Auscultation is the technique of listening to the internal sounds of the body, typically using an instrument called a stethoscope. This process allows healthcare professionals to assess the condition of various body systems by detecting and interpreting sounds that are normally produced or that indicate a change in health. The stethoscope acts as a sound amplifier, making it possible to hear subtle acoustic signals from organs like the heart, lungs, and intestines. Understanding the correct placement of the stethoscope is fundamental, as sound transmission varies significantly across the body’s surface. This guide details the precise locations on the chest, back, and abdomen to ensure accurate listening for the most common health assessments.
Essential Stethoscope Technique
Proper use of the stethoscope begins with the earpieces, which should be angled forward to align with the natural slope of the ear canals for optimal sound transmission. The chest piece of a standard stethoscope features two sides: the diaphragm and the bell.
The diaphragm is the larger, flat side and is used for picking up high-frequency sounds, such as typical heartbeats, lung sounds, and most bowel sounds. To use the diaphragm effectively, it must be pressed firmly against the patient’s skin.
The bell is the smaller, cup-shaped side designed to detect low-frequency sounds, which include certain heart murmurs and vascular sounds. When using the bell, it is applied lightly to the skin, with just enough pressure to form a seal. Pressing too hard stretches the skin and filters out the low-pitched sounds it is meant to capture.
For all auscultation, the chest piece should be placed directly on the bare skin. Clothing creates friction that can obscure or mimic true body sounds. A quiet environment is also necessary to hear the often faint internal sounds clearly.
Key Locations for Cardiac Auscultation
Listening to the heart requires locating four specific areas on the chest wall. These areas correspond not to the valves’ physical location, but to where the sound of each valve closing is best transmitted. The examination typically begins with the aortic area, which is situated at the second intercostal space just to the right of the sternal border.
Moving directly across the chest, the pulmonic area is found at the second intercostal space, adjacent to the left sternal border. The third area, often called Erb’s point, is located at the third intercostal space immediately to the left of the sternum. This site is useful for hearing both the first and second heart sounds, and certain murmurs.
The tricuspid area is located at the fourth or fifth intercostal space, directly along the lower left sternal border. The final and most lateral point is the mitral area, which is located at the fifth intercostal space, positioned along the midclavicular line. This imaginary line runs down from the middle of the collarbone. This location is considered the apex of the heart and is where the closure of the mitral valve is heard most clearly.
Mapping the Lung Fields
Auscultating the lungs requires a systematic approach across the entire torso, as the lung tissue extends across the anterior, posterior, and lateral chest walls. For lung sounds, the diaphragm of the stethoscope is used exclusively. The examination should follow a “ladder pattern,” moving from side to side at the same level to compare symmetrical lung regions, which helps identify differences in airflow.
On the anterior chest, the upper lobes are accessed above the fourth rib, with placement sites generally located superior to the breasts and pectoral muscles. The middle lobe of the right lung and the lingula of the left lung are heard in the lower anterior chest, though the posterior surface offers the best access to the majority of lung tissue.
When listening to the back, the patient should be seated upright, and the stethoscope is placed in several spots between the spine and the scapula. It is important to avoid placing the chest piece directly over the scapula or other bony structures, as this dampens the sound.
The posterior examination is particularly important because the lower lobes, which contain the largest volume of lung tissue, extend down to the eleventh or twelfth thoracic vertebra. The lateral fields are assessed at the mid-axillary line, which is the side of the chest, usually requiring one or two spots on each side. The patient should be instructed to breathe deeply through their mouth at each placement site to generate audible airflow.
Listening to Abdominal and Vascular Areas
The stethoscope is an important tool for assessing the abdomen and major blood vessels. For bowel sounds, the abdomen is conceptually divided into four quadrants: the right upper, right lower, left upper, and left lower. Bowel sounds are typically heard using the diaphragm and are assessed by listening in one location within each of the four quadrants.
To assess vascular areas, the bell of the stethoscope is used with light pressure over the path of major arteries. Key vascular sites include:
- The abdominal aorta, auscultated in the midline area between the xiphoid process and the umbilicus.
- The renal arteries, located about three centimeters superior and lateral to the umbilicus.
- The iliac arteries, found about three centimeters inferior and lateral to the umbilicus.
- The carotid arteries in the neck, which are routinely checked for turbulent flow, requiring careful and light placement of the bell to avoid compressing the vessel.