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Approach to chronic cough in children د هالة الرفاعي • INTRODUCTION • Coughing is an important defensive reflex that protects from aspiration of foreign • materials, and enhances clearance of secretions and particulates from the airways. Healthy children may • cough on a daily basis; one study documented an average of 11 cough episodes every 24 hours • However, a cough may also be the presenting symptom of a serious underlying pulmonary or • extrapulmonary disease. The causes of chronic cough in children are quite different from that of adults, • so evaluation and management of children should not be based on adult protocols. Adolescents 15 years • and older may be evaluated using guidelines for adults • The differential diagnosis of chronic cough in children includes subacute and chronic infections • bacterial bronchitis • pertussis, • mycoplasma, tuberculosis • foreign body aspiration, and cough dominant • asthma • Gastroesophageal reflux, upper airway cough syndrome (formerly • known as postnasal drip syndrome), and sinusitis are sometimes implicated because of associations with • chronic cough in adults, but their role in causing chronic cough in children is controversial [ • Less • common disorders must be excluded if the cough is unusually severe and/or frequent, or when there is • evidence of failure to thrive, growth retardation, purulent sputum, exertional dyspnea, hypoxemia, chest • pain, or hemoptysis • chronic cough appears to be common, with an estimated prevalence of 5 to 7 • percent in preschoolers, and 12 to 15 percent in older children • Cough is more common among • boys than girls up to 11 years of age • and may be less common in developing countries than in • affluent countries [ DEFINITION • There is no consensus as to the length of time in the definition of chronic cough in • children. The American College of Chest Physicians, Thoracic Society of Australia and New Zealand, • and many studies have defined chronic cough as one that lasts more than four weeks, because most acute • respiratory infections in children resolve within this interva • In comparison, guidelines from the • British Thoracic Society define chronic cough as one that lasts more than eight weeks • However, • these guidelines also describe a "prolonged acute cough" as one that lasts at least three weeks PHYSIOLOGY • Each cough occurs through the stimulation of a complex reflex arc • This • is initiated by the irritation of cough receptors that exist not only in the epithelium of the upper and lower • respiratory tracts, but also in the pericardium, esophagus, diaphragm, stomach, and external ear • • • • Chemical receptors sensitive to acid, heat mechanical cough receptors can be triggered by touch or displacement. The proximal airways (larynx and trachea) are more sensitive to • mechanical stimulation, the distal airways more sensitive to chemical stimulation. Irritation at the • bronchiolar and alveolar level does not cause cough • Impulses from stimulated cough receptors traverse afferent branches of the vagus nerve to a "cough • center" in the medulla and nucleus tractus solitarius, which itself is under control by higher cortical • centers. The cough center generates an efferent signal that travels down the vagus, phrenic, and spinal • motor nerves to expiratory musculature to produce the cough • The mechanical events of a cough can be divided into three phases • Inspiratory phase: Inhalation, which generates the volume necessary for an effective cough. • Compression phase: Closure of the larynx combined with contraction of muscles of chest wall, • diaphragm, and abdominal wall result in a rapid rise in intrathoracic pressure. • Expiratory phase: The glottis opens, resulting in high expiratory airflow and the coughing sound. • Large airway compression occurs. The high flows dislodge mucus from the airways and allow • removal from the tracheobronchial tree. • The specific pattern of the cough depends on the site and type of stimulation. Mechanical laryngeal • stimulation results in immediate expiratory stimulation (sometimes termed the expiratory reflex), • probably to protect the airway from aspiration; stimulation distal to the larynx causes a more prominent • inspiratory phase, presumably to generate the airflow necessary to remove the stimulus • Cough is an important defensive reflex that is required to maintain the health of the • lungs. Children who do not cough effectively are at risk for atelectasis, recurrent pneumonia, and chronic • airways disease from aspiration and retention of secretions • Many disorders can impair a child's ability to • cough effectively, resulting in persistent cough. Children with neuromuscular disease and chest wall • deformities may not generate a deep enough inspiratory volume or expiratory flow necessary for • effective clearance of secretions due to defective "pump" mechanisms • Children with reduced • function of the abdominal wall musculature are particularly at risk for ineffective cough. Children with • tracheobronchomalacia • ("floppy" airways), or with obstructive airways diseases, often do not generate • the high flow rates needed for effective clearance of secretions. Individuals with laryngeal disorders, • including those with tracheostomies, may not achieve sufficient laryngeal closure to generate the • increased intrathoracic pressures necessary for an effective cough [ DIAGNOSTIC APPROACH • Children with chronic cough should be evaluated with a detailed history, physical examination, chest • radiograph, and (if the child is able) spirometry • This evaluation often provides sufficient • information to categorize the cough as specific (ie, caused by an underlying disease) or nonspecific • Specific cough — The causes of specific chronic cough fall into the following general categories • • • • • • • • Asthma Persistent bacterial bronchitis Chronic suppurative lung disease and bronchiectasis Airway abnormality (congenital, foreign body, or neoplastic) Aspiration Chronic or less common infections Interstitial lung disease Extrapulmonary causes: cardiac abnormalities, ear conditions • The sequence of evaluation for these disorders is informed by the age and presenting features of the • child. Identification of the presenting features and cough characteristics is important because many are • easily recognizable and strongly suggestive of a specific cause; this is less true in adults. • Key symptoms and signs — Certain symptoms and signs are highly predictive of a specific cough. • These signs or symptoms narrow the diagnostic possibilities and call for further specific testing or • referral • Chronic wet cough • Wheezing or crepitations • Onset after an episode of choking, or sudden onset while eating or playing • Abnormal chest radiography or spirometry • Associated cardiac or neurologic abnormalities • Failure to thrive, feeding difficulties, or hemoptysis • the symptom of a chronic wet cough, with or without production of purulent sputum, is • always pathologic and warrants investigations for a persistent endobronchial infection (persistent • bacterial bronchitis or chronic suppurative lung disease), retained airway foreign body, or • immunodeficiency • Nonspecific cough — If symptoms suggesting specific cough are absent and the chest radiograph and • spirometry are normal • the possibility of asthma should be considered and pursued with an empiric • trial of bronchodilators and other asthma medications • If there is no response, the child should be considered to have a nonspecific cough, and the medication • should be stopped. The child and parents should be reassured and the patient observed over time for • possible emergence of specific symptoms • HISTORY — The diagnostic approach outlined above requires a detailed history, which should focus on • the following key elements • Age and circumstances at onset — Neonatal onset of coughing should prompt consideration of • congenital malformations (eg, tracheobronchomalacia), conditions predisposing to aspiration • tracheoesophageal fistula, laryngeal cleft, or a neurological disorder), or chronic pulmonary infections • (eg, cystic fibrosis or ciliary dyskinesia • A cough that begins suddenly while playing or eating, especially in the toddler age range, should raise • suspicion of an aspirated foreign body in the airway. The physician should specifically ask about a • history of choking, because this may have occurred weeks before and the family may not voluntarily • recall the information. Even if there is no history of choking, a foreign body remains a diagnostic • possibility • An episode of severe pneumonia can damage the airways, making the child vulnerable to chronic cough. • More rarely, severe pneumonia may cause frank bronchiectasis. A psychogenic or habitual cough also • often begins after an upper respiratory infection. Nature of the cough • . • Chronic paroxysmal cough triggered by exercise, cold air, sleep, or allergens is • often seen in patients with asthma. • Barking or brassy cough suggests a process in the trachea or more • proximal airways, such as airway malacia, laryngotracheobronchitis, spasmodic croup, or foreign body • Staccato cough in young infants can be the result of infection with Chlamydia trachomatis. Cough that is • honking ("Canadian Gooselike") • and disappears at night suggests a psychogenic or habitual cough. • A chronic productiv coughe • suggests a suppurative process, and may require further • investigation to exclude • Bronchiectasis • cystic fibrosis immune deficiency, or congenital • malformation • active infection • Acute or subacute paroxysmal cough suggests infection with pertussis or parapertussis; this characteristic • cough can be retriggered by subsequent upper respiratory illness Timing and triggers • The timing and triggers associated with cough can help guide diagnosis • Cough • due to asthma typically occurs following exposure to characteristic asthma triggers (ie, allergens, smoke, • exercise, cold air, or viral infection), and typically worsens during sleep • Cough associated with nasal • problems typically is worst during changes of position, • while cough due to bronchiectasis typically is • worst and most productive early in the day. • Cough that is triggered during swallowing is suggestive of aspiration, either primary or due totracheoesophageal fistula or laryngeal abnormalities • Cough in the first hour after meals, or which is • worse while supine, may reflect gastroesophageal reflux Associated symptoms • A history of dyspnea or hemoptysis should trigger a search for an underlying • lung disease • Hemoptysis should also raise concerns of bronchiectasis, cavitary lung disease (tuberculosis • or bacterial abscesses), heart failure, hemosiderosis, neoplasm, foreign bodies, vascular lesions, endobronchial lesions, catamenial bleeding, and clotting disorders • Cough, with or without symptoms of pancreatic insufficiency, recurrent endobronchial infection, and/or • failure to thrive should raise suspicion of cystic fibrosis • Cough associated with persistent fever, and/or • failure to thrive, or weight loss should raise suspicion of chronic infection and immune deficiency • Children with neurologic impairment or seizures frequently have chronic aspiration • Anaphylactic reactions to food can include cough but are unlikely to present with recurrent cough in the • absence of other symptoms of anaphylaxis Past medical history • The past medical history should include an account of the pregnancy, labor, and • delivery, as well as the neonatal course • Low birth weight and/or premature neonates are at risk for • developing atopic sensitization and asthma. • The past medical history should also include questions related to eczema and pulmonary infections. In • preschool children, a history of infantile eczema is often associated with inhalant allergy Family history • Family history of atopy or asthma increases the risk in offspring, and suggests a • diagnosis of either allergic rhinitis or asthma in the child with chronic cough • Family history of • cystic fibrosis or primary ciliary dyskinesia should raise suspicion for these disorders. • A careful history • should be obtained for current illness in family members or close contacts; such individuals with cough, • weight loss, and night sweats should arouse suspicion of tuberculosis. In some cases, the possibility of • HIV transmission from mother to child should be assessed • Social history and environmental exposures • Passive or active exposure to smoke from tobacco • marijuana, cocaine or other chemical irritants can result in chronic cough • In addition, woodburning • stoves cause indoor air • pollution and can predispose children to respiratory infection s Gas stoves are also associated with • respiratory symptoms in children • It is important to elicit any history of contact with pets or other animals, as cough may be induced by • allergy to the animals. Similarly, the location of the child's home and travel history may be relevant. • Local epidemiology can inform the diagnostic considerations, especially with respect to endemic fungal • and parasitic infections • Histoplasmosis is commonly associated with exposure to birds and • bats, and echinococcosis with exposure to dogs and sheep • Medications — Response to prior therapy may yield some diagnostic clues regarding the cause of • chronic cough. Previous response to antihistamines suggests a component of rhinitis and postnasal drip, • while a response to inhaled bronchodilators suggests possible asthma. • Any medications taken by the patient should be reviewed carefully; angiotensin converting enzyme • (ACE) inhibitors are a wellestablished • cause of chronic cough. Patients previously treated with cytotoxic • drugs or thoracic radiation are at risk of interstitial lung disease. PHYSICAL EXAMINATION • General examination — The physical examination should pay close attention to the following signs of • chronic underlying disease • General appearance of chronic illness • Poor growth, thinness, or obesity • Increased work of breathing, retractions, accessory muscle use, chest wall hyperinflation or • deformity, abnormal breath sounds (reduced intensity, asymmetry, wheezing, stridor, crackles) • Shiners, swollen nasal turbinates, nasal obstruction, nasal polyps, allergic nasal crease, halitosis, • tonsillar hypertrophy, pharyngeal cobblestoning, high arched or cleft palate, hoarseness • • • • Tympanic membrane scarring or frank otorrhea Abnormal heart sounds, abnormal pulses Hepatoand/ or splenomegaly, abdominal masses, bloating, rectal prolapse • Edema of the extremities, cyanosis and/or clubbing of the digits • Rashes and other skin lesions (eg, scars of healed recurrent impetigo) Chest examination • Polyphonic wheezing (ie, many different pitches) with cough is typical of asthma; the wheezing occurs • on expiration and sometimes also on inspiration • Many children with asthma are also atopic and exhibit • signs of rhinitis, conjunctivitis, and/or eczema • Other causes of polyphonic wheezing include viral • bronchiolitis, obliterative bronchiolitis, bronchiectasis (cystic fibrosis, allergic bronchopulmonary • aspergillosis, primary ciliary dyskinesia), bronchopulmonary dysplasia, heart failure, immunodeficiency, bronchomalacia, and aspiration syndromes. Monophonic wheezing • Monophonic wheezing (a single, distinct noise of one pitch and starting and stopping at one discrete • time) and cough should always raise suspicion of large airway obstruction caused by foreign body • aspiration or malacia and/or stenosis of the central airways • lymphadenopathy, and mediastinal • tumors can cause extrinsic large airway obstruction. Tuberculosis should always be considered in a child • with a monophonic wheeze, particularly in areas where the disease is prevalent CHEST RADIOGRAPHY • In addition to a thorough history and physical examination, a chest • radiograph should be obtained. If foreign body aspiration is suspected because of the age, clinical • presentation or history, frontal films should be obtained during both inspiration and expiration, to • evaluate for unilateral lung hyperinflation that would suggest airway obstruction. Similar information can • be obtained from the combination of frontal, right lateral decubitus, and left lateral decubitus • radiograph PULMONARY FUNCTION TESTS • Spirometry will show signs of obstruction in diseases that • obstruct the airways, and restriction in interstitial or chest wall restrictive processes. Suboptimal effort on • the part of the child will also result in a restrictive picture; thus, spirometry should be conducted by a • technician proficient in testing children • If an obstructive pattern is seen on the expiratory flowvolume • loop, the reversibility of the obstruction • can be assessed by measuring FEV1 before and after inhalation of a bronchodilating agent. A positive • response to bronchodilators establishes the presence of airway reactivity, and is suggestive of asthma but • does not rule out other disorders BRONCHOSCOPY • The primary indication for urgent bronchoscopy in children with chronic cough • is for suspected foreign body aspiration. • Bronchoscopy is also valuable in the evaluation of suspected airway malacia, tracheoesophageal fistula, • or stenosis • Patients with presumed infectious etiologies in whom a sputum sample is not obtained or • yields negative results can be evaluated with flexible bronchoscopy to perform bronchoalveolar lavage • for bacterial, fungal, and mycobacterial cultures. Bronchial brushings can also be taken for patients with • suspected ciliary dyskinesia, although nasal brushings also may be used OTHER TESTS • Esophageal pH monitoring — • Whether gastroesophageal reflux disease (GERD) is an important cause • of isolated chronic cough in children is controversial. Most authorities suggest that this is not a common • Sinus imaging • Tuberculin testing • Allergy testing SUMMARY AND RECOMMENDATIONS • There is no consensus definition of the time frame for chronic cough in children. Chronic cough is • often defined as a cough lasting more than four weeks, because most acute respiratory infections in • children resolve within this interval. Other schemes define chronic cough as one that last more than • eight weeks but also recognize that a relentlessly progressive cough often warrants evaluation prior • to eight weeks • Chronic cough can be a symptom of congenital anomalies, genetic disease, airway obstruction, • infection, airway inflammation without infection (as in asthma), neoplasia, or psychogenic • processes • The evaluation of a child with chronic cough should include a detailed history, physical • examination, chest radiograph, and spirometry (when possible • Symptoms and signs that are highly predictive of a specific cough include chronic wet cough, • wheezing or crepitations, onset after a choking episode, abnormal chest radiography or spirometry, • associated cardiac or neurologic abnormalities, and failure to thrive, feeding difficulties, or • hemoptysis. These signs or symptoms narrow the diagnostic possibilities and call for further • specific testing or referral • The symptom of a chronic wet cough in a young child, usually indicates persistent bacterial • sinusitis or retained foreign body شكرا •