Diagnosing and treating chesty infants

A short trial of inhaled corticosteroid is probably the best approach

Recurrent cough and wheeze in infancy are common problems in general practice and paediatric outpatient clinics. Population based research indicates that only a minority of such infants have asthma. 1 2 For example, data from the 1970 British cohort study showed that only 23% of infants who had had four or more attacks of wheezing in the first year of life had evidence of asthma at the age of 10. Studies over the past decade have provided a better understanding of the factors that lead to these symptoms in infants who have asthma and those who do not, at least in parts of the world with a Western lifestyle.

The intrathoracic airways of infants are vulnerable to obstruction because of their narrow calibre, and those infants who are born with the narrowest airways seem to be prone to lower respiratory tract illness during viral infections.3 The airways of most infants with recurrent wheeze are not characterised by the bronchial hyperresponsiveness4 typical of asthma.2 Certain infections (respiratory syncitial virus, adenovirus, pertussis) seem to be capable of inducing airway disease that can cause symptoms for months or even years.1 6 Exposure to cigarettes, especially antenatally, can cause abnormal airway function from birth and increases the risk of respiratory illness.7 Premature birth, even without neonatal respiratory illness, predisposes to cough and wheeze in infancy.8

Although these studies illuminate the epidemiology of recurrent lower respiratory tract illness in infancy, they do little to help the clinician faced with a persistently “chesty” infant, who needs to ask two important questions: Does this child have asthma? And will inhaled drugs relieve these symptoms? We need clinically based research to determine whether features such as age at onset of symptoms, symptom pattern, and atopic family histories will allow us to identify infants who will benefit from asthma medication. A family history of atopy is often thought to identify infants with asthma, but this may not be reliable.9 Can the techniques of pulmonary function testing in infancy (currently a research tool) be used to differentiate between asthma and other causes of recurrent cough and wheeze?

For many families the consequence of doctors' uncertainty is 12–18 months of escalating and often erratic prescribing of asthma medication—oral bronchodilator, inhaled bronchodilator, and low dose inhaled corticosteroid. Since most of these infants do not have asthma, their parents commonly see no benefit from these drugs, and studies confirm that in most cases they are ineffective.10 Nevertheless, since some children with atopic asthma present in infancy2—and in principle should benefit from inhaled drugs—most doctors would want to offer the benefits of treatment to the minority of wheezy infants whose unpleasant symptoms can be relieved.

In this predicament it is common to opt for a trial of oral or inhaled bronchodilator. This rarely provides clarification because symptoms fluctuate hourly and it is impossible to decide whether any improvement is spontaneous or due to the drug. Similarly, low doses of inhaled corticosteroid rarely produce noticeable improvement—possibly because of the small proportion of aerosol that reaches the airways in this age group.11 12

Faced with an infant with recurrent cough or wheeze, one needs to consider whether a sweat test or other investigations are needed. I would investigate those whose symptoms appear within one month of birth or who have failure to thrive, incessant symptoms, or persistent auscultatory findings in the chest. At the other end of the range are infants with noisy breathing but whose quality of life is unaffected (“happy wheezers”), who probably do not require any medication.

For infants with distressing symptoms, I would advocate a trial of moderately high dose inhaled corticosteroid (doses found at step 3 of the United Kingdom guidelines for children under 5 years 13 for around six to eight weeks, along similar principles to the two week trial of oral corticosteroid used in older patients when the cause of respiratory symptoms is uncertain. For the minority whose symptoms improve substantially—as judged by a reduction in sleep disturbance, for example—the diagnosis is probably asthma, and subsequent treatment can follow the published guidelines.13 Any improvement might, of course, be coincidental, but this will become apparent when treatment is stepped down in asymptomatic individuals. For those infants who show no improvement, there is no justification for continuing to prescribe any drug.

Perhaps the biggest challenge for the doctor is telling the parents that there is no medication that will help their child's symptoms but that in most cases the condition will improve as the airways enlarge and as respiratory infections become less frequent with age. Parents generally appreciate honesty and prefer not to spend 18 months administering treatment without noticeable benefit. Facing up to our lack of treatment for these patients requires more time talking to parents but in the longer term probably reduces the number of calls the parents make on medical services.14