1 Describe the cough reflex.

Stimuli that induce cough can be mechanical (e.g., foreign body, dust), chemical (e.g., capsaicin, acetic acid), or inflammatory mediators (e.g., histamine, bradykinin, prostaglandin E₂). Such stimuli interact with cough receptors in the upper and lower airways that cause production of mediators, such as tachykinins and neurokinin A. Stimulation of the cough receptors is transmitted via the vagus nerve to the “cough center” of the brainstem (probably located in the pons). The efferent limb of the cough pathway is poorly understood, but is known to include the spinal cord from C3 to S2, spinal nerves, and the recurrent laryngeal nerve (for glottic closure). Activation of the efferent pathway causes constriction of the expiratory muscles, which produces increased airway pressure against the closed glottis. The airway also narrows slightly. When the glottis is suddenly opened, air is expelled at a high velocity, clearing the airway of secretions and foreign material.

2 How is a cough suppressed?

As with respiration, cough is largely involuntary but can be suppressed voluntarily to a certain extent (cortical modulation). Opioids that suppress cough (e.g., morphine) are believed to produce this effect by acting centrally on the cough center. Inhalation of nebulized lidocaine suppresses cough by affecting cough receptors in the airway.

3 Is the cough reflex mediated by the same pathway that produces bronchospasm?

It has been widely held that airway hypersensitivity (asthma/bronchospasm) and cough are manifestations of the same physiologic mechanism. By this thinking, persistent coughing, such as wheezing, is a common presentation of asthma. This view has led to the current trend of diagnosing children with persistent coughing as being asthmatic (“cough variant” asthma), even when these patients have no other evidence of bronchospasm (dyspnea, exercise intolerance, abnormal spirometry findings). However, recent evidence suggests that while airway hypersensitivity and cough receptor sensitivity can be triggered by the same stimuli, this probably occurs via two different pathways. For most children, it appears that persistent coughing results solely from increased sensitivity of cough receptors in the upper and lower airways and does not represent true asthma/bronchospasm.

Chang AB: Cough, cough receptors, and asthma in children. Pediatr Pulmonol 28:59–70, 1999.

4 How much coughing is normal?

One of the primary obstacles in studying cough in children has been that this symptom is difficult to reliably measure. Reproducibility of survey questions is poor, and, unlike the situation with asthma, there is no validated subjective cough scoring system. Fortunately, a new device that a child can wear like a Holter monitor provides an objective measurement of coughing. When this device was used with “normal” children who had no history of asthma and no respiratory illnesses in the previous 4 weeks, the mean cough frequency over 24 hours was 11.3 episodes (range, 1–34 episodes). Thus, the frequency of coughing episodes varies widely even among children without respiratory problems.

Munyard P, Bush A: How much coughing is normal? Arch Dis Child 74:531–534, 1996.

5 What is the most common cause of persistent cough?

While the differential diagnosis of persistent cough (>2 weeks) in children is relatively broad (Table 9-1), the most common cause is probably postviral or inflammatory cough, which has been variably called nonspecific cough, isolated cough, or cough illness. Children who develop a viral upper respiratory tract infection may continue to cough long after other viral symptoms (e.g., rhinitis, fever) have subsided. These patients have a persistent, dry cough (particularly at night), but do not have wheezing, chest tightness, dyspnea on exertion, or other symptoms of bronchospasm. This type of cough may persist for several weeks before resolving spontaneously.

Table 9-1 Differential Diagnosis of Persistent Cough by Age

Infancy (<1 year)

Infection: viral, bacterial, chlamydial

Anatomic abnormalities: tracheomalacia, vascular rings

Cystic fibrosis

Bronchopulmonary dysplasia (premature infants)

Preschool (1–5 years)

Asthma

Infection

Foreign-body aspiration

Cystic fibrosis

School age (5–18 years)

Asthma

Infection (especially mycoplasma)

Smoking

Psychogenic causes

Hay AD, Wilson AD: The natural history of acute cough in children aged 0 to 4 years in primary care: A systematic review. Br J Gen Pract 52:401–409, 2002.

6 Do gastroesophageal reflux disease (GERD) and sinusitis commonly cause persistent cough?

No. When confounding factors such as airway hyperreactivity and atopy are removed, prospective, controlled studies among children with GERD and sinusitis who also have persistent coughing have shown no reduction in cough with treatment of these two underlying conditions. Prior studies that showed a benefit were generally anecdotal or were not placebo controlled. To date, no reliable evidence indicates that persistent cough is related to either GERD or sinusitis.

Chang AB, Phelan PD, Sawyer SM, et al: Airway hyperresponsiveness and cough-receptor sensitivity in children with recurrent cough. Am J Respir Crit Care Med 155:1935–1939, 1997.

7 Is cough-variant asthma underdiagnosed?

In fact, the opposite is more likely the case (i.e., it is probably overdiagnosed). In the past, children with persistent cough accompanied by signs of true bronchospasm such as exercise intolerance, but without wheezing, often were not diagnosed with asthma. The syndrome of cough and acute exertional dyspnea was first identified in a series of adult patients in 1975, and the term cough-variant asthma was coined in 1979. Before that time, cough-variant asthma was certainly underdiagnosed. Now, however, the diagnosis of asthma in children with isolated cough has been widely embraced. In fact, some have suggested that recent increases in the prevalence of asthma are largely due to expanding the diagnostic criteria to include children with isolated cough. This has occurred despite evidence that most of these patients do not respond to conventional asthma therapy (see next question). It would appear that the pendulum has swung too far, and we are currently overdiagnosing and overtreating asthma in patients with simple postviral coughing.

Benedictis FM, Selvaggio D, Benedictis D: Cough, wheezing and asthma in children: Lesson from the past. Pediatr Allergy Immunol 15:386–393, 2004.

8 Do children with persistent cough respond to standard therapy for asthma?

Given the caveats described in the previous question, it is safe to say that children with true cough-variant asthma should respond to treatment with bronchodilators and/or steroids within hours to a few days. However, these patients represent a relatively small percentage of the children presenting to the emergency department (ED) with persistent coughing. Most will have postviral cough, which does not respond to conventional asthma therapy. Therefore, unless a child with persistent cough has a history that suggests a true bronchospastic etiology (severe coughing and dyspnea occurring consistently with exertion), it is not generally wise to make a de novo diagnosis of cough-variant asthma and initiate bronchodilator or steroid treatment. Conversely, if a child has been receiving conventional asthma therapy for several days to weeks and coughing has not decreased, the patient is very unlikely to have cough-variant asthma and the asthma treatments can be stopped.

Thompson F, Masters IB, Chang AB: Persistent cough in children and the overuse of medications. J Paediatr Child Health 38:578–581, 2002.

9 Does cough due to bronchitis respond to treatment with antibiotics?

Bronchitis seems to be a diagnosis in search of significance. Most clinicians use the term bronchitis when referring to a patient with a persistent, productive cough without evidence of pneumonia. Yet if the diagnostic criteria are poorly defined in adults (how much sputum? how often?), the situation with children is worse. The primary issue with children is that they do not cough up sputum; they swallow it. Consequently, diagnosing bronchitis in a child is usually difficult or impossible, since sputum production can rarely be established or quantified. At any rate, studies in adults have shown no efficacy in treating bronchitis with antibiotics, and studies in children show no efficacy in treating persistent cough with antibiotics.

O’Brien KL, Dowell SF, Schwartz B, et al: Cough illness/bronchitis—principles of judicious use of antimicrobial agents. Pediatrics 101:178–181, 1998.

10 Does antibiotic treatment of cough due to an upper respiratory tract infection prevent subsequent pneumonia?

Although most clinicians acknowledge that frequent use of antibiotics to treat viral upper respiratory tract infections is an important cause of increasing antibiotic resistance in bacteria, this practice continues to be widespread. One justification for the use of antibiotics in such cases is to provide prophylaxis against subsequent pneumonia. However, at least nine trials have assessed the utility of antibiotic prophylaxis for patients with upper respiratory tract infection, and a meta-analysis of these trials reported no effect of antibiotic treatment in preventing pneumonia.

Dowell SF, Schwartz B, Phillips WR, et al: Appropriate use of antibiotics for URIs in children: Part II. Cough, pharyngitis, and the common cold. Am Fam Physician 58:1113–1123, 1998.

Gadomski AM: Potential interventions for preventing pneumonia among young children: Lack of effect of antibiotic treatment for upper respiratory infections. Pediatr Infect Dis J 12:115–120, 1993.

11 Do commonly used cough medications work?

In a word, no. Numerous studies have addressed this question, and the bulk of evidence indicates that the commonly used pediatric cough preparations are no more effective in suppressing cough than placebo. This includes dextromethorphan, guaifenesin, and codeine. Furthermore, many of the pediatric cough medicines also contain potentially dangerous agents such as decongestants that, if used in excessive doses, can cause cardiac arrhythmias in children. Despite these facts, we continue to spend over $2 billion annually in the United States for cough and cold preparations—another testament to the power of advertising and its influence on medicine.

Schroeder K, Fahey T. Over-the-counter medications for acute cough in children and adults in ambulatory settings. Cochrane Database of Systematic Reviews, Vol. 2, 2005.

12 What problem should come to mind if a toddler presents with a persistent, nagging cough after a severe choking spell?

This is the classic history for foreign-body aspiration. Parents of a young child who has ongoing episodes of moderate to severe coughing should be questioned about the occurrence of a choking spell. The child (who is preverbal and cannot tell what happened) typically has a small toy or bead in his or her mouth, takes a breath, and has the object enter the trachea; at this point a severe choking spell ensues. If the object is about the size of the trachea, and it cannot be expelled with coughing, the child will quickly develop signs of severe upper airway obstruction. Yet if the object is smaller than the diameter of one of the mainstem bronchi, it may lodge there so that the child recovers with only a persistent cough. A patient with normal lungs will have adequate oxygenation and ventilation despite complete occlusion of one mainstem bronchus. Expiratory chest radiographs may show decreased “deflation” of the affected lung. In a young child, or uncooperative child, bilateral decubitus x-rays may show the same finding. However, if the story is classic, it is wise to consult an otolaryngologist even if the chest radiographs are normal.

13 What is habitual cough?

Habitual (or psychogenic) cough is a type of conversion reaction, in which a child responds to stressors by developing symptoms such as abdominal pain, headache, or difficulty breathing but there is no organic disease. The onset of persistent symptoms may be followed by an extensive, yet unrevealing, medical workup (e.g., multiple sets of laboratory results, multiple computed tomographic scans). Typically, there is an issue of secondary gain—for example, obtaining increased attention, preventing parents from fighting, avoiding school—that may only be reinforced by repetitive medical tests. Habitual cough is one of the more straightforward conversion reactions to manage in the ED because unlike symptoms such as difficulty breathing or severe headache, children rarely die from cough. As such, a patient with habitual cough can often be discharged from the ED, after a specific plan for outpatient follow-up (with the child’s pediatrician or possibly a pulmonologist) has been formulated, without significant doubt or worry that the child is being sent home with a potentially dangerous illness.

de Jongste JC, Shields MD: Chronic cough in children. Thorax 58:998–1003, 2003.

14 What are the characteristics of a patient with habitual cough?

One of the most striking aspects of this condition is the disconnect between the reaction of the parents and the reaction of the child—the parents are often extremely upset and anxious while the child appears unconcerned. Parents are commonly “at the end of their rope” and are coming to the ED for a second opinion. The child may already have had one or more normal chest radiographs or blood test results obtained by other health care providers. A patient with habitual cough is typically older (school-aged or adolescent), has missed multiple (sometimes many) days of school, is not awakened from sleep at night by the cough, and has a completely normal physical examination. Aspiration of a foreign body can generally be excluded because the patient is old enough to deny it. The cough itself will often sound like a “honk”—harsh, loud, and impossible to ignore.

Bush A: Paediatric problems of cough. Pulm Pharm Therapeutics 15:309–315, 2002.

15 How is habitual cough managed in the ED?

As with most other types of conversion reaction, habitual cough cannot always be diagnosed conclusively in the ED. It is generally a diagnosis of exclusion, that is, after any potentially significant conditions (e.g., pneumonia, bronchospasm, pneumothorax) have been ruled out. Sometimes this subject can be gently broached with parents, although their reaction may be very defensive (“Are you saying this is all in her head?”). Establishing rapport by demonstrating genuine concern, listening carefully, and avoiding an accusatory or judgmental tone is essential. In some situations, it may be better to leave discussion of this diagnosis to the private pediatrician or specialist (e.g., a pulmonologist).

16 What is one thing parents should always do if their child has a persistent cough?

They should stop smoking and forbid others from smoking in the house where the child resides.

17 What is the strangest cause of persistent cough?

Although this is certainly open to debate, perhaps the oddest cause of persistent cough is an eyelash stuck in the child’s ear. Curiously, stimulation of the external auditory canal or the tympanic membrane by an eyelash can repetitively provoke the cough reflex in a child. Unlike other otic foreign bodies, an eyelash does not cause pain or diminish hearing and may therefore go undetected for an extended time. Furthermore, it may not be immediately obvious on otoscopy. Consequently, it is wise to carefully examine the ears of a child with persistent coughing in hopes of finding this rare and elusive, yet easily remedied, cause of a troublesome symptom.