Bronchiolitis is a respiratory illness that affects the smallest airways in the lungs, called bronchioles. It is a common condition, particularly among infants and young children, but it can also occur in adults. Bronchiolitis is typically caused by a viral infection, which leads to inflammation and congestion in the bronchioles, making it difficult to breathe. While the condition is generally mild and resolves on its own, severe cases may require hospitalisation and supportive treatment.

Causes of Bronchiolitis

Bronchiolitis is often caused due to the following reasons:

Viral Infections:

Respiratory syncytial virus (RSV) is the most common cause of viral bronchiolitis, especially in children under 2 years old. It is a highly contagious virus that spreads from coughing or sneezing through respiratory droplets.
Other viruses that can cause bronchiolitis include influenza, parainfluenza, adenoviruses, and human metapneumovirus. These viruses infect and inflame the small airways (bronchioles) in the lungs, leading to the symptoms of bronchiolitis.

Environmental Exposures:

Exposure to certain fumes or chemicals, such as those found in e-cigarettes, ammonia, bleach, or chlorine, can cause bronchiolitis obliterans in adults.
Respiratory infections and adverse reactions to medications can also lead to bronchiolitis obliterans in adults.

Other Risk Factors:

Premature birth, congenital heart or lung conditions, and a weakened immune system can increase the risk of developing severe viral bronchiolitis in infants and young children.
Not being breastfed and exposure to second-hand smoke are also risk factors for viral bronchiolitis in children.

Symptoms of Bronchiolitis in Children

In children: Bronchiolitis typically begins with symptoms like those of a common cold, including:

Runny and/or stuffy nose
Cough
Fever
Irritability
Poor appetite
Breathing problems, such as wheezing

These symptoms can progress and worsen with time, leading to more severe respiratory issues. In some cases, children may have trouble breathing, which requires immediate medical attention.

Symptoms of Bronchiolitis in Adults

In adults: Bronchiolitis is often characterised by chronic and progressive bronchiolitis obliterans. Common symptoms include:

Dry cough
Shortness of breath, particularly during exertion
Wheezing

These symptoms can be triggered by exposure to lung irritants and may indicate a life-threatening condition if not treated promptly.

Diagnosis of Bronchiolitis

The diagnosis of bronchiolitis is primarily based on clinical evaluation, including a directed history and physical examination. The symptoms and signs of bronchiolitis can vary in severity, from mild upper respiratory tract infection to severe respiratory distress. Key diagnostic features include:

History and Physical Examination:

The patient may experience fever, cough, and rhinorrhoea in the first 2-3 days, followed by tachypnoea, wheezing, and crackles.
Signs of respiratory distress include grunting, nasal flaring, indrawing, retractions, or abdominal breathing.

Diagnostic Tests:

Pulse Oximetry: To evaluate oxygenation levels.
Chest Radiograph: To rule out other causes, such as pneumonia, for severe cases.
RSV Antigen Test: For seriously ill children to identify the causative virus.

Differential Diagnosis:

Asthma: Especially in children over 18 months with a history of wheezing and a family history of asthma.
Gastroesophageal Reflux: Multiple episodes of wheezing in infants may indicate this condition.
Foreign Body Aspiration: Sudden onset of wheezing without upper respiratory infection symptoms, especially with asymmetric lung examination.
Heart Failure: In infants with a left-to-right shunt, manifesting at 2-3 months.

Laboratory Testing:

Blood Work: It is not necessary for mild cases but may be used to rule out other causes in severe cases.
Imaging Studies: It is not necessary for diagnosis but may be used to rule out other causes in severe cases.

Clinical Practice Guidelines:

The American Academy of Paediatrics recommends that bronchiolitis be diagnosed clinically without diagnostic testing, except in severe cases.

Treatment of Bronchiolitis

Treatment of Bronchiolitis includes the following options:

Supportive Care:

The mainstays of treatment are airway support, supplemental oxygen, and support of fluids and nutrition.
This includes providing plenty of fluids, using saline nose drops/sprays, and using a bulb syringe to remove mucus.
Propping up the head with an extra pillow can also help, but this should not be done for infants under 1 year old.

Medications:

Antibiotics and cold medicines are ineffective in treating bronchiolitis, a viral infection.
Bronchodilators (e.g., albuterol) may be tried, but their effectiveness is limited, and they should only be continued if there is an objective improvement.
Corticosteroids are not effective and are not recommended for routine use.
Ribavirin may benefit immunocompromised patients but is not recommended for routine use.

Hospitalisation:

About 3% of children with bronchiolitis require hospitalisation.
In the hospital, treatments may include IV fluids, oxygen therapy, and mucus removal through suctioning the nose and mouth.
In severe cases, the child may require mechanical ventilation to aid breathing.

Recovery:

Most cases of bronchiolitis resolve within 2-3 weeks without needing specific treatment.

Hospitalised children are typically sent home within 2-8 days once their symptoms improve.
Bronchiolitis is a common respiratory illness that can be concerning, particularly for parents of young children. However, most cases resolve without complications with proper supportive care and monitoring. It is essential to seek medical attention if symptoms worsen or the child shows signs of respiratory distress, as prompt treatment can prevent severe complications.

Reference links:

https://www.lung.org/lung-health-diseases/lung-disease-lookup/bronchiolitis/symptoms-diagnosis-treatment
https://www.mayoclinic.org/diseases-conditions/bronchiolitis/symptoms-causes/syc-20351565
https://my.clevelandclinic.org/health/diseases/8272-bronchiolitis
https://www.webmd.com/lung/what-is-bronchiolitis