Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at NSU
Pathophysiology of cough:
- large particles reach the upper respiratory structures - removed by coughing unless lodged as foreign body
- small particles reach the bronchioles - removed by mucociliary activity
- smallest particles reach the alveoli - removed by alveolar macrophages by phagocytosis
Cough expels particles from the airway at "the speed of sound."
Defined as cough of less than 4-week in duration. The most common cause is acute upper respiratory infection (URTI). The cough is usually non-productive or minimally productive of sputum (phlegm).
Frequent viral infection (normal frequency is up to 8-10 per year) with acute cough can mimic chronic cough. Acute cough due to repeated viral infections is associated with normal chest X-ray. This type of cough is unresponsive to asthma therapy with ICS or LTRA.
Defined as cough of greater than 4-week in duration. Evaluation is indicated.
Chronic cough is very common and it is the 5th most frequent cause of patient visits. The most common cause of chronic cough in children is cough-variant asthma.
Cough suppressants (cough syrup) are prescribed on a "massive scale" in children but there is little evidence for efficacy beyond the placebo effect and the natural resolution of the cough.
The current guidelines (see the references at the end of the article) divide chronic cough into specific and nonspecific categories.
Placebo effect can have a considerable impact, Treatment should be based on the etiology of the cough. Adult studies may not be applicable to children, for example, GERD is a common cause in adults but relatively rarer in children, foreign body aspiration should be considered in children.
Chronic productive purulent cough always requires intervention.
Differential diagnosis of cough, a simple mnemonic is GREAT BAD CAT TOM. Click here to enlarge the image: (GERD (reflux), Laryngopharyngeal Reflux (LPR), Rhinitis (both allergic and non-allergic) with post-nasal drip (upper airway cough syndrome, UACS), Embolism, e.g. PE in adults, Asthma, TB (tuberculosis), Bronchitis, pneumonia, pertussis, protracted/persistent bacterial bronchitis (PBB), Aspiration, e.g foreign body in children, Drugs, e.g. ACE inhibitor, CF in children, Cardiogenic, e.g. mitral stenosis in adults, Achalasia in adults, Thyroid enlargement, e.g. goiter, "Thoughts" (psychogenic), Other causes, Malignancy, e.g. lung cancer in adults).
Diagnosis of chronic cough
History - ask about duration (months vs. years), seasonal trends (e.g. allergic asthma triggered by ragweed), times of day when present (night cough could be GERD), associated symptoms, triggers (e.g. exercise in EIB), inhaled foreign body or choking at any age (50% of aspirated foreign bodies have no history), successful and unsuccessful therapies, recent weight loss (ominous sign - cancer or severe infection), recurrent infections (could indicate immune deficiency (PIDD) or ciliary dyskinesia).
Physical examination - assess growth and development for nutritional status and/or obesity, upper respiratory tract for signs of allergic rhinitis (pale boggy trubinates, allergic shiners, Dennie's line), chronic sinus disease, postnasal drip, nasal polyps (CF, PIDD), ear-cough reflex (foreign body in the ear triggers cough in 5% of children).
Specific chronic cough - clinical clues for diagnosis
- auscultatory findings (asthma, CF)
- cardiac abnormalities
- chest pain or dyspnea
- elevated respiratory rate
- chest wall deformity
- digital clubbing
- productive purulent cough (CF, foreign body)
- difficulty with exercise (EIB)
- failure to thrive (CF)
- recurrent bacterial pneumonia (CF, PIDD)
- feeding difficulty - aspiration from the "top" (swallowing problem) or "below" (GERD)
- hemoptysis - never "normal"
- immune deficiency
- congenital anomaly
- neurodevelopmental condition - aspiration risk
Evaluation of nonspecific cough:
- chest X-ray - CF, pneumonia. "If you suspect meningitis, do an LP. If you suspect CF, do a sweat test." The current newborn screening identifies 95% of children with CF - this means that 5% of children with CF are not identified at birth and present with symptoms later in life.
- spirometry - asthma
If CXR and spirometry are normal, observe for 1 to 2 weeks.
Treatment of nonspecific cough
- an antibiotic (macrolide) for "wet" productive cough. A 2-week course of amoxycillin clavulanate achieves cough resolution in children with chronic wet cough, supporting the diagnosis of protracted/persistent bacterial bronchitis (PBB, http://goo.gl/4Vmtd).
- a trial of inhaled steroid (ICS) for dry cough
Specific chronic cough
Diagnostic evaluation includes:
- infants and toddlers - chest X-ray and sweat chloride test
- infants and toddlers - evaluate for aspiration - due to either gastroesophageal reflux (GERD) ("bottom") or swallowing disorder ("top")
- infants and toddlers - immunodeficiency studies - quantitative immunoglobulins (IgGAME), nitroblue tetrazolium test (NBT) or even better DHR, complete blood count with differential
- reversible airway obstruction - spirometry if older than 5 years, followed by aerosolized bronchodilator, check for reversible obstruction 15 minutes later. If positive (more than 12% reversibility), treat for asthma.
- older children - chest X-ray, sweat chloride, pulmonary function tests (PFTs), and immunodeficiency studies
- computed tomography (CT) for bronchiectasis, interstitial lung disease (ILD), and congenital lesions. Use a pediatric CT protocol to minimize radiation
- flexible bronchoscopy for microbiological culture and airway assessment
- rigid bronchoscopy (performed by otolaryngologist (ENT) for aspirated foreign body (right mainstem bronchus is the typical place)
Chronic cough causes in children when using a step-by-step approach:
- 25% asthma. Asthma is the most common chronic respiratory disease, affecting up to 10% of adults and 30% of children (JACI, 2011).
- 23% prolonged bronchitis, protracted/persistent bacterial bronchitis (PBB) (responds to antibiotics)
- 20% upper airway cough syndrome or UACS (post-nasal drip)
- 5% GERD
- 2% bronchiectasis
Chronic cough causes in children when using "order all test from the beginning" approach. Work-up included chest X-ray, bronchoscopy, pulmonary function tests (PFTs) with bronchial challenge, sweat chloride, pH probe for GERD, and immunoglobulin levels (IgGAME):
- 28% GERD
- 22% allergic rhinitis or post-nasal drip (upper airway cough syndrome, UACS)
- 13% asthma
- 5% infection
- 3% aspiration
- 20% multiple etiologies - this is due to all tests done concurrently
Age-based diagnosis of chronic cough:
- infancy - aspiration, asthma, cystic fibrosis, recurrent respiratory tract infections, passive smoke exposure, congenital heart disease
- early childhood - aspiration, asthma, foreign body aspiration, cystic fibrosis, bronchiectasis, chronic sinusitis
- late childhood and adolescence - asthma, bronchiectasis, cystic fibrosis, infection, foreign body aspiration, active or passive cigarette smoke, psychogenic cough, sinusitis, post-nasal drip
Aspirated (retained foreign body
This can occur at any age. There is a positive initial history only in 30% of cases - the yield can be increased to 50% by focused questioning.
Ask about high risk habits - eating nuts, chewing on pencil eraser, etc.
Imaging: inspiratory-expiratory or bilateral decubitus plain films, CT may be necessary
The ultimate diagnosis and treatment is with rigid bronchoscopy by ENT.
Psychogenic cough (habit cough)
Typically diagnosed in pre-teens and teenagers. It disappears during sleep. Diagnostic evaluation is non-revealing. There is no response to medications (ICS or antibiotics).
Chronic, persistent cough - without wheezing - may be the only manifestation of asthma. More than 60% bronchial obstruction is needed to produce wheezing - asthma can occur without wheezing - spirometry is required for diagnosis.
Cough-variant asthma presents as dry cough at night. It worsens with exercise (EIA) and nonspecific triggers (cold air).
Cough-variant asthma responds to asthma therapy with ICS.
Cough-variant asthma is diagnosed with pulmonary function testing (PFTs) with response to bronchodilator.
The most common cause of chronic cough in children is cough-variant asthma.
Cough suppressants in children - there are no randomized controlled trials to support efficacy. The suppression could be hazardous, especially with productive cough.
Treat viral-related cough with increased fluid intake and humidity (aerosolized saline, etc.).
The cough suppressant dosing guidelines for adults are imprecise in children. An alternative is throat lozenges ("Halls", etc.).
Chronic cough in children – Sally L. Davidson Ward. Audio-Digest Pediatrics, Volume 56, Issue 10, May 21, 2010.
Guidelines for evaluating chronic cough in pediatrics: ACCP evidence-based clinical practice guidelines. Chang AB, Glomb WB. Chest. 2006 Jan;129(1 Suppl):260S-283S.
Guidelines for evaluating chronic cough in pediatrics: ACCP evidence-based clinical practice guidelines. Agency for Healthcare Research and Quality.
How should one investigate a chronic cough? Cleveland Clinic Journal of Medicine, 2011.
Tips to Remember: Cough in Children. Allergy Tips brochures by AAAAI.
Allergies are bad, sure -- but do you know what happens when your kid inhales a nut. ChicagoTribune.com, 2011.
Green or yellow phlegm likely to be bacterial - confirming beliefs by doctors & patients http://goo.gl/zff8X and http://goo.gl/cwKGs
Diagnostic algorithm for the approach to children with chronic cough. ER, 2011.
Diagnostic Checklist (mobile version) - UToronto and standard web version
Childhood cough - 2012 BMJ review.
Child with chronic cough - WAO interactive case http://goo.gl/yK48I
AInotes - Chronic Cough (Pediatric) http://bit.ly/Ue0g83
Differential diagnosis of chronic cough in children. Allergy and Asthma Proceedings, Volume 35, Number 2, March/April 2014 , pp. 95-103(9) http://buff.ly/1mpq9oy
Clinical approach from the concept of cough hypersensitivity - figure: http://buff.ly/1Jej9Cq
Chronic Cough - COLA video lecture http://bit.ly/URcUQa: