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    Heart and breath sounds: Listening with skill

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    CE Center

    RN/MCPHU Home Study Program

    Heart and breath sounds: Listening with skill

    This article is approved for 2.0 ANCC/AACN contact hours.
    After reading it you should be able to:

    1. Analyze physical findings noted during cardiac auscultation.
    2. Analyze physical findings noted during respiratory auscultation.

    This test is no longer available for CE credit.

    Expired May 2004

    Heart and breath sounds:
    Listening with skill


    MARY-BETH MORIARTY is a clinical nurse in the coronary intensive care unit at Saint Francis Hospital and Medical Center in Hartford, Conn.

    Auscultating heart and lung sounds is a fundamental component of a physical assessment. Making sense of what you hear takes knowledge, a sharp ear, and practice.

    Listening to heart and lung sounds is a routine—but challenging—part of your patient care. Even in the best circumstances these sounds can be difficult to hear. In addition, heart sounds last slightly more than 0.10 seconds, and their pitch begins at the lowest level detectable by the human ear.1 Knowledge of technique, which I will cover here, and frequent practice will sharpen your ear.

    Let's start with preparation. Before you even place your stethoscope on your patient's chest, you want as much quiet as possible. First, explain what you're going to do and make sure the patient is comfortable before you begin. If a television is on in the room, turn the volume off. If there's a lot of noise in the hallway, close the door. You may need to do this anyway to ensure privacy during the exam.

    Use a stethoscope with a bell and a diaphragm. (If your stethoscope is electronic, it will have bell and diaphragm modes that you can alternate between with the press of a button.) The bell is best suited for hearing low-pitched sounds, and the diaphragm for high-pitched sounds. The ear pieces—no matter what type of stethoscope you are using—should fit snugly and align with the angle of your ear canals.

    To avoid transmission of extraneous noise, be sure to remove any item you may have hung on your stethoscope. (Avoid the habit some nurses have of using their stethoscope to hang rolls of tape, tourniquets, or a hospital badge.) Then, expose the patient's chest and place the head of the stethoscope directly on the skin instead of listening through the patient's gown. Stand at the patient's right side with the stethoscope tubing extended across the chest. Make sure that the tubing is not touching the chest or resting on the sheets or side rail.

    You may begin auscultation at the top (base) of the heart and proceed down to the apex, or follow the reverse order, listening first at the apex and proceeding up to the base.2,3 Either approach is acceptable; what is important is that you use the same approach for the entire exam. Here, I'll describe the base-to-apex approach.

    Start with the patient supine with the head of the bed elevated 30 degrees. Auscultate all areas first with the diaphragm. To begin, place it firmly against the right side of the chest in the second intercostal space close to the sternum. Then move to the left side and listen in the same space at the left sternal border. Continue down the left sternal border, auscultating in the third and fourth intercostal spaces. Finish by auscultating the apex, which is usually found in the fifth left intercostal space just below the nipple—the midclavicular line.

    Repeat the sequence, using the bell of the stethoscope. When you position the bell, use just enough pressure to create a seal between it and the skin. Exerting greater pressure than that will stretch the skin across the bell, creating a diaphragm and thereby reducing your ability to hear low-pitched sounds.

    Identifying sounds in systole and diastole

    At each auscultation point, concentrate first on identifying the primary heart sounds—S1 and S2. These are best heard with the diaphragm. S1 coincides with closure of the mitral and tricuspid valves and the beginning of ventricular systole. It's most intense over the apex. S1 is a lower-pitched, more pronounced sound than S2.

    S2 indicates closure of the aortic and pulmonic valves and the onset of diastole. It's best heard in the second intercostal space at the right sternal border. S2 is higher-pitched than S1 and has a clipped, closing sound.

    In patients with normal heart rates, diastole is a few hundredths of a second longer than systole, making it easier to identify S2. However, diastole shortens with tachycardia, and this difference disappears, making it more difficult to distinguish between S1 and S2 in a tachycardic patient. When that's the case, continue to auscultate and place the index finger of your free hand on the patient's carotid artery. Lightly palpate the pulse. S1 is the sound you'll hear at the same time you feel the pulse.4

    After you've identified S1 and S2, shift your focus to detecting extra heart sounds. When you do hear one, note when it occurs in relation to S1 and S2. If the extra sound follows S1 or S2 very closely, you may actually be hearing a splitting of that heart sound.

    Remember S1 and S2 coincide with the closure of two valves, each of which produces its own sound. The closures of the mitral valve (M1) and of the tricuspid valve (T1 ) usually occur so close together that the human ear is able to detect only one sound, S1.4

    But a delay in tricuspid valve closure may leave enough time for the ear to hear M1 and T1 separately. A split S1 is best heard in the fifth intercostal space at the left sternal border. It's an uncommon sound, but can occur in patients with right bundle branch block.4

    Aortic (A2) and pulmonic (P2) valve closures produce S2. Delayed pulmonic valve closure can occur during inspiration because venous return—blood coming into the right side of the heart—increases with inspiration. This increase in volume prolongs right ventricular systole and thus delays pulmonic valve closure, producing a split S2.5 During expiration venous return falls, so there's no delay in P2 closure and the split disappears. This kind of splitting is a normal or physiologic finding.

    In some cases, though, a split S2 may be abnormal. A wide gap between A2 and P2 can occur with right bundle branch block. A split S2 heard during expiration is called a reverse, or paradoxical split. It's associated with left bundle branch block, ventricular pacing, advanced left ventricular failure, and aortic stenosis. A fixed split—one heard on both inspiration and expiration—occurs with atrial septal defects (ASD). S2 heart sounds are best heard in the second and third intercostal spaces along the left sternal border.

    An S3 heart sound also comes very soon after S2, occurring early in diastole as the mitral and tricuspid valves open and blood rushes into the ventricles. An S3 is normal in children and young adults, especially women and patients with a thin build. In those over 40 years of age, however, S3 is an abnormal finding indicating ventricular dysfunction. In this case blood from the atrium is trying to enter a ventricle that wasn't completely emptied in the previous contraction.

    Because it's an early diastolic sound, S3 can be difficult to distinguish from a physiologic S2 split. However, unlike a split S2 sound, an S3 remains constant during the respiratory cycle. Its pitch is softer and best heard with the bell. An S3 heard at the apex is one of the first clinical findings in left ventricular failure. An S3 in the third to fifth intercostal spaces at the right sternal border indicates right heart failure.5

    An S4 is heard just before S1, making it a late diastolic sound. It occurs when atrial contraction pumps volume into a stiff, noncompliant ventricle. You'll most often hear an S4 in a patient with a condition that causes left ventricular hypertrophy, such as hypertension or aortic stenosis. Compliance can also be affected by ischemia, so you may also hear an S4 in a patient who's recently had an MI. You won't hear an S4 in a patient with atrial fibrillation, however, because in this case there's no atrial contraction.

    Like S3, S4 is best heard with the bell at the apex. When you have difficulty hearing these sounds, try turning the patient toward his left side. This maneuver brings the heart closer to the anterior chest wall and thus improves sound transmission.

    Listening for murmurs

    Murmurs are sounds created by turbulent blood flow. They can occur at any time during the cardiac cycle. When you detect a murmur, you need to listen for a minute or more to determine its characteristics—the timing, pitch, quality, intensity, and pattern. You'll also want to identify where you hear it the loudest and if the sound radiates to other areas.

    To establish timing, focus on whether you hear the murmur continuously, during systole (after S1 and before S2) or during diastole (after S2 and before S1). When the murmur is confined to either systole or diastole, determine whether you hear it at the beginning (early), middle (mid), or end (late).

    Systolic murmurs typically fall into two categories: mid-systolic and holosystolic (or pansystolic). A mid-systolic murmur begins after S1 and concludes before S2. You should notice a distinct gap between the two heart sounds and the murmur. Pay particular attention to the gap before S2. It will help you to distinguish a mid-systolic murmur from a holosystolic murmur, which is heard immediately after S1 and right up to S2 without any pauses.

    Once you've established its timing, shift your focus to the murmur's actual sound. Is it high-pitched, low-pitched, or somewhere in between? How would you describe its quality? Is it harsh or musical? Rumbling or blowing? What is its intensity? Do you have to really concentrate to hear a faint sound? Or do you notice the sound as soon as you put your stethoscope on the chest?

    Murmurs are graded on a six-point scale. In a grade I murmur, the sound is barely audible, whatever the patient's position. A grade II murmur is faint; a grade III is moderately loud, and a grade IV is somewhat louder and may be accompanied by a thrill. A grade V murmur is loud enough to be heard with the stethoscope held just above the chest wall. It is accompanied by thrills, as is a grade VI murmur, which is so loud that you can hear it without a stethoscope.6

    Listen also for a particular pattern or shape to a murmur. Some murmurs begin softly and then become louder (crescendo). Others start out very loud and then taper off (decrescendo). You may also hear a murmur that combines the two patterns just described. It will start off softly, grow increasingly louder until it peaks, and then taper off (crescendo-decrescendo). Lastly, you may find the murmur does not change at all, making it a plateau murmur.

    After you've established these characteristics, concentrate on the murmur's location. Where do you hear it best? Is it most noticeable at the apex or in the second or third intercostal space? Does the sound travel or radiate to the neck, back, or axilla? The answers to each of these questions will help you hone in on the murmur's possible cause.

    Not every murmur is worrisome

    While it's true that most murmurs are associated with some form of valve dysfunction, not every murmur is cause for alarm. Systolic murmurs often occur in patients with no other evidence of cardiac disease, in which case they're known as innocent or physiologic murmurs. These murmurs are created by turbulent flow as the left ventricle ejects blood through the aortic valve into the aorta.

    Innocent murmurs are mid-systolic and have a quick crescendo-decrescendo pattern. They are usually medium-pitched, faint, and best heard in the area of the aortic valve—the second intercostal space at the right side of the sternum—with little or no radiation.

    When the increase in turbulence occurs because of an increase in flow associated with conditions that raise heart rate or circulating volume—for example, anemia, pregnancy, or fever—the murmur may also be called a flow murmur. A flow murmur has the same characteristics as an innocent murmur but disappears when the condition causing the increased flow is resolved.

    Systolic murmurs that indicate heart disease

    A systolic murmur that's associated with cardiac disease is usually preceded by an ejection sound that coincides with the opening of the affected valve. This is a high-pitched, sharp, clicking sound that's best heard with the diaphragm. A description of how to identify specific murmurs is provided here and in the "Identifying murmurs" box.

    Blood being pushed through a narrowed or stenotic aortic valve creates a mid-systolic murmur that has a crescendo-decrescendo pattern. An aortic stenosis murmur is often medium-pitched and varies in quality. It's best heard in the second right intercostal space and radiates to the carotid arteries or left sternal border. An ejection sound typically indicates a congenital defect.

    Pulmonic stenosis murmurs are also mid-systolic and have a crescendo-decrescendo pattern. They are medium-pitched and often harsh. They're heard in the second or third left intercostal spaces and can radiate to the neck or shoulder. Early ejection sounds are typical. When the murmur is severe, you'll also often hear a wide S2 split. This type of defect is usually congenital.

    Hypertrophic cardiomyopathy can also create a mid-systolic murmur resulting from the very rapid ejection of blood from the enlarged muscular ventricle. This murmur has a crescendo-decrescendo pattern that is best heard in the third and fourth left intercostal spaces at the sternal border. It can radiate down to the apex, but, unlike aortic and pulmonic stenosis murmurs, its sound doesn't travel up to the neck. The murmur of hypertrophic cardiomyopathy has a harsh quality and a medium pitch. You may also often hear an S4 at the apex.2

    Holosystolic murmurs occur with mitral or tricuspid valve regurgitation. These murmurs have a plateau pattern caused by the backward flow of blood through a valve that should be closed.

    Mitral regurgitation produces a high-pitched blowing murmur. It's best heard at the apex and often radiates to the left axilla. You may also detect an S3, indicating volume overload in the left ventricle.

    Mild mitral regurgitation is often associated with mitral valve prolapse, which is the ballooning of the posterior valve leaflet into the left atrium during systole. In this case you'll hear a systolic click or highpitched clicking sound before the murmur. Mitral regurgitation can also occur with papillary muscle damage, post-MI. If you suspect this, report it immediately.

    Tricuspid regurgitation produces a high-pitched blowing murmur, but it's heard at the lower left sternal border. This type of murmur, unlike a mitral regurgitation murmur, can become more intense during inspiration, and it radiates to the right of the sternum or xiphoid area but not into the axilla.

    A ventricular septal defect (VSD) produces a loud, highpitched, harsh holosystolic murmur. You'll hear this kind of murmur in the third, fourth, and fifth intercostal spaces as blood flows through the septum from the left to the right ventricle, producing a plateau pattern. VSD murmurs have a wide range of radiation. They are often congenital but may occur after an MI, in which case, it's an emergency. Report it immediately.

    Diastolic murmurs that indicate heart disease

    Unlike systolic murmurs, diastolic murmurs always indicate heart disease. They can be early, mid-diastolic, or late. An early diastolic murmur begins immediately after S2 and usually tapers off to silence before the next S1. A mid-diastolic murmur is heard shortly after S2 and then either tapers off or blends into a late diastolic murmur. You'll notice the beginning of a late diastolic murmur about half to two-thirds of the way between S2 and S1. Since it continues up to the next S1, a late diastolic murmur is also described as presystolic.

    Aortic regurgitation is the most common cause of an early diastolic decrescendo murmur. This is a high-pitched blowing sound that's heard in the second right intercostal space and Erb's point and may radiate to the left or right sternal border.

    A soft aortic regurgitation murmur can be mistaken for breath sounds. To help tell the difference, have the patient sit up and lean forward. Then ask the patient to exhale and wait a few seconds before taking the next breath. Any blowing sound you hear now will be a murmur. You may also detect an ejection sound. Severe regurgitation is associated with an S3 or S4.

    Pulmonic regurgitation is heard in the second left intercostal space and may radiate to the left lower sternal border. It, too, is a high-pitched, blowing sound that increases with inspiration. It is usually associated with pulmonary hypertension.

    The murmur of mitral stenosis is a low-pitched, rumbling sound. It typically begins with an opening snap that follows S2. Mild stenosis often produces a mid-systolic murmur. Murmurs that continue into late diastole are associated with severe disease.4 Mitral stenosis murmurs have little or no radiation. To improve auscultation, position the patient on his left side and place the bell on the apex.

    Tricuspid stenosis produces a murmur heard in the fourth left intercostal space at the sternal border. It has a low-pitched, rumbling sound that increases with inspiration. In patients with rheumatic heart disease, it usually occurs in combination with other valve problems.

    How to listen for breath sounds

    When you've finished assessing heart sounds, move on to auscultate lung sounds. Start with the back, and, if possible, have the patient sit up, lean forward, and cross his arms in front of his chest. This position brings the scapulae up, allowing better auscultation. If your patient is unable to sit up, turn him from side to side to auscultate the posterior lung fields. When you do this, keep in mind that the dependent lung is the best ventilated, making it the side in which you'll be more likely to hear crackles and wheezes.2

    As with the auscultation of heart sounds, place the diaphragm directly on the skin. Apply firm pressure and auscultate in the intercostal spaces. Try not to listen over bone. Begin at the top and work your way down the back. Listen in the same area on both sides of the spine before moving down to the next intercostal space. (See figures in the "A road map for respiratory assessment" box.)

    When you reach the inferior angles or tips of the scapulae, widen your range and auscultate out along both sides of the chest to the midaxillary line. That way you'll be sure you've assessed all lung fields. When you're finished, have the patient lie back with his arms slightly extended from his sides and begin auscultating the anterior chest.

    Use the same approach as you did for the back. In this case, though, the first auscultation site will be above the clavicle. That's where you'll hear breath sounds in the apices, or topmost portions of the lungs, and the trachea. Again, move from side to side and work from top to bottom at the midclavicular line. When you reach the nipple line, move out along the side of the chest to the midaxillary line. Be sure to include the sixth and seventh intercostal spaces, because that's where you'll find the lung bases. Normal or vesicular breath sounds are soft, low-pitched sounds primarily heard during inspiration. Vesicular sounds can be heard anywhere, but you are more likely to hear them in the posterior lung fields and less likely to hear them near the trachea or bronchi.

    Tracheal breath sounds, as the name implies, are heard in the neck over the trachea. These sounds are louder and have a higher pitch than vesicular sounds. Tracheal breath sounds can be heard during both inspiration and expiration.

    Bronchial or tubular breath sounds are coarse, fairly highpitched sounds heard over the trachea and manubrium. Expiratory sounds last longer than inspiratory. When auscultated in other areas, bronchial breath sounds are an abnormal finding caused by air loss in the affected lung tissue. Pneumonia is a common cause of abnormal bronchial sounds; infection causes the alveoli to fill with fluid, leukocytes, and red blood cells—a change known as consolidation.

    Air loss also affects transmission of vocal sounds. So when you think you hear abnormal bronchial sounds, ask the patient to say "ee" several times as you continue to auscultate the area. If there is air loss, you'll hear "ay" instead of "ee." This phenomenon is called egophony.

    Spoken words heard over a consolidated area will be loud and clear rather than the normal finding, which is muffled and indistinct. Note this change as bronchophony. Whispered words, too, will be louder and clearer—a finding called whispered pectoriloquy.

    Bronchovesicular breath sounds combine bronchial and vesicular sounds. These sounds are medium-pitched and last as long during expiration as they do during inspiration. Bronchovesicular sounds are abnormal when heard anywhere other than in the first or second intercostal spaces anteriorly and between the scapulae posteriorly (which is the location of the mainstem bronchi). They are associated with the early stages of pulmonary disease.

    Adventitious sounds, which are also abnormal, fall into two major categories: wheezes and crackles. Wheezes are continuous sounds with a musical quality. Wheezing can occur with any condition that narrows the airways. Asthma and chronic bronchitis are common causes.

    High-pitched wheezes have a whistling quality. Lower-pitched snoring sounds, also referred to as rhonchi, are associated with secretions in the larger airways. If you suspect that's the case, ask the patient to cough, which may clear the secretions and improve lung sounds.

    Suspect stridor instead of wheezes when you hear a loud high-pitched wheeze in the upper airways. Stridor signals some degree of upper airway obstruction and becomes more intense during inspiration. Since this kind of obstruction can lead to respiratory arrest, report this finding immediately.

    Crackles are distinct scratchy sounds with a shorter duration than wheezes. Fine crackles sound much the same as rubbing a few strands of hair between two fingers or against the diaphragm of a stethoscope. If the patient has a lot of chest hair, wet it down lightly before auscultating an area and be sure to hold the diaphragm firmly to eliminate this extraneous sound.

    Fine crackles are thought to be caused by the sudden equalization of pressure as airways pop open. Fine crackles that are heard late in inspiration in the lung bases are an early sign of congestive heart failure. Coarser crackles are associated with air flowing through secretions or lightly closed airways.

    Crackles may also be heard in a normal person with shallow respirations, upon awakening, for example. Have the patient cough and then breathe deeply; the crackles may have cleared.

    Technique improves with practice

    The more you practice auscultating heart and lung sounds, the easier it will be to identify what they signify or suggest. Yet, no matter how experienced you become, in some patients, auscultation may still pose a challenge. A patient's size and weight can affect the transmission of sound—decreased breath sounds, for instance, may be a result of obesity.

    An increase in the anterior-posterior diameter of the chest can make it almost impossible to auscultate heart sounds. In this case, you may be able to hear only when you turn the patient to the left side, bringing the left ventricle closer to the chest wall or by auscultating in the epigastrium just below the xiphoid process of the sternum.7

    This technique may also be helpful if the patient has a lot of muscle or adipose tissue that muffles heart and lung sounds. When you're examining a female patient with large or pendulous breasts, use your free hand to hold the breast up and position the stethoscope head as close to the chest wall as possible; if that isn't helpful, move her onto her left side, as described.

    If these approaches don't bring much success, you'll need to shift your focus and rely on other clinical findings to provide the best care possible.

    As with any complicated technique, it takes time to master auscultation. Remember that it's a skill well worth the effort you put into it. It can enable you to identify problems early and evaluate a patient's progress during treatment and recovery.


    1. Guyton, A. C., & Hall, J. E. (2000). Textbook of medical physiology (10th ed.). Philadelphia: W. B. Saunders.

    2. Bates, B., Bickley, L., & Hoekelman, R. (1999). Bates' guide to physical examination and history taking. (7th ed.). Philadelphia: J. B. Lippincott.

    3. Willerson, J. T., & Cohn, J. N. (2000). Cardiovascular medicine (2nd ed.). New York: Churchill Livingstone.

    4. Darovic, G. (1995). Hemodynamic monitoring: Invasive and noninvasive clinical application (2nd ed.). Philadelphia: W. B. Saunders.

    5. Whalen, D., & Kelleher, R. (1998). Cardiovascular patient assessment. In M. Kinney, S. Dunbar, et al. (Eds.), AACN clinical reference for critical care nursing (4th ed.). St. Louis: C. V. Mosby.

    6. Ludwig, L. M. (1998). Cardiovascular assessment for home healthcare nurses. Part 2. Home Healthcare Nur, 16(8), 547.

    7. Braunwald, E., Zipes, D., & Libby, P. (2001). Heart disease: A textbook of cardiovascular medicine (6th ed.). Philadelphia: W. B. Saunders.

    Cardiac assessment points



    Above, the five locations for cardiac auscultation are superimposed over the heart and rib cage. When assessing a patient, begin either at the base of the heart (point 1) and proceed downward through the next four, or start at the apex (point 5) and work back up.

    Identifying murmurs

    Murmurs are caused by turbulent blood flow through narrowed or abnormally functioning valves. They're grouped according to when they occur during the cardiac cycle. Murmurs associated with mitral and tricuspid valve stenosis are best heard with the bell of the stethoscope, the others listed below, with the diaphragm.
    Sound Where it's most audible What you'll hear; what it implies

    Systolic murmurs associated with cardiac disease

    Aortic stenosis

    Second right intercostal space; sound may radiate to neck or left sternal border.

    Medium-pitched, often harsh, grating sound, occurring at mid-systole, most often with rheumatic heart disease and congenital valve disorders; intensifies when patient squats or lies flat.
    Pulmonic stenosis Second or third left intercostal space; sound radiates toward the shoulder and neck. Also medium-pitched, mid-systolic, and often harsh sound; louder on inspiration and when patient is supine. Generally heard in congenital valve disease.
    Hypertrophic cardiomyopathy

    Third and fourth left intercostal spaces at the sternal border; can radiate down to the apex, but doesn't travel up to the neck.

    Medium-pitched, mid-systolic murmur. Has a harsh quality. Results from the very rapid ejection of blood from the enlarged muscular ventricle.
    Mitral regurgitation Apex, fifth intercostal space, left midclavicular line; sound may radiate to left axilla and back. High-pitched, blowing sound occurring throughout systole. Often associated with mitral valve prolapse; common in rheumatic heart disease and after rupture of a ventricle's papillary muscle; worsens during expiration and when patient is supine or on left side.
    Tricuspid regurgitation Lower left sternal border; sound may radiate to right sternum. Also high-pitched, blowing, and holosystolic; heard in right ventricular failure and rheumatic heart disease; intensifies on inspiration and when patient is supine.

    Ventricular septal defect (VSD)

    Third, fourth, and fifth intercostal spaces; wide range of radiation. Loud, high-pitched, harsh holosystolic murmur heard as blood flows through the septum from the left to the right ventricle. Often congenital but may occur after an MI.

    Diastolic murmurs
    Aortic regurgitation Second right intercostal space and Erb's point; sound may radiate to left or right sternal border.

    High-pitched, blowing sound that increases when patient leans forward and holds breath; heard during diastole in rheumatic and congenital heart disease, Marfan's syndrome; aortic stenosis often a concurrent problem.

    Pulmonic regurgitation Second left intercostal space; sound may radiate to left lower sternal border. High-pitched, blowing sound increases with inspiration; usually associated with pulmonary hypertension.
    Mitral stenosis Apex, fifth intercostal space, left midclavicular line; sound gets louder with patient on left side; little or no radiation.

    Low-pitched, rumbling sound that increases with exercise, inspiration, and left lateral position. Commonly caused by rheumatic heart disease, often accompanied by opening snap.

    Tricuspid stenosis Fourth left intercostal space, at sternal border. Low-pitched, rumbling sound that increases with inspiration; in patients with rheumatic heart disease, it usually occurs in combination with other valve problems.


    A road map for respiratory assessment

    The drawings on these pages help you link the surface of the patient's body to the underlying anatomy. This respiratory "road map" also pinpoints commonly used auscultation points that will enable you to evaluate each of the five lobes. By referring to the imaginary lines drawn down the front, back, and side, you can also document your findings more precisely and more readily interpret those of your colleagues.



    Stethoscope options

    A stethoscope is an essential piece of equipment in the auscultation process. The acoustic stethoscope is the one most nurses use when learning auscultation. It has a diaphragm on one side for high-pitched sounds and a bell on the other for low-pitched sounds. The tubing is thick and heavy, which helps to conduct sound.1

    Newer electronic stethoscopes pick up and amplify sounds and send them to speakers in the earpieces. Electronic stethoscopes, which run on batteries, automatically filter out ambient noise and offer volume control. To switch between the bell and diaphragm modes, the clinician simply presses a button.


    1. Seidel, H. M., Ball, J. W., et al. (1995). Mosby's guide to physical examination (3rd ed.). St. Louis: Mosby-Year Book.


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    Mary-Beth Moriarty, RN, BSN
    The author is a staff nurse in the coronary and cardiac surgery intenwsive care unit at Saint Francis Hospital, Hartford, Conn.