Auscultation of Breath Sounds in IPF

Auscultation of the lungs is an important component of a physical examination because respiratory sounds provide vital information regarding the physiology and pathology of lungs and airways obstruction.¹ The ability to distinguish normal breath sounds from various abnormal adventitious sounds is essential to make an accurate medical diagnosis.¹ Breath sounds are generated by airflow in the respiratory tract and include normal and adventitious sounds.¹ Adventitious sounds are additional respiratory sounds superimposed on normal breath sounds and usually indicate pulmonary disorders.¹ For many years a complex, conflicting, and confusing body of terms was used to describe respiratory sounds.² In order to establish a more objective naming system, in 1985 an ad hoc committee of the International Lung Sounds Association agreed on a nomenclature that divided adventitious sounds into 2 major categories: continuous sounds or wheezes, and discontinuous sounds or crackling noises (Table 1).² These terms are defined acoustically (eg, frequency, duration, initial deflection width, etc) and do not assume a generating mechanism or location.³⁴

Table 1.
Lung Sound Nomenclature. Adapted from Mikami R, et al. Chest. 1987;92:342-345.

Lung Sound Category	Term
Discontinuous
FineHigh pitched, low amplitude, short duration	Fine crackles
CoarseLow pitched, high amplitude, long duration	Coarse crackles
Continuous
High pitched	Wheezes
Low pitched	Rhonchus

Breath Sounds of Idiopathic Pulmonary Fibrosis (IPF)

Bilateral fine crackles on chest auscultation are detected in 60% of patients with IPF.⁵ These crackles have a distinctive “Velcro-like” character and are heard during middle to late inspiration.⁶ They tend to be heard almost exclusively over the dependent lung regions and are changed very little by coughing.⁶ The sounds may be gradually or suddenly extinguished by having the patient bend forward, thus removing the effect of gravity.⁷ These fine crackles are generated when previously collapsed alveoli suddenly reopen during late inspiration.⁷

Listen to the examples below to hear breath sounds recorded from patients with IPF.

Note: recordings were made with a 3M Littmann Electronic Stethoscope 3200 in a clinic setting with patients at rest.

Breath Sounds of Chronic Obstructive Pulmonary Disease (COPD)

In patients with COPD breath sounds may be diminished and expiration is prolonged.⁸ Coarse crackles heard at the beginning of inspiration are commonly heard in patients with COPD, especially those with chronic bronchitis.⁷ These crackles have a “popping-like” character, vary in number and timing and may be heard over any lung region.⁶ These early inspiratory crackles are frequently heard during expiration as well and coughing may cause these sounds to disappear.⁶ These coarse crackles are caused by the movement of boluses of gas through an intermittently occluded airway.⁷

Listen to the examples below to hear breath sounds recorded from patients with COPD.

Note: recordings were made with a 3M Littmann Electronic Stethoscope 3200 in a clinic setting with patients at rest.

Normal Breath Sounds

Normal breath sounds are characterized by a low noise heard during inspiration. During expiration these noises are hardly audible.¹ The sound is not musical, and there are no discrete peaks.⁴ The inspiratory component of the sound is mostly generated within the lobar and segmental airways while the expiratory component is produced from more proximal areas.⁴ Air turbulence is thought to generate normal lung sounds.⁴

Listen to the examples of normal breath sounds.

Note: recordings were made with a 3M Littmann Electronic Stethoscope 3200 in a clinic setting with patients at rest.

References

1. Reichert S, Gass R, Brandt C, Andres E. Analysis of respiratory sounds: state of the art. Clin Med Circ Respirat Pulm Med. 2008;2:45-58.
2. Mikami R, Murao M, Cugell DW, et al. International Symposium on Lung Sounds. Synopsis of proceedings. Chest. 1987;92:342-345.
3. Cugell DW. Lung sound nomenclature. Am Rev Respir Dis. 1987;136:1016.
4. Pasterkamp H, Kraman SS, Wodicka GR. Respiratory sounds. Advances beyond the stethoscope. Am J Respir Crit Care Med. 1997;156:974-987.
5. Epler GR, Carrington CB, Gaensler EA. Crackles (rales) in the interstitial pulmonary diseases. Chest. 1978;73:333-339.
6. Kraman SS. Lung sounds for the clinician. Arch Intern Med. 1986;146:1411-1412.
7. Forgacs P. The functional basis of pulmonary sounds. Chest. 1978;73:399-405.
8. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease. American Thoracic Society. Am J Respir Crit Care Med. 1995;152:S77-121.