Chronic cough

OVERVIEW: What every practitioner needs to know

Are you sure your patient has chronic cough? What are the typical findings for this disease?

Cough is the most common reason that patients present to doctor offices. Chronic cough in children is common, disruptive and can be difficult to treat. Chronic cough is defined as a cough lasting four weeks or longer. A persistent cough is a common source of frustration for patients and a common reason for specialty consultation. Patient and family perception that the cough is being minimized or not taken seriously commonly leads to breakdown in communication between doctor and patient.

Key Historical Points in evaluation of chronic cough:

• Timing of cough; day, night with or without feeds

• Character of cough: dry vs wet

• Response to bronchodilator

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• Seasonal variation

• Response to exercise

Often a symptom diary is a helpful and vital tool in evaluation.

Key Physical Exam findings to concentrate on evaluation of chronic cough:

1. Digital Clubbing

2. Examination of oral pharynx

3. Auscultation of Chest; wheezing, crackles

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

The evaluation of the child with chronic cough should be guided by the history and physical examination and by a careful attention to the differential diagnosis. At no time should the family’s concerns regarding the disruptive nature of the cough be disregarded or minimized. Effective communication will be essential when communicating the results of the evaluation.

Pulmonary Function Testing

Standard Pulmonary Function Testing (PFT) including spirometry and lung volume measurements are usually possible in children aged 8 and over. Children aged 6 to 8 years can usually perform acceptable spirometry. PFTs should be performed in any child capable. The presence of an obstructive defect with a response to bronchodilator would strongly suggest that asthma is the diagnosis and likely the cause of the cough.

Children aged 3 – 6 years of age can often cooperate with lung function measurement by the forced oscillation technique or impulse oscillometry. If airway resistance is elevated and falls in response to bronchodilator administration, this again suggests airway reactivity or asthma.

More advance PFTs in patients with unclear diagnosis includes bronchial provocation with methacholine, cold air or exercise. These tests may demonstrate airway reactivity not seen at baseline.

The most common laboratory test indicated in evaluation of chronic cough is a sweat chloride analysis or sweat test. The sweat test is currently the preferred screening test for Cystic Fibrosis (CF); it is more sensitive than commercially available genotype panels and the results are usually returned much faster, usually the same day. As 60% of children with CF diagnosed symptomatically present with chronic cough or wheeze, it is an important consideration in the patient with chronic cough. With more than 1800 CF mutations identified, the degree of disease at presentation remains highly variable. The old maxim has never been truer, “No child can look too well to have a sweat test.”

In selected patients, a target allergy evaluation or immune function evaluation may also be indicated.

Would imaging studies be helpful? If so, which ones?

A chest radiograph is the most commonly utilized imaging study in evaluating a child with chronic cough. An abnormal study will guide further evaluation and treatment while a normal chest radiograph can reduce anxiety regarding more serious diagnoses.

A chest CT scan may be necessary if bronchiectasis is being considered.

Sinus imaging may be indicated for excluding sinus disease.

In young patients with possible tracheobronchomalacia, the possibility of vascular compression should be considered. This can often be excluded with an esophagram. Alternatively, a thoracic MRI can give an excellent image of the cardiac structures and vasculature without radiation.

Confirming the diagnosis

A management pathway for chronic cough in childhood has been proposed by Chang and colleagues and is currently being evaluated by multicenter randomized controlled clinical trial. If validated it may become a standard for the approach to children with a chronic cough.

If you are able to confirm that the patient has Chronic Cough, what treatment should be initiated?

Treatment of Chronic Cough is directed at the etiology when established. It is important to recognize that in many cases the cause may be multifactoral: patients with asthma often have post nasal drip, for example; and habit cough can develop in the face of post-infectious cough and asthma.

While a complete discussion of the treatment of every possible cause of cough is beyond the scope of this section, a review of some highlights for certain entities follows:

Asthma

When the diagnosis of asthma is confirmed or strongly suspected in the patient with chronic cough, a short course of oral prednisone and frequent inhaled bronchodilators usually improves the symptoms rapidly. Afterwards, the decision to initiate daily asthma controller therapy will need to be confronted.

Common pitfalls in the treatment of asthma as cause of chronic cough:

1. Inadequate course of oral prednisone is used. Use 2 mg/kg/Day for 5 – 7 days.

2. Bronchodilators are not given at the same time as the prednisone and are not given frequently. Use albuterol at least four times a day until better. Many patients will choose to stop bronchodilators when steroids are prescribed unless specifically instructed by physician to use both drugs concurrently.

3. Poor inhaler technique. All metered dose inhalers (MDIs) need to be used with a valved holding chamber regardless of the patient’s age. Patients who use the MDI without a spacer will have poor medication deposition.

4. Failure to tell the patient that asthma is the diagnosis. Using euphonisms such as “reactive airways disease” will likely result in non-adherence.

5. Failure to start controller therapy, or stopping controller therapy soon after symptoms abate.

Posterior Pharyngeal Irritative Cough / Post Nasal Drip

This common cause of chronic cough can be difficult and frustrating to treat. The effect of the disruption on the family and patient should not be under emphasized. Treatment options are usually limited to intra nasal steroids (which are often not effective) and oral antihistamines. Some patients have some relief from ceterizine but often, the older more sedating antihistamines are more effective. Some patients have some relief with local care such as lozenges or hot drinks.

Cough suppressants are not recommended for pediatric patients.

Gastroesophageal Reflux related Chronic Cough

Gastroesophageal Reflux Disease (GERD) can cause irritation of the laryngeal structures and reflexive cough. Many patients who have chronic cough also have some element of GERD. Laryngoscopy has often been used to demonstrate irritated and inflamed laryngeal structures in pediatric patients with chronic cough.

Less commonly, esophageal pH measurements or esophagoscopy has been used.

Some patients with chronic cough and GERD will have improvement of their symptoms when acid reduction therapy is initiated. The addition of a proton pump inhibitor to the regimen of the patient with chronic cough and signs of GERD is now standard at most centers. Recent studies, however, have been inconsistent in documenting a reduction in cough after initiation of GERD therapy. Many patients appear to have chronic cough and GERD coincidently and a causative relationship is not established.

Habit Cough

There are many treatment modalities that have been reported to have some success in psychogenic or habit cough. The treatment will be most successful if the patient and family are accepting and optimistic about its success. Underlying stressful situations should be identified and dealt with when possible. Techniques that have been reported to be successful with habit cough include:

– Family therapy or psychotherapy directed at underlying stressors

– Behavior modification

– Relaxation techniques

– Hypnotherapy

– Suggestion therapy

– Deceptive therapy, using a bedsheet wrapped on the chest as a placebo was popular at one time but is less commonly used at present.

A common pitfall in the treatment of chronic cough is impatience with the therapy which can take time to work in the setting of an irritated airway and premature cessation of successful treatment.

What are the possible outcomes of Chronic Cough?

With patience and careful attention to all details, most cases of chronic cough will resolve. Unfortunately, cough commonly returns especially in the face of cessation of therapy. One challenge is separating future acute coughs from a return of the chronic cough.

What causes this disease and how frequent is it?

Cough is not a disease; it is a symptom of many diseases, each one having its own epidemiology. See Table I.