Listening to internal body sounds, known as auscultation, relies on the proper use and placement of a stethoscope. This instrument amplifies the faint noises produced by the heart, lungs, and abdomen. A standard stethoscope chest piece typically features two distinct parts designed to capture different sound frequencies. The flat, larger side, called the diaphragm, is best for detecting high-pitched sounds like normal heartbeats, lung sounds, and bowel movements. Conversely, the smaller, concave side, or the bell, is used for low-frequency sounds, such as specific heart murmurs or vascular sounds, and requires light placement to function correctly.
Auscultation Points for Lung Sounds
Listening to the lungs requires a systematic approach to cover all lobes and compare symmetric areas of the chest. The diaphragm of the stethoscope is generally used for lung auscultation because breath sounds are typically high-pitched. The patient should be sitting upright, if possible, and instructed to breathe deeply through the mouth to maximize sound transmission.
To assess the front (anterior) of the chest, placement begins just above the clavicles to listen to the top portions of the lungs, known as the apices. The stethoscope is then moved downward in a pattern that zig-zags from one side of the chest to the other, staying along the midclavicular line to avoid the heart and breast tissue. This side-to-side pattern is important for comparing the quality and volume of air entry in corresponding lung fields.
On the back (posterior) of the chest, auscultation begins above the shoulder blades (scapulae) and proceeds downward, comparing sides symmetrically. The arms should ideally be crossed in the lap to move the scapulae out of the way, providing better access to the lung tissue beneath. The posterior chest primarily covers the lower lobes of the lungs, extending down to the level of the tenth thoracic vertebra.
For the sides (lateral) of the chest, listening is done in the midaxillary line, which runs down from the armpit. This area is particularly useful for hearing the right middle lobe, which is not easily accessed from the front or back.
Auscultation Points for Heart Sounds
Auscultating the heart requires precise placement over four main areas corresponding to where the sounds of the four heart valves are best transmitted to the chest wall. The first two areas are located in the second intercostal space (the gap between ribs), which is identified by locating the sternal angle. The sound of the aortic valve is best heard at the second intercostal space just to the right of the sternum. The pulmonic valve sound is listened for at the second intercostal space just to the left of the sternum.
Moving down the left side of the sternum, the tricuspid valve area is found at the fourth or fifth intercostal space along the left sternal border. The final point is the mitral valve area, also called the apex, which is located at the fifth intercostal space on the left, positioned along the midclavicular line. This apical site is where the heart’s strongest beat is usually felt and heard.
The diaphragm is used with firm pressure to hear the high-pitched “lub-dub” sounds of the valves closing (S1 and S2) and most regurgitant murmurs. The bell, applied lightly to the skin, is used to detect lower-pitched sounds, such as specific gallops or certain types of murmurs.
Auscultation Points for Abdominal Sounds
Abdominal auscultation is performed to assess both the sounds of the digestive system and the flow of blood through major vessels. For the digestive system, the diaphragm is pressed lightly against the abdomen to listen for bowel sounds, which are generally high-pitched. The standard technique involves listening systematically to all four quadrants: the right lower, right upper, left upper, and left lower quadrants.
Normal bowel sounds are gurgling noises produced by peristalsis and occur every five to thirty seconds. If sounds are absent, listening for a full five minutes is necessary before confirming no bowel sounds are present. To listen for vascular sounds, or bruits, the bell is used because these sounds of turbulent blood flow are typically low-pitched.
The aorta is auscultated centrally, typically between the xiphoid process and the umbilicus. To check the renal arteries, the stethoscope is placed a few centimeters above and to the sides of the umbilicus. The iliac arteries are checked a few centimeters below and to the sides of the umbilicus.