Lung Sound Recognition—Comprehensive Study Notes

Overview of the “Name-That-Lung-Sound” Flash-Card Game

• A rapid-fire quiz show format used to reinforce recognition of common lung sounds.
• Nine questions were presented, each featuring an audio clip the audience had to identify.
• After each clip, the correct answer and its typical clinical contexts were supplied.

Master List of Lung Sounds Covered (Questions 1 – 9)

1. Polyphonic Wheeze

• Definition: Multiple musical tones heard simultaneously during expiration (sometimes inspiration) caused by airflow through numerous narrowed bronchi.
• Audio Qualities: High-pitched, “musical,” varying in pitch (“polyphonic”).
• Key Clinical Associations:
  • Asthma: widespread bronchoconstriction → multiple airways narrow.
  • COPD: chronic airway inflammation + mucus → diffuse obstruction.
• Pathophysiology: Turbulent airflow through airways of different calibers → multiple frequencies.

2. Fine Crackles

• Definition: Short, high-pitched “popping” sounds, usually heard at end-inspiration.
• Audio Qualities: Like rolling strands of hair between fingers next to ear.
• Key Clinical Associations:
  • Interstitial lung fibrosis (early stage).
  • Pneumonia (particularly when alveoli partially filled with exudate).
  • Congestive heart failure (CHF) with pulmonary edema.
• Mechanism: Sudden opening of small airways/alveoli collapsed by fluid, fibrosis, or exudate.

3. Vesicular Breath Sounds

• Definition: Normal breath sound heard over most lung fields.
• Audio Qualities: Soft, low-pitched rustling; inspiration > expiration (ratio ≈ 3:1).
• Significance: Indicates patent, healthy peripheral airways & alveoli.

4. Coarse Crackles

• Definition: Louder, lower-pitched, bubbling/gurgling sounds; may be heard in both inspiration and expiration.
• Key Clinical Associations:
  • Advanced interstitial lung fibrosis (thicker, less compliant parenchyma).
  • Pneumonia (larger airways full of secretions).
  • CHF (more severe pulmonary edema).
• Mechanism: Air coursing through larger fluid-filled bronchi/bronchioles.

5. Bronchial Breath Sounds

• Definition: Loud, hollow, high-pitched sounds normally heard over trachea/main bronchi.
• Abnormal When: Auscultated over peripheral lung fields.
• Abnormal Implications:
  • Pneumonia with consolidation (airless alveoli transmit central sounds).
  • Dense lung fibrosis.
  • Lung abscess.
  • Lung collapse (atelectasis) adjacent to pleural effusion.
• Audio Pattern: Inspiration ≈ expiration; pronounced pause between phases.

6. Inspiratory Stridor

• Definition: Harsh, vibratory, monophonic sound during inspiration caused by extrathoracic airway obstruction.
• Classic Patient Population: Children.
• Common Pediatric Causes:
  • Croup (laryngotracheobronchitis).
  • Foreign body aspiration (lodged in larynx/trachea).
• Emergency Indicator: Suggests critical airway narrowing—evaluate & treat promptly.

7. Rhonchi

• Definition: Low-pitched, snoring/gurgling sounds that may clear or change after coughing.
• Key Clinical Associations:
  • Bronchitis (mucus in large airways).
  • Pneumonia (secretions/inflammatory debris).
• Pathophysiology: Air moving through secretions or large airway obstruction.

8. Monophonic Wheeze

• Definition: Musical, single-pitch wheeze heard over one area, usually during expiration.
• Mechanism: Localized obstruction of a single airway.
• Potential Etiologies:
  • Airway secretions plugging one bronchus.
  • Foreign body (e.g., peanut lodged in segmental bronchus).
  • Endobronchial tumor.
• Clinical Pearl: Focal wheeze warrants imaging/bronchoscopy to rule out obstructive lesion.

9. Pleural Friction Rub

• Definition: Creaking/leathery sound occurring when inflamed pleural surfaces rub during respiratory cycle.
• Timing: Heard in both inspiration and expiration; often localized to a small area.
• Typical Causes:
  • Pleurisy (pleuritis from infection, infarction, autoimmune disease).
  • Pleural tumors or metastatic disease.
• Exam Tip: Ask patient to hold breath—if sound stops, it is pleural; if it continues, consider pericardial friction rub.

Comparative Summary Table (Quick Reference)

• Wheeze: Continuous, musical (polyphonic vs. monophonic).
• Stridor: High-pitched, inspiratory, upper airway emergency.
• Rhonchi: Low, snoring, clears with cough.
• Crackles: Discontinuous; fine vs. coarse correspond to small vs. large airway/alveolar involvement.
• Pleural Rub: Grating, stops with breath hold.

Clinical Integration & Practical Implications

• Accurate lung-sound identification accelerates differential diagnosis at bedside.
• Emergency recognition:
  • Inspiratory stridor demands airway assessment.
  • Localized monophonic wheeze may signal obstructive tumor requiring urgent imaging.
• Follow-up Investigations:
  • Crackles in CHF → consider chest X-ray + BNP.
  • Bronchial breath sounds peripherally → order chest radiograph for consolidation.
• Therapy Links:
  • Polyphonic wheeze (asthma) responds to bronchodilators \beta_2-agonists & steroids.
  • Rhonchi in bronchitis → airway clearance + antibiotics if bacterial.
• Ethical/Philosophical Note: Early auscultation skills reduce need for costly imaging and shorten diagnostic delay, embodying high-value, patient-centered care.

Mnemonic Connections

• "Wheezes = Whistles" (musical).
• "Crackles = Chronically scarred or Cardiac fluid."
• "Rhonchi = Rattling secretions."
• "Pleural rub = Rough pleura."
• "Stridor = upper airway obstructions (letters I line up)."

Linking Back to Foundational Principles

• Lung acoustics derive from fluid-dynamics: turbulent vs. laminar flow (Reynolds>2000 produces audible vibrations).
• Sound transmission is enhanced through consolidated tissue due to higher density, explaining bronchial sounds in pneumonia.

Real-World Relevance

• Primary-care and emergency clinicians use these auditory clues to triage respiratory distress.
• Tele-health electronic stethoscopes increasingly incorporate AI that categorizes sounds—mirroring this flash-card exercise.

Key Takeaways

• Mastery of nine fundamental lung sounds provides >80\% of clinically relevant auscultatory data.
• Always relate the sound to location, phase of respiration, and patient context to refine diagnosis.