Introduction
Breath sounds or respiratory sounds are created by air movement during inspiration and expiration in the respiratory system. These sounds can be heard with a stethoscope. Breath sounds can be normal and adventitious or added sounds like crackles, whales, pleural friction rubs, stertor, and stridor. The sounds are classified based on the pitch and intensity of the sound heard during auscultation with a stethoscope.
What Are Normal Breath Sounds?
Normal breath sounds are vesicular, bronchovesicular, bronchial, and tracheal. These are named based on the location of auscultation. Normal breath sounds are identified by the duration and quality of the sound. They are differentiated by the sound's frequency, intensity, and quality.
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Tracheal sound is heard over the trachea (above the central notch in the collar bone). It is a loud and high-pitched sound. The expiratory sound duration is equivalent to the inspiratory sound.
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Bronchial sound is heard over the manubrium (just above the collar bones). It is a loud and high-pitched sound. The expiratory sound duration is longer than the inspiratory sound. It is further classified into tubular, hollow, and amphoric breath sounds.
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Tubular sound is a high-pitched bronchial sound. It is present during consolidation, pulmonary fibrosis, chest wall collapse, and mediastinal tumors with a patent bronchus.
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A cavernous sound is a low-pitched sound. It is heard over the abscess and bronchiectasis cavity with a patent bronchus.
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Amphoric sound is a low-pitched sound with a high-pitched overtone like a metal sound. It is heard over a large cavity with a patent bronchus and open pneumothorax. Amphoric breath sound indicates alveolar destruction.
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Bronchovesicular sound is heard between the first and second intercostal space (space between the ribs) in the front and between the scapulae (triangular-shaped bones in the upper back). It is an intermediate sound. The expiratory sound duration is about equivalent to the inspiratory sound duration.
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Vesicular sound is heard over most of the lung region. It is a soft, low-pitched rustling sound. The expiratory sound duration is shorter than the inspiratory sound duration. The intensity of inspiration is greater than expiration.
How Are Breath Sounds Produced?
Normal breath sound is produced when the air flows through the tracheobronchial tree. But, breath sounds are produced only during turbulent and vorticose airflow. Laminar flow is silent. The air moves in a direction parallel to the walls of the tracheobronchial tree. Turbulent air movement produces sound because the air molecules collide with each other and with the walls. The vortices or whirlpools are produced when air enters a wider channel from a small opening.
What Does Absent or Decreased Sound Indicate?
Absent or decreased breath sounds are seen :
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In pneumonia, pleural effusion and heart failure occur when air or fluid is in or around the lungs.
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When the chest wall thickness is increased.
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In emphysema, when a portion of the lungs is over-inflated.
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When airflow to a portion of the lungs is reduced.
What Are Abnormal Breath Sounds?
The abnormal breath sounds include:
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Wheeze is a continuous whistling sound. Wheeze is high-pitched and heard during expiration. It is produced when the airways are narrowed. It is seen in conditions like asthma and chronic obstructive pulmonary disease (COPD). It can be heard without a stethoscope.
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Rhonchi are high-pitched coarse, rattling sounds heard during inspiration. Rhonchi are produced when secretions are present in bronchial airways. This sound is similar to snoring. It is seen during acute bronchitis and COPD.
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Stridor is a continuous, high-pitched, wheeze-like sound during inspiration and expiration. It occurs when the airflow is blocked in the airway or the back of the throat. It is seen during epiglottis and laryngeal edema, foreign body obstruction, and traumatic chest or neck injury.
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Rales, called crackles, are continuous, high or low-pitched, small clicking, bubbling, or rattling sounds produced during inspiration. These sounds are also described as moist, dry, fine, and coarse. It occurs in pneumonia, pulmonary edema, tuberculosis, bronchitis, and left-sided heart failure.
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An inspiratory gasp is a high-pitched whooping sound produced during inspiration. It is seen in pertussis (whooping cough).
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The pleural friction rub is a discontinuous, low-pitched sound with many repeated rhythmic sounds. It is seen during inflammation of the pleural membrane (lining of the lungs) and lung tumors.
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Hamman's sign or mediastinal crunch is a discontinuous, crunching, crackling, or rasping sound. It is heard over the precordium from the third to fifth intercostal space, along with the heartbeat. It occurs in pneumomediastinum and pneumopericardium.
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Grunting is a continuous, low-pitched sound that resembles snoring. It is produced in pneumonia, cardiac abnormalities, and surfactant deficiency. It is heard during expiration.
What Are the Complications?
Abnormal breath sounds are common and manageable disorders but may cause some emergency problems.
Abnormal sounds may be present with the following conditions:
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Cyanosis (bluish discoloration of the skin).
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Nasal flaring.
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Difficulty in breathing or shortness of breath.
It is important to consult a physician if any of the above complications are present.
What Are the Tests Done?
The physician asks for the following tests to determine the cause of abnormal breath sounds.
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CT (computed tomography) scan.
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Chest X-ray.
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Blood tests.
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Pulmonary function tests measure the volume of air inhaled and exhaled and its efficiency.
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A sputum culture test is done to detect the presence of microorganisms.
How Are Abnormal Breath Sounds Treated?
The treatment options depend on the diagnosis and the cause and severity of the symptoms. Medications are given to treat infections and to open the airways. In asthma, COPD, or bronchitis cases, breathing treatments are advised to open the airway. Inhalers or other medications are prescribed for asthma patients to reduce airway inflammation and prevent asthma attacks. Hospitalization is essential if there is fluid in the lungs or if there is airway obstruction.
Conclusion
Breath sounds produced during breathing can be normal or abnormal. It is important to differentiate between normal and abnormal sounds to diagnose respiratory problems. Auscultation of the respiratory system is vital in diagnosing normal and abnormal breath sounds. It is essential to consult a doctor when abnormal breath sounds are noticed. Early diagnosis and treatment prevent the development of further complications.
