglobulinaemia, common variable immune deficiency or IgA/IgG deficiency
2) HIV infection
3) Ataxia telangiectasia
What is primary ciliary dyskinesia (PCD)?
An autosomal recessive genetic defect leading to either reduced efficacy or complete inaction of bronchial cilia.
How can PCD predispose to bronchiectasis?
PCD causes problems with mucociliary clearance leading to increased susceptibility to low-grade infections and irritation from foreign particulates.
What is Young’s syndrome?
A rare condition associated with:
a) bronchiectasis
b) reduced fertility
c) rhinosinusitis
What is yellow-nail syndrome?
A rare syndrome associated with:
a) pleural effusions
b) lymphoedema
c) dystrophic nails
Bronchiectasis occurs in around 40% of patients.
What is a key feature in the history in bronchiectasis?
Chronic, productive cough.
Possible presenting features in bronchiectasis in children?
- Chronic, productive cough (definitely)
Maybe:
- Purulent sputum
- Chest pain
- Wheeze
- Breathlessness on exertion
- Haemoptysis
- Recurrent or persistent LRTIs
Possible examination findings in bronchiectasis in children?
- May be entirely normal
- Finger clubbing
- Inspiratory crackles
- Wheezing
The purpose of investigation of children with suspected bronchiectasis is two-fold.
What are the 2 reasons?
1) Confirm diagnosis
2) Look for cause
What is the gold standard investigation to diagnose bronchiectasis?
High resolution CT (HRCT)
What may a high resolution CT show in bronchiectasis?
- bronchial wall thickening
- diameter of bronchus larger than that of the accompanying bronchial artery (‘Signet ring’ sign)
- visible peripheral bronchi.
Different patterns seen on HRCT can occur with different aetiologies.
What aetiologies would the following patterns indicate:
a) Bilateral upper lobe bronchiectasis
b) Unilateral upper lobe bronchiectasis
c) Focal bronchiectasis (lower lobe)
a) CF
b) Post-TB infection
c) Foreign body inhalation
What are some investigations that may be helpful in determining the underlying cause in bronchiectasis in children?
1) Chloride sweat test –> CF
2) FBC –> assess lymphocyte and neutrophil counts
3) Immunoglobulin panel –> immunoglobulin deficiency
4) Specific antibody levels to vaccinations e.g. pneumococcal or Hib (Haemophilus influenzae B) vaccine.
5) Bronchoscopy –> ciliary brush biopsy
6) HIV test
How may bronchiectasis present on lung function tests?
Spirometry may be completely normal in mild disease.
In advanced disease there can either be an obstructive pattern or a mixed obstructive and restrictive pattern, as severe scarring begins to compromise lung compliance.
What are the 3 aims of managing children with bronchiectasis?
1) symptom relief
2) prevent progression of lung disease
3) ensure normal growth and development
Management options in bronchiectasis?
1) Chest physiotherapy
2) Exacerbations and antibiotics
3) Bronchodilators (if have wheeze)
4) Follow up regularly
What are the 3 most commonly isolated organisms causing bronchiectasis exacerbations?
1) H. influenzae
2) Strep. pneumoniae
3) Moraxella catarrhalis
What are some complications of bronchiectasis in children? (5)
- Recurrent infection
- Life-threatening haemoptysis
- Lung abscess
- Pneumothorax
- Poor growth and development
Prognosis of bronchiectasis in children?
Entirely dependent on the underlying cause.
In patients with post-infective disease, treatment should halt disease progression.
In those children with more complex underlying pathology e.g. HIV infection, their prognosis depends heavily on the progression of the causative disease.
What bacteria causes TB?
Mycobacterium tuberculosis
What type of organism is Mycobacterium tuberculosis?
Aerobic, acid-fast bacilli
How is Mycobacterium tuberculosis mostly spread?
Via droplet infection
Risk factors for TB?
1) Immunosuppression e.g. HIV, immunosuppressant drugs
2) Diabetes mellitus, end-stage renal disease
3) Previous lung disease (silicosis)
4) Smoking
5) Drug abuse, alcoholism
6) Malnutrition, poverty
7) Certain living conditions (prisons, homeless shelters)
8) Occupational (hospitals)
Do the majority of individuals who come into contact with TB develop the disease?
No –> the majority of individuals never develop the clinical disease and there is immediate clearance of the organism
1ary disease vs latent infection in TB?
1ary disease –> rapid progression to active disease if the immune response is inadequate.
Latent –> caseating granuloma formation (this can go on to reactivate and progress to symptomatic disease later in life)
Reactivation of TB inefction can occur in what situation?
Occurs when the immune response is suppressed.
Is latent TB infection contagious?
No
Is latent TB infection symptomatic?
No
Constitutional symptoms of active TB?
- Fever: usually gradual onset and low-grade
- Night sweats
- Weight loss, anorexia, and malaise
What is the most common form of TB?
Pulmonary TB
Symptoms of pulmonary TB?
- Dyspnoea
- Cough (+/- haemoptysis)
- Chest pain
Chest exam:
- crackles
- bronchial breath sounds
- may be normal
Describe cough in TB
over 2 to 3 weeks; initially dry, later productive
What 2 tests can investigate for latent TB infection in a person exposed to M tuberculosis but without signs of active disease?
1) Tuberculin skin test (TST).
2) Interferon-gamma release assays (IGRAs)
Both tests evaluate cell-mediated immunity.
CXR findings in TB?
- hilar lymphadenopathy
- effusion
- pulmonary infiltrates
- calcification
CXR findings in reactivation TB?
Upper lobe cavitary lesion
What is the gold standard test for active TB?
Sputum culture
Sputum analysis is a key investigation in TB.
What are the 3 possible tests?
1) Sputum microscopy
2) Culture (gold standard)
3) NAAT
What stain identifies the TB bacilli with sputum microscopy?
Acid-fast stain (Ziehl-Neelsen stain) identifies the bacilli.
What 4 drugs are used in the management of TB?
1) Rifampicin
2) Isoniazid
3) Pyrazinamide
4) Ethambutol
Which TB drug is a potent liver enzyme inducer?
Rifampicin
What are 3 side effects of rifampicin?
1) hepatitis
2) orange bodily secretions
3) flu-like symptoms
Which TB drug is a liver enzyme inhibitor?
Isoniazid
What are 3 key side effects of isoniazid?
1) peripheral neuropathy
2) hepatitis
3) agranulocytosis
How can peripheral neuropathy be prevented during treatment with isoniazid?
pyridoxine (Vitamin B6)
Which TB drug increases risk of gout?
Pyrazinamide
How can Pyrazinamide cause gout?
Causes hyperuricaemia
Which TB drug requires checking visual acuity before starting?
Ethambutol –> can cause optic neuritis
What are some complications of pulmonary TB?
Haemoptysis
Pneumothorax
Bronchiectasis
Pulmonary destruction
Fistula
Tracheobronchial stenosis
Malignancy
Chronic pulmonary aspergillosis.
What is miliary TB?
massive spread with multiple organ involvement
Who is screened for latent TB infection?
- Individuals with recent exposure (contacts).
- Health care workers.
- Homeless shelters and prisons.
- Individuals with increased risk of reactivation: HIV.
- Travellers from high-incidence countries.
