An Overview of Breath Sounds

Lung sounds on ausculation such as wheezing, stridor, rhonchi, and more

Breath sounds may be heard with a stethoscope during inspiration and expiration in a technique called auscultation. Abnormal lung sounds such as stridor, rhonchi, wheezes, and rales, as well as characteristics such as pitch, loudness, and quality, can give important clues as to the cause of respiratory symptoms. While the "art" of careful auscultation is often downplayed with the advent of easily accessible imaging and laboratory tests, a thorough lung exam that also includes inspection, palpation, and percussion remains a cornerstone in diagnosing conditions ranging from asthma to heart failure.

Auscultation of the Lungs: Evaluating Breath Sounds

There are reasons that many physicians wear a stethoscope around their neck—and they go far beyond listening to your heart. Even when listening to your lungs, there are many nuances that can help a physician ensure you are healthy—or make a challenging diagnosis.

Listening to the lungs (auscultation) is best done in a quiet room, with a person sitting, mouth open, and through as little clothing as possible. The diaphragm of the stethoscope provides the best audio, but a stethoscope is, for the most part, an aesthetic invention first used in 1816.

In a pinch, listening to the chest with an ear pressed closely to the skin can provide a lot of information (though minus the magnification), and this is exactly how Hippocrates began the practice of auscultation.

When listening to the lungs, the exam should extend from the top of the lungs down to the lower lung fields, with auscultation performed on the anterior chest, posterior chest, as well as under the armpits (mid-axillary region).

Auscultation Etiquette

Ideally, auscultation should be performed beneath clothing. Prior to applying the stethoscope, providers should warm the diaphragm (unless an emergency warrants immediate assessment). Deeper breaths allow breath sounds to be heard more easily, but sometimes a break during the exam is needed to avoid lightheadedness.

Basics

There are several characteristics that doctors note when listening to the lungs. (The other aspects of a lung exam, including inspection, palpation, percussion are discussed later in this article.)

Normal Breath Sounds

There are three primary types of normal breath sounds that may be heard depending on location.

Tracheal Breath Sounds: Tracheal breath sounds are loud, high pitched, and are heard primarily over the trachea (the lower neck) in healthy people.

Bronchial Breath Sounds: Bronchial breath sounds are heard over the large bronchi (over the breastbone or sternum in the mid-chest region and between the shoulder blades on the back). They are higher-pitched and louder than breath sounds heard over other parts of the lungs but quieter and more hollow-sounding (tubular) compared with tracheal breath sounds. The expiratory phase is usually longer than the inspiratory phase, and there is a pause between inspiration and expiration.

Bronchial breath sounds are sometimes heard in other regions of the lungs (due to sound transmission) with conditions such as pneumonia, lung tumors, atelectasis (collapse of part of a lung), or a pneumothorax.

Vesicular Breath Sounds: People are often more familiar with vesicular breath sounds, as they are the sounds heard over much of the lungs. They are lower-pitched and softer than tracheobronchial breath sounds. Inspiration is longer than expiration and there is no pause between inspiration and expiration.

Ratio of Inspiration to Expiration

As noted, the ratio of inspiration to expiration can vary depending on where you listen. The normal ratio of inspiration to expiration (vesicular breath sounds) is 1-2 at rest and while sleeping, and 1-1 with exertion. A change in this ratio can give clues to the presence of disease. For example, with obstructive lung diseases such as emphysema, the ratio may instead be 1-4 or even 1-5.

Frequency and Pitch

The pitch or frequency of breath sounds can be described as high or low. Pitch is especially helpful when abnormal breath sounds are present.

Intensity (Loudness)

The intensity or loudness of breath sounds can be described as normal, decreased ( diminished), or absent. Intensity is usually higher in the bases than at the top of the lungs (apices). When lying down on one side, breath sounds are usually loudest on the side of the chest closest to the exam table.

Decreased or absent breast sounds may be noted in a number of different conditions:

  • When there is fluid around the lungs, such as with a pleural effusion
  • When there is air around the lungs, as with a pneumothorax
  • If the lungs are overinflated, such as with emphysema
  • When airflow to a region of the lungs is reduced, such as with an obstruction due to a tumor or foreign body
  • If the thickness of the chest wall is increased, such as with obesity

Quality (Timbre)

Quality can be thought of as the "musical characteristics" of the breath sounds, including things such as overtones and harmonics. Wheezing tends to have a musical sound that includes more than one note, while stridor is often monophasic.

Vocal Resonance

Doctors can gain additional information by having you speak while they listen to your lungs.

Whispered Pectoriloquy: With pectoriloquy, your doctor will have you quietly whisper a word (two-syllable words work best). If consolidation is present (such as with pneumonia) words that are whispered may be heard clearly.

Egophony: With egophany, a physician will have you speak a capital "E" while she listens to your chest. If lung consolidation is present (such as pneumonia), it may sound to her like a nasal capital "A."

Decreased transmission of vocal sounds may occur in conditions such as a pneumothorax.

Abnormal or Adventitious Breath Sounds and Causes

There are a number of different terms used to describe abnormal or adventitious breath sounds, and these can be very confusing. Some are heard with a stethoscope (auscultation), but some may be heard without. These sounds can differ based on whether they are predominant during inspiration or expiration, in the quality of the sounds, and more.

Wheezing

Wheezing is a term used to describe high whistling sounds in the lungs, and is usually more pronounced with expiration. These sounds may also be described as squeaky, musical, or like moaning (when they are low pitched). When musical, wheezes may sound like a single note or multiple notes, with single notes more common with disease in the small airways, and multiple notes or different tones heard when larger airways are involved.

Wheezing is not always abnormal, and may be heard in healthy people with forced expiration after a deep breath. They are usually continuous.

Squawks: The term squawk is used to describe very short wheezes that usually occur late during inspiration, and may be seen with conditions such as pneumonia, lung fibrosis, or bronchiolitis obliterans.

Causes: There are many possible causes of wheezes, with obstructive airway disease most common. Potential causes include:

  • Asthma: While common, not all wheezing is due to asthma. It's also important to note that with severe asthma, there may be little or no wheezing. Air needs to be moving to generate the wheezing sound, and wheezes may appear to go away even though the condition is serious worsening.
  • COPD: Chronic obstructive pulmonary diseases such as emphysema, chronic bronchitis, and bronchiectasis are commonly associated with wheezing.
  • Foreign body aspiration
  • Bronchitis

Wheezing may be diffuse and generalized, such as with asthma, or occur focally in one region due to obstruction by a foreign body or tumor.

Stridor

Stridor refers to a high pitched sound with a musical quality that is heard mostly with inspiration. Stridor should be dressed urgently as it can indicate a medical emergency. It is a continuous sound found when a blockage occurs in the upper airways, and is usually loudest over the neck.

Causes: Obstruction in the upper airways is less common than that in the lower airways, and may be due to:

  • Epiglottitis: Epiglottitis is a condition characterized by inflammation of the epiglottis and is a medical emergency. When the epiglottis swells, it can block off the entry of air into the lungs, and even placing a tube to breathe (endotracheal tube) can be challenging.
  • Croup (laryngotracheitis)
  • Foreign body in the upper airways
  • Tracheal stenosis or tracheomalacia
  • Vocal cord dysfunction
  • Laryngomalacia

Inspiratory Gasp

With pertussis (whooping cough), a high-pitched "whoop" may be heard after coughing

Rhonchi

Rhonchi, in contrast to wheezes, are described as low pitched clunky or rattling sounds, though sometimes they resemble snoring. They often clear with coughing, and are usually caused by an obstruction or build-up of mucus in the large airways.

Rales or Crackles

Rales or crackles are also referred to as "crepitation" and are often an intermittent (discontinuous) sound that is most pronounced with inspiration. The sounds have been described as clunky, rattling, crackling, clinking, or popping, and occurs when the smaller airways open suddenly during inspiration.

Crackles can be further defined as moist or dry and fine or coarse, with fine crackles thought to be related more to small airway disease and coarse crackles seen with large airway conditions.

Causes: Crackles are often related to the build-up of fluid in the alveoli (the tiniest airways) of the lungs. Some causes include:

Pleural Rub

A pleural rub is a gritty sound that has been likened to the sound of walking on fresh snow or sitting down on a leather couch. Unlike rales, the sound does not clear with coughing. A pleural rub may occur during both inspiration and expiration.

Causes: Conditions that cause inflammation of the membranes lining the lungs (pleura) can result in a rub, such as:

Other Parts of a Lung Examination

In addition to listening (auscultation) there are several other components to a thorough lung examination.

Inspection

Visualization of the chest is an important part of a lung exam along with listening and palpating (touching). Physicians note a number of factors during inspection.

  • Respiratory rate: Respiratory rate has been coined the neglected vital sign, and its importance can't be understated. In the hospital setting, it can sometimes be more valuable than blood pressure or heart rate in predicting prognosis. A normal respiratory rate in an adult is less than 20 breaths over a period of one minute while at rest.
  • Pattern of breathing: The pattern of breathing can be as important as the rate. One type of irregular breathing, Cheyne Stokes respirations, is common in people who are dying (but can be seen in healthy people as well).
  • Symmetry of chest expansion
  • Depth of breathing

Terms describing respiratory rate include:

  • Tachypnea, referring to rapid, shallow breaths
  • Hyperpnea, referring to deep and labored breathing
  • Bradypnea, referring to a respiratory rate that is too slow
  • Apnea, literally means "no breath"

Palpation

Palpation or feeling the chest is also important. Findings may include

  • Tactile fremitus: A palpable sensation (vibration) is transmitted to the chest wall with breathing. This may be decreased with a pleural effusion or pneumothorax.
  • Tenderness: The chest may be tender due to rib fractures, inflammation of the rib joints, and more.

Percussion

Percussion or tapping on the chest is the final aspect of a comprehensive lung exam. Laying one finger on the chest and tapping that finger with another usually results in a resonant sound. Abnormal findings may include:

  • Hyperresonance: Resonance may be increased with emphysema or a pneumothorax
  • Hyporesonance (dull sound with percussion): A decrease in resonance may be found with a pleural effusion or pneumonia

Other Physical Signs of Lung Disease

There are a number of other physical signs that may give clues to lung disease, and a lung exam should be performed along with a general physical exam when time allows.

  • Skin color: A glimpse at a person's skin color may demonstrate palor due to anemia (that, in turn, can cause rapid breathing). Cyanosis refers to a bluish appearance of the fingers, lips, and mouth that is associated with a low oxygen content in the blood.
  • Clubbing: A term called clubbing describes fingers that take on an upside-down spoon appearance and is associated with lung disease, especially lung cancer or interstitial lung disease. Clubbing can sometimes also be seen in healthy people.
  • Nasal flaring: Widening of the nostrils with breathing may be a sign of difficulty breathing in children and adults who are unable to describe their symptoms.
  • Use of accessory muscles: The diaphragm is the primary muscle used in breathing, but with respiratory distress, the use of accessory muscles in the neck and chest can sometimes be a telltale sign of trouble.
  • Lymph nodes: Enlarged lymph nodes just above the collar bones (supraclavicular lymph nodes) or neck (cervical lymph nodes) may be associated with lung cancer or lymphomas in the chest.
  • Gum disease/dental decay: Dental infections and decay may suggest a lung abscess or aspiration pneumonia.
  • Mental status: Confusion or loss of consciousness may occur due to low oxygen levels (hypoxia).
  • Other factors that could affect breathing or the lung exam may be noted, such as obesity (associated with decreased breath sounds) or scoliosis.

Diagnosis and Evaluation

Depending on breath sounds heard on auscultation as well as symptoms and risk factors, other tests may be recommended.

  • Chest X-ray: It's important to note that while a chest X-ray can be very helpful in diagnosis, a negative chest X-ray can't necessarily rule out several lung conditions. For example, chest X-rays miss up to 25% of lung cancers.
  • Lateral soft tissue X-ray of the neck: On X-ray, the "thumb sign" may be seen with epiglottitis
  • Chest CT scan: To look for tumors, foreign bodies, and much more
  • VQ scan (ventilation/perfusion scan)
  • Oximetry
  • Arterial blood gases (ABGs)
  • Pulmonary function tests
  • Lung plethysmography for restrictive lung diseases such as idiopathic pulmonary fibrosis
  • Sputum cytology/culture
  • Laryngoscopy
  • Bronchoscopy
  • Complete blood count
  • D-dimer blood test for pulmonary embolism

A Word From Verywell

Using auscultation to evaluate breath sounds is an important part of a physical examination, and while inexpensive and easy to perform, provides a wealth of information that can help in diagnosing lung diseases and other conditions. Just as the respiratory rate has been coined the neglected vital sign, the art of auscultation is easily overlooked with the technology available to physicians today. The old adage that "the squeaky wheel gets the oil" hasn't lost its edge today. Taking the time to ask your doctor what she is listening for, and what she hears on your exam, is a good start toward being your own advocate in your health care.

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Article Sources

  • Broaddus, V. Courtney. Murray and Nadels Textbook of Respiratory Medicine. Saunders, 2015.

  • Sarkar M, Madabhavi I, Niranjan N, Dogra M. Auscultation of the Respiratory System. Annals of Thoracic Medicine. 2015. 10(3):158-168. doi:10.4103/1817-1737.160831