Bronchiolitis

Definition

Inflammation of the bronchioles, the very small airways in the lungs.

Epidemiology

Apparently its the commonest serious respiratory infection of infancy. A whopping 2-3% of all infants are admitted to hospital each year with the disease. It's mostly seen in the <1 year old and almost unheard of above 2.

Pathophysiology

It's usually caused by RSV (respiratory syncitial virus), which is the problem in about 80% of cases. Basically, the virus causes inflammation in the bronchioles. Because babies are tiny, they have very small airways. These are bad for inflamation, for the following reason:

• If you have a 100μm airway, and the wall inflames and becomes an extra 10μm thick, your airway goes down to 80μm. That's a 35% loss in area, which shouldn't affect you too badly.
• If you only have a 50μm airway to start with, and you lose that 10μm, you are left with 30μm. That's a 64% loss, which is a lot more of a problem.

This is one reason why, for babies, bronchiolitis is a big cause of hospitalisation, whereas adults never have a problem with it. Other common viral causes are influenza and rhinovirus.

Risk Factors

• Being under the age of 2.
• Bottle feeding - babies who are breast fed have better immune systems
• Premature birth
• Parents who smoke
• Contact with other children, especially school age, since they are full of bugs.

Clinical Features

• Wheezing
• Coughing
• Increased rate of breathing
• Recession of chest
• Distress
• Cyanosis, if it gets bad

Investigations

Diagnosis is made by examination. Tests can be done for RSV, but this won't affect treatment. Sometimes they will do a chest xray to exclude pneumonia.

Management

Since its usually viral, there's not much you can do. Provide them with oxygen if they need it. Bronchodilators and steroids have both been widely shown to be completely useless, although it might be worth trying the salbutamol, just in case you have misdiagnosed, and its viral wheeze. But aside from that, you just sit back and wait.

Prognosis

It usually clears up within 2 weeks, although they might have similar problems with cough and wheeze on occasion in their subsequent early childhood.