Daniel O’Neill, BSc [Hons], RN, GIBiol, PGDip, ALS, ATNC.
Staff Nurse and Student Extended Nurse Practitioner, Accident and Emergency Department, Frimley Park Hospital, Surrey
This paper examines the use of the stethoscope in relation to clinical assessment within the acute sector, in particular in accident and emergency departments [A&E].
The stethoscope was invented by French physician R.T.H. La[ep6]nnec in 1819 [McFerran, 1998]. A simple stethoscope consists of a diaphragm or an open bell-shaped structure, which is applied to the body, connected by rubber or plastic tubes to shaped earpieces for the examiner [McFerran, 1998]. Stethoscopes, the workhorse of practice, have stood the test of time and have been proven to be robust and reliable [Tytan Medical, 2003].
Modern stethoscopes are extremely sensitive and highly advanced instruments, which will continue to improve even more [Tytan Medical, 2003]. Electronic stethoscopes are available and, in this hospital, are mainly used by cardiologists. In A&E ordinary ones are used, from personal preference.
The stethoscope allows the practitioner to assess a patient’s cardiac, respiratory and intestinal state and is an integral tool in professional nursing practice. It is used to listen [auscultation] to the body’s sounds during a physical examination and assessment. Health-care professionals routinely auscultate a patient’s lungs, heart, and intestines to evaluate the frequency, intensity, duration, number, and quality of sounds [Kummar and Clark, 1999].
In A&E nurses mainly use stethoscopes for chest auscultation. In the community they are generally used when monitoring blood pressure.
Using the stethoscope
Before using a stethoscope, the practitioner must tell the patient what he or she wants to assess and seek permission [NMC, 2002]. The patient should be placed in a comfortable position: either sitting upright leaning forward for cardiorespiratory assessment or lying supine or lateral for abdominal auscultation.
The practitioner should address any anxieties, so the patient is relaxed. Being tense can increase heart rate muscle tone [Welsby, 1996]. Once the patient has given consent, is relaxed and in the correct position, the practitioner can begin.
The practitioner must ensure the earpieces of the stethoscope are placed comfortably into the ears. If they are too tight this will this not only cause discomfort, but reduce sound quality; a snug fit is required to ensure good passage of sound down the auditory canal [Kummar and Clark, 1999].
The tubing should be as short as possible, preferably around 48cm. Conducting sound through a shorter distance of tubing reduces further background noise [3M Health Care, 2003].
The practitioner should firmly apply the chest piece to the area of the body about to be auscultated. The diaphragm is normally used for high-frequency sounds and murmurs, and the bell for low and medium frequency sounds [3M Health Care, 2003].
The chest piece should always be placed against the patient’s skin and not over clothing, as the latter reduces the validity and accuracy of sounds and picks up the rubbing of clothing fibres [3M Health Care, 2003].
The diaphragm should be applied with reasonable pressure, ensuring that the patient is not hurt, and the bell piece should be applied lightly. Stretching the tubing can decrease quality of sound.
Assessment
Cardiovascular assessment
Assessment of the cardiovascular system using a stethoscope is common. The heart has four chambers. The two upper chambers are called the atria; and the two lower chambers are called the ventricles. Valves that temporarily close to permit blood flow in only one direction are located between the atria and ventricles, and between the ventricles and the major arteries from the heart and to the lungs [Marieb, 1998].
Normal heart sounds are called S1 and S2. They are the ‘lubb-dupp’ sounds thought of as the heartbeat and are produced when the heart valves close. Because the heart is also divided into a ‘right side’ and a ‘left side’, sometimes these sounds may be divided; most commonly noted is a ‘split S2’, caused when the right and left ventricles contract at very slightly different times [Marieb, 1998]. This is a normal finding, but occasionally the nature of the split can indicate an abnormality such as enlargement of one of the ventricles [Kummar and Clark, 1999].
Murmurs are blowing, whooshing, or rasping sounds. They are the result of vibrations caused by turbulent blood-flow patterns. This can happen when a valve does not close tightly, such as with mitral regurgitation, or when the blood is flowing through a narrowed opening or a stiff valve, such as with aortic stenosis [Kummar and Clark, 1999].
A murmur does not necessarily indicate a disease or disorder, and all heart disorders do not cause murmurs [Kummar and Clark, 1999]. Murmurs are classified or graded according to the examiner’s ability to hear them. On this scale, grade I means barely detectable. An example of a murmur description is a ‘grade II/VI murmur’, meaning the murmur is grade II on a scale of I to VI [Kummar and Clark, 1999].
The health-care practitioner should also note the location where the murmur is loudest.
The stethoscope is placed over the following areas of the chest in order to auscultate heart sounds [Figure 1]:
- Aortic area: second intercostal space along the right base [a]
- Pulmonic area: second intercostal space along left base [b]
- Tricuspid area: fourth and fifth intercostal space along the lower left sternal border [c]
- Mitral area: cardiac apex [d]
- Xiphoid [e].
Lung assessment
Normal lung sounds occur in all parts of the chest area, including above the clavicle and as low as the bottom of the rib cage. When listening to the lungs, the categories of findings include:
- Normal breath sounds
- Decreased or absent breath sounds
- Abnormal breath sounds.
Absent or decreased sounds are inaudible [absent] or reduced in volume [decreased] compared with other areas of the lung when the lungs are examined with a stethoscope. They reflect reduced airflow to a portion [segment] of the lungs; overinflation of a portion of the lungs, such as with emphysema; air or fluid around the lungs; or sometimes increased thickness of the chest wall, namely pneumothorax or haemothorax [Marieb, 1998].
There are several types of abnormal breath sounds: rales, rhonchi, and wheezes are the most common [Marieb, 1998].
Rales: Rales - crackles or crepitations - are small clicking, bubbling, or rattling sounds in a portion of the lung. They are believed to occur when air opens closed alveoli [air spaces]. Typical ways to describe rales include moist, dry, fine, coarse.
Rhonchi: Rhonchi are sounds that resemble snoring. They are produced when air movement through the large airways is obstructed or turbulent.
Wheezes: Wheezes are high-pitched, musical sounds produced by narrowed airways, often occurring during expiration [Welsby, 1996].
Where to auscultate Figure 2 shows where to auscultate when examining the lungs. The process has seven steps, as follows:
- 1. Systematic examination
- 2. From apex to base
- 3. Side to side
- 4. Symmetrical comparison
- 5. Anterior aspect
- 6. Posterior aspect
- 7. Lateral aspect.
Abdominal sounds
Abdominal sounds [bowel sounds] are made by the movement of the intestines as they push food through. Since the intestines are hollow, bowel sounds can echo throughout the abdomen, much like the sounds heard from water-pipes. Most bowel sounds are benign and simply indicate that the gastrointestinal tract is working [Welsby, 1996]. However, in some instances abnormal bowel sounds provide valuable information about the health of the body.
Absent bowel sounds Take, for example, absent bowel sounds - ileus. The examiner is unable to hear any bowel sounds after listening to the abdomen, indicating a lack of intestinal activity [Welsby, 1996]. Many medical conditions may lead to this but it is important to evaluate it further because gas, secretions, and intestinal contents can accumulate and rupture the bowel wall.
Reduced bowel sounds Reduced [hypoactive] bowel sounds include a reduction in the loudness, tone, or regularity of the bowel sounds. They indicate a slowing of intestinal activity. Hypoactive bowel sounds are normal during sleep, and also occur normally for a short time after the use of certain medications and after abdominal surgery [Marieb, 1998]. Very often decreased or absent bowel sounds may indicate constipation.
Increased bowel sounds Increased [hyperactive] bowel sounds are sometimes heard even without a stethoscope. Hyperactive bowel sounds reflect an increase in intestinal activity. This can sometimes be seen in patients with diarrhoea and after eating [Marieb, 1998].
Abdominal sounds are always evaluated alongside symptoms such as nausea, vomiting, presence or absence of bowel movements or gas. If bowel sounds are hypo- or hyperactive, and are accompanied by other abnormal symptoms, continued evaluation by a health-care professional is important. For example, absent bowel sounds after a period of hyperactive bowel sounds can indicate that rupture of the intestines, or strangulation of the bowel with subsequent death [necrosis] of the bowel tissue may have occurred [Marieb, 1998].
Considerations for practice
The stethoscope should be able to detect both faint, high-pitched sounds and low-pitched sounds; it should have short tubing, snug earpieces, and a chest piece consisting of both a diaphragm and bell [3M Health Care, 2003].
Various types of stethoscope are available, from expensive advanced devices such as the Littmann Cardiology III through to cheaper standard stethoscopes. Companies have carried out their own research looking at the quality of the tubing and chest piece, and have had their products evaluated in practice by cardiorespiratory physicians. But a search by this author of Medline, Cinahl, the British Medical Journal and the British National Library found few objective studies comparing different brands. One worth mentioning is a comparison by Lukin et al [1996].
In the more expensive models there have been developments such as sensitive diaphragms designed to detect more subtle sounds. The tubing is designed to be more soundproof, allowing only the noise detected by the chest piece to travel up the tubing and into the earpiece.
The quality of the stethoscope can make a difference in auscultation of the patient, according to manufacturer claims and reports by doctor colleagues. These state that using a cheaper model could potentially lead to faint heart murmurs being missed [3M Health Care, 2003; Tytan Medical, 2003].
Training and education
Auscultation is very subjective and depends on the ability and preferences of the individual performing it. Research shows cardiologists are more proficient at using auscultation to diagnose heart conditions compared with other health professionals [Perloff, 1990].
Education and training is important. Auscultation used to be predominantly a doctor’s role, but over the years the skill has shifted to nurses and physiotherapists, who now routinely use a stethoscope [Robinson, 1993].
Doctors are taught to auscultate throughout their five-year training, while physiotherapists are taught during their three-year training. Nurses, however, are not taught auscultation in training. This is mostly a post-registration skill taught in critical care courses such as the emergency care, coronary care and nurse practitioner courses.
Education should enable the practitioner to differentiate the sounds produced and understand why they are occurring. Knowledge of anatomy and physiology as well as the tool’s application are needed to understand why certain sounds are produced and make suitable clinical decisions.
This author would argue in favour of combined clinical training for nursing and medical students in certain core areas of practice, including A&E, to ensure the same standards, and ultimately to deliver safe practice and a high-quality service.
Infection control
The potential for passing on ear infections is an increased risk when communal stethoscopes hung up in the department are used by a lot of people.
This highlights the importance of cleaning and maintaining stethoscopes. Both personal and communal stethoscopes should be prepared regularly before being used.
The stethoscope should be cleaned with soap and water and allowed to dry naturally, and should be checked for cracks/splits and other damage every week.
The chest piece should be cleaned with an alcohol wipe when used between different patients, as there is a potential cross-infection risk.
Conclusion
The stethoscope is an invaluable tool in the assessment of heart, lung and abdominal sounds. It is easy to use, portable, relatively inexpensive, relative safe to use in practice and when used correctly is invaluable for detecting pathological disease in patients.
Practitioners need knowledge of how the stethoscope works, an understanding of the pathophysiology of the human body and of infection risks to ensure the tool is safely and correctly used for the benefit of the patient.
Combined nursing and medical training in assessment, anatomy and physiology would ultimately ensure that appropriate standards were achieved.
The evidence-based approach to clinical practice aims to deliver appropriate care in an efficient manner to each patient. The lack of research comparing stethoscope types and comparing the way different health professionals use stethoscopes is a gap that needs addressing in order to ensure the best possible care for patients. Such information would help practitioners to perfect their skills.
An increased evidence base would enable nurses to be selective about which items of clinical information to attend to, to generate a broader range of initial hypotheses and to link these together in an efficient and meaningful way [Carnevali, 1993].
Only by questioning practice, conducting and reviewing research periodically, can nurses deliver informed, high-quality care to their patients.
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