![]() Sound is produced by vibrations in air or other compressible media that are transmitted as waves and provide the stimulus for the subjective sensation of hearing. In order to accomplish this goal, it is necessary to understand the basic principles of sound production and transmission. The goal of clinical auscultation is to relate the sounds heard to the underlying pathology of the tissues examined. Principles of Sound Production and Transmission Since then, the stethoscope has evolved into its current form and has become one of the most cost effective diagnostic instruments available to clinicians. It was not until the early 1800’s that the stethoscope was “discovered” by Rene Laennec (1781 to 1826) who used a rolled cylinder of paper to listen to a patient’s chest. Robert Hooke (1635 to 1703)Įarly auscultation was performed by placing one’s ear directly on the patient’s body. I have been able to hear very plainly the beating of a man’s heart… who knows, I say, but that it may be possible to discover the motions of the internal parts of bodies… by the sound they make. With each movement of the heart, when there is the delivery of a quantity of blood from the veins to the arteries, a pulse takes place and can be heard within the chest. You shall know by this that the chest contains water and not pus, if in applying the ear during a certain time on the side, you perceive a noise like that of boiling vinegar. There are several historical references to auscultation in medical literature. ![]() The intensity and character of breath sounds help determine the location and pathology of thoracic disease.Īuscultation, or listening to the sounds within the body, is a fundamental examination procedure in clinical medicine. Abnormal, or adventitious, sounds are classified as crackles, wheezes, stertor, and stridor. Normal breath sounds are classified as bronchial, bronchovesicular, and vesicular. The character of the sound that is heard at the surface is determined by the factors influencing the production of the sound, and acoustical characteristics of the intervening tissues. Breath sounds originate in the large airways due to turbulence in airflow. Differences in the acoustical density of tissues result in attenuation, reflection, and refraction of these sound waves. Auscultable sounds originate as mechanical vibrations within compressible media that are then transmitted through the tissues as sound waves. Differences in the intensity and character of sounds can be useful in distinguishing underlying thoracic pathology. ![]() Many clues as to both respiratory and cardiac function and disease can be obtained through proper auscultation. Listen to rales here on the Medzcool YouTube channel.Thoracic auscultation and percussion are two of the most useful and economical procedures of a physical examination. Rales are usually broken up into more specific types, based on the way they sound. When these tiny sacs are damaged or weighed down with fluid or mucus, they can make a crackling sound as they attempt to fill with air. These are tiny sacs of air and inflate and deflate with each breath. ![]() This usually occurs in the smaller parts of the lungs, like the alveoli. These sounds are formed when air moves into closed spaces. The terms rales or crackles have been used interchangeably and are usually a matter of preference, not a difference in the condition. Rales are a higher-pitched sound sometimes called crackles or bibasilar crackles. Listen to rhonchi here on the Medzcool YouTube channel. The sound you hear is the the sound the air makes as it moves around the blockage. These sounds are produced when there is something blocking the airway, like fluid. Rhonchi can either come and go on and inhale or exhale or be heard continuously. It can be heard on an inhale or exhale, and it’s often compared to the sound of snoring. This low-pitched sound that usually starts in the larger airways in the lungs. The difference between the two is in the pitch and the exact cause of the sound. Rales and rhonchi can both be coarse, even crackling sounds.
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