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
