Auscultation, the practice of listening to the body using a stethoscope, is a foundational method healthcare providers use to assess a patient’s health. Providers listen to various internal sounds, including the sounds of air moving through the respiratory system, collectively termed breath sounds. Breath sounds are categorized based on their acoustic qualities and location. The three primary normal categories are vesicular, bronchovesicular, and bronchial sounds, each reflecting air movement in different parts of the lung structure. Interpreting these sounds provides immediate insight into the physical state of the lungs and air passages.
Defining Bronchial Sounds
Bronchial sounds are characteristic noises generated by air turbulence rushing through the large-diameter airways. These sounds originate in the trachea and the main bronchi, where the volume and speed of the air create a loud, harsh, and hollow noise. Due to their origin, bronchial sounds are sometimes referred to as tubular sounds. Normally, these sounds are heard directly over the trachea in the neck area and over the upper sternum on the anterior chest. They may also be heard posteriorly between the shoulder blades, the region closest to the main bronchi.
Acoustic Properties
Bronchial sounds possess distinct acoustic properties, characterized by a high pitch and a loud, intense quality, often described as hollow or tubular. This loud quality results from turbulent airflow within the wide, rigid walls of the trachea and main bronchi. A defining feature is the relationship between the inspiratory and expiratory phases. The expiratory phase is typically longer in duration and louder than the inspiratory phase (I < E). Furthermore, a distinct, brief pause exists between the end of inspiration and the start of expiration, which is absent in other normal breath sounds.
When Bronchial Sounds Indicate Illness
The presence of bronchial sounds over the peripheral lung fields, where only soft vesicular sounds should normally be heard, is a significant sign of underlying illness. This abnormal finding, known as bronchial breathing, suggests a change in the physical structure of the lung tissue. In a healthy lung, sounds from the large airways are filtered and muffled by the air-filled alveoli before reaching the chest wall. When loud bronchial sounds are transmitted to the periphery, it is because the normally air-filled tissue has become dense or “consolidated” with fluid, mucus, or inflammatory cells. Consolidated tissue, such as that caused by pneumonia or severe atelectasis (lung collapse), acts as a much more efficient conductor of high-frequency sound waves.