Introduction
The ideal position for auscultation is to place the patient in a sitting position. If a patient is to remain recumbent, roll the patient from one side to the other to examine the back. If the patient cannot be rolled from side to side, such as in certain ICU settings, auscultation over the anterior chest can be done to yield a more limited examination.
When auscultating, the patient should inhale and exhale through the mouth, deeper than their usual breaths. Auscultation should be performed with the diaphragm of the stethoscope applied directly to the skin, as clothing and other materials can dampen or distort perceived sounds. Auscultate in a pattern as shown in the images below. This should occur symmetrically between the two hemithoraces so that sounds may be compared between sides. Start near the apices and move down in a ladderlike pattern until below the level of the diaphragm is reached or breath sounds are no longer appreciated. This should be performed over the anterior and posterior chest.
The sounds heard during auscultation can be classified as breath sounds, created by air movement through the airways, and adventitious, or added sounds, which have multiple mechanisms of generation. [5, 6] Breath sounds can be classified as vesicular, bronchial, or absent/attenuated. [5, 6]
Vesicular Sounds
Vesicular sounds are generated by the turbulent flow of air through the airways of healthy lungs. These are typically soft and are characterized by inspiratory sounds that last longer than expiratory sounds. Normal lung tissues have a substantial amount of airspace to attenuate and soften the sound. These vesicular sounds vary considerably from patient to patient; thus, it is important to compare one hemidiaphragm to another by listening in a symmetrical pattern, as shown in the image below. [7]
Bronchial Breath Sounds
Bronchial breath sounds often result from consolidation within lung parenchyma with a patent airway leading to the involved area. The resulting breath sounds are amplified through the consolidation, leading to a louder breath sound. [6, 8] Typically, there is a pause between inspiratory and expiratory sounds, as the involved parenchyma does not fill with air during this time in inspiration. The pitch is usually high, as the sounds arise from the bronchi, and the expiratory phase generally lasts longer and is as intense as, or more intense than, the inspiratory phase. [6, 8]
Absent/Attenuated Sounds
Absent/attenuated sounds occur when there is no airflow to the region being auscultated. This can occur in a pneumothorax, hemothorax, pleural effusion, or parenchymal consolidation, which includes the feeding airway. [1, 2]
Adventitious sounds can be classified as crackles, wheezes, rhonchi, or stridor. These sounds occur in addition to the breath sounds described above.
Crackles
Crackles are sounds that are intermittent, nonmusical, very brief, and more pronounced during inspiration. The sound of hair being rubbed between one’s fingers is often used as an example to describe these types of sounds. Crackles can be classified as fine or coarse, depending on their sound quality. [9]
Fine crackles are typically produced by the forced reopening of alveoli that had closed during the previous expiration. These crackles are softer, and higher in pitch, while coarse crackles are louder and lower in pitch. Coarse crackles are typically a combination of alveolar reopening and bubbling of air through retained secretions in smaller airways. [7, 10, 11, 12]
Crackles can also be categorized as early or late, depending on when they are appreciated during the respiratory cycle. Early inspiratory crackles occur immediately after initiation of inspiration and are more often associated with interstitial lung disease. [7] Late inspiratory crackles begin in the first half of inspiration and continue until the end of inspiration. This type of crackle is more often associated with pulmonary edema and asthma. [13]
Table 2 summarizes typical differential diagnoses for varying types of crackles, based on their location within the respiratory cycle and their character. [7, 10, 11, 12] Note that each disease can present with multiple type of crackles simultaneously.
Table 2. Differential Diagnoses of Crackles (Open Table in a new window)
Location in Respiratory Cycle | Fine | Coarse |
Early inspiratory | Usual interstitial pneumonia Desquamative interstitial pneumonia Sarcoidosis Miliary tuberculosis Allergic alveolitis Asbestosis | Chronic bronchitis COPD |
Late inspiratory | Atelectasis Asthma CHF Pulmonary edema Pneumonia/Consolidation Scleroderma | Fibrosing alveolitis |
Mid-inspiratory and expiratory | Bronchiectasis, which can be secondary to the following:
|
Wheezes
Wheezes are continuous, high-pitched, musical, predominantly expiratory sounds that are produced by air flowing through narrowed bronchi, causing fluttering and resonance of the bronchial walls. Thus, they are caused by pathology leading to the narrowing of bronchi, most commonly COPD, asthma, and bronchitis. [5, 6, 9]
Rhonchi
Rhonchi are low-pitched snorelike sounds that may occur throughout the respiratory cycle. They are often characterized by secretions within the large airways and can be heard in a wide variety of pathologies, any of which cause increased secretions, such as in cystic fibrosis, pneumonia, bronchitis, pulmonary edema, or emphysema. [5, 6, 12]
Stridor
Stridor is a loud, rough, continuous, high-pitched sound that is pronounced during inspiration; it indicates proximal airway obstruction. The sound is created by turbulent air flowing through a narrowed trachea or larynx and is loudest over the trachea. This is commonly a medical emergency and should be recognized early. Diagnoses that may present with stridor include epiglottitis, vocal cord dysfunction, croup, and airway edema (which could be secondary to trauma or an allergic reaction). [1, 2]
Pectoriloquy/Egophony
When abnormal breath sounds or adventitious sounds are appreciated on auscultation, it is important to examine the area with the abnormality more thoroughly. This includes auscultating around the area of the abnormality to define its extent, as well as using voice-generated sounds.
When spoken words travel through aerated lung, they are attenuated by airspaces as they move toward the periphery. However, when a consolidation is present, this aeration and attenuation is reduced. This causes increased transmission of whispered words, called pectoriloquy. This reduced aeration also results in a change of the pitch of the transmitted sounds, called egophony.
Whispered pectoriloquy can be elicited by having the patient whisper a repeated phrase (typically “ninety nine”). The transmitted sounds will be louder over the area of consolidation. Egophony can be elicited by having the patient say “ee,” and the transmitted sound will be heard as “aay” over an area of consolidation. Changes in pectoriloquy for several common disorders are shown in Table 1. [1, 2]
Nonpulmonary Sounds
Nonpulmonary sounds must also be appreciated during auscultation of the chest. One important nonpulmonary sound is a mediastinal crunch, caused by pneumomediastinum. This sound is characterized by crackles synchronous with cardiac contraction, and not with respiration. The patient can be asked to temporarily cease respiration to appreciate this difference.
Another important sound is a pleural rub, which can be appreciated as having a sandpaperlike quality and is typically present throughout the respiratory cycle. Inflammation or neoplasia can cause thickening of the pleural surfaces, which then creates more friction when sliding along one another, creating this sound.