Cough is a very frequent reason why patients consult their family doctor and seek advice from the community pharmacist. Together with breathlessness, it is one of the commonest symptoms of lung disease.1 Cough is not only a symptom, but also a very rapid defence mechanism that both protects and clears the airways. Coughing may also be looked upon as a means of spreading infection via droplets and contamination of objects.peer-reviewe

Cacciottolo, Joseph M.

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Issue 9  Respiratory Supplement 2005    the chronic✱ill         17Coughing may be voluntary but it isusually an involuntary reaction tostimulation of cough receptors in theairways.  The cough centre in themedulla oblongata reacts to stimuliarising from receptors in the nose,nasopharynx, tracheobronchial tree,and the pleura.  The slightestinhalation of minute amounts offoreign matter is enough to trigger thecough reflex.Cough: a defencemechanismand a symptomDepartment of Medicine, University of Malta Medical School, MaltaE-mail: joseph.cacciottolo@um.edu.mtKeywords: cough, smoking, post-nasal drip, asthma, gastro-oesophagela reflux,diagnostic protocolJoseph M Cacciottolo MD, DScCough is a very frequent reason why patients consult theirfamily doctor and seek advice from the communitypharmacist. Together with breathlessness, it is one of thecommonest symptoms of lung disease.1 Cough is not only asymptom, but also a very rapid defence mechanism that bothprotects and clears the airways.  Coughing may also be lookedupon as a means of spreading infection via droplets andcontamination of objects.The physiology of coughing involvesquite a complex sequence.  There isfirst deep inhalation, and a closedglottis seals the air within the lungs.The abdominal and other respiratorymuscles contract forcefully, raisingpressure within the lungs to over100mmHg.  The vocal cords andepiglottis suddenly open, releasing theair in the lungs at exhalation velocitiesof over 100km/h.Complications of coughing areinfrequent and are usually mild, such ashoarseness and headaches.  Recurrentsevere bouts may however lead to suchcomplications as urinary incontinence,disruption of surgical wounds,subconjunctival haemorrhages and ribfractures.  Chronic coughing oftencauses persons to be self-conscious andmay affect the quality of lifesignificantly.2The most common cause of acutecough is the common cold and usuallysubsides without the need for anytreatment; other causes are acutesinusitis, pertussis and asthma.3Occasionally, acute cough is a symptomof serious disease such as congestiveheart failure, pulmonary embolism,pneumonia or inhalation of a foreignbody.Chronic cough may be defined as acough of more than eight weeks’duration.4,5  Cigarette smoking is aleading cause of chronic cough and thesymptom is directly related to thenumber of cigarettes smoked per day.6About 25% of those who smoke half apacket per day report a chronic cough,and this figure rises to over 50% amongthose who smoke more than twopackets daily.  Many smokers acceptcoughing as normal and may not seekmedical attention for a cough thatpersists.  Cough is also an importantsymptom of lung cancer, a diseasepredominantly prevalent amongsmokers.  Indeed, a change in thecharacter or pattern of coughing in asmoker should always be thoroughlyinvestigated.The four most common causes ofchronic cough among non-smokers arepost-nasal drip, asthma, gastro-oesophageal reflux and post-infectiousbronchial infection.  Patients with post-nasal drip syndrome also complain of asensation of something dripping intothe throat, a tickle in the throat,hoarseness, nasal congestion and/ordischarge.  If sinusitis is the cause ofpost-nasal drip, combined treatmentwith antibiotics, intranasalcorticosteroids and decongestants may18          the chronic✱ill     Issue 9  Respiratory Supplement 2005be necessary.7Asthma may cause chronic coughacross all age groups and must beconsidered in the differential diagnosisof most patients presenting with thissymptom.  When cough is the onlysymptom of this condition, the termcough-variant asthma is used.Treatment for this form of asthma is thesame as for asthma presenting withother symptoms: anti-inflammatorytreatment being the mainstay oftherapy, and use of bronchodilators forrapid relief.8Gastro-oesophageal reflux (GOR)occurs when acidic stomach contentsleak into the oesophagus or higher up.The most likely pathogenesis isstimulation of vagally mediatedreceptors in the oesophagus, and theactual aspiration of stomach contentscausing cough is uncommon.  Patientswith GOR may complain of chestdiscomfort and heartburn; howeverchronic cough may be the onlysymptom present.  Diagnosis of GOR-related cough can be made withcertainty when the symptoms respondto anti-reflux therapy.9Chronic inflammation of the airwaysis an important trigger of persistentcough, and chronic bronchitis due toexposure to tobacco smoke or otherrespiratory irritants is the commonestcause in this respect; other causesinclude bronchiectasis.  Coughing maypersist following acute respiratory tractinfection and is due to ongoinginflammation.  This cough eventuallyresolves, however treatment is oftennecessary to ease discomfort.Occasionally, cough occurs as aside-effect of medication and the classof drugs most commonly implicated isangiotensin converting enzyme (ACE)inhibitors.  A review of the literaturesuggests that around 10% of patientstreated with an ACE inhibitor may havecough as a side-effect, rapidly resolvingwhen the drug is withdrawn.10Treatment with beta-blockers may causeincreased airway resistance andconsequent provocation of coughingespecially among patients sufferingfrom asthma and COPD.Psychogenic cough occurs morefrequently in children; however it haslower rates of resolution among adults.Emotional and psychological problemsare the likely causes and this diagnosiscan only be made after all otherpossibilities have been ruled out.  Mostpatients with psychogenic coughneither have this symptom during sleepnor during enjoyable distraction.  Insome patients, coughing is a nervoustic, occurring only when they becomeupset or self-conscious. 11When coughing is transient, and ofa trivial nature, investigations are notnecessary and only symptomatic reliefis warranted.  When the cough becomeschronic, evaluation should begin with adetailed history and a physicalexamination initially focusing on thenose, the nasopharynx and the lungs.Easily identifiable causes, such as ACEinhibitor use and exposure to irritantfumes, should be addressed.  A chest X-ray should be considered very early inthe evaluation process, and morespecific tests considered should this beabnormal or if the cough persists.Algorithms for evaluating cough havebeen drawn by a Consensus Panel of theAmerican College of Chest Physiciansand the European Respiratory SocietyTask Force5, and suggest a sequentialapproach both for immunocompetentand for immunologically-incompetentadults.When pharmacologic treatment ofcough becomes necessary, distinctionbetween anti-tussive therapy and pro-tussive therapy is important.1   Non-specific cough suppressants such ascodeine and dextromethorphan aredirected at the symptom and not at thecause.  They are indicated whenspecific therapy cannot be given orwhen this has not yet treated thecause.12  They are also given whenspecific therapy cannot work, as inadvanced and inoperable lung cancer.Coughing is necessary for mucusclearance and this may be facilitated byagents that increase cougheffectiveness, often by makingexpectoration easier.  In practice,however, evidence of clinical utility ofthese agents is not clear.1. ACCP Consensus Panel. Managing cough as adefense mechanism and as a symptom.CHEST 1998;114 (suppl) 1338-1815.2. French CT. Irwin RS, Fletcher KE, Adams TM.E. Evaluation of cough-specific quality of life.Chest 2002;121:1123-31.3. Curley FJ, Irwin RS, Pratter MR et al. Coughand the common cold. Am Rev Respir Dis1988:138:305-11.4. Irwin RS, Madison JM. The diagnosis andmanagement of cough. N Engl JMed;2003;43:1715-21.5. ERS Task Force. The diagnosis andmanagement of chronic cough. Eur Respir J2004; 24:481-92.6. Janson C, Chinn S, Jarvis D, Burney P.Determinants of cough in young adultsparticipating in the European CommunityRespiratory Health Survey. Eur Respir J 2001;18:647-54.7. Sen RP, Walsh TE. Fibreoptic bronchoscopy forrefractory cough. Chest 1991;99:33-35.8. Irwin RS, French CT, Smyrnios NA, Curley FJ.Interpretation of positive results of amethacholine inhalation challenge and 1week of inhaled bronchodilator use indiagnosing and treating cough-variantasthma. Arch Intern Med 1997;157:1981-87.9. Kijander TO, Salomaa ER, Hietanen EK, TerhoED. Chronic cough and gastro-oesophagealreflux: a double blind placebo controlled trialwith omeprazole. Eur Respir J 2000;16:633-638.10. McEwan JR, Choudry N, Street R, Tuller RW.Change in cough reflex after treatment withenalapril and rampiril. Br Med J 1989;299:13-16.11. Irwin RS, Madison JM.  Symptom research onchronic cough: a historical perspective.  AnnInter Med 2001; 134:809-14.12. Irwin RS, Curley FJ, French CL. Chroniccough.  The spectrum and frequency, keycomponents of the diagnostic evaluation andoutcome of specific therapy.  Am Rev RespirDis 1990; 141:640-7.References

Cough : a defence mechanism and a symptom

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Cough : a defence mechanism and a symptom

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