The Respiratory System

INTRODUCTION

The respiratory system plays a vital role in gas exchange — delivering oxygen to the blood and removing carbon dioxide. Any dysfunction in this system can lead to serious health problems. Understanding respiratory disease requires a structured history, followed by a thorough clinical examination and appropriate investigations.

Patients may complain of:

• Breathlessness (dyspnoea)
  
  

• Cough
  
  

• Sputum production
  
  

• Wheezing
  
  

• Chest pain
  
  

• Haemoptysis (coughing up blood)
  
  

HISTORY TAKING IN RESPIRATORY DISEASE

A careful and systematic history is essential. The clinician should assess each presenting symptom in detail, as well as the patient’s general health, environment, and risk factors.

1. BREATHLESSNESS (DYSPNOEA)

Definition:
Breathlessness is the subjective sensation of uncomfortable or difficult breathing. It is a common but non-specific symptom.

Key features to ask about:

• Onset:
  
  

  • Sudden: May suggest pulmonary embolism, pneumothorax, or acute left ventricular failure.
    
    

  • Gradual: May occur with asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, or pleural effusion.
    
    

• Duration and pattern:
  
  

  • Continuous or intermittent?
    
    

  • Worse at night? (paroxysmal nocturnal dyspnoea)
    
    

  • Occurs only on exertion or also at rest?
    
    

• Posture-related symptoms:
  
  

  • Orthopnoea: Difficulty breathing when lying flat. Classically seen in heart failure.
    
    

  • Paroxysmal nocturnal dyspnoea: Episodes of severe breathlessness that wake the patient from sleep.
    
    

• Associated symptoms:
  
  

  • Cough, wheeze, sputum, fever, chest pain
    
    

• Effect on lifestyle:
  
  

  • Ask about exercise tolerance and ability to perform daily activities (e.g., climbing stairs, walking on level ground).
    
    

2. COUGH

Definition:
A reflex action that helps clear the airways of irritants, mucus, or foreign particles. It can be a symptom of many respiratory conditions.

Ask about:

• Duration:
  
  

  • Acute (<3 weeks): Often infective (e.g., viral or bacterial bronchitis).
    
    

  • Chronic (>8 weeks): May suggest chronic bronchitis, post-nasal drip, asthma, or gastro-oesophageal reflux.
    
    

• Character:
  
  

  • Dry or non-productive: Common in early viral infections, asthma, or interstitial lung disease.
    
    

  • Productive (with sputum): Indicates infection, bronchiectasis, chronic bronchitis.
    
    

• Timing:
  
  

  • Worse in the morning: bronchiectasis or chronic bronchitis.
    
    

  • Nocturnal cough: asthma or gastro-oesophageal reflux.
    
    

• Triggers:
  
  

  • Cold air, smoke, talking, lying flat
    
    

• Medication history:
  
  

  • Angiotensin-converting enzyme (ACE) inhibitors can cause a persistent dry cough.
    
    

3. SPUTUM PRODUCTION

Sputum is expectorated mucus from the lower airways.

Inquire about:

• Quantity:
  
  

  • Large volumes may suggest bronchiectasis or lung abscess.
    
    

• Colour:
  
  

  • Clear/white: Often non-infective
    
    

  • Yellow/green: Bacterial infection
    
    

  • Rusty: Pneumococcal pneumonia
    
    

  • Frothy, pink: Pulmonary oedema
    
    

  • Black: May occur with coal dust exposure or fungal infection
    
    

  • Foul-smelling: Anaerobic infection (e.g., lung abscess)
    
    

• Consistency and presence of blood: Suggests haemoptysis
  
  

4. HAEMOPTYSIS

Definition:
Expectoration (coughing up) of blood or blood-stained sputum.

Causes:

• Acute bronchitis (most common)
  
  

• Bronchial carcinoma
  
  

• Tuberculosis
  
  

• Bronchiectasis
  
  

• Pulmonary embolism
  
  

• Pneumonia
  
  

• Lung abscess
  
  

• Pulmonary vasculitis (e.g., Wegener’s granulomatosis)
  
  

Important considerations:

• Differentiate from blood originating in the nose or gastrointestinal tract.
  
  

• Estimate the volume and frequency.
  
  

• Haemoptysis in a smoker or older adult requires investigation for malignancy.
  
  

5. WHEEZE

Definition:
A high-pitched, musical sound heard during breathing, especially on expiration. It results from narrowed or obstructed airways.

Causes:

• Widespread wheeze: Asthma, COPD, allergic reactions
  
  

• Unilateral or localised wheeze: Suggests obstruction by a tumour or foreign body
  
  

Ask whether the wheeze is audible to the patient or others, and when it occurs (e.g., during exercise or at night).

6. CHEST PAIN

Ask about:

• Character:
  
  

  • Sharp, stabbing pain worsened by inspiration or coughing suggests pleuritic pain (pleurisy, pulmonary embolism).
    
    

  • Dull, central chest pain may suggest tracheitis or central tumours.
    
    

• Location and radiation
  
  

• Associated symptoms: Breathlessness, cough, haemoptysis
  
  

Note: Always rule out cardiac causes of chest pain.

7. SYSTEMIC SYMPTOMS

• Fever and rigors: Infections such as pneumonia, tuberculosis, abscess
  
  

• Weight loss: Cancer, chronic infections, fibrosis
  
  

• Fatigue and malaise: Chronic hypoxia or infection
  
  

• Night sweats: Tuberculosis or lymphoma
  
  

• Ankle oedema: Right heart failure or pulmonary hypertension
  
  

• Clubbing: Occurs in bronchiectasis, lung cancer, pulmonary fibrosis
  
  

SUMMARY OF KEY QUESTIONS TO ASK IN RESPIRATORY HISTORY:

1. Are you short of breath? When and under what conditions?
   
   

2. Do you have a cough? What type and how long?
   
   

3. Are you bringing up sputum? What is its nature and quantity?
   
   

4. Have you coughed up blood?
   
   

5. Do you wheeze? When?
   
   

6. Have you had any chest pain? Describe it.
   
   

7. Do you have fever, weight loss, fatigue, or night sweats?
   
   

8. Any history of lung disease, smoking, occupational exposure, recent travel?
   
   

Understanding the clinical significance of respiratory signs is key to accurate diagnosis. The following is a detailed guide for interpreting findings during the respiratory examination.

INSPECTION FINDINGS AND THEIR SIGNIFICANCE

1. Cyanosis
   
   

   • Central cyanosis (bluish discoloration of lips and tongue):
     Suggests hypoxaemia (low oxygen saturation of arterial blood), usually seen in:
     
     

     • Chronic lung disease (e.g., COPD)
       
       

     • Congenital heart disease with right-to-left shunting
       
       

     • Massive pulmonary embolism
       
       

   • Peripheral cyanosis (fingers, toes):
     Indicates vasoconstriction or low cardiac output. Can occur with cold exposure or shock.
     
     

2. Finger Clubbing
   Indicates long-standing hypoxia or systemic disease. Common causes include:
   
   

   • Lung cancer (especially non-small cell types)
     
     

   • Bronchiectasis
     
     

   • Lung abscess
     
     

   • Pulmonary fibrosis
     
     

   • Cystic fibrosis
     
     

   • Empyema
     
     

3. Use of Accessory Muscles / Tripod Position
   
   

   • Patients with severe respiratory distress may use sternocleidomastoids, scalenes, and adopt a tripod position (sitting forward, hands on knees) to improve ventilation.
     
     

4. Pursed-lip Breathing
   
   

   • Seen in COPD; it helps keep airways open during expiration and improves gas exchange.
     
     

5. Chest Wall Deformities
   
   

   • Barrel chest: Seen in emphysema due to lung hyperinflation.
     
     

   • Pectus excavatum: May reduce lung capacity.
     
     

   • Pectus carinatum: Less common; may indicate underlying skeletal disorders.
     
     

   • Kyphoscoliosis: Causes restrictive lung disease.
     
     

PALPATION FINDINGS AND THEIR SIGNIFICANCE

1. Tracheal Deviation
   
   

   • Shift towards the lesion: Lung collapse, upper lobe fibrosis
     
     

   • Shift away from lesion: Tension pneumothorax, large pleural effusion, massive tumour
     
     

2. Chest Expansion
   
   

   • Reduced on one side: Suggests lung collapse, pleural effusion, or consolidation
     
     

   • Bilateral reduction: Suggests COPD, pulmonary fibrosis, or neuromuscular weakness
     
     

3. Tactile Vocal Fremitus
   
   

   • Increased: Consolidated lung (sound vibrations travel better through solid lung)
     
     

   • Decreased or absent: Pneumothorax, pleural effusion, or collapse with bronchial obstruction
     
     

PERCUSSION FINDINGS AND THEIR SIGNIFICANCE

1. Normal Note:
   
   

   • Resonant sound over healthy lungs
     
     

2. Dullness:
   
   

   • Consolidation (e.g., pneumonia)
     
     

   • Lung collapse
     
     

   • Tumour mass
     
     

3. Stony Dullness:
   
   

   • Classic sign of pleural effusion due to fluid accumulating between pleural layers
     
     

4. Hyperresonance:
   
   

   • Seen in pneumothorax (air in pleural space)
     
     

   • Also in severe emphysema (over-inflated lungs)
     
     

AUSCULTATION FINDINGS AND THEIR SIGNIFICANCE

1. Breath Sounds
   
   

   • Vesicular breath sounds (normal):
     Soft, low-pitched with no pause between inspiration and expiration.
     
     

   • Bronchial breath sounds:
     Harsh, high-pitched with a distinct pause between inspiration and expiration.
     Indicative of:
     
     

     • Lung consolidation (e.g., pneumonia)
       
       

     • Above a pleural effusion (due to lung compression)
       
       

     • Cavity communicating with a bronchus
       
       

   • Absent breath sounds:
     Seen in:
     
     

     • Pneumothorax
       
       

     • Pleural effusion
       
       

     • Massive collapse
       
       

     • Obstructing tumour
       
       

2. Added Sounds
   
   

   • Crackles (Crepitations):
     
     

     • Fine end-inspiratory: Pulmonary fibrosis, congestive heart failure (due to fluid in alveoli)
       
       

     • Coarse: Bronchiectasis, pneumonia, or COPD with secretions
       
       

   • Wheezing:
     
     

     • Musical, high-pitched sounds on expiration
       
       

     • Seen in asthma, COPD, and sometimes heart failure (cardiac asthma)
       
       

   • Pleural Rub:
     
     

     • Harsh, grating sound heard during inspiration and expiration
       
       

     • Indicates pleural inflammation (pleurisy), common in pulmonary embolism or pneumonia
       
       

   • Stridor:
     
     

     • Loud inspiratory sound due to upper airway obstruction (e.g., tumour, foreign body)
       
       

3. Vocal Resonance
   
   Ask the patient to repeat a phrase such as “ninety-nine” or “one-one-one” while auscultating.
   
   

   • Increased vocal resonance:
     Suggests lung consolidation — sound travels better through solid lung tissue.
     
     

   • Decreased or absent:
     Seen in pleural effusion, pneumothorax, or lung collapse with bronchial obstruction
     
     

   • Bronchophony:
     Abnormally clear voice sounds over the lungs — suggestive of consolidation
     
     

   • Egophony:
     When the spoken “ee” is heard as “ay” — a classic sign of consolidation over an effusion
     
     

   • Whispering pectoriloquy:
     Whispered words are clearly audible through the stethoscope — suggests lung consolidation.
     
     

CORRELATING SIGNS WITH COMMON CONDITIONS

1. Lobar Pneumonia (Consolidation)
   
   

   • Dull percussion
     
     

   • Bronchial breath sounds
     
     

   • Increased vocal fremitus and resonance
     
     

   • Crackles and possible pleural rub
     
     

2. Pleural Effusion
   
   

   • Stony dull percussion
     
     

   • Decreased breath sounds
     
     

   • Decreased fremitus
     
     

   • Reduced expansion
     
     

   • Bronchial breath sounds above the fluid level (compressed lung)
     
     

3. Pneumothorax
   
   

   • Hyperresonant percussion
     
     

   • Absent breath sounds
     
     

   • Tracheal deviation away (in tension pneumothorax)
     
     

   • Decreased fremitus
     
     

   • Reduced expansion
     
     

4. Chronic Obstructive Pulmonary Disease (COPD)
   
   

   • Decreased breath sounds
     
     

   • Hyperresonance
     
     

   • Prolonged expiration
     
     

   • Wheeze
     
     

   • Use of accessory muscles
     
     

   • Barrel-shaped chest
     
     

5. Fibrosis
   
   

   • Fine end-inspiratory crackles
     
     

   • Reduced chest expansion
     
     

   • Tracheal deviation toward affected side
     
     

   • Reduced percussion note
     
     

   • Clubbing may be present
     
     

Investigations are selected based on the history and physical findings. The aims are to:

• Confirm the diagnosis
  
  

• Assess the severity
  
  

• Monitor response to treatment
  
  

• Identify complications
  
  

1. CHEST X-RAY (CXR)

The chest X-ray is often the first-line imaging test.

It can identify:

• Consolidation: Suggests pneumonia or infection
  
  

• Pleural effusion: Fluid appears as a meniscus or blunting of the costophrenic angle
  
  

• Lung collapse: Reduced volume with mediastinal shift toward the affected side
  
  

• Pneumothorax: Absent lung markings with a visible pleural line
  
  

• Mass lesions: Tumours or metastatic deposits
  
  

• Interstitial patterns: Suggest interstitial lung disease or pulmonary oedema
  
  

• Hyperinflation: Seen in COPD
  
  

• Calcification: Suggests healed infections or malignancy
  
  

Systematic review of a chest X-ray includes:

• Patient details and film orientation
  
  

• Lung fields
  
  

• Heart size and borders
  
  

• Diaphragm contours
  
  

• Hilar structures
  
  

• Pleura and costophrenic angles
  
  

• Bones and soft tissues
  
  

Limitations:

• May not detect early disease or small lesions
  
  

• Supine films are harder to interpret
  
  

2. SPIROMETRY AND LUNG FUNCTION TESTS

Spirometry measures airflow and lung volumes. It is essential in diagnosing and monitoring:

• Obstructive diseases (asthma, COPD)
  
  

• Restrictive diseases (fibrosis, neuromuscular disorders)
  
  

Key spirometry values:

• FEV₁ (Forced Expiratory Volume in 1 second): Volume of air expired in the first second
  
  

• FVC (Forced Vital Capacity): Total volume of air exhaled
  
  

• FEV₁/FVC ratio:
  
  

  • <70%: Suggests obstructive pattern
    
    

  • Normal or high with reduced FVC: Suggests restriction
    
    

Flow-volume loops:

• Useful to differentiate fixed vs variable obstruction, and intrathoracic vs extrathoracic lesions
  
  

Full pulmonary function tests (PFTs) may include:

• Lung volumes (TLC, RV): To assess hyperinflation or restriction
  
  

• Diffusion capacity for carbon monoxide (DLCO): Reduced in interstitial disease or emphysema
  
  

3. ARTERIAL BLOOD GASES (ABGs)

ABGs assess gas exchange and acid–base balance, especially in patients with:

• Acute breathlessness
  
  

• Suspected hypoventilation
  
  

• COPD
  
  

• Severe asthma
  
  

• Suspected acidosis or alkalosis
  
  

Parameters include:

• pH
  
  

• PaO₂ (partial pressure of oxygen)
  
  

• PaCO₂ (partial pressure of carbon dioxide)
  
  

• HCO₃⁻ (bicarbonate)
  
  

Interpretation:

• Hypoxaemia (low PaO₂) suggests ventilation-perfusion mismatch or diffusion impairment
  
  

• Hypercapnia (raised PaCO₂) indicates hypoventilation
  
  

• Assess whether any compensatory metabolic changes are present
  
  

4. PEAK EXPIRATORY FLOW RATE (PEFR)

Measured using a handheld device. It is useful in:

• Diagnosing asthma
  
  

• Monitoring response to treatment
  
  

• Detecting diurnal variability or triggers
  
  

Low PEFR suggests airflow obstruction. Serial monitoring helps detect early deterioration in asthmatics.

5. PULSE OXIMETRY

A non-invasive method to estimate oxygen saturation (SpO₂). Normal values are 95–100% on room air.

Limitations:

• Cannot detect hypercapnia
  
  

• Inaccurate in poor perfusion states or with nail varnish
  
  

Used for screening, triage, and home monitoring.

6. MICROBIOLOGY AND SEROLOGY

Sputum Analysis:

• Assess for colour, volume, consistency
  
  

• Microscopy for cells and organisms
  
  

• Culture and sensitivity to guide antibiotic therapy
  
  

• Acid-fast bacilli (AFB) testing in suspected tuberculosis
  
  

Throat swabs and nasal aspirates:

• Used in children or for viral studies
  
  

Blood cultures:

• In febrile patients with suspected pneumonia or sepsis
  
  

Serology:

• For atypical organisms (e.g., Mycoplasma, Legionella)
  
  

• HIV testing in suspected immunocompromise
  
  

7. BRONCHOSCOPY

A flexible or rigid instrument is passed into the airways.

Uses:

• Visualise lesions or tumours
  
  

• Take biopsies
  
  

• Collect bronchoalveolar lavage for culture or cytology
  
  

• Remove foreign bodies
  
  

• Identify bleeding sources
  
  

Indications:

• Haemoptysis
  
  

• Persistent localised wheeze
  
  

• Unexplained opacity on X-ray
  
  

• Suspected cancer
  
  

• Lung infections in immunocompromised patients
  
  

8. HIGH-RESOLUTION COMPUTED TOMOGRAPHY (HRCT)

More sensitive than chest X-ray for interstitial and small airway diseases.

Findings:

• Ground-glass opacities: inflammation, infection
  
  

• Honeycombing: fibrosis
  
  

• Tree-in-bud pattern: small airway disease (e.g., tuberculosis)
  
  

Used in:

• Interstitial lung disease
  
  

• Bronchiectasis
  
  

• Pulmonary embolism (with contrast — CT pulmonary angiography)
  
  

9. ULTRASOUND AND PLEURAL TAPPING

Chest ultrasound helps:

• Identify and locate pleural effusion
  
  

• Guide thoracocentesis (needle aspiration of pleural fluid)
  
  

Pleural fluid analysis includes:

• Appearance
  
  

• Protein content (to differentiate transudate vs exudate)
  
  

• Cytology for malignant cells
  
  

• pH, glucose, LDH
  
  

• Culture and Gram stain
  
  

10. VENTILATION-PERFUSION (V/Q) SCAN

Assesses air and blood flow in the lungs.

Used in:

• Suspected pulmonary embolism when CT is contraindicated
  
  

• Evaluation of lung function before surgery
  
  

Interpretation:

• Mismatch between ventilation and perfusion suggests embolism