Historical aspect and evolution of the method
The founder of instrumental (mediate) auscultation is the prominent French clinician René Théophile Hyacinthe Laënnec. A key date in the history of this diagnostic technique is 1816, when Laënnec first proposed using a specialized device to listen to the patient—the stethoscope.
This invention was prompted by a very specific clinical situation. The physician needed to examine a young female patient of a full-bodied constitution. Due to these anatomical features, direct auscultation—where the physician places their ear directly against the patient's body—was extremely difficult. To solve this, Laënnec used a regular notebook rolled tightly into a tube. This simple solution allowed him to hear the sounds of heart action remarkably clearly.
This very event marked the beginning of mediate auscultation. In his early practice, Laënnec used a rigid tube: one end was firmly applied to the patient's precordial region, and the other directly to the physician's ear. This approach significantly improved the quality of transmitted sound compared to classical direct auscultation.
Over time, the design of the instrument underwent significant evolution:
- Initial stage: predominantly wooden tubes with flared ends were used. This was monaural auscultation (listening with only one ear).
- Modern stage: today, exclusively binaural instruments designed for both ears are used. They are equipped with comfortable flexible sound-conducting tubes and specialized earpieces.
Types of modern instruments for auscultation
In modern medical practice, three main types of instruments are used for auscultation, each with its own design features:
- Stethoscope. This represents the classic diagnostic instrument, with the sound-receiving part typically shaped like an open bell.
- Phonendoscope. The main difference of this device is the presence of a special membrane (usually made of plastic) stretched tightly over the end of the instrument applied to the patient's body. This membrane forms a closed chamber that repeatedly amplifies sound through resonance.
- Stethoscope-phonendoscope. This is the most common and versatile combined device today. It combines both a bell (acting as a stethoscope) and a diaphragm (acting as a phonendoscope) in a single rotating assembly. The physician can quickly switch between these two modes depending on diagnostic goals.
Technical requirements for the stethoscope-phonendoscope
To ensure high-quality and error-free diagnostics, the instrument used must strictly comply with a number of technical criteria.
Sound-receiving part (chest piece):
- The walls of the chest piece must be completely smooth; any defects or burrs are unacceptable.
- The membrane must have sufficient stiffness while remaining elastic.
- The instrument must be equipped with a reliable and convenient mechanism for switching between stethoscope and phonendoscope modes.
Sound-conducting system:
- The optimal tube length varies within 30–38 cm. Shorter tubes transmit sound waves much better, but excessively short variants cause serious inconvenience when working with the patient.
- The walls of the sound-conducting tube must be thick enough to ensure reliable isolation from external ambient noise.
Earpieces (ear tips):
- The ear tips must be elastic.
- Their main function is to ensure the tightest possible closure of the physician's external auditory canal, thereby creating the necessary system airtightness.
Technique and clinical application
Proper auscultation technique is critical for obtaining reliable data. The main rule is firm contact. The chest piece of the instrument should be pressed against the patient's skin firmly enough to ensure continuous contact along the entire circumference (edge) of the bell or diaphragm.
Avoidance of artifacts. The physician must carefully monitor this. The high risk of side noise effects caused by the friction of the membrane against the patient's body hair must always be taken into account. Such sounds can mimic pathological phenomena and lead to diagnostic errors.
Clinical application of the method:
- Objects of examination: traditionally, the patient's lungs, heart, blood vessels, and intestines are subjected to auscultation.
- Physical basis: sound vibrations that regularly and rhythmically occur during the normal functioning of these organs are recorded.
- Diagnostic value: the method is entirely based on a deep knowledge of physiological norms. Any pathology is detected either through a noticeable change in the normal auscultatory picture or through the appearance of new, additional (pathological) sounds.
Place of auscultation in the clinical examination algorithm
Auscultation occupies a strictly defined place in the protocol of a patient's physical examination.
- Sequence of actions: listening is performed only after the physician has completed taking the medical history (questioning), visual inspection, palpation, and percussion.
- Targeted approach: preliminary examination stages provide the physician with a mass of information to formulate initial diagnostic hypotheses. This allows auscultation to be performed not blindly, but in a highly targeted manner, checking specific clinical assumptions.
- Dynamic monitoring: repeated (so-called dynamic) auscultation provides immense diagnostic information. It allows the specialist to detect the appearance of entirely new sound phenomena in real-time during the course of the disease.
Briefly: answers to topical questions
What are the auscultation points for heart valves?
The auscultation points for heart valves correspond to the sites where sound phenomena are best transmitted along the blood flow.
- Mitral valve — auscultated at the cardiac apex.
- Tricuspid valve — evaluated at the base of the xiphoid process.
- Aortic valve — auscultated in the second intercostal space to the right of the sternum.
- Pulmonary valve — in the second intercostal space to the left of the sternum.
Another important area is Botkin-Erb's point (third intercostal space to the left of the sternum), where the maximum diastolic murmur of aortic regurgitation is often heard.
What are the pathological murmurs in cardiac auscultation?
Various pathological murmurs may be heard during cardiac auscultation.
- Systolic murmur — heard in mitral regurgitation, aortic stenosis, or relative tricuspid regurgitation.
- Diastolic murmur — characteristic of mitral stenosis, aortic regurgitation, and relative pulmonary valve regurgitation (Graham Steell murmur). Diastolic murmurs also include the independent Austin Flint murmur at the cardiac apex.
- Pericardial friction rub — may be heard in pericarditis.
By timbre, murmurs can be blowing, scraping, saw-like, or musical.
What are the rules for performing pulmonary auscultation?
Pulmonary auscultation is performed observing the principle of strict symmetry and using special methodological techniques.
- Principle of symmetry — sound phenomena are strictly compared over symmetrical areas of the lungs on the right and left.
- Assessment of respiratory phases — phenomena are best heard during inspiration (inspirium), but the characteristics of expiration (expirium) also have diagnostic significance.
- Dynamic shifting — to clarify the borders of a pathological process, the stethoscope is moved with each breath from a normal area to the affected zone.
- Cough test — used to differentiate rales from crepitation and pleural friction rub.
What is crepitation and how does it sound during auscultation?
Crepitation is an alveolar sound phenomenon occurring when a small amount of exudate is present in the alveoli, causing their adhered walls to separate during inspiration. On auscultation, crepitation sounds like a distinctive crunching or crackling. The acoustic analogue of this sound is the sound of rubbing a lock of hair between the fingers near the ear. Key features of the phenomenon:
- It is heard exclusively at the height of inspiration.
- It does not change or disappear after a cough (independent of it).
Class and exam questions
What is the main difference between a stethoscope and a phonendoscope?
A stethoscope is a simple funnel, whereas a stethoscope-phonendoscope is equipped with a taut membrane that forms a chamber and amplifies sound through resonance.
Why should the sound-conducting tubing not be longer than 38 centimeters?
An excessively long tubing impairs the transmission of sound from the organ to the physician's ear. Short tubes transmit sound significantly better, although overly short ones are inconvenient to work with.
At what stage of the physical examination is auscultation performed?
Auscultation is performed strictly after completing the history taking, inspection, palpation, and percussion, which allows the physician to test already formed hypotheses.
How can the patient's hair affect the auscultation results?
Friction of the stethoscope membrane against the patient's hair can generate extraneous noise (artifacts) that are easily mistaken for pathological sound phenomena.
What else to study on this topic
- Lung auscultation: primary and adventitious breath sounds
- Heart auscultation: heart sounds and intracardiac murmurs
- Blood vessel auscultation
- Bowel auscultation and assessment of peristalsis
- Formulating diagnostic hypotheses based on physical examination methods
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