THE NATIONAL MEDICAL JOURNAL OF INDIA VOL. 7. NO.4, 1994

Everyday Practice177

Cough: Diagnosis and treatmentS. GAUDE GAJANAN

INTRODUCtIONCough is a complex physiological event that protects thelungs from mechanical, chemical and thermal injury. It is anormal reflex in all healthy people following inhalation andaspiration of foreign material. Cough, however, can also beharmful. It is often the only sign of serious disease, maycontribute to the spread of airborne infection, and in somecases, result in severe functional or structural damage to thebody. It may be an exhausting and debilitating experiencethat contributes to the morbidity of acute self-limiting as wellas chronic and incurable diseases. Since there may be manycauses for a patient's cough, its treatment also differs. Theprevalence of cough in the population depends on the extentof smoking and other environmental factors and varies from5% to 40%. The reasons why patients with chronic cough(i.e. longer than three weeks) seek medical attention arelisted in Table I.

PHYSIOLOGYCough usually results from the stimulation of sensory nervesin the airways. The nerves that initiate cough are pre-dominantly situated in the upper airways, for it is here thatthe greatest protection against the ingress of foreign materialis required. Each cough involves a complex reflex arc thatbegins with the irritation of receptors. Impulses from thesereceptors are conducted to the central area by way of afferentnerves and are then passed down through the appropriateefferent nervous pathways to expiratory muscles (Fig. 1).Knowledge of the location of receptors and afferent nervouspathways is helpful in determining the cause of cough. Coughcaused by mechanical irritation results from stimulation ofmyelinated and/or non-myelinated sensory nerves in the lungand that caused by direct chemical stimulation results fromactivation of receptors in the larynx or 'C' fibre endingsin the lungs.

There are three phases of the cough mechanism thatproduce high initial expiratory flows and then a decreasingcross-sectional area of the airways. In the first phase, thewide opening of the glottis permits rapid entry of largeamounts of air into the lungs. During the second phase, thecough begins with the closure of the glottis (by the actionsof adductor muscles of the arytenoid cartilages), continueswith the active contraction of the expiratory muscles, andends with the sudden opening of the glottis. The glottiscloses, during the third, expiratory phase, after the function

lawaharlal Nehru Medical College, Nehru Nagar, Be\gaum 590010,Karnataka, India

S. GAUDE GAJANAN Department of Respiratory Diseases andTuberculosis

© The National Medical Journal of India 1994

TABLEI. Reasons why patients with chronic cough seek medicalattention"

Reason Reason

Something wrongExhaustionSelf-consciousnessInsomniaLife style changeMusculoskeletal painHoarsenessExcessive perspirationDizziness

Fear of cancerHeadacheFear of tuberculosisRetchingVomitingNauseaAnorexiaSyncope or near syncope

• in decreasing order of prevalence

of cough is carried out, i.e. the removal of undesired materialfrom the respiratory tract.

All pathological conditions that lead to an ineffectivecough interfere with either the inspiratory or expiratoryphases of cough, with most conditions affecting both.Patients with a variety of extra pulmonary disorders may notcough effectively when their inspiratory or expiratory effortsare limited due to pain, weakness or depression of the centralnervous system. Cough may be ineffective in pulmonarydiseases characterized by reduced expiratory flow rates.These include extrinsic compression, endobronchial lesions,foreign bodies and secretions in the tracheobronchial tree.

CAUSESCough can be produced by a large number of diseases locatedin a variety of anatomical sites. Any disorder that stimulatescough receptors or efferent nervous pathways is capableof producing a cough. Therefore, only a summary of thediagnostic features of the most common causes of cough islisted in Table II.

Viral infectionsThese are the most frequent causes of cough in all age groupsand are common during winter. The infection may be in thetonsils, pharyngeal wall, larynx or bronchi. Other associatedsymptoms are also present. The cough is usually paroxysmaland may be productive. Superadded bacterial infectionsperpetuate and exacerbate the cough.

Bacterial infectionsIn maxillary sinusitis this may be the only complaint. Thecough is often productive and is probably triggered bystimulation of receptors in the posterior nasopharynx orwithin the sinuses. Bacterial infection is the common causeof an exacerbation of cough in chronic obstructive pulmonarydisease (CaPO). The cough is related to the excess secre-tions that overwhelm the already compromised mucociliarymechanism.

Cough is also a very common symptom in patients whohave pneumonia, being present in almost every patient sometime during the course of the illness.

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Receptors

LarynxTracheaBronchiEar canalPleuraStomach

Nose JParanasal sinuses --~>:.

Pharynx

PericardiumDiaphragm

Afferents

Branches ofvagus nerve

THE NATIONAL MEDICAL JOURNAL OF INDIA

Cough Centre

Trigeminal ---~>::.nerve

:>

>

/'

VOL. 7, NO.4, 1994

Efferents

Vagus supplieslarynx, tracheaand bronchi

Diffusely locatedin the medulla nearthe respiratory centre ~under control ofhigher brain centres

Phrenic and otherspinal motornerves supplydiaphragm andother expiratorymusculature

Cause

TABLE II. Clues to the aetiology of chronic cough

FIG 1. Components of the cough reflex

.>Glossopharyngeal" ./

nerve /

Phrenic nerve

Important findings Diagnostic test

Chronic obstructive pulmonarydisease

Post-viral bronchitis

Chronic rhinosinusitis

Asthma

Bronchogenic carcinoma

Foreign body

Aspiration pneumonitis

Pulmonary fibrosis

Psychogenic

Smoker; self-perpetuatingcough decreases after stoppingsmoking; rhonchi on auscultation

Cough persists for weeks afterupper respiratory infection;increased by cold air, respiratoryirritants

Cough follows upper respiratorytract infection or allergenexposure; throat clearing andpostnasal drip; granularpharyngitis mucopurulentsecretionsAssociated dyspnoea andwheezing; increased by cold air,irritants, exercise, allergens

Change in chronic cough or'new' cough in smokers

Sudden onset of cough afterchoking; localized wheeze

Elderly with swallowingdifficulties; oesophageal disease-achalasia, hiatus hernia;crepitations at lung bases

Non-productive cough; progressivedyspnoea; crepts and clubbing

No nocturnal cough; youngpatients; emotionally unstable

Obstructive airway disease byspirometry

X-ray of paranasal sinuses

Reversible airway obstruction(pulmonary function test,FEV1 estimation)

Abnormal chest X-ray; positivesputum cytology;bronchoscopy

Abnormal chest X-ray, ifradiopaque; atelectasis;bronchoscopyBarium swallow maydemonstrate active aspiration

Interstitial pattern on chestX-ray; restrictive pattern onpulmonary function tests

Diagnosis by exclusion

Trigeminal, facialand hypoglossalnerve suppliesupper airways andaccessoryrespiratorymuscles

GAUDE GAJANAN : COUGH: DIAGNOSIS AND TREATMENT

Chronic obstructive pulmonary disease (COPD)The cough is usually productive and self-propagating, isincreased in the morning but may be severe enough to bepresent throughout the day. The sputum is usually mucoidand on occasion is streaked with blood. Secondary viral orbacterial infections lead to exacerbation of cough.

BronchiectasisCough is the most prominent symptom in these patientsand there is usually expectoration of copious amounts ofmucopurulent secretion. Sputum on standing separates into3 layers: a foamy top layer, a serous intermediate layerand a bottom layer of pus and debris.

AsthmaCough may be the predominant or, at times, the onlypresenting symptom in patients with asthma. It may bepresent in the absence of wheezing and is often intractable,non-productive and paroxysmal. 'Cough asthma' has beenidentified as a common cause of coughing in children andyoung adults.

Lung cancerCough is a common symptom in patients with lung cancer,occurring in 70% to 90% of patients some time during theclinical course. However, it is the first symptom of diseasein less than 20% of patients.

Pulmonary fibrosisCough is present in most patients with interstitial lungdisease and is probably caused by excessive distension anddistortion of the airways by the fibrous tissue.

MiscellaneousDrugs such as beta-blockers and angiotensin convertingenzyme (ACE) inhibitors (captopril, enalapril, etc.) havebeen known to cause cough. Cough due to ACE inhibitorscan be sudden, paroxysmal and distressing. It is present in5% to 20% of patients taking these drugs, and in somepatients necessitates their withdrawal.

Postnasal drip due to pharyngo-laryngeal diseases cangive rise to cough. Recurrent aspiration and foreign bodyinhalation (especially in children) are also important causesof chronic cough. Thyroid masses or traumatic neuromas areadditional causes of an incapacitating cough. Sometimes,diseases of the pleura, pericardium and diaphragm can leadto a chronic cough.

Psychogenic coughThis diagnosis should be made only after excluding othercommon causes. Psychogenic cough is usually non-productive,does not occur at night and, is most prevalent in adolescentsand responds to commonly used cough suppressants.

COMPLICATIONSAs a result of vigorous muscular activity during coughing,high intrathoracic pressures (up to 800 mmHg) may begenerated. While pressures of this magnitude are higher thannecessary for an effective cough, they assume importancebecause of the musculoskeletal, pulmonary, cardiovascular,central nervous system and other complications which mayresult (Table III).

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TABLE III. Complications of cough

MusculoskeletalAsymptomatic rise in serum creatinine phosphokinaseRupture of rectus abdominis muscleRib fracturePulmonaryPneumomediastinumPneumothoraxPulmonary emphysemaCardiovascularLoss of consciousnessRupture of subconjunctival. nasal and anal veinsBradycardia. second and third degree heart blockCentral nervous systemCough syncope

MiscellaneousConstitutional symptomsUrinary incontinenceDisruption of surgical wounds

DIAGNOSTIC EVALUA nONA good history and careful physical examination are the twoimportant aspects in evaluating a patient with chronic cough.Routine laboratory tests are often not helpful. Chest X-ray,X-ray of the paranasal sinuses and pulmonary function testsshould be appropriately applied. Laryngoscopy and fibreopticbronchoscopy are performed, when other investigations failto reveal the cause of cough. Special gastroenterologicalstudies should be done when the history suggests aspiration.Helpful diagnostic clues and useful tests for causes of coughare listed in Table II.

THERAPYWhen cough performs no useful function and is hazardous,antitussive therapy is indicated. It can be categorized asspecific or non-specific.

Specific therapyThis is directed at either the aetiology or the presumedpathophysiological mechanism responsible for cough. Thismay be surgical (for lung cancer, polyps or bronchiectasis) ormedical (antibiotics for pneumonia and sinusitis or cessationof smoking in patients with CaPO). Bronchial asthma andchronic rhinosinusitis occur commonly and may require longterm therapy. Bronchodilators are the mainstay of therapyfor patients with 'cough asthma'. Decongestants and anti-histamines are useful in chronic rhinosinusitis. Gastro-oesophageal reflux is treated with dietary modification,antacids and H2 receptor blockers.

Non-specific therapyThis is useful if it decreases the frequency or intensity ofcough as assessed by objective cough counting or standardizedquestionnaires. Non-specific antitussive drugs can beclassified according to how and where they might theoreticallycontrol the cough reflex. The various groups are:

Drugs that may alter mucociliary factors irritating coughreceptors. The drugs in this group include expectorants,mucolytics and those that increase mucociliary clearance.Some of the drugs that can be used clinically are: bromhexine

180

(30 mg tid), carbocysteine (2.25-3 mg tid), and iodinatedglycerol (60 mg qid).

Drugs that may increase the threshold or latency of theafferent limb of the cough reflex. Local anaesthetics are themain drugs in this group. When inhaled, they preventsensory nerve traffic in both myelinated and non-myelinatednerves. The use of inhaled local anaesthetics is empirical andshould be confined to patients without asthma, as they mightprecipitate bronchoconstriction by removing all protectivereflexes from the lung. The maximum dose depends on thepatient's response.

Drugs that may increase the threshold or latency of thecough centre. Numerous narcotics and non-narcotic agentscan be classified in this group. Some of these are: Codeine(20 mg bid), dextromethorphan (10-20 mg qid), glaucine(30 mg tid), diphenhydramine (25-50 mg every 4-6 hourly),and caramiphen (10 mg qid).

Drugs that may increase the threshold or latency of theefferent limb of the cough reflex. Aerosolized ipratropiumbromide, an atropine-like substance, has been shown to beeffective in patients with chronic bronchitis. It may exert itsantitussive effect by acting on the efferent limb or on thecough receptors by altering mucociliary factors.

Drugs that may decrease the strength of contraction ofthe respiratory skeletal muscles. Although they have not beenstudied as antitussive agents, neuromuscular blocking

THE NATIONAL MEDICAL JOURNAL OF INDIA VOL. 7, NO.4, 1994

agents can be classified in this section. They should only beconsidered in patients with uncontrollable spasms of cough-ing who are 'bucking the ventilator' or could be immediatelyplaced on mechanical ventilatory support.

Protussive therapyProtussive therapy is defined as a treatment that aims toincrease cough effectiveness with or without increasingcough frequency. When cough performs a useful functionand is inadequate, this therapy is indicated. The most widelyused drug in this group is acetylcysteine. It is usuallyadministered by nebulized aerosols and can also be instilledthrough a tracheostomy or bronchoscope to liquefy largeamounts of thick sputum. The other drugs that can be used asaerosols to liquefy tenacious secretions are hypertonic salineand carbocysteine.

CONCLUSIONTherapy for cough is complex and should be administeredcarefully, not reflexly. Patients treated with inappropriatecough preparations may often suffer for years from asymptom that can be effectively treated. When a systematicand rational diagnostic approach is used, a specific aetiologycan be usually found and successful therapy can then beinitiated. Antitussive therapy should be used only as anadjuvant.

The Indian Journal of Cancer Chemotherapy will now bepublished as Indian Journal of Medical and PaediatricOncology. The first issue will be out in August 1994. Addressarticles to:

Dr Asha AnandMedical Oncology DepartmentGujarat Cancer Research InstituteAsarwaAhmedabad 380 012

Or

Dr R. GopalMedical Oncology DepartmentTata Memorial HospitalParelBombay 400 012