An Overview of Breath Sounds

Countless times, you've probably had your doctor place a stethoscope on your chest and ask you to inhale. What exactly are doctors listening for? The answer is many things.

The practice of using a stethoscope to examine a patient is known as auscultation. When used to check a person's breathing, it can reveal important aspects of lung health and overall wellness. A thorough lung exam, which also includes a physical exam, remains a cornerstone in diagnosing conditions ranging from asthma to heart failure.

This article explains how doctors check your lungs using a stethoscope during auscultation. It also covers the different sounds they hear and possible conditions that can be related to abnormal breathing.

Listening to the Lungs

Listening to the lungs is best done in a quiet room while you sit with your mouth open. Ideally, the stethoscope should be placed beneath clothing (or, next best, on as little clothing as possible). Before applying the stethoscope, doctors should warm its base so it's more comfortable, but this step may be skipped if it's an emergency.

Doctors will listen to different spots from the top of the lungs down to the lower lung area. They will check from the front (anterior) of the chest, the back (posterior) chest, as well as under the armpits (mid-axillary region).

Deeper breaths allow breathing 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 a stethoscope is not available.

Normal Breath Sounds

During lung auscultation, your doctor listens for different sounds as you inhale, known as inspiration, and exhale, known as expiration. Depending on where the stethoscope is placed, your doctor will be able to check three primary types of normal breath sounds.

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 when the doctor moves the stethoscope 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 breathing sounds heard over other parts of the lungs. However, these sounds are quieter and more hollow-sounding than tracheal breath sounds.

Bronchial breath sounds are also sometimes heard in other regions of the lungs with various conditions. These include pneumonia, lung tumors, atelectasis (partially collapsed lung), or a pneumothorax (completely collapsed lung).

With bronchial breath sounds, the exhaling phase is usually longer than the inhaling phase, and there's a pause between the two.

Vesicular Breath Sounds

People are often more familiar with vesicular breath sounds because these are the sounds heard over much of the lungs. They're lower-pitched and softer than tracheobronchial breath sounds.

Inspiration is longer than expiration and there is no pause between inhaling and exhaling.

Ratio of Inspiration to Expiration

As noted, the relationship between inspiration and expiration can vary depending on where you listen. This is calculated as a ratio that compares one to the other. The normal ratio of inhalation to exhalation in bronchial breath sounds is 1:2 at rest and while sleeping. This means it takes twice as long to exhale as it takes to inhale. After exercising, the ratio is 1:1, which means the time it takes for each is the same.

A change in this ratio may indicate that there's a problem. 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 lower part of the lungs than at the top of the lungs.

When lying down on one side, breath sounds are usually loudest on the side of the chest closest to the exam table.

Decreased breath sounds may be related to a number of different conditions:

• When there's fluid around the lungs, such as with pleural effusion
• When there's air around the lungs, as with 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. Wheezing tends to have a musical sound that includes more than one note, while stridor often has just one.

Vocal Resonance

Your doctor may have you speak while they listen to your lungs. This can help identify signs of consolidation of lung tissue—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 that's typically one or two syllables. If consolidation is present, words that are whispered (which normally sound muffled) will be heard clearly.
• Egophony: Doctors 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 doctors 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.)

Abnormal Breath Sounds

There are a number of different terms used to describe abnormal or adventitious breath sounds, and these can be very confusing. These sounds can differ based on whether they're heard mostly during inhalation or exhalation, the quality of the sounds, and other factors.

The four most common sounds doctors are checking for are wheezing, stridor, rales, and rhonchi.

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're 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. 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

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's a continuous sound that occurs when there's 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

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. They come and go, and often sounds that are most pronounced when you inhale. 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

Less Common Sounds

Whooping Cough

Whooping Cough (pertussis) is less common than it used to be thanks to vaccines, but it does still strike children fairly regularly. With this illness, a high-pitched "whoop" sound may be heard after coughing. This is called an inspiratory gasp, which is typically broken up by hacking coughs. 

Pleural Rub

Another less common sound your doctor may hear is called pleural rub. This 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 inhalation and exhalation.

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. Your doctor will also consider observation from a physical exam as well as the results of any tests done to determine if your abnormal breathing is related to a specific disease or condition.

Examination

Observing the chest is an important part of a lung exam along with listening and palpating (touching). Doctors pay attention to 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 a problem. 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 also be important. 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

Your doctor may use some specific terms when explaining your respiratory function. These include:

• Tachypnea: Rapid, shallow breaths
• Hyperpnea: Deep and labored breathing
• Bradypnea: 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 vibration is transmitted to the chest wall with breathing. This may be decreased with 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: There may be greater resonance with emphysema or pneumothorax.
• Hyporesonance: A decrease in resonance may be found with pleural effusion or pneumonia, creating a dull sound with percussion.

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 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.

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: This shows adenoids and tonsils when they're enlarged, the oral and nasal airways, part of the trachea (windpipe), and the epiglottis.
• Chest CT scan: To look for tumors, foreign bodies, and much more
• Ventilation/perfusion (VQ) scan: Doctors can see airways and blood flow to the lungs.
• Oximetry: This measures oxygen levels in the blood.
• Arterial blood gases (ABGs): This shows how well your lungs move oxygen into the blood and remove carbon dioxide.
• Pulmonary function tests: These measure how well your lungs work.
• Lung plethysmography: Doctors use this to check for restrictive lung diseases such as idiopathic pulmonary fibrosis.
• Sputum cytology/culture: This test checks for bacterial infections.
• Laryngoscopy: A tube is inserted through the mouth to view the voice box.
• Bronchoscopy: Doctors insert a scope with a camera into your lungs.
• Complete blood count (CBC): This is a standard blood test.
• D-dimer blood test: This checks for a pulmonary embolism.

Summary

Having your lungs listened to with a stethoscope is a normal part of most doctor visits. This seemingly unimportant action is an essential part of evaluating your overall health. The sound, rhythm, and speed of your breathing can reveal a great deal. Doctors listen for subtle aspects. 

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. If anything abnormal is detected during an exam, your doctor will look for other signs that might point to a pulmonary disorder or another health issue. 

A Word From Verywell

Auscultation can be an easily overlooked tool with the technology available to healthcare providers 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 healthcare providers 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.