Respiratory Auscultation – Learn the Basic of Breath Sounds Now
Listening to breath sounds, auscultation, is a crucial clinical method for assessing respiratory problems in patients. This article provides detailed descriptions of different respiratory sounds, accompanied by audio recordings for educational purposes.
I encourage you to listen to all the audio samples on this page. For an experience similar to using a stethoscope, it is advisable to use headphones.
Most of the breath sounds in this article were recorded using a Littmann 3200 electronic stethoscope, and some using the Littmann CORE digital stethoscope that I currently use, widely respected electronic stethoscopes for auscultation.
To effectively perform auscultation, certain conditions and practices should be observed:
A quiet setting is crucial for auscultation as it aids in clearly hearing the breath sounds.
Proper Patient Positioning:
Ideally, the patient should be seated during auscultation to allow complete access to all chest areas. However, the anterior chest regions can still be examined when the patient is lying down.
Direct Contact with Skin:
The stethoscope should make direct contact with the patient’s bare skin. This approach is preferred to avoid listening through clothing, which can create misleading friction sounds. In cases where the patient has a hairy chest, moistening the area with warm water may help.
Ensuring the patient’s comfort is essential. Auscultation can usually be conducted while the patient breathes normally. Requests for deep breaths should be minimal to avoid exhausting the patient. This consideration is particularly important as detailed respiratory examination is often performed when a respiratory ailment is suspected. Overexerting a patient with respiratory difficulties is counterproductive.
Key Guides for Auscultation
During auscultation, the following three key questions should guide the examination:
Intensity of Breath Sounds:
Are the breath sounds louder, softer, or normal compared to standard breath sounds?
Character of Breath Sounds:
Do the breath sounds sound normal or are there unusual qualities?
Presence of Adventitious Sounds:
Are there any extra or unusual sounds that are not typically present in normal breathing?
By focusing on these aspects, a more accurate assessment of the patient’s respiratory health can be achieved.
Mechanism of Breath Sounds Production
Breath sounds are generated in the major airways, specifically the trachea and the major bronchi.
Contrary to a common misconception, alveoli, the small air sacs in the lungs, do not produce these sounds. The air flow velocity in the alveoli is too low to create the turbulence necessary for audible sounds during auscultation.
A Clarification on Breath Sounds:
- When auscultating at the trachea, the sound typically heard is known as bronchial breath sound. This is distinct from what is commonly referred to as the ‘normal’ breath sound, which is vesicular.
- The bronchial breath sound is naturally produced at the trachea.
- The vesicular breath sound is what is normally heard over the chest wall, in the respiratory areas.
- The bronchial breath sounds, originating in the major airways, must traverse through various tissues, including the air in the bronchi and bronchioles, and the walls of the alveoli, to reach the body’s surface, where they are auscultated.
- During this journey, certain high frequencies of the sound are absorbed (attenuated), altering the sound’s character. This altered sound is referred to as the vesicular breath sound.
Understanding this fundamental concept is crucial for discussing the origin of abnormal sounds in different conditions, which will be explored in subsequent sections of this article.
Normal Breath Sounds
Vesicular Breath Sounds
The vesicular breath sound is recognized as the normal breath sound heard over most lung fields during auscultation. Characteristically, it is soft and has a low pitch (low frequency). Notably, the expiratory phase in vesicular breathing is shorter than the inspiratory phase. This shorter expiratory phase is due to the high-pitched sounds produced in the latter two-thirds of expiration being filtered out, leaving the low-pitched sounds more prominent.
The quality of vesicular breath sounds can be likened to the sound of rustling dry leaves, a gentle and continuous noise.
The term “vesicular breath sound” was coined by René Laennec, the inventor of the stethoscope. Laennec originally believed that these sounds were produced by air flowing through the alveoli, hence the name. However, as previously discussed, this is a misnomer since the alveoli do not generate these sounds. The term has persisted in medical terminology, reflecting the historical context of its origin rather than its physiological accuracy.
Abnormal Breath Sounds
Absent or Decreased Breath Sounds
Absent or decreased breath sounds on auscultation can be indicative of several medical conditions. Here are some common causes:
- Asthma: Typically characterized by decreased breath sounds due to narrowed airways.
- Atelectasis (Lung Collapse): When bronchial obstruction persists, breath sounds may become absent. In cases of upper lobe atelectasis, tracheal sounds may still be audible due to the trachea being drawn towards the collapsed area.
- Fibrosis: This condition generally leads to decreased breath sounds. However, if fibrosis is present in the upper lobes, adjacent tracheal sounds may be heard as the trachea is pulled towards the side of atelectasis.
- Emphysema: This lung condition is often marked by decreased breath sounds, as a result of over-inflated and destroyed alveoli.
- Pleural Effusion: In this condition, breath sounds can be reduced or absent. If the effusion is large, bronchial breath sounds may be heard at the upper level of the fluid.
- Pneumothorax: Characterized by decreased or absent breath sounds, this condition occurs when air enters the pleural space, causing lung collapse.
- ARDS (Acute Respiratory Distress Syndrome): In the late stages of ARDS, breath sounds may be decreased.
Vesicular breath sounds might also be softer in certain individuals, particularly:
- Frail persons
- The elderly
- Obese individuals
- Very muscular people
These variations are due to differences in body composition and structure, which can affect the transmission of lung sounds.
Listen to the audio of a diminished vesicular breath sound above.
Harsh Vesicular Breath Sounds
When vesicular breath sounds become harsher and slightly prolonged, it can be indicative of certain physiological conditions:
- Rapid Deep Ventilation: This is commonly observed post-exercise. After physical activity, the increased demand for oxygen and the body’s effort to expel more carbon dioxide result in deeper and more rapid breathing. This change in breathing pattern can make the vesicular breath sounds more pronounced and extended.
- Persons with Thinner Chest Walls: Individuals with thinner chest walls may exhibit harsher and slightly longer vesicular breath sounds. The reduced amount of tissue and muscle overlying the lungs in such individuals can make the sounds more directly audible, thus altering their perceived character.
Listen to the audio of harsh vesicular breath sound above.
Bronchovesicular Breath Sounds
Bronchovesicular breath sounds are characterized by their moderate intensity and pitch.
In these sounds, the durations of inhalation and exhalation are equal.
The optimal locations for listening to these sounds during auscultation are:
- In the front of the chest, specifically at the 1st and 2nd intercostal spaces.
- At the back of the chest, in the interscapular areas, which align with the mainstem bronchi.
Listen to the audio of bronchovesicular breath sound above.
Bronchial Breath Sounds
Bronchial breath sounds are typically loud and high-pitched, with a distinct sound quality that seems close to the stethoscope.
These sounds have a hollow characteristic. A notable feature is the pause between the inhalation (inspiratory) and exhalation (expiratory) phases of breathing, where both phases are of equal duration.
It is important to note that bronchial breath sounds should normally only be heard over the manubrium. If these sounds are detected in areas other than the manubrium or the trachea (which is not a standard site for auscultation), it suggests an abnormality. Conditions associated with bronchial breath sounds include:
- The upper level of pleural effusion
- Fibrosis in the upper lobe
- Collapse of the upper lobe
- Bronchopleural fistula
To effectively identify bronchial breathing during auscultation, focus primarily on the hollow nature of the sound. Once this characteristic is noted, verify that it is bronchial breathing by assessing the gap between the inspiratory and expiratory phases and confirming their equal length.
Avoid solely relying on identifying the gap or equality of phases to diagnose bronchial sounds. This approach can be time-consuming and often leads to missing bronchial sounds. By concentrating on the hollow sound quality, accurate identification of bronchial breath sounds is more likely.
Crackles are short, intermittent sounds commonly heard during inspiration.
Also known as crepitations or rales, crackles are categorized as:
- Fine: These are high-pitched and very brief.
- Coarse: These have a lower pitch and last slightly longer.
There are two primary mechanisms that produce crackles:
- Opening of Closed Small Airways: This can be likened to the sound made when you wet your lips, gently close them, and then suddenly open them, producing a ‘plop’ sound. Fine crackles are similar and occur when the terminal bronchioles rapidly open.
- Air Bubbles Moving Through Secretions: This happens in conditions like pulmonary oedema and resolving pneumonia, where air moves through fluid or mucus in the lungs.
To understand these sounds better, listening to audio recordings of crackles can be helpful.
Crackles can be indicative of various conditions, including:
- Pulmonary oedema
- Lung consolidation
- Pulmonary fibrosis
- Chronic bronchitis
- Interstitial lung disease
Recognizing crackles during auscultation is important for diagnosing and understanding these respiratory conditions.
Wheezes are continuous, high-pitched, musical sounds typically heard during expiration.
These sounds are created when air moves through airways that are narrowed due to factors like secretions, foreign bodies, or obstructive lesions. The length of the wheeze within the respiratory cycle is generally indicative of the extent of airway obstruction.
Wheezes can be likened to the sound of a violin being played.
There are two categories of wheezes:
- Monophonic Wheezes: These suggest an obstruction in a single airway, often due to a malignant tumor compressing a bronchiole.
- Polyphonic Wheezes: These indicate a more generalized airway obstruction, such as in asthma.
Listening to audio recordings of wheezes can aid in understanding these distinctions.
Wheezes can be caused by a variety of conditions, including:
- Chronic bronchitis
- Acute bronchitis
- Pulmonary oedema in some cases
The presence of expiratory wheezing usually means the patient’s peak expiratory flow rate is less than 50% of the normal, often seen in dynamic bronchoconstriction as in bronchial asthma.
Inspiratory wheezing often indicates a more fixed bronchoconstriction, typically caused by tumors, foreign bodies, or fibrosis. Monophonic wheezes, particularly during inspiration, can be especially concerning as they often signify compression of a small number of bronchioles, commonly observed in cases like bronchogenic carcinoma.
The location of the wheezes on the chest also provides clues to their cause. Generalized bronchoconstriction, as seen in asthma, results in wheezes that are audible across all respiratory areas and are typically polyphonic.
The term ‘rhonchi’ (singular – rhonchus) is sometimes used interchangeably with wheezes. However, ‘rhonchi’ are also characterized distinctly, as will be described below.
Rhonchi are low-pitched, continuous sounds that resemble wheezes but usually indicate obstruction in slightly larger airways, often due to secretions. They are frequently described as a coarse, rattling sound similar to snoring, typically resulting from secretions in the bronchial airways. The term ‘rhonchi’ is the plural of ‘rhonchus’.
Although ‘rhonchi’ are primarily used to describe these specific sounds, the term is also sometimes employed synonymously with wheezes. This dual usage can be a source of confusion; however, it’s important to differentiate between the two based on their pitch and the implied size of the obstructed airway. Rhonchi (low-pitched, suggesting larger airway obstruction) are distinct from wheezes (high-pitched, indicating narrower airway obstruction).
Squawks, aka Squeaks
Squawks, also called squeaks, are characterized as short, inspiratory wheezes and are almost invariably accompanied by crackles. These sounds are brief and have a distinctive “squeaky” quality, often leading to them being colloquially referred to as squeaks.
The presence of squawks in a patient’s lung sounds can indicate certain medical conditions, including:
- Pneumonia: Characterized by consolidation.
- Hypersensitivity Pneumonitis: An inflammatory syndrome affecting the lung parenchyma due to allergic reaction to inhaled organic dusts, chemicals, or other antigens.
- Interstitial Fibrosis: A condition involving the scarring or thickening of the interstitial tissue that supports the air sacs in the lungs, often leading to chronic and progressive lung disease.
Recognizing squawks during auscultation is essential, as it can provide significant clues to diagnosing these respiratory conditions.
The term “rales” is considered outdated in modern medical terminology, but it was previously used as a synonym for crackles, particularly referring to coarse crackles. Pronounced as ‘raahls’, this term has largely been replaced in clinical settings by the more specific term “crackles.”
Stridor is a distinctive, loud inspiratory sound, most audible over the trachea during inhalation. It indicates a partial obstruction of the trachea or larynx, often caused by conditions that narrow the upper airway. Due to its implication of a potentially life-threatening obstruction in the breathing pathway, stridor is considered a medical emergency that requires prompt evaluation and management.
The high-pitched, harsh sound of stridor arises from turbulent air flow through the narrowed section of the upper respiratory tract. It can be a critical clinical sign in conditions such as severe allergic reactions, infections, foreign body aspiration, or other causes of airway obstruction. Prompt recognition and timely intervention are crucial in managing patients presenting with stridor.
Pleural rubs are creaking sounds created by the friction between inflamed or roughened pleural surfaces rubbing against each other. This friction arises when the two layers of the pleura, which normally slide smoothly over each other during breathing, become irritated or diseased.
These sounds can be either discontinuous or continuous and are often localizable to a specific area on the chest wall. Pleural rubs can be heard during both the inspiratory and expiratory phases of breathing.
Common causes of pleural rubs include:
- Pleuritis (Pleurisy): Inflammation of the pleural layers, often causing sharp chest pain that worsens with breathing or coughing.
- Pleural Effusion: Sometimes above the level of the fluid accumulation in the pleural space, pleural rubs can be heard.
- Pneumothorax: The presence of air in the pleural space, which can disrupt the normal lubrication between the pleurae, leading to pleural rubs.
Recognizing pleural rubs during auscultation is important as they are a key indicator of pleural pathology and can guide further diagnostic and therapeutic interventions.
Here is a clinical pearl: When a patient with dry pleurisy (pleuritis without effusion) suddenly experiences relief from pain and the associated pleural rub sound disappears, it often indicates the development of a pleural effusion. In dry pleurisy, the pain is typically caused by the inflamed pleural surfaces rubbing against each other. However, when fluid begins to accumulate in the pleural space, it can separate these surfaces, reducing or eliminating the friction and consequently the pain and the rub sound.
This change can initially seem like an improvement in the patient’s condition, but the underlying cause could be the accumulation of fluid in the pleural cavity, which is a new development.
Abnormal Vocal Sounds (Resonance)
The patient is often requested to speak a specific word, typically ’99’, to test for vocal resonance.
Bronchophony refers to the clear, loud transmission of vocal sounds through the lungs and chest wall, which can be heard using a stethoscope. In a normal lung, when a patient speaks, the sound transmitted through the lung tissue is typically muffled and indistinct due to the air-filled spaces which absorb and scatter sound waves.
However, the phenomenon of bronchophony is observed over lung areas where the alveoli are filled with fluid or replaced by solid tissue. Conditions such as pneumonia, lung collapse, or tumors can lead to bronchophony. In such cases, the spoken word, in the typical example ’99’, is heard more clearly and loudly through the stethoscope. This is because the fluid or solid tissue in the lungs conducts sound better than air, making the voice sounds more distinct and louder than normal.
Listen to the audio recording of bronchophony: Patient is speaking ‘ninety-nine’ in the above example.
Egophony, also spelled as aegophony, is a phenomenon where voice sounds resonate more when listening to the lungs using a stethoscope. This often occurs when lung tissue is compressed, as in cases of pleural effusion, or becomes consolidated due to conditions like pneumonia or lung tumors.
During lung examination, the patient is asked to vocalize the sound ‘e’. In cases of egophony, this sound is auscultated as resembling the sound ‘a’, and it takes on a nasal quality. To understand this, you can simulate it by pinching your nose and saying ‘e’, which will sound more like ‘a’. This change happens because abnormal lung tissues transmit high-frequency sounds more effectively while filtering out lower frequencies. Consequently, the patient’s voice, when heard through the stethoscope over the affected area, has a high-pitched, nasal, or bleating character.
For a clearer understanding, listen to an audio recording above where the patient says ‘eee’ that can demonstrate the distinctive sound of egophony.
Auscultation in Abnormal conditions
When listening to a recording of lung sounds in a case of lobar pneumonia, the bronchial breath sounds and end-inspiratory crackles are key indicators of the disease’s presence and severity.
In the context of pulmonary edema, a condition characterized by the accumulation of excess fluid in the lungs, the presence of fine crackles in the recording is a significant clinical finding. These crackles are indicative of fluid within the alveoli.
Auscultation remains a fundamental cornerstone in a clinician’s toolbox for evaluating the respiratory system. While this comprehensive guide equips you with the theoretical knowledge and practical skills to decipher the symphony of breath sounds, remember, experience is a master teacher. Hone your listening skills through diligent practice, correlating findings with clinical presentations and imaging. By becoming a master of interpretation, you’ll transform the whisper of the lungs into a clear clinical narrative, guiding diagnosis and optimizing patient care.
Have you checked the article on Symphony of the Stomach? It provides valuable insights into borborygmi, shedding light on this phenomenon in the digestive system.