An Overview of Breath Sounds

Breath sounds may be heard with a stethoscope during inspiration and expiration—a practice known as 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

In addition to using a stethoscope to listen to your heart, doctors also use it to listen to your lungs. They are keeping an ear out for the many nuances in breath sounds that can help ensure you are well or identify a possible concern.

Listening to the lungs is best done in a quiet room with a person sitting with their mouth open. Ideally, auscultation should be performed beneath clothing (or, next best, through as little clothing as possible). Prior to applying the stethoscope, providers should warm its diaphragm (unless an emergency warrants immediate assessment) for comfort.

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).

Deeper breaths allow breath sounds to be heard more easily. Sometimes a break during the exam is needed to avoid lightheadedness.

A stethoscope is useful because it helps magnify internal sounds, but an ear pressed closely to the skin can provide a lot of information when one is not available.

There are several characteristics that doctors note when listening to the lungs.

Normal Breath Sounds

Three primary types of normal breath sounds may be heard, depending on location the stethoscope is placed:

Tracheal Breath Sounds

Tracheal breath sounds are loud and 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 also 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 (collapsed lung).

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 (bronchial 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

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 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. This can help identify signs of consolidation of lung tissue—that is, when air that typically fills airways is replaced with a fluid, such as pus.

They can do this through the following methods:

• Whispered pectoriloquy: Your doctor will have you quietly whisper a word (typically one that is two-syllables). If consolidation is present, words that are whispered may be heard clearly.
• Egophony: A physician will have you say "E" while they listen to your chest. If lung consolidation is present, it may sound like a nasal "A" instead.
• Bronchophony: Your doctor will have you say "99" in a normal voice. If consolidation is present, they may hear it clearly or with more intensity. (The sound would be muffled with normal lung tissue.)

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

Abnormal Breath Sounds

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 one. These sounds can differ based on whether they are predominant during inspiration or expiration, the quality of the sounds, and more.

Wheezing

Wheezing is a term used to describe high whistling sounds in the lungs, and it 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. It is usually continuous.

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

There are many possible causes of wheezes, with obstructive airway disease being the most common. They 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 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; it is typically loudest over the neck. It is a continuous sound the occurs when there is a blockage in the upper airways.

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

• Epiglottitis: This is inflammation of the epiglottis (the flap of cartilage behind the tongue) and is a medical emergency. When the epiglottis swells, it can block off the entry of air into the lungs; 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" sound may be heard after coughing.

Rhonchi

Rhonchi, in contrast to wheezes, are described as low-pitched clunky or rattling sounds, though they sometimes 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 intermittent sounds that are most pronounced with inspiration. The sounds have been described as clunky, rattling, crackling, clinking, or popping, and they occur when the smaller airways open suddenly during inspiration.

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

These sounds are often related to the build-up of fluid in the alveoli, the tiniest airways of the lungs.

Some potential causes include:

• Pulmonary edema
• Right-sided heart failure
• Interstitial lung diseases, such as idiopathic pulmonary fibrosis
• Pneumonia

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.

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

• Pleurisy
• Lung tumors that extend to the pleura
• Pleural mesothelioma (a malignant tumor of the pleura)

Diagnosis and Evaluation

In addition to auscultation, there are several other components to a thorough lung examination. The sounds your doctor hears are considered alongside the information gleaned during the rest of your assessment, as well as the results of any tests done, to determine if your breathing is normal or to help reach a diagnosis.

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 overstated. 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 (though it can be seen in healthy people as well).
• Symmetry of chest expansion
• Depth of breathing

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, or another concern.

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 pallor due to anemia, which 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: This describes fingers that take on an upside-down spoon appearance. Clubbing is associated with lung disease, especially lung cancer or interstitial lung disease, though it 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).

There are other factors that could affect breathing or findings during the lung exam, including obesity or scoliosis. These, too, will be noted.

Labs and Imaging

Depending on the lung exam, as well as symptoms and risk factors, lab and imaging 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, about 30% of missed lung cancers occur due to scanning errors when reading chest X-rays.
• 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
• Ventilation/perfusion (VQ) scan
• Oximetry
• Arterial blood gases (ABGs)
• Pulmonary function tests
• Lung plethysmography for restrictive lung diseases such as idiopathic pulmonary fibrosis
• Sputum cytology/culture
• Laryngoscopy: A tube is inserted through the mouth to view the voice box.
• Bronchoscopy
• Complete blood count (CBC)
• D-dimer blood test for pulmonary embolism

A Word From Verywell

Auscultation can be an easily overlooked tool with the technology available to physicians today. However, it is an important part of a physical examination. While inexpensive and easy to perform, it provides a wealth of information that can help in diagnosing lung diseases and other conditions.

Taking the time to ask your doctors what they are listening for, and what they hear on your exam, is a good start toward being your own advocate in your health care.