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PubMed2005

Cardiac auscultation training of medical students: a comparison of electronic sensor-based and acoustic stethoscopes.

BACKGROUND: To determine whether the use of an electronic, sensor based stethoscope affects the cardiac auscultation skills of undergraduate medical students. METHODS: Forty eight third year medical students were randomized to use either an electronic stethoscope, or a conventional acoustic stethoscope during clinical auscultation training. After a training period of four months, cardiac auscultation skills were evaluated using four patients with different cardiac murmurs. Two experienced cardiologists determined correct answers. The students completed a questionnaire for each patient. The thirteen questions were weighted according to their relative importance, and a correct answer was credited from one to six points. RESULTS: No difference in mean score was found between the two groups (p = 0.65). Grading and characterisation of murmurs and, if present, report of non existing murmurs were also rated. None of these yielded any significant differences between the groups. CONCLUSION: Whether an electronic or a conventional stethoscope was used during training and testing did not affect the students' performance on a cardiac auscultation test.

Cardiology↗

PubMed2001

On stethoscope design: a challenge for biomedical circuit designers.

Most clinicians learned the art and science of auscultation using an acoustic stethoscope. While many models of electronic stethoscopes have been marketed over the years, none of them seem to do a very good job of emulating the most common forms of acoustic stethoscopes available. This paper is an appeal to biomedical circuit designers to learn more about the acoustics of commonly used stethoscopes and to develop an appropriate group of circuits which would emulate them much like music synthesizers can emulate almost any musical instrument. The implications are for creative designers to move toward a rational and acceptable design for both personal physician use and for telemedicine.

Equipment Design↗

PubMed2004

A prospective, randomised, double-blind study of comparative efficacy of immediate versus daily cleaning of stethoscope using 66% ethyl alcohol.

OBJECTIVE: Studies have demonstrated frequent contamination of stethoscope and usefulness of different disinfectants. Albeit, studies on the precise mode of cleaning and frequency of cleaning are lacking. This study was carried out to determine efficacy of 66% ethyl alcohol as disinfectant, rate of recontamination without cleaning and benefits of daily versus immediate cleaning. METHODOLOGY: Prospective, randomised, double blind study of 100 stethoscopes. Four cultures were obtained: before cleaning (Group A), immediately after cleaning with 66% ethyl alcohol (Group B), at the end of 4 days without cleaning (Group C) and at the end of 4 days after cleaning once a day (Group D). Samples were analysed using standard microbiological methods and Colony-forming unit (CFU) count and residual microorganism was computed for all the positive cultures. Medical staff was asked about the cleaning practices. Statistical analysis was carried out using 95% confidence interval and Chi-square test. RESULTS: 90% of the stethoscopes were contaminated with one or more microorganisms. Immediate cleaning and daily cleaning were associated with a significant reduction in the rate of contamination to 28% and 25% respectively. CFU count in groups B and D dropped to less than 10 in 75% and 84.7%, while the mean residual rates were 5.2% and 3.65% respectively. Groups B and D showed no statistically significant difference in terms of efficacy of disinfection. CONCLUSIONS: 66% ethyl alcohol is an effective disinfectant. The effects of immediate cleaning and cleaning once a day on residual flora on the diaphragm of stethoscope is comparable.

Disinfectants↗

PubMed1984

Measurement of left ventricular ejection fraction in pediatric patients using the nuclear stethoscope.

Left ventricular (LV) ejection fraction (EF) was measured in 25 patients, aged 2 weeks to 20 years (mean 8.6 years), using a portable nonimaging scintillation stethoscope. Technically satisfactory studies were obtained in 23 patients. LVEF was validated by cineangiography in 19 patients and by standard gated blood pool scintigraphy in 4. EF measured by the nuclear stethoscope correlated well with values obtained by cineangiography or scintigraphy (r = 0.869, p less than 0.001) over a wide range of EF values (18 to 79%). In children younger than 5 years (n = 11), the correlation (r = 0.728, p less than 0.02) was less satisfactory than in those older than 5 years (r = 0.926; p less than 0.001). Although modifications in the instrument and further clinical trials with the stethoscope are needed before the device becomes clinically useful to pediatric cardiologists, our data indicate that the nuclear stethoscope can provide reliable assessment of LVEF in pediatric patients.

Adolescent↗

PubMed2000

Stethoscopes and nosocomial infection.

Stethoscopes are an essential tool of the medical profession and can become a source of nosocomial infection. A study conducted in the Department of Pediatrics, Kasturba Medical College and Hospital showed a high carriage of methicillin resistant staphylococcus (69.76%) and multi-drug resistant Gram negative bacilli (20.93%) on regularly used stethoscopes. The antibiogram of the bacterial isolates strongly suggested these to be nosocomial strains. A verbal survey revealed that regular cleaning is not common among doctors. A policy regarding cleaning of stethoscopes with an effective disinfectant may be helpful in reducing hospital-associated infections.

Child↗

PubMed1997

Bacterial flora of stethoscopes' earpieces and otitis externa.

External otitis caused by Staphylococcus aureus was observed in a nurse after extensive use of a stethoscope. The infection recurred and a similar organism was isolated from the stethoscope's earpiece. The infection did not recur after the earpiece was cleansed after each use. In a prospective study, the bacterial flora of 35 earpieces was evaluated. Fifty-three isolates, 36 aerobic or facultative and 17 anaerobic, were recovered. The number of organisms per earpiece ranged from 14 to 204 (average 92 +/- 17). The predominant isolates were Staphylococcus epidermidis (16 isolates), Propionibacterium acnes (12), and Saureus (7). The study demonstrates the colonization of the stethoscope's earpiece with microorganisms that possess the potential for causing nosocomial infection.

Adult↗

PubMed2000

Potential infection hazards of stethoscopes.

This study was conducted to assess the bacterial flora carried on stethoscopes used by medical personnel and to study the effect of disinfection of stethoscopes on the flora. In the 106 stethoscopes sampled, Gram-positive organisms were the most (60%) frequently isolated. Among them, Staphylococcus aureus accounted for 15.8% of the flora of which 21% were resistant to methicillin. The rate of isolation of S aureus and methicillin resistant S aureus (MRSA) was higher in critical care units. Disinfection was found to significantly reduce the bacterial count.

Colony Count, Microbial↗

PubMed2003

Using a stethoscope in clinical practice in the acute sector.

Unlike doctors and physiotherapists, nurses do not learn to use stethoscopes as part of their normal training. This is mostly a post-registration skill, often taught in critical care courses. Yet the stethoscope is an invaluable tool in the assessment of heart, lung and abdominal sounds. This paper looks at when and how stethoscopes can contribute to patient care.

Critical Care↗

PubMed1963

Cardiovascular sound and the stethoscope, 1816 to 2016.

Cardiovascular sound escaped attention until Laennec invented and demonstrated the usefulness of the stethoscope. Accuracy of diagnosis using cardiovascular sounds as clues increased with improvement in knowledge of the physiology of circulation. Nearly all currently acceptable clinicopathological correlations were established by physicians who used the simplest of stethoscopes or listened with the bare ear. Certain refinements followed the use of modern methods which afford greater precision in timing cardiovascular sounds. These methods contribute to educating the human ear, so that those advantages may be applied which accrue from auscultation, plus the method of writing quantitative symbols to describe what is heard, by focusing the sense of hearing on each segment of the cardiac cycle in turn. By the year 2016, electronic systems of collecting and analyzing data about the cardiovascular system may render the stethoscope obsolete.

Auscultation↗

PubMed1990

Placement of esophageal stethoscope by acoustic criteria does not consistently yield an optimal location for the monitoring of core temperature.

The esophageal stethoscope has evolved into a device for both acoustic and core temperature monitoring. To test whether routine placement according to acoustic criteria results in placement of the core temperature sensor in the region of contiguity between the esophagus and the heart, we determined the depth of placement electrocardiographically. All patients were undergoing nonthoracic elective operations requiring general anesthesia and tracheal intubation. First, we established that different observers selected the same esophageal depth within +/- 1 cm electrocardiographically, using the criterion of a symmetric biphasic P wave of maximal amplitude (7 patients). Then, in 30 more patients, we compared routine acoustic placements with the depths of the maximal-amplitude biphasic P wave. Stethoscopes placed according to acoustic criteria were within +/- 3 cm of P-wave depths in 15 of 30 patients. In the remaining patients, measured discrepancies ranged up to 13.5 cm. We conclude that the prevailing stethoscope design, with a thermistor at the tip, below the acoustic window, does not ensure placement of the thermistor within the optimal region for monitoring of core temperature. A modification in design that would take advantage of the reliability of electrocardiographic positioning is suggested.

Acoustics↗

PubMed1995

Stethoscope contamination in the neonatal intensive care unit.

The level of contamination of stethoscopes used in a neonatal intensive care unit was studied, along with the practices used for cleaning these items. A policy of alcohol cleaning was introduced and the effect of this change on the level of bacterial growth was observed after a six-week period. It was found that 71% of stethoscopes had a significant bacterial growth and that this was reduced to 30% after the cleaning procedure change (P < 0.05). Stethoscopes and other equipment are a potential source of nosocomial infection on the neonatal intensive care unit.

Alcohols↗

PubMed1977

The use of the Doppler stethoscope in the evaluation of varicoceles.

Twenty-eight clinically detectable varicoceles of various sizes were examined with a Doppler ultrasonic stethoscope. Retrograde blood flow through the left internal spermatic vein was confirmed in all cases irrespective of size of the vascular abnormality. The Doppler stethoscope also was used to evaluate 13 patients suspected of having varicoceles but with inconclusive physical examinations. Retrograde flow through the internal spermatic vein could likewise be auscultated in 5 of these patients. Finally, the Doppler stethoscope was used to determine the adequacy of internal spermatic vein ligation in 5 postoperative patients whose seminal dysfunction persisted despite what appeared to be a surgically effective correction of aberrant gonadal venous flow.

Epididymis↗

PubMed1991

Hand-free stethoscope--method and instrument for more reliable blood pressure measurements.

Measurement of blood pressure is subject to two sources of variation: biological and measurement variation. It is important to bear in mind that the ability to interpret the Korotkoff sounds correctly determines the levels of both systolic and diastolic blood pressure. To improve the ability to distinguish between the Korotkoff phases, the handfree stethoscope and the hand-free method were developed. The improved stethoscope head was fixed under the edge of the cuff, thus reducing the noise generated from physiological tremor and other movements. This resulted in more distinct Korotkoff sounds. Furthermore, the new method reduced the spreading of blood pressure values. In 107 patients the average systolic blood pressure recording was 3.1 mmHg higher and the average diastolic blood pressure was 3.5 mmHg lower. We conclude that the new stethoscope and technique provide a means of significantly improving the indirect measurement of blood pressure.

Adult↗

PubMed1980

The Doppler stethoscope in the diagnosis of subclinical varicocele.

Fifty-six patients (112 testicular cords) were examined using the Doppler stethoscope. Venous reflux was detected in all patients with a clinically obvious varicocele and in 77% of patients where a varicocele was suspected but not clinically demonstrated. The incidence of bilateral varicoceles was 21%. The Doppler stethoscope showed that 20% of patients continued to have venous reflux post-operatively. It is concluded that the Doppler stethoscope is a useful instrument in the diagnosis of clinical varicoceles and in the assessment of post-operative results.

Auscultation↗

PubMed1990

[Use of stethoscope by mothers of asthmatic children ages 1-5].

The mothers of 24 asthmatic children aged 1-5 years, who visited a department of family medicine at the time of the attacks, were assigned alternately to 2 groups. The experimental study group got guidance and instruction in the use of the stethoscope, and also participated in a self-management educational program led by the family physician. The control group only got guidance and participated in the latter program. The purpose of the study was to determine whether mothers could assume more responsibility in decision-making with regard to their children's asthmatic attacks after basic technical guidance in the use of the stethoscope and in the interpretation of auscultatory findings. The results show that the initial steps in self-management were adequate in the 2 groups. These included recognition of the first signs of asthma in the child, a relaxed attitude (not to panic), the dispensing of suitable amounts of fluid, and the administration of bronchodilator medication without waiting for the physician's examination. Instructions to continue bronchodilator drugs, both oral and by inhaler, were more detailed in the experimental group. During the year of follow-up there were fewer visits to the clinic and the emergency room and no hospital admissions by those in the experimental group. The main conclusion of this study is that in conjunction with a self-management program, it is possible to teach mothers to use a stethoscope, to correctly interpret the auscultatory findings and accordingly, to give adequate treatment. This reduces clinic and emergency room visits and hospital admissions, relieves anxiety, and increases confidence in coping with this illness.

Adult↗

PubMed1988

Flammability of esophageal stethoscopes, nasogastric tubes, feeding tubes, and nasopharyngeal airways in oxygen- and nitrous oxide-enriched atmospheres.

This study determines the flammability of materials in the oral cavity and pharynx during anesthesia in an environment of potentially high oxygen (O2) and nitrous oxide (N2O) concentrations where an ignition source (cautery, laser) may be in close proximity. The materials tested included esophageal stethoscopes, Salem sump nasogastric tubes, enteric feeding tubes, and plastic and rubber nasopharyngeal airways. Flammability was determined using oxidant O2 and oxidant N2O indices of flammability. The oxidant O2 and oxidant N2O indices of flammability are defined as the minimum fraction of oxidant (O2 or N2O) in nitrogen diluent that supports a candle-like flame for a given fuel source. The oxidant O2 index of flammability for esophageal stethoscopes is 0.218, for Salem sump nasogastric tubes 0.229, for enteric feeding tubes 0.192, for plastic nasopharyngeal airways 0.196, and for rubber nasopharyngeal airways 0.172. The oxidant N2O index of flammability for esophageal stethoscopes is 0.430, for Salem sump nasogastric tubes 0.430, for enteric feeding tubes 0.375, for plastic nasopharyngeal airways 0.415, and for rubber nasopharyngeal airways 0.366. These indices are linearly additive.

Auscultation↗

PubMed1997

Home self-monitoring of blood pressure: is fully automated oscillometric technique as good as conventional stethoscopic technique?

Home blood pressure (HBP) measurement is becoming increasingly popular as an additional source of information for the practicing physician. Whether HBP measured with a fully automated oscillometric device (oHBP) is more reliable than HBP measured with an aneroid sphygmomanometer and a stethoscope (sHBP) remains unclear. We compared sHBP with oHBP using as a reference method daytime ambulatory blood pressure (ABP), as this is believed to be a better index of an individual's overall level of pressure. Forty-six hypertensive patients measuring HBP with aneroid devices were retrained by a standard 30 min protocol that included training in the technique of measurement, checking patients' devices, and testing patients' performance in stethoscopic measurement. Patients were randomized to measure for 2 weeks either sHBP using their own calibrated aneroid devices or oHBP using a validated fully automated oscillometric device (Omron HEM-705CP). Then 24 h ABP monitoring was performed (SpaceLabs 90207) and patients crossed over for a second 2 week period by using the alternative HBP measurement technique. Mean sHBP was not different from mean oHBP, and there was a close correlation between them (r = 0.82/0.76 for systolic/diastolic BP, P < .001). Daytime ABP was not different from oHBP or sHBP and was closely related to both of them (oHBP, r = 0.59/0.72 systolic/diastolic BP, P < .001; sHBP, 0.50/0.65, P < .001). Age was significantly related with diastolic ABP-sHBP difference (r = 0.33, P < .05). These results suggest that HBP measured with validated fully automated oscillometric devices is equally reliable in predicting average ABP as that measured with calibrated aneroid sphygmomanometers used by very carefully trained patients. In clinical practice, HBP monitoring by using reliable automated devices is probably more feasible than to achieve a high standard of stethoscopic HBP measuring technique.

Adult↗

PubMed2002

Fiber-optic stethoscope: a cardiac monitoring and gating system for magnetic resonance microscopy.

A fundamental problem associated with using the conventional electrocardiograph (ECG) to monitor a subject's cardiac activity during magnetic resonance imaging (MRI) is the distortion of the ECG due to electromagnetic interference. This problem is particularly pronounced in MR microscopy (MRI of small animals at microscopic resolutions (< 0.03 mm(3))) because the strong, rapidly-switching magnetic field gradients induce artifacts in the animal's ECG that often mimic electrophysiologic activity, impairing the use of the ECG for cardiac monitoring and gating purposes. The fiber-optic stethoscope system offers a novel approach to measuring cardiac activity that, unlike the ECG, is immune to electromagnetic effects. The fiber-optic stethoscope is perorally inserted into the esophagus of small animals to optically detect pulsatile compression of the esophageal wall. The optical system is shown to provide a robust cardiac monitoring and gating signal in rats and mice during routine cardiac MR microscopy.

Animals↗