Breaking Down Breath Sounds for Respiratory Students

A respiratory therapist is using a stethoscope listen to the breath sounds of the elderly patient.

Auscultating, or listening to, the lung sounds of pulmonary patients is going to be something a respiratory therapist does at least 20 times a day if not much more.  Understanding what each sound is, how to categorize it, and what to do about it is such a critical skill in our field and yet it can all be very confusing for students. 

Part of the puzzlement comes from the confusion about terminology over the years.  It is no wonder that this skill can be such a head scratcher for students.  In clinical rotations you hear ALL the words that have ever been used to describe lung sounds.  

You know, THESE words:  rales, rhonchus, crepitations, wheezes, sonorous exhalations, crackles, etc.  and yet, many of these words no longer have a place on your board exams so they aren’t taught in respiratory class.  That said, we cannot stop medical providers who came before us from using obsolete terminology, but we can be sure we don’t confuse ourselves when we sit for our boards.

When it comes to auscultation, just like everything else in respiratory school, knowing what is normal is the best way to recognize when something is abnormal.  The NBRC breaks down breath sounds into Normal “Vesicular” and Abnormal “Adventitious” sounds.

Normal/Vesicular Breath Sounds

Normal breath sounds can be heard over the large airways such as the trachea and bronchus and bilaterally throughout the lung fields.  Sounds heard near the large airways will be loud and somewhat harsh. Air moves quickly through these airways and the sounds should be easily identifiable.

At the trachea the airflow sounds high pitched and there is a noteworthy pause at the end of inspiration followed by expiratory flow that is about double the length of the inspiratory time.  

As you move to either side of the sternum, anteriorly, bronchial breath sounds can be heard between the second rib (intercostal space) and the fourth rib.  Posterialy, bronchial sounds can be heard on either side of the spinal column from the third rib to the sixth rib.  Bronchial sounds are loud and can be high or low pitched.  They can be described as “hollow” or “tunnel like” and there is no pause between inspiration and expiration.  

Moving past the segmental bronchi, the sounds become more reduced because the chest wall, muscles and lung tissues muffle the sounds.  In most of the peripheral lung fields of a normal, healthy patient, vesicular sounds should be soft and lower in pitch with a longer inspiration and a shorter expiration with no pause between.  Expiratory sounds fade quickly and can be difficult to hear. 

Vesicular breath sounds can be described as bilateral, increased, decreased, unequal or absent.  When auscultating RTs use a side to side technique comparing one lung to the other in order to be able to identify areas where there is a difference leading to possible issues the patient may be having in those areas of the lungs.

When Vesicular Sounds are Adventitious

Vesicular sounds are normal when they are auscultated in the proper locations.  Tracheal sounds at the trachea, bronchial sounds at the bronchus.  Neither sound should be heard in the periphery.  

If they are heard outside of their normal anatomic locations, they are adventitious and point to some kind of consolidation, fibrosis, or atelectasis in that area of the lung.  

An example of this in a charting note might be “Bronchial breath sounds heard over the right posterior mid lung”.  This would alert the RT to look further, possibly suggest an X-ray.  

Abnormal/Adventitious Breath Sounds

The NBRC classifies adventitious breath sounds into three categories:  Crackles, Wheezes, and Pleural Friction Rubs.  These three categories are further broken down by their pitch, location and timing, helping to diagnose the underlying cause for the sound.  

Crackles: Fine, Coarse and Medium

Fine crackles (previously called rales) are usually heard upon inspiration and are often described as short, sharp and popping, which makes sense since they are thought to be sounds made as the alveoli “pop” open from a collapsed or fluid filled state.  

Crackles are usually high pitched and located in the dependent regions of the lungs.  When an RT hears these sounds in a postoperative patient they might suggest incentive spirometry as post-anesthesia patients can develop atelectasis due to shallow breathing during and after surgery.  

Diuretics may be ordered when these sounds are heard in a patient who has a history of CHF or pulmonary edema.  If the patient is having oxygenation issues despite supplemental oxygen, positive pressure therapy can be suggested by the RT for a patient with persistent fine crackles.

Congestive heart failure vector illustration. Labeled medical problem vs healthy organ comparison scheme. Illness symptoms infographic with educational dilated ventricle, cardio oxygen supply diagram.

Coarse Crackles (previously called rhonchi) are loud, low pitched, explosive popping sounds that can mainly be heard over the large airways upon both inspiration and exhalation and signal that there are secretions built up in that airway. Coarse crackles usually will clear if the patient generates a good cough.  

In patients on ventilatory support, the sound will clear with suctioning.  I have had students describe coarse crackles as the sound you hear when someone is eating a crunchy snack nearby.  Coarse crackles are mainly loud, crunching sounds that are often related to bronchitis and bronchiectasis.

Medium crackles are very similar to coarse crackles, just not quite as loud and don’t easily disappear after a cough.  They are related to middle and smaller airway secretions.  RTs hearing these sounds have described them as medium volume coarse popping sounds.  RTs may make a recommendation of bronchial hygiene therapy for patients with persistent medium crackles.

Wheezes: Monophonic, Polyphonic & Stridor “musical” breath sounds

The second adventitious breath sound we often hear is wheezing.  Wheezes are often described as musical as they are caused by air passing through narrowed airways.  Wheezes are continuous and can be heard upon inhalation or exhalation or both.  Sometimes they are only heard in one area of the lung and sometimes they are heard throughout all areas of the lungs. 

When wheezing makes the same sound; the same musical tone each time you hear it without really changing it is referred to as monophonic (Mono = One). Monophonic wheezing is often caused by a single airway being partially blocked.  

When the wheezing has many different notes about it; it is referred to as polyphonic (Poly = many) suggesting that many airways are partially blocked.  

Bilateral expiratory wheezing is usually caused by bronchoconstriction likely due to an obstructive lung disease like asthma or COPD and the first recommendation is usually bronchodilator therapy.  

Unilateral wheezing may be a sign of a foreign body obstruction.  RTs should investigate further to find the cause of a unilateral wheeze.  

Stridor is more of a high pitched sound that can be described as loud, barking, or crowing that is heard upon inspiration and is caused by upper airway obstructions.  If the sound is coming from above the glottis it points to epiglottitis.  

Human larynx anatomy. This illustration is medical diagram.

If stridor comes from below the glottis it points to swelling in that area possibly from croup or post extubation inflammation.  Depending on what the cause of the stridor is, the treatment can be as simple as a dose of nebulized racemic epinephrine or as dramatic as re-intubation to maintain a patent airway.

Pleural Friction Rub

The final adventitious breath sound that you will come across on your boards is the pleural friction rub.  When the surfaces surrounding the lung become inflamed they rub against one another with inhalation leading to a sound usually described as grating or creaking.  

Lung pleura and pleural cavity medical vector illustration on white background eps10

Pleural friction rub has been described as “stepping down on fresh snow” or “leather rubbing up against itself”.  The sound can be mistaken for coarse crackles, but when the patient is asked to cough, the sound is unaffected.  

Pleural friction rubs are most commonly caused by viral or bacterial infections that have led to pleurisy – the swelling of the pleura surrounding the lungs and that of the chest wall.  Once the cause is known, the usual treatment is steroids and antibiotics.

Obviously this is not an exhaustive list of ALL the sounds an RT might come across with his stethoscope against a patient’s chest wall, but crackles, wheezes, and pleural friction rubs are sort of the BIG 3 of breath sounds.  

Remember to always be systematic when auscultating your patient side to side comparing all the lobes, anterior, posterior and lateral.

About Anne Wandycz BS, RRT-NPS-ACCS 7 Articles
Anne is a staff Respiratory Therapist at Children's Specialized Hospital, Toms River, NJ as well as an adjunct instructor in the Respiratory Care program at Brookdale Community College, Lincroft, NJ.