It refers to wheezing infants less than 2 years of age. It sounds the same as the noise in asthma - a whistling noise as your child breathes out.

However the mechanism causing the wheezy noise is different so infants may not respond to usual asthma management.

Asthma in children older than 2 or 3 years affects the medium and small airways (air tubes, bronchi) so they become narrow. The narrowing of the airways, which is partly due to spasm of the muscles around the airways, causes difficulty breathing and a tightness in the chest. This causes wheezing, a whistling noise when the child breathes out.

In infants less than 6 months, bronchiolitis, a viral infection affecting the very small airways may also give a similar picture. There is no specific treatment for bronchiolitis but some babies need help with feeding and some need extra oxygen.

What causes wheezing in infants?

It is caused by narrow airways but generally not spasm of the muscles that you get with asthma. In infants, the air tubes (bronchi) are small anyway.

When an infant gets a cold, their membranes all become swollen. You will have seen your child with a blocked nose because the nose membranes (the lining of the nose) are all swollen.

Well, the air tubes (bronchi) also get swollen membranes (or lining) so that the passage in the middle becomes smaller. When the airway is already narrow (because you're just a small human being) and then you get swollen lining of the tube, it becomes even narrower.

Narrow air tubes (bronchi) can make it hard to breathe and so your infant may show signs of working harder to breathe and have the whistling noise as he breathes out.

Will these infants develop asthma later in life?

No. Most infants will not develop asthma later in life. 80% of infants who wheeze in the first year of life will not continue to have symptoms after the age of 3 years.

Because most of these infants will not have asthma later in life, most doctors will not refer to this as infant asthma but will use the term transient infantile wheeze or viral induced wheeze.

What triggers these episodes?

The main trigger is a viral upper respiratory tract infection, like a cold.

What are symptoms?

The main symptom is wheeze - this is a whistling noise that occurs when the baby breathes out. Your baby will also probably have a runny nose because he will have a cold.

You may see that your infant is having to work harder to breathe - so you may notice his ribs becoming prominent as he breathes in and out.

He may also be coughing.

What is the treatment of Transient Infantile Wheeze?

Because there is usually no spasm causing the narrow airways, medications called bronchodilators that open up the airways, don't usually work.

However, it is worth trying as some infants will respond but no treatment has been shown to work very well all the time in this group of children. The treatments are given via a spacer with a mouthpiece and the medicine is pumped into the spacer.

The drugs that can be tried are:

• Salbutamol / Albuterol - these are conventional asthma medications that act by reducing spasm of the muscles around the airways thereby relaxing them
• Ipratropium bromide - I often use this in infants less than 2 years as it may help "dry" up the airway. It acts by relaxing the airways but it also has a drying effect on membranes which is why I think it works in young children who don't actually have spasm of the airways

For children admitted to hospital, a short course of oral steroids or inhaled steroids can shorten the attack.

Sometimes, no treatment works and infants just have to get over the wheezing themselves. Luckily, they are often quite happy even though they are having to work harder to breathe.

When should I seek medical attention?

You should seek medical attention for your infant if:

• he is working really hard for each breath
• he looks blue or a poor color
• he is unable to drink enough to keep from being dehydrated
• he is so tired from working so hard at breathing that he is floppy or overly drowsy
• he is too breathless to speak
• you are really worried about your infant

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