Guide — Fundamentals
Breath Sounds & Lung Auscultation
The stethoscope is the RT’s fastest diagnostic instrument — when you listen systematically. This guide builds the listening sequence, defines the normal sounds and where each belongs, and catalogs the adventitious sounds, their mechanisms, and what they tell you to do next.
9 min read · Fundamentals
Written by Apex Respiratory Editorial Team
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Overview
Auscultation answers two questions at the bedside: is air reaching this region of lung, and is anything getting in its way? A sound is only meaningful against the sound you expect to hear at that spot, so the skill is half technique and half knowing the normal map. Done well, it guides therapy in seconds — before and after every bronchodilator, suction pass, or recruitment maneuver.
Key Concepts — Technique & Normal Sounds
Auscultate systematically: diaphragm on bare skin, top to bottom, comparing each point with its mirror on the opposite side. Have the patient breathe slowly and deeply through an open mouth, and listen through a full inspiration and expiration at every site so late or expiratory findings are not missed.
| Sound | Normal Location | Quality | When Abnormal |
|---|---|---|---|
| Vesicular | Most of the peripheral lung fields | Soft, low-pitched; inspiration longer than expiration | Normal everywhere peripherally; diminished if airflow or transmission is reduced. |
| Bronchovesicular | Over the main bronchi — 1st/2nd interspaces anteriorly, between the scapulae | Medium pitch; inspiration and expiration roughly equal | Abnormal if heard in the peripheral lung, where it suggests consolidation. |
| Bronchial / tracheal | Over the trachea and manubrium | Loud, high-pitched, hollow; expiration longer than inspiration | Abnormal over the lung periphery — implies consolidation transmitting central sounds outward. |
The recurring principle: a normal sound in the wrong place is an abnormal finding. Bronchial breath sounds are perfectly normal over the trachea, but hearing them out in the lung periphery points to consolidation transmitting central sound through airless tissue.
Assessment & Findings — Adventitious Sounds
| Sound | Acoustic Quality | Mechanism | Common Causes |
|---|---|---|---|
| Fine crackles (rales) | Brief, high-pitched, Velcro-like; late inspiration | Sudden reopening of collapsed small airways | Pulmonary fibrosis, early pulmonary edema, atelectasis reopening |
| Coarse crackles | Louder, lower-pitched, bubbling | Air moving through secretions or fluid in airways | Secretions, pneumonia, pulmonary edema |
| Wheezes | High-pitched, musical; usually expiratory | Air forced through narrowed lower airways | Bronchospasm, asthma, COPD; monophonic = single fixed obstruction |
| Rhonchi | Low-pitched, snore-like; often clears with cough | Secretions or narrowing in the large airways | Large-airway secretions, bronchitis |
| Stridor | High-pitched; predominantly inspiratory | Turbulent flow through a critically narrowed upper airway | Croup, epiglottitis, post-extubation edema, foreign body — airway emergency |
| Pleural friction rub | Grating, creaking; both inspiration and expiration | Inflamed pleural surfaces rubbing together | Pleuritis, pleural inflammation |
| Diminished / absent | Reduced or no audible airflow | Blocked airflow or impaired sound transmission | Pneumothorax, pleural effusion, severe obstruction, poor inspiratory effort |
Two quick discriminators carry most of the bedside value: pitch and location tell wheeze (lower-airway, expiratory) from stridor (upper-airway, inspiratory); the cough test tells rhonchi (clears) from crackles (persists).
RT Priorities & Interventions
- Auscultate before and after therapy. Listen before and after a bronchodilator to gauge whether wheezing and air movement improved, and before and after suctioning to confirm secretions cleared. The post-treatment exam is your evidence the intervention worked.
- Treat stridor as an airway emergency. Inspiratory stridor means the upper airway is narrowing — escalate immediately for airway assessment; a routine bronchodilator is not the answer.
- Respect the silent chest.A previously wheezing asthmatic who goes quiet while deteriorating is losing airflow, not improving — prepare for urgent escalation and possible ventilatory support.
- Localize and act on focal findings. Unilateral absent sounds after a procedure or in a deteriorating patient raise pneumothorax or mainstem migration — correlate with the clinical picture and act.
- Document with precision.Name the sound, the phase, and the location (“coarse crackles, right base, inspiratory”) so the trend across shifts is readable.
Common Pitfalls
- Auscultating over a gown or clothing, which generates friction artifact that mimics crackles and rubs. Listen on bare skin.
- Missing a silent chest — reading the disappearance of a wheeze as improvement rather than the loss of airflow it usually is.
- Confusing rhonchi with crackles. Have the patient cough: rhonchi clear or shift, crackles do not.
- Listening to only one phase of the breath, or skipping side-to-side comparison, so an asymmetry or a late-inspiratory finding goes undetected.
Board Exam Pearls
- Inspiratory stridor = upper-airway obstruction and an emergency; expiratory wheeze = lower-airway narrowing. Pitch and phase are the discriminators the exam wants.
- Fine, late-inspiratory “Velcro” crackles point to pulmonary fibrosis; coarse, bubbling crackles point to secretions or edema.
- Rhonchi clear with coughing; crackles do not. That single test separates the two on a stem.
- Unilateral absent breath sounds with deterioration suggests pneumothorax (or, on a ventilator, a right-mainstem intubation) — a classic exhibit-question finding.
FAQ
What is the difference between crackles and rhonchi?
Crackles (rales) are discontinuous, popping sounds from the sudden opening of collapsed small airways or air bubbling through fluid; they do not clear with coughing. Rhonchi are continuous, low-pitched, snore-like sounds from secretions or narrowing in the larger airways, and they often clear or change after a cough. The cough test is the fastest bedside discriminator: if it clears, think rhonchi and large-airway secretions; if it persists, think crackles.
Why is stridor an emergency?
Stridor is a high-pitched, mostly inspiratory sound produced by turbulent flow through a critically narrowed upper airway — larynx or trachea. Unlike wheezing, which reflects lower-airway narrowing, stridor signals that the airway the patient breathes through is closing. Causes include croup, epiglottitis, post-extubation laryngeal edema, anaphylaxis, and foreign body. It demands immediate airway assessment and escalation, not routine bronchodilator therapy.
What does a silent chest mean in an asthma attack?
It is an ominous sign, not a reassuring one. Wheezing requires enough airflow to make the airways oscillate. In a severe, decompensating asthma exacerbation, airflow can drop so low that the wheeze disappears — the 'silent chest.' A patient who was wheezing loudly and goes quiet while looking worse is heading toward respiratory failure and needs urgent escalation, not relief that the wheeze stopped.
How do I auscultate correctly?
Listen with the diaphragm directly on bare skin — never over a gown or clothing, which creates artifact. Move systematically and compare side to side at matched levels, working top to bottom, anterior and posterior. Have the patient breathe slowly and deeply through an open mouth, and listen through a full inspiration and expiration at each point so you do not miss late-inspiratory or expiratory findings.
Put it to work
Keep the whole catalog at your fingertips. The breath sounds quick reference distills every normal and adventitious sound into a scannable bedside card for fast recall.
Open the Breath Sounds Quick Reference →Related Resources
Sources
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021. Bedside assessment of the patient.
- Bickley LS, Szilagyi PG. Bates' Guide to Physical Examination and History Taking. 13th ed. Wolters Kluwer; 2021.
- Bohadana A, Izbicki G, Kraman SS. Fundamentals of lung auscultation. N Engl J Med. 2014;370(8):744-751.