The clinical characteristics of normal and adventitious sounds are summarized.
Clinical Characteristics and Correlations of Respiratory Sounds
| Respiratory Sound | Clinical Characteristics | Clinical Correlation |
| Normal tracheal sound | Hollow and nonmusical, clearly heard in both phases of respiratory cycle | Transports intrapulmonary sounds, indicating upper-airway patency; can be disturbed (e.g., become more noisy or even musical) if upper-airway patency is altered; used to monitor sleep apnea; serves as a good model of bronchial breathing |
| Normal lung sound | Soft, nonmusical, heard only on inspiration and on early expiration | Is diminished by factors affecting sound generation (e.g., hypoventilation, airway narrowing) or sound transmission (e.g., lung destruction, pleural effusion, pneumothorax); assessed as an aggregate score with normal breath sound; rules out clinically significant airway obstruction* |
| Bronchial breathing | Soft, nonmusical, heard on both phases of respiratory cycle (mimics tracheal sound) | Indicates patent airway surrounded by consolidated lung tissue (e.g., pneumonia) or fibrosis |
| Stridor | Musical, high-pitched, may be heard over the upper airways or at a distance without a stethoscope | Indicates upper-airway obstruction; associated with extrathoracic lesions (e.g., laryngomalacia, vocal-cord lesion, lesion after extubation) when heard on inspiration; associated with intrathoracic lesions (e.g., tracheomalacia, bronchomalacia, extrinsic compression) when heard on expiration; associated with fixed lesions (e.g., croup, paralysis of both vocal cords, laryngeal mass or web) when biphasic |
| Wheeze | Musical, high-pitched; heard on inspiration, expiration, or both | Suggests airway narrowing or blockage when localized (e.g., foreign body, tumor); associated with generalized airway narrowing and airflow limitation when widespread (e.g., in asthma, chronic obstructive lung disease); degree of airflow limitation proportional to number of airways generating wheezes; may be absent if airflow is too low (e.g., in severe asthma, destructive emphysema) |
| Rhonchus | Musical, low-pitched, similar to snoring; lower in pitch than wheeze; may be heard on inspiration, expiration, or both | Associated with rupture of fluid films and abnormal airway collapsibility; often clears with coughing, suggesting a role for secretions in larger airways; is nonspecific; is common with airway narrowing caused by mucosal thickening or edema or by bronchospasm (e.g., bronchitis and chronic obstructive pulmonary disease) |
| Fine crackle | Nonmusical, short, explosive; heard on mid-to-late inspiration and occasionally on expiration; unaffected by cough, gravity-dependent, not transmitted to mouth | Unrelated to secretions; associated with various diseases (e.g., interstitial lung fibrosis, congestive heart failure, pneumonia); can be earliest sign of disease (e.g., idiopathic pulmonary fibrosis, asbestosis); may be present before detection of changes on radiology |
| Coarse crackle | Nonmusical, short, explosive sounds; heard on early inspiration and throughout expiration; affected by cough; transmitted to mouth | Indicates intermittent airway opening, may be related to secretions (e.g., in chronic bronchitis) |
| Pleural friction rub | Nonmusical, explosive, usually biphasic sounds; typically heard over basal regions | Associated with pleural inflammation or pleural tumors |
| Squawk | Mixed sound with short musical component (short wheeze) accompanied or preceded by crackles | Associated with conditions affecting distal airways; may suggest hypersensitivity pneumonia or other types of interstitial lung disease in patients who are not acutely ill; may indicate pneumonia in patients who are acutely ill |
References:
- Bohadana A, Izbicki G, Kraman SS. Fundamentals of lung auscultation. N Engl J Med. 2014 Feb 20;370(8):744-51. [Medline]
- Pasterkamp H, Kraman SS, Wodicka GR. Respiratory sounds. Advances beyond the stethoscope. Am J Respir Crit Care Med. 1997 Sep;156(3 Pt 1):974-87.[Medline]
Created May 05, 2014.
