Breath sounds

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Introduction

The auscultation of breath sounds is a fundamental part of any patient assessment. Breath sounds, which are also known as respiratory or lung sounds, are auscultated with a stethoscope. Breath sounds can be best heard while a stethoscope is positioned on the intercostal spaces either anteriorly or posteriorly. This reference will serve to provide healthcare professionals with a guide to improve auscultation skills. Though its ideal use is to educate students, the repetition can help to reinforce existing providers knowledge or dispel common misconceptions. The focus of this guide will be to differentiate between types of breath sounds by providing a brief description of the sound followed by audio examples.

Normal Lung Sounds

Normal breath sounds are classified as tracheal, bronchial, and vesicular sounds. The patterns of normal breath sounds are created by the effect of body structures on air moving through airway. Normal lung sounds can be considered abnormal when the sound occurs in an area in which the sounds should not be present.

Vesicular

Vesicular breath sounds are caused by the normal movement of air through the bronchioles during inspiration and expiration. They are characterize by a hollow blowing sound that is even and low pitched which diminishes in intensity during the expiratory phase.

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Bronchial

Bronchial sounds are present over the large airways near the second and third intercostal spaces. These sounds are more tubular and hollow sounding than vesicular sounds. They are typically louder and higher in pitch than vesicular breath sounds.

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Tracheal

Tracheal breath sounds are heard midline over the trachea. These sounds are harsh due to the more turbulent airflow through the larger vessels and sound like air is being blown through a pipe.

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Adventitious Breath Sounds (Abnormal)

Rhonchi and Wheezes

Wheezes are classified as either a sibilant wheeze or a sonorous wheeze (rhonchi). They are caused by a partial obstruction in the airway that is commonly attributed to secretions or bronchoconstriction.

Sibilant Wheeze (Wheezes)

The sibilant wheeze is what most healthcare professionals refer to as wheezing. They are characterized by a high pitched continuous sound that occurs either the end of inspiration or during the expiratory phase. They are caused by the narrowing of airways around an obstruction. During inspiration, the elasticity of the airways will cause them to dilate which will allow air to flow around the obstruction. As the airways contract during exhalation, airflow will increase causing the high pitched sounds associated with wheezing.

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Sonorous Wheeze (Rhonchi)

The sonorous wheeze that is commonly referred to as rhonchi, is caused by the same expansion and narrowing of the airways as sibilant wheezes. The difference between the two is that rhonchi is typically associated with secretions that are obstructing the larger airways. This causes a lower pitched vibrating sound on auscultation that is similar to snoring. Because rhonchi are caused by airway secretions they can usually be heard both during the inspiratory phase and expiratory phases (biphasic).

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Stridor

Stridor is caused by an obstruction in the larynx, and requires immediate intervention as it can cause death. It is characterized by a high pitched sounds originating from the throat that can be heard without a stethoscope. Common causes of stridor are airway edema, aspiration and airway infections.

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Crackles / Rales

Crackles formerly known as rales (standardized by the American Thoracic Society and American College of Chest Physicians in 1977), are caused by interstitial fluid or plasma that has leaked in the airways. They are characterized as discontinuous high pitched bubbling sounds, which are similar to the sound of air blowing through a straw in liquid. Crackles are classified by the extent of the fluid in the airways as either fine, medium, or coarse. An example of a death rattle is provided as it illustrates the extent to which crackles can develop to the point of death.

Fine Crackles

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Coarse Crackles

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Death Rattle

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Pleural Rub

A pleural rub is most commonly caused by an inflammation of either the visceral and/or parietal pleura. It is characterized by a low pitched grating sound similar to the sound of walking on snow. In order to determine if the rub is being caused by the pleural lining or the pericardium you must perform a brief inspiratory hold maneuver, if the rub continues during the maneuver it is most likely a pericardial rub.

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