Childhood Respiratory Illness Flashcards
What is bronchiolitis?
Bronchiolitis describes inflammation and infection in the bronchioles, the small airways of the lungs.
This is usually caused by a virus. Respiratory syncytial virus (RSV) is the most common cause.
When and in who does bronchiolitis commonly occur?
Bronchiolitis is very common in winter. Bronchiolitis is generally considered to occur in children under 1 year. It is most common in children under 6 months. It can rarely be diagnosed in children up to 2 years of age, particularly in ex-premature babies with chronic lung disease.
When a virus affects the airways of adults, the swelling and mucus are proportionally so small that it has little noticeable effect on breathing. 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.
How does bronchiolitis commonly present?
Coryzal symptoms. These are the typical symptoms of a viral upper respiratory tract infection: running or snotty nose, sneezing, mucus in throat and watery eyes. Signs of respiratory distress Dyspnoea (heavy laboured breathing) Tachypnoea (fast breathing) Poor feeding Mild fever (under 39ºC) Apnoeas are episodes where the child stops breathing Wheeze and crackles on auscultation
What are the signs of respiratory distress?
One of the foundations of paediatrics is being able to spot the signs of respiratory distress:
Raised respiratory rate Use of accessory muscles of breathing, such as the sternocleidomastoid, abdominal and intercostal muscles Intercostal and subcostal recessions Nasal flaring Head bobbing Tracheal tugging Cyanosis (due to low oxygen saturation) Abnormal airway noises
Name abnormal airway noises and what they may suggest?
Wheezing is a whistling sound caused by narrowed airways, typically heard during expiration
Grunting is caused by exhaling with the glottis partially closed to increase positive end-expiratory pressure
Stridor is a high pitched inspiratory noise caused by obstruction of the upper airway, for example in croup
What is the typical course of RSV causing bronchiolitis?
Bronchiolitis usually starts as an upper respiratory tract infection (URTI) with coryzal symptoms. From this point around half get better spontaneously. The other half develop chest symptoms over the first 1-2 days following the onset of coryzal symptoms. Symptoms are generally at their worst on day 3 or 4. Symptoms usually last 7 to 10 days total and most patients fully recover within 2 – 3 weeks. Children who have had bronchiolitis as infants are more likely to have viral induced wheeze during childhood.
When should admission be considered for a child with bronchiolitis?
Most infants can be managed at home with advice about when to seek further medical attention. Reasons for admission include:
Aged under 3 months or any pre-existing condition such as prematurity, Downs syndrome or cystic fibrosis
50 – 75% or less of their normal intake of milk
Clinical dehydration
Respiratory rate above 70
Oxygen saturations below 92%
Moderate to severe respiratory distress, such as deep recessions or head bobbing
Apnoeas
Parents not confident in their ability to manage at home or difficulty accessing medical help from home
How is bronchiolitis managed?
Typically patients only require supportive management. This involves:
Ensuring adequate intake. This could be orally, via NG tube or IV fluids depending on the severity. It is important to avoid overfeeding as a full stomach will restrict breathing. Start with small frequent feeds and gradually increase them as tolerated.
Saline nasal drops and nasal suctioning can help clear nasal secretions, particularly prior to feeding
Supplementary oxygen if the oxygen saturations remain below 92%
Ventilatory support if required
There is little evidence for treatments such as nebulised saline, bronchodilators, steroids and antibiotics.
How does ventilatory support assist children with bronchiolitis?
As breathing gets harder, the child gets more tired and less able to adequately ventilate themselves. They may require ventilatory support to maintain their breathing. This is stepped up until they are adequately ventilated:
High-flow humidified oxygen via tight nasal cannula (i.e. “Airvo” or “Optiflow”). 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.
Continuous positive airway pressure (CPAP). This involves using a sealed nasal cannula that performs in a similar way to Airvo or Optiflow, but can deliver much higher and more controlled pressures.
Intubation and ventilation. This involves inserting an endotracheal tube into the trachea to fully control ventilation.
How can ventilation assessed in a child with respiratory distress?
The most helpful signs of poor ventilation are:
Rising pCO2, showing that the airways have collapsed and can’t clear waste carbon dioxide.
Falling pH, showing that CO2 is building up and they are not able to buffer the acidosis this creates. This is a respiratory acidosis. If they are also hypoxic, this is classed as type 2 respiratory failure.
What is palivizumab and how is it used in children at risk of bronchiolitis?
Palivizumab is a monoclonal antibody that targets the respiratory syncytial virus. A monthly injection is given as prevention against bronchiolitis caused by RSV. It is given to high risk babies, such as ex-premature and those with congenital heart disease.
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 viral induced wheeze?
Viral-induced wheeze describes is an acute wheezy illness caused by a viral infection. Small children (typically under 3 years) have small airways. When these small airways encounter a virus (commonly RSV or rhinovirus) they develop a small amount of inflammation and oedema, swelling the walls of the airways and restricting the space for air to flow. This inflammation also triggers the smooth muscles of the airways to constrict, further narrowing the space in the airway.
This swelling and constriction of the airway caused by a virus has little noticeable effect on the larger airways of an older child or adult, however due to the small diameter of a child’s airway, the slight narrowing leads to a proportionally larger restriction in airflow. This is described by Poiseuille’s law, which states that flow rate is proportional to the radius of the tube to the power of four. Therefore, halving the diameter of the tube decreases flow rate by 16 fold.
Air flowing through these narrow airways causes a wheeze, and the restricted ventilation leads to respiratory distress. For some reason, certain children are much more prone to this airway swelling than others. There seems to be a hereditary element, so when assessing a wheezy child ask about a family history of viral-induced wheeze. These children are at higher risk of developing asthma in later life.
How can you differentiate between viral induced wheeze and asthma?
The distinction between a viral-induced wheeze and asthma is not definitive. Generally, typical features of viral-induced wheeze (as opposed to asthma) are:
Presenting before 3 years of age
No atopic history
Only occurs during viral infections
Asthma can also be triggered by viral or bacterial infections, however it also has other triggers, such as exercise, cold weather, dust and strong emotions. Asthma is historically a clinical diagnosis, and the diagnosis is based on the presence of typical signs and symptoms along with variable and reversible airflow obstruction.
How does viral induced wheeze present?
Evidence of a viral illness (fever, cough and coryzal symptoms) for 1-2 days preceding the onset of:
Shortness of breath
Signs of respiratory distress
Expiratory wheeze throughout the chest
Neither asthma or viral induced wheeze will give a focal wheeze- in these patients suspect other cause such as inhaled FB or tumour and investigate further.
How is viral induced wheeze managed?
Management of viral-induced wheeze is the same as acute asthma in children.
