Clinical Approach to Cough
Comprehensive Practical Framework1. Symptom Overview
Understanding the clinical significance and classification of cough
Cough is one of the most common symptoms encountered in primary care, accounting for approximately 30 million physician visits annually in the United States alone. It represents roughly 8% of all outpatient visits and is the single most common reason for seeking medical attention. Chronic cough affects 10-20% of the adult population worldwide and significantly impacts quality of life, causing sleep disturbance, social embarrassment, urinary incontinence, and even rib fractures in severe cases. Understanding the systematic approach to cough is essential for every family medicine practitioner.
Definition
Cough is a sudden, forceful expulsion of air from the lungs through the mouth. It is a complex protective reflex mechanism involving coordinated activation of respiratory muscles following stimulation of sensory receptors in the airways and other anatomical sites. Cough serves the vital physiological function of clearing the airways of secretions, foreign particles, and irritants.
Classification by Duration
| Category | Duration | Common Causes | Clinical Significance |
|---|---|---|---|
| Acute | Less than 3 weeks | Viral upper respiratory tract infection, acute bronchitis, pneumonia, pertussis, allergic rhinitis exacerbation | Most self-limited; focus on identifying serious causes such as pneumonia or pulmonary embolism |
| Subacute | 3 to 8 weeks | Post-infectious cough, pertussis, bacterial sinusitis, asthma exacerbation | Often represents resolving acute process; consider pertussis and post-infectious causes |
| Chronic | Greater than 8 weeks | Upper airway cough syndrome, asthma, gastroesophageal reflux disease, chronic bronchitis, angiotensin-converting enzyme inhibitor use | Requires systematic evaluation; multiple etiologies often coexist |
Classification by Character
Productive (Wet) Cough
Cough associated with sputum production. The character and color of sputum provides diagnostic clues: clear or white suggests viral infection or asthma; yellow or green suggests bacterial infection or eosinophilic inflammation; rust-colored suggests pneumococcal pneumonia; pink and frothy suggests pulmonary edema; blood-streaked warrants urgent evaluation for malignancy, tuberculosis, or pulmonary embolism.
Non-Productive (Dry) Cough
Cough without significant sputum production. Common in viral upper respiratory infections, angiotensin-converting enzyme inhibitor-induced cough, early asthma, gastroesophageal reflux disease, and interstitial lung disease. A persistent dry cough in a non-smoker with normal chest radiograph suggests one of “The Big Three” causes.
Sputum Characteristics and Their Significance
| Sputum Appearance | Typical Causes | Clinical Considerations |
|---|---|---|
| Clear or mucoid | Viral infection, asthma, chronic bronchitis | Generally benign; may represent baseline in chronic conditions |
| Yellow or green (purulent) | Bacterial infection, eosinophilic bronchitis | Color alone does not reliably distinguish viral from bacterial |
| Rust-colored | Pneumococcal pneumonia | Classic but not pathognomonic; requires chest imaging |
| Pink and frothy | Pulmonary edema | Urgent evaluation for heart failure required |
| Blood-streaked or frank hemoptysis | Bronchitis, malignancy, tuberculosis, pulmonary embolism, bronchiectasis | Always warrants thorough investigation; red flag symptom |
Classification by Pattern and Timing
| Pattern | Description | Suggests |
|---|---|---|
| Nocturnal predominance | Worse when lying down at night | Asthma, gastroesophageal reflux disease, heart failure, upper airway cough syndrome |
| Morning predominance | Worst upon awakening | Chronic bronchitis, bronchiectasis (productive of large volume sputum) |
| Post-prandial | Occurs after eating | Gastroesophageal reflux disease, aspiration |
| Exercise-induced | Triggered by physical activity | Asthma (especially exercise-induced bronchoconstriction) |
| Seasonal pattern | Predictable occurrence with seasons | Allergic rhinitis, seasonal asthma |
| Paroxysmal | Sudden bursts of repeated coughing | Pertussis (whooping cough), foreign body, asthma |
| Barking or seal-like | Harsh, barking quality | Croup, tracheal pathology, psychogenic cough |
Key Concept: “The Big Three”
In non-smoking adults with chronic cough and a normal chest radiograph, three conditions account for more than 90% of cases:
- Upper airway cough syndrome (previously called post-nasal drip syndrome) — approximately 20-40%
- Asthma (including cough-variant asthma) — approximately 20-30%
- Gastroesophageal reflux disease — approximately 10-40%
Importantly, up to 25% of patients have multiple simultaneous causes contributing to their cough. A systematic approach that addresses all three possibilities is essential for successful management.
Impact on Quality of Life
Understanding the Burden of Chronic Cough
Chronic cough significantly impairs quality of life. Common complications and associated symptoms include:
- Sleep disturbance — reported by up to 75% of patients
- Urinary incontinence — affects up to 55% of women with chronic cough
- Chest and abdominal wall pain — from repeated muscular strain
- Rib fractures — in severe or prolonged cases
- Social embarrassment — leading to avoidance of social situations
- Syncope or pre-syncope — cough syncope from decreased venous return
- Headache — from increased intracranial pressure during coughing
2. Pathophysiology and Mechanisms
Understanding the underlying mechanisms of cough
Understanding the cough reflex arc is fundamental to comprehending why various conditions cause cough and how treatments work. The cough reflex is a complex, coordinated response that can be triggered from multiple anatomical sites, explaining why such diverse conditions—from ear wax impaction to gastroesophageal reflux—can all present with cough as the primary symptom.
The Cough Reflex Arc
| Component | Structure | Function |
|---|---|---|
| Receptors | Cough receptors in airways, pharynx, external ear canal, esophagus, pericardium, diaphragm | Detect mechanical and chemical stimuli; initiate afferent signal |
| Afferent Pathway | Vagus nerve (primary), trigeminal nerve, glossopharyngeal nerve, phrenic nerve | Transmit sensory information from receptors to the brainstem cough center |
| Integration Center | Medullary cough center in the brainstem (nucleus tractus solitarius region) | Process afferent input and coordinate efferent motor response; subject to voluntary control from higher cortical centers |
| Efferent Pathway | Vagus nerve, phrenic nerve, spinal motor nerves to intercostal and abdominal muscles | Transmit motor commands to effector muscles |
| Effectors | Diaphragm, intercostal muscles, abdominal muscles, laryngeal muscles | Execute the three phases of cough: inspiratory, compressive, and expulsive |
The Three Phases of Cough
1. Inspiratory Phase
Action: Deep inspiration with glottis open
Mechanism: Contraction of diaphragm and external intercostal muscles
Purpose: Maximizes lung volume to generate sufficient expiratory force
2. Compressive Phase
Action: Forced expiration against closed glottis
Mechanism: Contraction of abdominal and internal intercostal muscles with glottis closure
Purpose: Builds intrathoracic pressure up to 300 mmHg
3. Expulsive Phase
Action: Sudden glottis opening with explosive air release
Mechanism: Rapid airflow (up to 500 mph) through narrowed airways
Purpose: Expels mucus, foreign particles, and irritants from airways
Cough Receptor Types and Clinical Relevance
Rapidly Adapting Receptors (RARs)
Location: Epithelium of larger airways (trachea, main bronchi)
Stimuli: Mechanical stimulation, rapid lung inflation/deflation, inhaled irritants
Clinical relevance: Activated by mucus accumulation, foreign bodies, and airway instrumentation; mediate cough from bronchitis and aspiration
C-Fiber Receptors
Location: Throughout airways, lung parenchyma, and bronchial vasculature
Stimuli: Chemical irritants (capsaicin, bradykinin, prostaglandins), inflammatory mediators, acid
Clinical relevance: Key role in inflammatory conditions (asthma), angiotensin-converting enzyme inhibitor cough (bradykinin), and gastroesophageal reflux disease; become sensitized in chronic cough
Slowly Adapting Receptors (SARs)
Location: Airway smooth muscle
Stimuli: Lung stretch and inflation
Clinical relevance: Primary role in Hering-Breuer reflex; modulate cough sensitivity rather than directly initiating cough; may contribute to cough in hyperinflated states
Anatomical Distribution of Cough Receptors
Receptor Density Principle: Cough receptor density is highest in the larynx and carina, explaining why these areas are most sensitive to triggering cough. The density progressively decreases toward the peripheral airways.
| Anatomical Site | Receptor Density | Afferent Nerve | Clinical Correlation |
|---|---|---|---|
| Larynx | Very high | Superior laryngeal branch of vagus | Laryngeal hypersensitivity syndrome; post-viral vagal neuropathy |
| Carina and main bronchi | Very high | Vagus nerve | Central tumors; foreign body impaction |
| Trachea | High | Vagus nerve | Tracheitis; tracheomalacia |
| Pharynx | Moderate | Glossopharyngeal nerve | Upper airway cough syndrome; pharyngitis |
| External auditory canal | Low | Arnold’s nerve (auricular branch of vagus) | Arnold’s nerve reflex; ear wax impaction or hair touching tympanic membrane |
| Distal esophagus | Low | Vagal afferents | Gastroesophageal reflux disease (distal esophageal-tracheobronchial reflex) |
| Pericardium and diaphragm | Low | Phrenic nerve | Pericarditis; subdiaphragmatic abscess |
How Common Conditions Cause Cough
| Condition | Mechanism | Treatment Implication |
|---|---|---|
| Upper airway cough syndrome (post-nasal drip) | Secretions from nasal and sinus mucosa drain posteriorly, mechanically stimulating pharyngeal and laryngeal cough receptors; histamine release sensitizes receptors | First-generation antihistamines (anticholinergic properties reduce secretions), decongestants, nasal corticosteroids |
| Asthma and cough-variant asthma | Eosinophilic airway inflammation releases mediators (prostaglandins, leukotrienes, histamine) that sensitize C-fiber receptors; bronchoconstriction stimulates rapidly adapting receptors | Inhaled corticosteroids to reduce inflammation; bronchodilators for acute relief |
| Gastroesophageal reflux disease | Two mechanisms: (1) Microaspiration of gastric contents directly irritates laryngeal and tracheobronchial receptors; (2) Esophageal-tracheobronchial vagal reflex—acid in distal esophagus triggers cough without aspiration | Proton pump inhibitors (high-dose, twice daily); lifestyle modifications; may require 2-3 months for full effect |
| Angiotensin-converting enzyme inhibitor-induced cough | Inhibition of angiotensin-converting enzyme prevents breakdown of bradykinin and substance P in airways; accumulation of these mediators sensitizes C-fiber receptors | Discontinue angiotensin-converting enzyme inhibitor; switch to angiotensin receptor blocker (does not affect bradykinin metabolism); cough resolves in 1-4 weeks |
| Non-asthmatic eosinophilic bronchitis | Eosinophilic inflammation of airways without bronchial hyperreactivity; eosinophil-derived mediators sensitize cough receptors | Inhaled corticosteroids; responds similarly to asthma treatment but without bronchodilator benefit |
| Post-infectious cough | Viral infection damages airway epithelium, exposing sensory nerve endings; transient receptor hypersensitivity and inflammation persist after infection resolves | Usually self-limited (3-8 weeks); inhaled corticosteroids or ipratropium may accelerate resolution |
| Chronic bronchitis | Mucus hypersecretion from goblet cell hyperplasia stimulates rapidly adapting receptors; chronic inflammation sensitizes C-fibers | Smoking cessation essential; mucolytics may provide modest benefit |
| Interstitial lung disease | Fibrosis distorts airways and stimulates mechanoreceptors; associated inflammation activates C-fibers; traction bronchiectasis contributes | Treat underlying disease; antifibrotic therapy in idiopathic pulmonary fibrosis; symptomatic treatment challenging |
Often Overlooked Mechanism: Arnold’s Nerve Reflex
The auricular branch of the vagus nerve (Arnold’s nerve) innervates the external auditory canal and tympanic membrane. Stimulation of this area—by ear wax, hair touching the eardrum, hearing aids, or even otoscope examination—can trigger coughing in 2-4% of the population. This “Arnold’s nerve reflex” or “ear-cough reflex” is frequently forgotten as a cause of unexplained chronic cough. Always examine the ears in patients with refractory cough!
Cough Hypersensitivity Syndrome
A Unifying Concept in Chronic Cough
Cough hypersensitivity syndrome describes a state of heightened cough reflex sensitivity that may explain why some patients cough excessively to stimuli that would not trigger cough in healthy individuals. Key features include:
- Central sensitization: Amplified processing of cough signals in the brainstem and cortex
- Peripheral sensitization: Lowered threshold of airway sensory nerves due to inflammation or nerve damage
- Laryngeal hypersensitivity: Excessive response to laryngeal stimulation, often with associated throat symptoms
- Clinical clues: Patients report cough triggered by talking, laughing, strong odors, cold air, or eating—stimuli that do not normally cause cough
This concept helps explain patients with chronic refractory cough who have undergone extensive evaluation and treatment without resolution.
3. History Taking
A comprehensive approach to eliciting the cough history
Red Flags — Require Urgent Evaluation
- Hemoptysis — Malignancy, tuberculosis, pulmonary embolism, bronchiectasis
- Unintentional weight loss greater than 5% — Malignancy, tuberculosis, chronic infection
- Night sweats — Tuberculosis, lymphoma, other malignancy
- Fever persisting beyond 1 week — Pneumonia, tuberculosis, abscess, empyema
- Hoarseness lasting more than 3 weeks — Laryngeal carcinoma, recurrent laryngeal nerve involvement
- Smoker over age 40 with new or changed cough — Lung cancer screening indicated
- Significant dyspnea or hypoxia — Pneumonia, pulmonary embolism, heart failure
- Choking episode or sudden onset — Foreign body aspiration
Systematic History: The “COUGHS” Approach
Use the mnemonic “COUGHS” to ensure comprehensive history taking:
- C — Character and Course: What does the cough sound like (dry, wet, barking, whooping)? When did it start? Is it getting better, worse, or staying the same? Continuous or episodic?
- O — Output and Other symptoms: Is there sputum? What color and volume? Associated symptoms: wheeze, dyspnea, chest pain, heartburn, nasal congestion, throat clearing, fever?
- U — Understand triggers and timing: What makes it worse (cold air, exercise, eating, lying down, talking, strong odors)? What makes it better? Time of day pattern (nocturnal, morning, post-prandial)?
- G — General history: Past medical history (asthma, allergies, reflux, heart disease), medications (especially angiotensin-converting enzyme inhibitors), smoking history (pack-years), occupational exposures, travel, pets
- H — How does it affect you?: Impact on sleep, work, social activities. Complications (incontinence, syncope, chest wall pain). Previous treatments tried and their effects
- S — Sick contacts and setting: Household members with similar symptoms? Recent upper respiratory infection? Pertussis exposure? Tuberculosis risk factors?
Targeted Questions by Suspected Cause
| Suspected Cause | Key Features | Ask This Question |
|---|---|---|
| Upper airway cough syndrome (post-nasal drip) | Throat clearing, nasal congestion, sensation of secretions in throat | “Do you feel mucus dripping down the back of your throat?” “Do you frequently need to clear your throat?” |
| Asthma or cough-variant asthma | Episodic wheeze, known triggers, nocturnal symptoms, personal or family history of atopy | “Does cold air, exercise, or exposure to dust or pets trigger your cough?” “Do you ever hear a whistling sound when you breathe?” |
| Gastroesophageal reflux disease | Heartburn, regurgitation, worse after meals or when supine; may occur without typical reflux symptoms | “Is your cough worse after eating or when lying down?” “Do you have heartburn, acid taste, or regurgitation?” “Do you wake up coughing at night?” |
| Angiotensin-converting enzyme inhibitor-induced cough | Dry, tickling cough; onset typically weeks to months after starting medication | “Are you taking any blood pressure medications?” “When did you start taking [medication name]?” “Did the cough start after beginning this medication?” |
| Pertussis (whooping cough) | Paroxysmal cough with inspiratory “whoop,” post-tussive vomiting, prolonged course | “Do you have fits of coughing that leave you breathless?” “Do you vomit after coughing spells?” “Has anyone you know been diagnosed with whooping cough?” |
| Chronic bronchitis | Productive cough most days for at least 3 months in 2 consecutive years; smoking history | “Do you cough up phlegm most days?” “How many years have you smoked, and how many cigarettes per day?” |
| Bronchiectasis | Large volume purulent sputum, recurrent respiratory infections, morning cough productive of cupfuls | “Do you cough up large amounts of sputum, especially in the morning?” “Have you had frequent lung infections?” |
| Lung cancer | Change in chronic cough character, hemoptysis, weight loss, smoking history | “Has the character of your cough changed recently?” “Have you coughed up any blood?” “Have you lost weight without trying?” |
| Heart failure | Orthopnea, paroxysmal nocturnal dyspnea, peripheral edema, pink frothy sputum | “Do you need to prop yourself up on pillows to sleep?” “Do you wake up suddenly short of breath at night?” “Have your ankles been swelling?” |
| Interstitial lung disease | Progressive dyspnea, dry cough, occupational or medication exposures, connective tissue disease | “Are you becoming more short of breath with activities?” “Have you been exposed to asbestos, silica, or birds?” “Do you have any autoimmune conditions?” |
Medication and Social History
Medications That Cause Cough
- Angiotensin-converting enzyme inhibitors — Most common drug-induced cause; affects 5-20% of users; dry, tickling cough; may occur weeks to months after initiation; resolves 1-4 weeks after discontinuation
- Beta-blockers (non-selective) — Can cause bronchospasm and cough in susceptible individuals, especially those with asthma or chronic obstructive pulmonary disease
- Inhaled medications — Inhaled corticosteroids (throat irritation, dysphonia), inhaled bronchodilators (paradoxical bronchospasm)
- Nitrofurantoin — Can cause acute or chronic pulmonary toxicity with cough
- Methotrexate and other immunosuppressants — Pneumonitis with dry cough and dyspnea
- Amiodarone — Pulmonary toxicity in up to 10% of users
- Statins — Rarely associated with interstitial lung disease
Social and Occupational History
- Smoking: Quantify in pack-years (packs per day × years smoked); current smokers: chronic bronchitis, lung cancer risk; former smokers: calculate time since cessation
- Vaping and e-cigarettes: Associated with e-cigarette or vaping product use-associated lung injury (EVALI); ask specifically about THC-containing products
- Occupation: Asbestos (construction, shipbuilding), silica (mining, sandblasting), coal dust, grain dust, animal proteins, isocyanates (painting, plastics)
- Home environment: Mold, birds (hypersensitivity pneumonitis), pets, heating and cooling systems, recent renovations
- Travel: Tuberculosis exposure (endemic areas), fungal infections (histoplasmosis, coccidioidomycosis)
- Hobbies: Bird keeping (bird fancier’s lung), hot tubs (hot tub lung from mycobacteria)
Duration-Specific History Focus
Acute Cough (less than 3 weeks)
- Preceding upper respiratory infection symptoms?
- Sick contacts?
- Fever, purulent sputum?
- Sudden onset (foreign body)?
- Pleuritic chest pain, dyspnea (pneumonia, pulmonary embolism)?
Subacute Cough (3-8 weeks)
- Did it follow an upper respiratory infection?
- Paroxysms with whooping or post-tussive vomiting (pertussis)?
- Gradual improvement or persisting at same intensity?
- New medications started?
- Sinus symptoms (bacterial sinusitis)?
Chronic Cough (greater than 8 weeks)
- Symptoms suggesting “The Big Three”?
- On angiotensin-converting enzyme inhibitor?
- Smoker or former smoker?
- Previous treatments tried and response?
- Any red flag symptoms?
4. Physical Examination
A systematic head-to-toe approach for cough
Systematic Framework: Use the “Head to Extremities” approach for complete examination of patients presenting with cough. Remember that cough receptors exist in multiple anatomical locations beyond the lungs, so a thorough examination includes ears, nose, throat, cardiovascular system, and abdomen.
General Inspection
- Appearance: Comfortable at rest versus respiratory distress? Cachexia suggesting malignancy? Cushingoid features from chronic steroid use?
- Respiratory effort: Tachypnea? Use of accessory muscles? Pursed lip breathing? Tripod positioning?
- Color: Central cyanosis (hypoxemia)? Pallor (anemia)? Plethora (polycythemia from chronic hypoxia)?
- Voice and speech: Hoarseness (laryngeal pathology, recurrent laryngeal nerve palsy)? Stridor (upper airway obstruction)? Ability to speak in full sentences?
- Cough character: If patient coughs during examination, note: dry versus productive, quality (barking, whooping), forcefulness, whether it sounds painful
Vital Signs
| Vital Sign | What to Look For | Clinical Significance |
|---|---|---|
| Temperature | Fever (greater than 38°C or 100.4°F) | Infection (pneumonia, bronchitis, tuberculosis, sinusitis); absence of fever does not exclude infection in elderly or immunocompromised |
| Heart Rate | Tachycardia (greater than 100 beats per minute) | Infection, hypoxemia, pulmonary embolism, anxiety, thyrotoxicosis; bradycardia may indicate beta-blocker use |
| Blood Pressure | Hypotension or hypertension | Hypotension suggests sepsis; hypertension—is patient on angiotensin-converting enzyme inhibitor? |
| Respiratory Rate | Tachypnea (greater than 20 breaths per minute) | Pneumonia, pulmonary embolism, heart failure, metabolic acidosis; part of pneumonia severity scores (CURB-65, PSI) |
| Oxygen Saturation | Hypoxemia (less than 94% on room air) | Significant lower respiratory tract involvement; consider pneumonia, pulmonary embolism, heart failure, interstitial lung disease |
Head, Ears, Eyes, Nose, and Throat Examination
Ears (Arnold’s Nerve)
- External auditory canal: Cerumen impaction? Hair touching tympanic membrane?
- Tympanic membrane: Otitis media? Perforation?
- Does otoscope examination trigger coughing? (Arnold’s nerve reflex)
Nose
- Nasal mucosa: Pale and boggy (allergic rhinitis)? Erythematous (infectious)?
- Nasal polyps visible?
- Septal deviation?
- Purulent discharge (sinusitis)?
Eyes
- Allergic shiners (dark circles from venous congestion)?
- Conjunctival injection (allergy, viral infection)?
- Scleral icterus (if considering metastatic disease)?
Oropharynx
- Cobblestone appearance of posterior pharynx (post-nasal drip)?
- Tonsillar enlargement or exudate?
- Mucus pooling in posterior pharynx?
- Dental disease (aspiration risk)?
Neck Examination
- Lymphadenopathy: Cervical (infection, malignancy), supraclavicular (concerning for thoracic malignancy—Virchow’s node on left)
- Thyroid: Goiter causing tracheal compression?
- Trachea: Midline or deviated? Tracheal tug (severe airflow obstruction)?
- Jugular venous pressure: Elevated (heart failure, cor pulmonale, superior vena cava obstruction)?
Respiratory Examination
Inspection
- Chest wall deformity: Kyphoscoliosis, pectus excavatum (restrictive lung disease)?
- Barrel chest: Increased anteroposterior diameter (chronic obstructive pulmonary disease, hyperinflation)?
- Symmetry of chest expansion: Asymmetry suggests unilateral pathology (effusion, consolidation, pneumothorax)
- Scars: Previous thoracic surgery, chest tube sites?
Palpation
- Chest expansion: Reduced overall (chronic obstructive pulmonary disease) or asymmetric (unilateral disease)?
- Tactile fremitus: Increased (consolidation), decreased (effusion, pneumothorax)
- Chest wall tenderness: Musculoskeletal cause of cough-related pain? Rib fracture from severe coughing?
Percussion
- Dullness: Consolidation (pneumonia), pleural effusion, mass
- Hyperresonance: Pneumothorax, severe emphysema, hyperinflation
- Compare sides systematically: Apex to base, anterior and posterior
Auscultation
| Finding | Description | Conditions |
|---|---|---|
| Polyphonic wheeze | Multiple musical pitches, predominantly expiratory | Asthma, chronic obstructive pulmonary disease, bronchitis (diffuse airway narrowing) |
| Monophonic wheeze | Single constant pitch, may be inspiratory or expiratory | Fixed airway obstruction: tumor, foreign body, mucus plug (focal lesion) |
| Stridor | High-pitched inspiratory sound, often audible without stethoscope | Upper airway obstruction: laryngeal tumor, epiglottitis, vocal cord dysfunction, tracheal stenosis |
| Fine crackles (rales) | Velcro-like sounds, typically end-inspiratory, do not clear with cough | Interstitial lung disease (pulmonary fibrosis), early pulmonary edema, pneumonia |
| Coarse crackles | Louder, lower-pitched, early inspiratory, may clear with cough | Bronchiectasis, chronic bronchitis, pneumonia with secretions |
| Bronchial breath sounds | Harsh, tubular quality heard over peripheral lung (normally only over trachea) | Consolidation (pneumonia), lung collapse with patent airway |
| Diminished breath sounds | Reduced air entry compared to contralateral side | Pleural effusion, pneumothorax, severe emphysema, obesity |
| Pleural friction rub | Creaking, grating sound during both inspiration and expiration | Pleuritis (infection, pulmonary embolism, malignancy, autoimmune disease) |
Cardiovascular Examination
- Jugular venous pressure: Elevated suggests right heart failure, cor pulmonale, or fluid overload
- Apex beat: Displaced (cardiomegaly)? Heaving (left ventricular hypertrophy)?
- Heart sounds: Third heart sound (S3) suggests heart failure; fourth heart sound (S4) suggests diastolic dysfunction
- Murmurs: Mitral stenosis (associated with hemoptysis), pulmonary hypertension signs
- Peripheral edema: Bilateral pitting edema suggests heart failure; unilateral suggests deep vein thrombosis (consider pulmonary embolism)
Abdominal Examination
- Hepatomegaly: Heart failure (congestive hepatomegaly), metastatic lung cancer
- Ascites: Heart failure, hepatic metastases, malignancy
- Epigastric tenderness: May suggest gastroesophageal reflux disease, peptic ulcer disease
- Obesity: Contributes to gastroesophageal reflux disease, obstructive sleep apnea (associated with chronic cough)
- Hernias: Chronic cough can cause or exacerbate inguinal and umbilical hernias
Extremities
- Clubbing: Lung cancer, bronchiectasis, interstitial lung disease, cystic fibrosis, empyema; absent in chronic obstructive pulmonary disease and asthma
- Peripheral cyanosis: Poor perfusion, hypoxemia
- Nicotine staining: Confirms active smoking
- Joint abnormalities: Rheumatoid arthritis, other connective tissue diseases (associated interstitial lung disease)
- Calf tenderness or asymmetry: Deep vein thrombosis (consider pulmonary embolism as cause of cough)
Expected Physical Examination Findings by Etiology
| Condition | General Appearance | Respiratory Findings | Other Findings |
|---|---|---|---|
| Upper airway cough syndrome | Usually well-appearing | Often normal; may have audible throat clearing | Cobblestone pharynx, nasal mucosal changes, post-nasal drip visible |
| Asthma | Normal between attacks; distressed during exacerbation | May be normal; polyphonic wheeze during exacerbation; prolonged expiratory phase | Eczema, allergic rhinitis signs (atopic triad) |
| Gastroesophageal reflux disease | Often normal | Usually normal | Epigastric tenderness possible; obesity; dental erosions (severe cases) |
| Angiotensin-converting enzyme inhibitor cough | Normal | Normal | Normal; history of antihypertensive use is the key |
| Chronic obstructive pulmonary disease | Barrel chest, pursed lip breathing, use of accessory muscles | Hyperresonance, diminished breath sounds, wheezes, prolonged expiration | Nicotine staining; cachexia in advanced disease |
| Pneumonia | Ill-appearing, febrile, tachypneic | Dullness to percussion, bronchial breath sounds, crackles, increased fremitus | Hypoxemia, tachycardia |
| Heart failure | Dyspneic, orthopneic | Bilateral basal crackles, pleural effusions (dullness) | Elevated jugular venous pressure, S3 gallop, peripheral edema, hepatomegaly |
| Interstitial lung disease | Progressive dyspnea, may appear comfortable at rest | Fine “Velcro” crackles at bases; may have clubbing | Signs of underlying connective tissue disease; clubbing |
| Lung cancer | May have cachexia, weight loss evident | May be normal; localized wheeze, signs of effusion or collapse possible | Lymphadenopathy (supraclavicular), clubbing, paraneoplastic signs |
| Bronchiectasis | Usually well; productive cough evident | Coarse crackles, often at bases; may have wheezes | Clubbing may be present |
Important Teaching Point
Normal physical examination is common! Many of the most frequent causes of chronic cough present with entirely normal physical examination findings. Upper airway cough syndrome, gastroesophageal reflux disease, cough-variant asthma, non-asthmatic eosinophilic bronchitis, and angiotensin-converting enzyme inhibitor-induced cough typically have normal chest examinations. A normal examination does not exclude significant pathology and should not delay appropriate investigation in patients with chronic cough or red flag symptoms.
5. Differential Diagnosis
Systematic approach organized by probability and clinical features
Acute Cough (Duration: Less Than 3 Weeks)
| Probability | Condition | Key Features | Red Flags |
|---|---|---|---|
| COMMON (approximately 80%) | Viral upper respiratory tract infection (common cold) | Nasal congestion, rhinorrhea, sore throat, low-grade fever; self-limited over 7-10 days | Symptoms persisting beyond 10 days without improvement |
| COMMON | Acute bronchitis | Productive cough following upper respiratory infection; may have mild wheeze; lasts 1-3 weeks | High fever, severe dyspnea, focal chest findings |
| COMMON | Acute exacerbation of asthma | Known asthmatic with increased cough, wheeze, dyspnea; identifiable trigger often present | Inability to speak in sentences, silent chest, cyanosis |
| COMMON | Allergic rhinitis exacerbation | Seasonal pattern, sneezing, itchy eyes and nose, clear rhinorrhea, known allergies | None specific; consider if symptoms severe or not responding |
| LESS COMMON (approximately 15%) | Community-acquired pneumonia | Fever, productive cough (purulent or rust-colored sputum), dyspnea, pleuritic chest pain | Hypoxia, tachypnea, hypotension, confusion (severe pneumonia) |
| LESS COMMON | Acute bacterial sinusitis | Symptoms beyond 10 days, facial pain/pressure, purulent nasal discharge, post-nasal drip | Periorbital swelling, severe headache, visual changes, high fever |
| LESS COMMON | Influenza | Abrupt onset, high fever, myalgias, headache, dry cough, prostration; seasonal pattern | Dyspnea, chest pain, altered mental status (complications) |
| UNCOMMON BUT SERIOUS (approximately 5%) | Pulmonary embolism | Sudden dyspnea, pleuritic chest pain, cough (may be dry or with hemoptysis), risk factors present | Hemoptysis, syncope, hypotension, hypoxia disproportionate to findings |
| UNCOMMON BUT SERIOUS | Foreign body aspiration | Sudden onset after choking episode, unilateral wheeze, may have witnessed aspiration event | Severe dyspnea, stridor, cyanosis |
| UNCOMMON BUT SERIOUS | Acute heart failure exacerbation | Dyspnea, orthopnea, paroxysmal nocturnal dyspnea, pink frothy sputum, known cardiac disease | Severe dyspnea at rest, hypoxia, hypotension |
Subacute Cough (Duration: 3 to 8 Weeks)
Clinical Approach to Subacute Cough:
- Step 1: Determine if this follows a respiratory infection — most subacute cough is post-infectious
- Step 2: Consider pertussis if paroxysmal cough, inspiratory whoop, or post-tussive vomiting
- Step 3: If no clear post-infectious etiology, evaluate as for chronic cough (especially “The Big Three”)
| Probability | Condition | Approximate Frequency | Key Distinguishing Features |
|---|---|---|---|
| COMMON | Post-infectious cough | 40-50% | Follows clear upper respiratory infection; gradually improving; normal chest examination and radiograph; resolves within 8 weeks |
| COMMON | Upper airway cough syndrome developing | 20-30% | Persistent post-nasal drip, throat clearing, nasal congestion following infection; may represent new diagnosis |
| LESS COMMON | Pertussis (whooping cough) | 10-20% | Paroxysmal cough with inspiratory “whoop,” post-tussive vomiting, prolonged course (up to 100 days); may lack classic features in adults |
| LESS COMMON | Asthma (new diagnosis or unrecognized) | 10-15% | Cough triggered by infection persists; nocturnal symptoms, exercise intolerance, response to bronchodilators |
| LESS COMMON | Bacterial sinusitis | 5-10% | Prolonged symptoms beyond 10 days, facial pain, purulent discharge, “double worsening” pattern |
| UNCOMMON | Mycoplasma or Chlamydophila pneumonia | 5% | Atypical pneumonia with prolonged dry cough, low-grade fever, may have extrapulmonary manifestations |
Chronic Cough (Duration: Greater Than 8 Weeks)
Step-by-Step Approach to Chronic Cough:
- Step 1: Rule out obvious causes — Is the patient taking an angiotensin-converting enzyme inhibitor? Is the patient a current smoker? Is the chest radiograph abnormal?
- Step 2: If chest radiograph normal and not on angiotensin-converting enzyme inhibitor and non-smoker, consider “The Big Three” — upper airway cough syndrome, asthma, gastroesophageal reflux disease (account for more than 90% of cases)
- Step 3: If initial workup negative, investigate for less common causes: non-asthmatic eosinophilic bronchitis, obstructive sleep apnea, bronchiectasis
- Step 4: Remember that multiple etiologies coexist in up to 25% of patients
| Probability | Condition | Approximate Frequency | Key Distinguishing Features |
|---|---|---|---|
| COMMON | Upper airway cough syndrome (post-nasal drip syndrome) | 20-40% | Sensation of secretions dripping, frequent throat clearing, nasal congestion, cobblestone pharynx; responds to antihistamines and nasal steroids |
| COMMON | Asthma (including cough-variant asthma) | 20-30% | Episodic symptoms, triggers (cold air, exercise, allergens), nocturnal cough, personal or family history of atopy; responds to inhaled corticosteroids |
| COMMON | Gastroesophageal reflux disease | 10-40% | May or may not have heartburn (up to 75% have “silent reflux”); worse after meals, when supine; requires prolonged proton pump inhibitor trial |
| LESS COMMON | Angiotensin-converting enzyme inhibitor-induced cough | 5-20% of ACE inhibitor users | Dry, tickling cough; onset weeks to months after starting medication; resolves 1-4 weeks after discontinuation |
| LESS COMMON | Non-asthmatic eosinophilic bronchitis | 10-15% | Chronic cough with sputum eosinophilia but normal spirometry and no bronchial hyperreactivity; responds to inhaled corticosteroids |
| LESS COMMON | Chronic bronchitis | 5-10% | Productive cough most days for at least 3 months in 2 consecutive years; smoking history; chronic obstructive pulmonary disease features |
| LESS COMMON | Bronchiectasis | 4-5% | Daily productive cough with large volume purulent sputum, recurrent infections; CT chest diagnostic |
| UNCOMMON BUT SERIOUS | Lung cancer | 2% | Smoker over 40, change in chronic cough character, hemoptysis, weight loss, hoarseness; chest imaging abnormal |
| UNCOMMON BUT SERIOUS | Tuberculosis | Less than 1% (higher in endemic areas) | Chronic cough, night sweats, weight loss, hemoptysis; risk factors (immigration, HIV, exposure) |
| UNCOMMON | Interstitial lung disease | Less than 1% | Progressive dyspnea with dry cough; fine “Velcro” crackles; clubbing; restrictive pattern on spirometry |
| UNCOMMON | Chronic heart failure | Variable | Nocturnal cough, orthopnea, paroxysmal nocturnal dyspnea, peripheral edema, cardiac history |
| UNCOMMON | Obstructive sleep apnea | Variable | Nocturnal cough, snoring, witnessed apneas, daytime somnolence, obesity; often coexists with gastroesophageal reflux disease |
Anatomical Approach to Cough
Upper Airway
Upper airway cough syndrome
Allergic rhinitis
Chronic sinusitis
Laryngitis
Laryngeal hypersensitivity
Obstructive sleep apnea
Central Airways
Asthma
Chronic bronchitis
Bronchiectasis
Foreign body
Endobronchial tumor
Tracheomalacia
Lung Parenchyma
Pneumonia
Interstitial lung disease
Lung cancer
Tuberculosis
Sarcoidosis
Pulmonary fibrosis
Extra-Pulmonary
Gastroesophageal reflux disease
Heart failure
Pericardial disease
Angiotensin-converting enzyme inhibitor use
Ear wax (Arnold’s nerve)
Psychogenic cough
Drug-Induced Cough
| Drug or Drug Class | Mechanism | Characteristics | Time to Resolution After Stopping |
|---|---|---|---|
| Angiotensin-converting enzyme inhibitors (lisinopril, enalapril, ramipril, etc.) | Inhibition of bradykinin breakdown leads to accumulation in airways, sensitizing C-fiber receptors | Dry, tickling, persistent cough; may occur weeks to months after initiation; affects 5-20% of users; more common in women and non-smokers | 1 to 4 weeks (may take up to 3 months in some cases) |
| Beta-blockers (non-selective: propranolol, nadolol) | Bronchospasm from beta-2 receptor blockade in susceptible individuals | Cough with wheeze; more likely in patients with asthma or chronic obstructive pulmonary disease; cardioselective agents safer | Days to 1-2 weeks |
| Inhaled corticosteroids | Local irritation of upper airway; fungal laryngitis (candidiasis) | Throat irritation, dysphonia, cough after inhalation; improved with spacer use and mouth rinsing | Days (with technique improvement) |
| Nitrofurantoin | Acute hypersensitivity reaction or chronic pulmonary fibrosis | Acute: fever, cough, dyspnea within days to weeks; Chronic: insidious dyspnea and cough over months to years | Acute: days to weeks; Chronic: may be irreversible |
| Methotrexate | Hypersensitivity pneumonitis | Dry cough, dyspnea, fever; can occur at any time during treatment; potentially life-threatening | Weeks to months; may require corticosteroids |
| Amiodarone | Direct pulmonary toxicity; phospholipidosis | Dry cough, progressive dyspnea; occurs in up to 10% of users; dose and duration dependent | Months; often requires corticosteroids; may be irreversible |
| Sirolimus and everolimus | Drug-induced pneumonitis | Cough, dyspnea, interstitial infiltrates on imaging | Weeks to months after discontinuation |
| Checkpoint inhibitors (pembrolizumab, nivolumab, etc.) | Immune-related pneumonitis | Cough, dyspnea; can occur weeks to months after starting therapy; potentially severe | Variable; often requires corticosteroids |
| Inhaled medications in general | Bronchospasm, airway irritation | Cough immediately after or shortly after inhalation | Immediate (with proper technique or alternative formulation) |
Quick Reference: “If You See This, Think This”
| Clinical Clue | Think This First | Next Step |
|---|---|---|
| Chronic cough + taking angiotensin-converting enzyme inhibitor | Angiotensin-converting enzyme inhibitor-induced cough | Stop angiotensin-converting enzyme inhibitor, switch to angiotensin receptor blocker; reassess in 1-4 weeks |
| Throat clearing + post-nasal drip sensation | Upper airway cough syndrome | Trial of first-generation antihistamine plus decongestant; consider nasal corticosteroids |
| Nocturnal cough + episodic wheeze | Asthma | Spirometry with bronchodilator response; if normal, consider methacholine challenge |
| Cough worse after meals or when supine | Gastroesophageal reflux disease | Empiric proton pump inhibitor trial (twice daily for 2-3 months) |
| Smoker over 40 with new or changed cough | Lung cancer until proven otherwise | Chest CT; urgent referral if abnormal |
| Hemoptysis + weight loss + night sweats | Tuberculosis or malignancy | Chest radiograph, sputum studies, CT chest; isolation if tuberculosis suspected |
| Paroxysmal cough + inspiratory whoop + post-tussive vomiting | Pertussis | Pertussis PCR or culture; treat with macrolide; notify public health |
| Daily large volume purulent sputum | Bronchiectasis | High-resolution CT chest |
| Progressive dyspnea + dry cough + fine crackles | Interstitial lung disease | High-resolution CT chest; pulmonary function tests; consider referral |
| Orthopnea + paroxysmal nocturnal dyspnea + peripheral edema | Heart failure | Brain natriuretic peptide, echocardiogram, chest radiograph |
| Cough triggered by ear examination | Arnold’s nerve reflex (ear pathology) | Examine ears for cerumen impaction, hair on tympanic membrane, foreign body |
6. Diagnostic Investigations
A stepwise, cost-effective approach guided by clinical suspicion
Baseline Investigations for All Patients with Chronic Cough
| Investigation | Purpose | What to Look For | Practical Points |
|---|---|---|---|
| Chest radiograph (posteroanterior and lateral) | Exclude parenchymal disease, masses, effusions, cardiomegaly | Mass lesions, infiltrates, interstitial markings, cardiomegaly, pleural effusion, hilar lymphadenopathy | Normal in most common causes of chronic cough (upper airway cough syndrome, asthma, gastroesophageal reflux disease); abnormal radiograph requires further investigation |
| Spirometry with bronchodilator response | Detect airflow obstruction; assess reversibility | FEV1/FVC ratio less than 0.7 indicates obstruction; greater than 12% and 200 mL improvement post-bronchodilator suggests asthma | Normal spirometry does not exclude asthma (may be normal between attacks); proceed to bronchoprovocation if clinical suspicion high |
Initial Approach in Primary Care
For chronic cough with normal chest radiograph in a non-smoker not taking an angiotensin-converting enzyme inhibitor, begin with empiric treatment for “The Big Three” based on clinical suspicion before pursuing extensive testing. Many patients respond to empiric therapy, avoiding unnecessary investigations.
Targeted Investigations by Suspected Etiology
If Suspecting Upper Airway Cough Syndrome
First-Line Tests
- Clinical diagnosis and empiric treatment trial: First-generation antihistamine (chlorpheniramine, diphenhydramine) plus decongestant for 2-4 weeks is diagnostic and therapeutic
- Nasal examination: Assess for mucosal edema, polyps, purulent discharge
Second-Line Tests
- Sinus CT scan: If symptoms suggest chronic sinusitis or empiric therapy fails; shows mucosal thickening, air-fluid levels, polyps
- Allergy testing: Skin prick tests or specific IgE if allergic rhinitis suspected; guides allergen avoidance
- Nasal endoscopy: Performed by ENT specialist to visualize posterior nasal cavity and nasopharynx
If Suspecting Asthma
First-Line Tests
- Spirometry with bronchodilator response: FEV1/FVC less than 0.7 with greater than 12% and greater than 200 mL improvement confirms reversible obstruction
- Peak expiratory flow variability: Greater than 20% diurnal variation over 2 weeks supports diagnosis
Second-Line Tests
- Methacholine challenge test: PC20 (concentration causing 20% fall in FEV1) less than 4 mg/mL is positive; highly sensitive—negative test essentially excludes asthma
- Fractional exhaled nitric oxide (FeNO): Greater than 50 parts per billion in adults suggests eosinophilic airway inflammation; supports asthma diagnosis
- Sputum eosinophil count: Greater than 3% supports eosinophilic airway disease (asthma or non-asthmatic eosinophilic bronchitis)
If Suspecting Gastroesophageal Reflux Disease
First-Line Tests
- Empiric proton pump inhibitor trial: High-dose twice daily (e.g., omeprazole 40 mg twice daily) for minimum 8 weeks; response supports diagnosis but may take 2-3 months for cough to improve
- Note: Up to 75% of patients with reflux-related cough have no typical symptoms (heartburn, regurgitation)
Second-Line Tests
- 24-hour esophageal pH monitoring (with impedance): Gold standard; correlates reflux episodes with cough events; useful if proton pump inhibitor trial inconclusive
- Upper gastrointestinal endoscopy: Identifies esophagitis, Barrett’s esophagus; normal in many patients with reflux cough
- High-resolution esophageal manometry: Assesses esophageal motility; useful if considering fundoplication
If Suspecting Non-Asthmatic Eosinophilic Bronchitis
Diagnostic Criteria
- Sputum eosinophilia: Greater than 3% eosinophils on induced sputum
- Normal spirometry: No airflow obstruction
- Negative bronchoprovocation: Normal methacholine challenge (PC20 greater than 16 mg/mL)
Supporting Tests
- Fractional exhaled nitric oxide: Often elevated (greater than 50 parts per billion)
- Response to inhaled corticosteroids: Confirms diagnosis therapeutically
If Suspecting Bronchiectasis
Diagnostic Tests
- High-resolution CT chest: Diagnostic gold standard; shows bronchial dilatation (signet ring sign), bronchial wall thickening, lack of tapering
- Sputum culture: Identify colonizing organisms (Pseudomonas aeruginosa, Haemophilus influenzae)
Etiological Workup
- Immunoglobulin levels: IgG, IgA, IgM (immunodeficiency)
- Aspergillus serology and IgE: Allergic bronchopulmonary aspergillosis
- Autoantibodies: If connective tissue disease suspected
- Cystic fibrosis testing: Sweat chloride, genetic testing if appropriate
If Suspecting Lung Cancer
Imaging
- CT chest with contrast: Characterize lesion, assess mediastinal lymph nodes, staging
- PET-CT: For staging if malignancy confirmed or highly suspected
Tissue Diagnosis
- Bronchoscopy with biopsy: For central lesions
- CT-guided biopsy: For peripheral lesions
- Sputum cytology: Low sensitivity but non-invasive
Empiric Treatment Trials as Diagnostic Tools
Sequential Empiric Therapy Approach
When the diagnosis is unclear and baseline investigations are normal, empiric treatment trials can serve as diagnostic tools. Response to therapy supports the diagnosis. This approach is particularly useful in primary care for “The Big Three” causes of chronic cough.
- Trial 1 — Upper airway cough syndrome: First-generation antihistamine (e.g., chlorpheniramine 4 mg three times daily) plus decongestant for 2-4 weeks; response expected within 2 weeks if upper airway cough syndrome is the cause
- Trial 2 — Asthma: Inhaled corticosteroid (e.g., fluticasone 250 mcg twice daily) with or without bronchodilator for 4-8 weeks; cough-variant asthma may take 6-8 weeks to respond
- Trial 3 — Gastroesophageal reflux disease: Proton pump inhibitor twice daily (e.g., omeprazole 40 mg twice daily) for minimum 8 weeks; reflux-related cough may take 2-3 months for significant improvement
Important: If one etiology is treated without improvement, add therapy for the next suspected cause rather than stopping the first treatment—multiple etiologies often coexist.
Investigation Algorithm Summary
| Step | Action | If Abnormal | If Normal |
|---|---|---|---|
| 1 | History and physical examination; identify red flags and obvious causes | Investigate and treat specific cause | Proceed to step 2 |
| 2 | Stop angiotensin-converting enzyme inhibitor if present | If cough resolves in 1-4 weeks, diagnosis confirmed | Proceed to step 3 |
| 3 | Chest radiograph | Investigate abnormality (CT, bronchoscopy, etc.) | Proceed to step 4 |
| 4 | Spirometry with bronchodilator response | If obstructive with reversibility, treat as asthma | Proceed to step 5 |
| 5 | Empiric treatment for “The Big Three” based on clinical features | Response confirms diagnosis; continue treatment | Proceed to step 6 |
| 6 | Advanced testing: methacholine challenge, FeNO, sputum eosinophils, 24-hour pH monitoring, CT chest | Treat identified cause | Consider specialist referral |
Additional Investigations for Specific Scenarios
| Clinical Scenario | Investigation | What It Shows |
|---|---|---|
| Suspected pertussis | Nasopharyngeal swab for Bordetella pertussis PCR; pertussis serology (IgG, IgA) | PCR positive early in illness; serology useful later; lymphocytosis on complete blood count is suggestive |
| Suspected tuberculosis | Sputum smear and culture for acid-fast bacilli (3 samples); tuberculin skin test or interferon-gamma release assay; chest radiograph | Smear shows acid-fast bacilli; culture confirms and allows sensitivity testing; upper lobe infiltrates, cavitation on imaging |
| Suspected heart failure | Brain natriuretic peptide (BNP or NT-proBNP); echocardiogram; chest radiograph | BNP greater than 100 pg/mL suggests heart failure; echocardiogram shows reduced ejection fraction or diastolic dysfunction; cardiomegaly and pulmonary congestion on radiograph |
| Suspected interstitial lung disease | High-resolution CT chest; pulmonary function tests (including diffusing capacity); autoimmune panel if connective tissue disease suspected | Reticular pattern, honeycombing, traction bronchiectasis on CT; restrictive pattern with reduced diffusing capacity on pulmonary function tests |
| Suspected pulmonary embolism | D-dimer; CT pulmonary angiography; lower extremity Doppler ultrasound | Elevated D-dimer (sensitive but not specific); filling defects on CT pulmonary angiography; deep vein thrombosis on ultrasound |
| Chronic refractory cough | Laryngoscopy; 24-hour pH-impedance monitoring; cough reflex sensitivity testing | Laryngoscopy may show vocal cord dysfunction, laryngopharyngeal reflux changes; pH-impedance correlates symptoms with reflux events |
Practical Pearl: Cost-Effective Approach
In most patients with chronic cough, a normal chest radiograph, and no red flags, a systematic empiric treatment approach guided by clinical features is more cost-effective than extensive upfront testing. Reserve advanced investigations (methacholine challenge, pH monitoring, CT chest) for patients who fail to respond to empiric therapy.
7. Pattern Recognition and Clinical Decision-Making
Practical algorithms and decision pathways
Step 1: Is This Urgent?
| Clinical Scenario | Urgency Level | Immediate Action |
|---|---|---|
| Massive hemoptysis (greater than 200 mL in 24 hours) | EMERGENT | Stabilize airway, position bleeding lung dependent, urgent bronchoscopy or interventional radiology; consider ICU admission |
| Severe respiratory distress, hypoxia (SpO2 less than 90%), cyanosis | EMERGENT | Supplemental oxygen, urgent chest radiograph, consider pneumonia, pulmonary embolism, severe asthma exacerbation, heart failure |
| Stridor or signs of upper airway obstruction | EMERGENT | Keep patient calm, prepare for airway management, urgent ENT or anesthesia consultation; consider foreign body, angioedema, epiglottitis |
| Suspected pulmonary embolism (dyspnea, pleuritic pain, risk factors) | EMERGENT | Calculate Wells score, D-dimer if low probability, CT pulmonary angiography if indicated; anticoagulation if confirmed |
| Hemoptysis (any amount) in smoker over 40 | URGENT | Chest radiograph same day; CT chest within 2 weeks; urgent pulmonology referral if mass suspected |
| Suspected pneumonia with comorbidities or severe features | URGENT | Calculate CURB-65 or PSI score; chest radiograph; blood cultures if admission indicated; initiate antibiotics promptly |
| Weight loss, night sweats, or tuberculosis risk factors | URGENT | Chest radiograph, sputum for acid-fast bacilli (3 samples), isolation precautions if tuberculosis suspected |
| Chronic cough without red flags, normal chest radiograph | ROUTINE | Systematic evaluation and empiric treatment for “The Big Three”; follow-up in 2-4 weeks |
| Acute cough with typical viral upper respiratory infection features | ROUTINE | Symptomatic treatment, reassurance, safety netting; return if worsening or not improving in 10 days |
Step 2: Classify by Duration
Acute (less than 3 weeks)
Proceed to Algorithm A
Focus: Rule out pneumonia, pulmonary embolism, heart failure; most cases are viral and self-limited
Subacute (3 to 8 weeks)
Proceed to Algorithm B
Focus: Post-infectious cough most common; consider pertussis; evaluate as chronic if not improving
Chronic (greater than 8 weeks)
Proceed to Algorithm C
Focus: Systematic approach to “The Big Three”; stop angiotensin-converting enzyme inhibitor; chest radiograph for all
Step 3: Follow the Appropriate Algorithm
Algorithm A: Acute Cough (Less Than 3 Weeks)
| Clinical Scenario | Most Likely Diagnosis | Action |
|---|---|---|
| Cough with nasal congestion, rhinorrhea, sore throat, low-grade fever, no dyspnea | Viral upper respiratory tract infection | Symptomatic treatment (analgesics, decongestants, honey for cough); reassurance; no antibiotics needed |
| Productive cough following upper respiratory infection, no fever, no focal findings | Acute bronchitis | Symptomatic treatment; antibiotics NOT indicated; may last 2-3 weeks; consider inhaler if significant wheeze |
| High fever, productive cough, dyspnea, focal chest findings (crackles, bronchial breathing) | Community-acquired pneumonia | Chest radiograph to confirm; calculate severity score (CURB-65); antibiotics per local guidelines; consider admission if score greater than or equal to 2 |
| Known asthmatic with cough, wheeze, dyspnea, identifiable trigger | Asthma exacerbation | Bronchodilator, assess severity, short course oral corticosteroids if moderate-severe; review maintenance therapy |
| Sudden onset dyspnea, pleuritic chest pain, risk factors (recent surgery, immobility, malignancy) | Pulmonary embolism | Calculate Wells score; D-dimer if low probability; CT pulmonary angiography if intermediate-high probability; anticoagulation if confirmed |
| Sudden onset cough after choking episode, unilateral wheeze | Foreign body aspiration | Chest radiograph (inspiratory and expiratory views); rigid bronchoscopy for removal if confirmed |
Algorithm B: Subacute Cough (3 to 8 Weeks)
| Clinical Scenario | Most Likely Diagnosis | Action |
|---|---|---|
| Cough following clear upper respiratory infection, gradually improving, no other symptoms | Post-infectious cough | Reassurance that resolution expected within 8 weeks; consider inhaled ipratropium or corticosteroid if troublesome |
| Paroxysmal cough with inspiratory “whoop,” post-tussive vomiting, known exposure | Pertussis | Nasopharyngeal swab for pertussis PCR; macrolide antibiotic (azithromycin 5 days); notify public health; household prophylaxis |
| Persistent nasal symptoms, facial pressure, purulent discharge beyond 10 days | Bacterial sinusitis | Antibiotics (amoxicillin-clavulanate first line) for 5-10 days; nasal saline, decongestants; CT sinus if recurrent |
| Cough not improving, features suggesting “The Big Three” | Undiagnosed chronic cough etiology | Evaluate as chronic cough (Algorithm C); do not wait until 8 weeks if pattern suggests chronic etiology |
Algorithm C: Chronic Cough (Greater Than 8 Weeks)
| Step | Clinical Scenario | Action |
|---|---|---|
| C1 | Patient taking angiotensin-converting enzyme inhibitor | Stop angiotensin-converting enzyme inhibitor; switch to angiotensin receptor blocker; reassess in 1-4 weeks (may take up to 3 months) |
| C2 | Current smoker | Counsel on smoking cessation; chest radiograph; if persists after 4 weeks of cessation, evaluate further |
| C3 | Chest radiograph abnormal | Investigate based on findings (CT chest, bronchoscopy, etc.); refer to specialist if mass, infiltrate, or unexplained abnormality |
| C4 | Symptoms suggest upper airway cough syndrome (throat clearing, post-nasal drip, nasal congestion) | Empiric trial: first-generation antihistamine plus decongestant for 2-4 weeks; add nasal corticosteroid if allergic features |
| C5 | Symptoms suggest asthma (episodic, triggers, nocturnal, wheeze) | Spirometry; if normal but suspicion high, methacholine challenge; empiric trial of inhaled corticosteroid for 6-8 weeks |
| C6 | Symptoms suggest gastroesophageal reflux disease (worse after meals, supine, heartburn) OR no clear etiology | Empiric proton pump inhibitor twice daily for minimum 8 weeks (may take 2-3 months for cough improvement) |
| C7 | Failed empiric therapy for all three conditions | Consider non-asthmatic eosinophilic bronchitis (sputum eosinophils, FeNO); 24-hour pH-impedance monitoring; high-resolution CT; specialist referral |
“What Do I Do If…” Decision Reference
| Clinical Situation | Immediate Action | Next Step |
|---|---|---|
| Patient on angiotensin-converting enzyme inhibitor with chronic cough | Stop angiotensin-converting enzyme inhibitor today; switch to angiotensin receptor blocker for blood pressure control | Reassess in 1-4 weeks; if cough resolves, diagnosis confirmed; if persists beyond 4 weeks, evaluate for other causes |
| Chronic cough patient has tried antihistamines, inhalers, and proton pump inhibitors without improvement | Verify adequate duration and dosing of each treatment; ensure compliance | Consider: multiple coexisting causes, non-asthmatic eosinophilic bronchitis (check sputum eosinophils), 24-hour pH monitoring, specialist referral |
| Smoker over 40 with new cough or change in chronic cough | Chest radiograph urgently; counsel smoking cessation | If chest radiograph abnormal: CT chest and pulmonology referral. If normal: CT chest still recommended given lung cancer risk; continue standard evaluation |
| Patient with cough and hemoptysis | Quantify hemoptysis; chest radiograph; assess hemodynamic stability | Massive hemoptysis: emergency management. Non-massive: CT chest, bronchoscopy; consider tuberculosis, malignancy, bronchiectasis, pulmonary embolism |
| Chronic cough with completely normal workup including specialist evaluation | Consider cough hypersensitivity syndrome, unexplained chronic cough, or psychogenic cough | Trial of neuromodulators (gabapentin, pregabalin); speech therapy for laryngeal hypersensitivity; cough suppression techniques |
| Suspected pertussis in adult | Nasopharyngeal swab for pertussis PCR; start macrolide empirically if high suspicion | Notify public health; household contacts need prophylaxis; advise patient cough may persist for weeks despite treatment |
| Cough triggered during ear examination | Examine for cerumen impaction, foreign body, hair touching tympanic membrane | Remove cerumen or foreign body; if cough resolves, Arnold’s nerve reflex confirmed |
| Patient requesting antibiotics for acute cough with viral features | Explain viral etiology and self-limited nature; discuss antibiotic resistance and side effects | Offer symptomatic treatments (honey, analgesics, decongestants); provide safety netting advice; delayed prescription only if clear indication |
Troubleshooting Refractory Chronic Cough
Ask These Questions When Cough Persists Despite Treatment
- Was the treatment duration adequate? Gastroesophageal reflux disease requires 2-3 months of proton pump inhibitor; cough-variant asthma may take 6-8 weeks to respond to inhaled corticosteroids
- Was patient compliance good? Verify patient is taking medications correctly and consistently (inhaler technique, timing of doses)
- Were all potential causes addressed? Up to 25% of patients have multiple coexisting etiologies—treat all suspected causes simultaneously rather than sequentially
- Is the diagnosis correct? Reconsider if patient not responding; arrange advanced testing (methacholine challenge, 24-hour pH-impedance, high-resolution CT)
- Are there multiple overlapping causes? If partial response to one treatment, add treatment for another etiology rather than stopping first treatment
- Has non-asthmatic eosinophilic bronchitis been excluded? Check sputum eosinophils or FeNO; responds to inhaled corticosteroids
- Could this be unexplained chronic cough or cough hypersensitivity syndrome? Consider if all evaluations negative; may benefit from neuromodulators or speech therapy
8. Clinical Pearls and Pitfalls
Practical wisdom — learn from successes and avoid common mistakes
Must-Know Clinical Pearls
“The Big Three” dominate chronic cough: Upper airway cough syndrome, asthma, and gastroesophageal reflux disease account for more than 90% of chronic cough in non-smokers with a normal chest radiograph. Always consider these first.
Multiple etiologies often coexist: Up to 25% of patients with chronic cough have more than one cause. If partial response to treatment for one condition, add therapy for another suspected etiology rather than abandoning the first treatment.
Silent reflux is common: Up to 75% of patients with gastroesophageal reflux disease-related cough do not have typical symptoms of heartburn or regurgitation. The absence of heartburn does not exclude reflux as a cause of cough.
Angiotensin-converting enzyme inhibitor cough takes time to resolve: After stopping the medication, cough may persist for 1-4 weeks (occasionally up to 3 months). Do not conclude it was not the cause after only a few days.
Check the ears: Arnold’s nerve reflex (ear-cough reflex) is frequently forgotten. Cerumen impaction or hair touching the tympanic membrane can cause chronic cough in 2-4% of patients. Always examine the ears in unexplained chronic cough.
Normal spirometry does not exclude asthma: Cough-variant asthma may have completely normal spirometry between episodes. If clinical suspicion is high, proceed to methacholine challenge testing or empiric inhaled corticosteroid trial.
First-generation antihistamines work better for upper airway cough syndrome: The anticholinergic properties of first-generation antihistamines (chlorpheniramine, diphenhydramine) help dry secretions. Second-generation antihistamines (loratadine, cetirizine) are less effective for cough.
Proton pump inhibitor treatment requires patience: Gastroesophageal reflux disease-related cough may take 2-3 months of twice-daily proton pump inhibitor therapy to improve significantly. Short treatment courses often fail.
Critical Pitfalls to Avoid
Prescribing antibiotics for acute bronchitis: Acute bronchitis is almost always viral. Antibiotics do not shorten duration or severity and contribute to antibiotic resistance. Yellow or green sputum does not indicate bacterial infection.
Stopping angiotensin-converting enzyme inhibitor evaluation too early: Cough may take 1-4 weeks (sometimes up to 3 months) to resolve after discontinuation. Wait at least 4 weeks before concluding it was not the cause.
Failing to obtain chest radiograph in chronic cough: All patients with chronic cough should have a chest radiograph. Missing lung cancer, tuberculosis, or interstitial lung disease can have devastating consequences.
Treating “The Big Three” sequentially rather than based on clinical features: Evaluate clinical features and treat the most likely diagnosis first; if multiple etiologies suspected, treat simultaneously. Do not rigidly follow a sequential protocol.
Ignoring red flags: Hemoptysis, weight loss, night sweats, hoarseness greater than 3 weeks, and new cough in a smoker over 40 require prompt investigation regardless of other symptoms.
Dismissing chronic cough as trivial: Chronic cough significantly impacts quality of life, causing sleep disturbance, urinary incontinence, social embarrassment, and depression. It deserves thorough evaluation and treatment.
Assuming normal physical examination excludes serious pathology: Many common causes of chronic cough (upper airway cough syndrome, gastroesophageal reflux disease, cough-variant asthma, angiotensin-converting enzyme inhibitor cough) have completely normal chest examinations.
Using cough suppressants without addressing underlying cause: Symptomatic treatment alone delays diagnosis and definitive treatment. Always search for and treat the underlying etiology.
Key Takeaways
- Duration guides approach: Classify cough as acute (less than 3 weeks), subacute (3-8 weeks), or chronic (greater than 8 weeks), as the differential diagnosis and management differ significantly for each category.
- Acute cough is usually viral: Most acute cough is caused by viral upper respiratory tract infection and is self-limited. Reserve antibiotics for confirmed bacterial pneumonia or specific indications.
- Subacute cough is often post-infectious: Following an upper respiratory infection, cough may persist for 3-8 weeks due to airway inflammation and receptor hypersensitivity. Consider pertussis if paroxysmal with post-tussive vomiting.
- Chronic cough requires systematic evaluation: Obtain chest radiograph for all; stop angiotensin-converting enzyme inhibitor if present; evaluate for “The Big Three” (upper airway cough syndrome, asthma, gastroesophageal reflux disease).
- Empiric treatment is often diagnostic: Response to empiric therapy for upper airway cough syndrome, asthma, or gastroesophageal reflux disease confirms the diagnosis and avoids extensive testing in most patients.
- Treatment duration matters: Allow adequate time for treatments to work—2-4 weeks for antihistamines, 6-8 weeks for inhaled corticosteroids, and 2-3 months for proton pump inhibitors.
- Multiple causes are common: Up to 25% of patients have more than one etiology. If partial response, add treatment for another suspected cause rather than abandoning the first.
- Red flags demand urgent action: Hemoptysis, unexplained weight loss, night sweats, persistent hoarseness, and new cough in smoker over 40 require prompt investigation to exclude malignancy and tuberculosis.
- Normal examination does not reassure: Many causes of chronic cough have entirely normal physical examination findings. Investigation and treatment should proceed based on clinical suspicion.
- Consider uncommon causes in refractory cases: Non-asthmatic eosinophilic bronchitis, obstructive sleep apnea, and Arnold’s nerve reflex are frequently missed. Cough hypersensitivity syndrome may explain truly refractory cases.
Quick Reference Algorithm
Systematic Approach to Chronic Cough:
- Identify and address red flags — hemoptysis, weight loss, night sweats, hoarseness, smoker with new cough require urgent investigation
- Stop angiotensin-converting enzyme inhibitor — if patient is taking one, switch to angiotensin receptor blocker and reassess in 1-4 weeks
- Obtain chest radiograph — abnormal findings direct further investigation; normal radiograph suggests “The Big Three”
- Evaluate for “The Big Three” — upper airway cough syndrome, asthma, gastroesophageal reflux disease based on clinical features
- Initiate empiric treatment — first-generation antihistamine plus decongestant for upper airway cough syndrome; inhaled corticosteroid for asthma; twice-daily proton pump inhibitor for gastroesophageal reflux disease
- Allow adequate treatment duration — 2-4 weeks for upper airway cough syndrome, 6-8 weeks for asthma, 8-12 weeks for gastroesophageal reflux disease
- If partial or no response, add or substitute — treat for additional suspected causes; consider advanced testing (methacholine challenge, pH monitoring, high-resolution CT)
- Refer to specialist — if cough persists despite adequate empiric treatment for all common causes, or if red flags present