14.6 An approach to chronic cough and cystic fibrosis
Introduction
Cough is the most common symptom of respiratory disease for which parents seek medical attention in young children. The presence of cough can indicate the entire spectrum of cardiorespiratory childhood illness, ranging from a symptom of the ‘common cold’ to a symptom of a severe, life-limiting disorder such as cystic fibrosis (CF). Most cough in children is acute and resolves promptly. Chronic cough is defined as cough lasting longer than 4 weeks. It is abnormal and deserves careful consideration of the cause. In the evaluation of children with chronic cough, determining which children require further investigations and/or treatment is a key management issue.
Pathophysiology
Cough is generally considered a reflex, but also can be voluntarily generated (or suppressed). Cough is comprised of three phases – inspiratory, compressive and expiratory – and serves as a vital defence mechanism for lung health. The forceful expiration occurs after a build-up of pressure in the thorax (up to 300 mmHg) by contraction of expiratory muscles against a closed glottis. This leads to expulsion of air at high velocity and sweeps material within airways towards the mouth. Inspiration of a variable volume of air occurs when cough is stimulated. Successive coughs may or may not be preceded by inspiration. Cough is an important component of normal respiratory function through two mechanisms. Firstly, mechanical stimulation of the larynx causes immediate expiratory efforts through the expiratory reflex, a primary defence mechanism that is stimulated when foreign objects (such as food or fluid) are inhaled. Secondly, cough enhances mucociliary clearance. The absence of a forceful cough (e.g. generalized muscular weakness) has important clinical repercussions, such as difficulty clearing secretions, atelectasis, lobar collapse and recurrent pneumonia.
Issues to keep in mind when the presenting symptom is cough:
• Cough usually resolves spontaneously (called the period effect), which makes evaluation of therapeutic interventions difficult.
• Many cough treatments are not based on the results of randomized controlled trials.
• As the aetiology and management of cough in childhood are quite different to that in adults, extrapolation of the adult cough literature to children can be harmful.
Approach to diagnosis and management
Figure 14.6.1 outlines a schematic approach to the diagnosis and management of chronic cough. The key questions are presented in Box 14.6.1. Initial categorization of cough into acute, subacute and chronic cough according to duration is helpful. There is, however, no strict definition of chronic cough. Most acute cough arises from respiratory viruses and settles within 2 weeks. Subacute cough commonly lasts from 2 to 4 weeks, whereas chronic cough can be defined as cough lasting longer than 4 weeks.
Fig. 14.6.1 Guide for approaching a child with a persistent cough. Symptoms and signs vary according to age and illness severity. Ba, barium; CRS, cough receptor sensitivity; CXR, chest X-ray; GOR, gastro-oesophageal reflux; HRCT, high-resolution computed tomography; TOF, tracheo-oesophageal fistula, TB, tuberculosis; UA, upper airway.
Clinical exampleAdrienne, a 13-year-old girl, was referred to a respiratory physician for a chronic cough. She had been managed incorrectly as an asthmatic for more than 10 years. On specific questioning, Adrienne said she had been coughing for as long as she could remember and indicated that her cough was worse in the mornings and that she often expectorated sputum. Her cough had been stable and she had not noticed any exertional dyspnoea. She had no growth failure and did not have digital clubbing. Given that she had some features of bronchiectasis, high-resolution computed tomography of her chest was performed and revealed focal changes in the right basal segment (Fig. 14.6.2). Her serum immunoglobulin levels were normal and she was Mantoux and sweat test negative. On flexible bronchoscopy, a retained foreign body (piece of shell) was visualized and removed from the right medial segment of her right lower lobe. The foreign body had caused prolonged partial bronchial obstruction and was the cause of Adrienne’s localized bronchiectasis.
It is important to define the aetiology of any child’s chronic cough. This child had features listed in Box 14.6.1 that indicate ‘specific cough’ and further investigations were indicated. For children, it is best for investigations to be performed in a children’s facility.
A key point in the assessment of chronic cough is whether it is specific or non-specific, according to the presence or absence of particular features (Box 14.6.2). Children aged less than 6 years do not generally expectorate sputum. Thus the productive cough of older children and adults manifests as a moist or ‘rattly’ cough in younger children. The presence of any of these symptoms or signs raises the possibility of an underlying disorder. Certain cough characteristics are associated with particular illness types (see Table 14.6.1).
Box 14.6.2 Symptoms and signs alerting to the presence of an underlying disorder
Table 14.6.1 Classical recognizable cough in children
| Cough characteristic | Associated illness type |
|---|---|
| Barking or brassy cough | Croup, tracheomalacia, habit cough |
| Honking | Psychogenic |
| Paroxysmal (with/without whoop) | Pertussis and paratussis |
| Staccato | Chlamydia in infants |
| Cough productive of casts | Plastic bronchitis |
The choice of investigation depends on the clinical findings. Minimum investigation of chronic cough in children is chest radiography and lung spirometry (if aged above 6 years). Diagnoses to be considered include bronchiectasis, asthma, retained foreign body, aspiration lung disease, atypical respiratory infections, cardiac anomalies and interstitial lung disease. If basic investigations are not helpful, referral to a general or respiratory paediatrician is indicated rather than further investigations.
Management of non-specific cough
The majority of children with non-specific cough have post-viral cough and/or increased cough receptor sensitivity. There is no serious underlying cause of non-specific cough and reassurance is a large part of management. Understanding and listening to parental concerns and expectations is important. There is no evidence that ‘over the counter’ (non-prescription) medications reduce cough in young children.
Identification of exposure to environmental tobacco smoke (ETS) in children and active smoking in adolescents is an important part of respiratory history-taking. ETS exposure can cause non-specific cough and exacerbate a variety of respiratory disorders. If smoking cessation cannot be achieved, aim to reduce smoking in enclosed spaces (e.g. house and car).
Habit cough is a cause of non-specific cough. The age of diagnosis is broad, but is commonly 4–15 years. Severe cases are more common in adolescents than in children. The cough is classically ‘honking’. It is generally absent in sleep and worse at times where attention is focused on the cough. Habit cough generally settles promptly once parents are aware that there is no underlying respiratory problem. Mental health expertise is required for those with more severe or prolonged symptoms, especially if there are other features of somatization or concerns of underlying psychopathology.
Cough, asthma and allergy
There is little doubt that children with asthma can present with cough. However, most children with non-specific chronic cough do not have asthma. Furthermore, although nocturnal cough is a feature of children with asthma, nocturnal cough alone is uncommonly due to asthma. If asthma ‘preventer’ medication is used, it should be introduced on a trial basis with early review (2–4 weeks) and cessation of medication if the cough does not respond to asthma therapy. Failure to do so will result in escalation of medication dose with the risk of significant side-effects (see Clinical example below).
Clinical exampleGino was first seen by a paediatric respiratory physician when aged 8 years. He had been receiving 2000 μg/day inhaled corticosteroids for the last 6 years for a chronic dry cough; he had been managed as an ‘asthmatic’ and his medications were escalated when his cough did not respond to the steroids. When seen, his chest X-ray findings and spirometry were normal, and he was cushingoid (Fig. 14.6.3). Earlier pictures of him showed a normal-sized 3-year-old boy and his 6-year-old brother’s body habitus was normal. Gino had been exposed to tobacco smoke and had an element of habitual cough. His asthma medications were subsequently withdrawn and his cough eventually subsided when he was no longer exposed to tobacco smoke and received appropriate counselling.
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