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At least 19 recordsLinked to original sources
PubMed1986

An electronic stethoscope is judged better than conventional stethoscopes for anesthesia monitoring.

A prototype electronic monitoring stethoscope was constructed from readily available, high-quality components. It consisted of a conventional precordial or esophageal probe connected to a microphone by a rubber adapter. The microphone was connected by lightweight wire to an amplifier and headphones. Twenty-one anesthesia clinicians evaluated the stethoscope and responded to a multiple-choice preference questionnaire. The electronic stethoscope was judged to perform better than the conventional stethoscope in most categories evaluated. The electronic device was perceived to be louder, clearer in sound reproduction, more efficacious for monitoring, and easier to use continuously, and its headphones were considered more comfortable than the conventional earpiece. Based on our results, we conclude that amplified stethoscopes have the potential to improve monitoring. Further development of electronic stethoscope monitoring seems warranted and is continuing.

Anesthesia↗
PubMedDate not supplied

[Comparison of auscultation findings using a classic stethoscope (Litmann 2120) and electronically amplified stethoscope (Medmax2)].

Heart auscultation has one of the key roles in beside diagnosis, especially in patients with cardiovascular diseases. Sometimes, because of the human cars' low sensitivity, a problem emerges in the proper evaluation of heart sounds and murmurs of lower frequencies. Our study compared two stethoscopes, the classic acoustic stethoscope (Littmann 2120) and an electronic one with the sound amplifier and the noise filtering system (Medmax2) in 10 patients examined by 10 physicians. Significantly better detection of low frequency sounds was found in favour of electronic stethoscope (chi 2 = 17.9; p < 0.0001). It is concluded that the selective amplificator improves the stethoscope performance and has its place in everyday bedside practice, especially in departments of cardiology.

Aged↗
PubMed1997

The stethoscope. A potential source of nosocomial infection?

BACKGROUND: Stethoscope diaphragms have been shown to harbor potentially pathogenic bacteria. OBJECTIVES: To assess bacterial contamination on the diaphragm and under the plastic rim that secures the diaphragm of stethoscopes of physicians, nurses, medical students, and house staff in an intensive care unit and a general medical ward of a large university hospital. Also to compare the effectiveness of various cleaning agents and assess the transmissibility of bacteria from contaminated stethoscopes to human skin. METHODS: Aerobic and anaerobic bacterial cultures were performed on 40 randomly selected stethoscopes. We compared the effects of isopropyl alcohol, sodium hypochlorite (bleach), and benzalkonium chloride swabs, as well as soap and water, on reducing bacterial contamination on the stethoscope diaphragm and under the rim. The transmissibility of Micrococcus luteus inoculated onto a stethoscope diaphragm to clean human skin was also determined. RESULTS: Eleven genera and species of bacteria were isolated, with coagulase-negative staphylococcus present on 100% of stethoscopes and Staphylococcus aureus on 38%. Clostridium difficile was not isolated. The mean (+/-SE) number of total colony-forming units was 158 +/- 33 per diaphragm and 289 +/- 54 per rim. Physicians' stethoscope diaphragms had significantly more colony-forming units of coagulase-negative staphylococci than those of nurses: 163 +/- 44 vs 50 +/- 12, respectively (P = .02). The most effective cleaning agent was isopropyl alcohol after cleaning the diaphragm surface, the stethoscope diaphragms contained 0.2 +/- 0.2 colony-forming units and the rims contained 2.2 +/- 1.5 colony-forming units (P = .01). In addition, M luteus was transferred from inoculated stethoscopes to human skin. CONCLUSIONS: Most stethoscopes harbor potential pathogens but are not a source of C difficile. Physicians' stethoscopes generally had a higher bacterial load than nurses' stethoscopes. Isopropyl alcohol is an effective cleaning agent when applied to the stethoscope diaphragm. Stethoscopes transfer M luteus to human skin, making it likely that other bacteria can be transferred as well.

Cross Infection↗
PubMed1996

Contaminated stethoscopes revisited.

BACKGROUND: Because of their universal use by medical professionals, stethoscopes can be a source of nosocomial infections. OBJECTIVE: To determine the frequency of contamination of stethoscopes with bacteria and fungi. METHODS: Cultures were obtained from 200 stethoscopes from four area hospitals and outpatient clinics in Houston, Tex. The frequency of stethoscope contamination in different groups of hospital personnel and medical settings was determined. We also measured the frequency of antimicrobial resistance of the staphylococcal strains that were isolated. RESULTS: One hundred fifty-nine (80%) of the 200 stethoscopes surveyed were contaminated with microorganisms. The majority of organisms that were isolated were gram-positive bacteria, primarily Staphylococcus species. Fifty-eight percent of the Staphylococcus species that were isolated, including four (17%) of 24 Staphylococcus aureus isolates, were resistant to methicillin. Physicians' stethoscopes were contaminated more often than those of other medical personnel groups (P = .02). Stethoscopes used only in designated areas were contaminated less frequently than stethoscopes belonging to individual medical personnel (P = .01). Although stethoscopes were contaminated in all areas, stethoscopes from the pediatric medical setting were contaminated less frequently than those from other hospital areas (P = .009). CONCLUSIONS: Stethoscope use may be important in the spread of infectious agents, including antimicrobial-resistant strains, and strategies to reduce the contamination of stethoscopes should be developed. We recommend disinfection of stethoscopes or regular use of disposable stethoscope covers.

Auscultation↗
PubMed1990

Observer reliability in detecting surreptitious random occlusions of the monaural esophageal stethoscope.

The esophageal stethoscope is used often during anesthesia to monitor ventilation and cardiac function. Deficiencies in observer vigilance may limit the effectiveness of this monitoring instrument. The aim of this study was to determine how long it took for an observer to detect a surreptitiously occluded monaural esophageal stethoscope in the setting of clinical anesthesia. During routine anesthesia, where an esophageal stethoscope was in use, a computer-guided device would artificially, silently, and at random time intervals, occlude the stethoscope tubing. Personnel using the stethoscope noted when they perceived the absence of stethoscope sounds. We studied 320 stethoscope occlusions in 32 patients. The time between stethoscope occlusion and detection was 34 +/- 59 seconds (mean +/- SD). Eighty-seven percent of detections were made in less than 60 seconds. However, 13% of detections were delayed for more than 60 seconds, and 2.3% for more than 240 seconds. While anesthesia personnel using an esophageal stethoscope could detect most stethoscope occlusions, failure to appreciate such episodes occurred in a small but significant number of cases. This suggests that the esophageal stethoscope has some definite limitations as a continuous monitor and that other monitoring techniques, such as oximetry, capnography, and ventilator disconnect alarms, as well as visual/tactile inspection of the patient, should be used as well.

Anesthesia, General↗
PubMed1995

Use of esophageal or precordial stethoscopes by anesthesia providers: are we listening to our patients?

STUDY OBJECTIVE: To ascertain current anesthesia utilization of esophageal and precordial stethoscopes in U.S. anesthesia training programs. DESIGN: Prospective, single-blind, incidence study. SETTING: Operating rooms of three tertiary care hospitals with major academic anesthesiology departments. SUBJECTS: Anesthesia faculty [MD and certified registered nurse-anesthetist (CRNA) staff] and anesthesia trainees (anesthesiology residents and student nurse-anesthetists). INTERVENTIONS: observe and record the placement (stethoscope device appropriately positioned) and utilization (stethoscope in place and connected to the ear piece of the anesthesia provider) of the esophageal or precordial stethoscope during general, regional, and monitored anesthesia care. MEASUREMENTS AND MAIN RESULTS: During 520 anesthetics, an esophageal stethoscope was inserted in 68% of subjects, a precordial stethoscope was positioned in 16%, and an anesthetic stethoscope was absent in 16% of cases. Utilization (stethoscope connected to earpiece) ranged from a low of 11% of cases to a high of 45%, depending on the institution. Overall, providers were listening via an anesthetic stethoscope in only 28% of anesthetics. CONCLUSIONS: Our data suggest infrequent utilization of esophageal and precordial stethoscopes in anesthesia training institutions. Thus, current anesthesia training may be fostering an environment where providers overlook a valuable minimally invasive, and cost-effective continuous monitor of patients' dynamic vital organ function.

Anesthesia Department, Hospital↗
PubMed1995

Stethoscopes: a potential vector of infection?

STUDY OBJECTIVES: To survey emergency care providers about their stethoscope-cleaning measures and to determine the correlation between these measures and the extent of Staphylococcus carriage. DESIGN: Prospective cross-sectional analysis. SETTING: University-affiliated community hospital ED. PARTICIPANTS: One hundred fifty health care providers, comprising emergency medicine house staff and attending physicians (n = 50), ED nurses (n = 50), and prehospital personnel working in Kent County, Michigan (n = 50). INTERVENTIONS: Providers were asked how often they cleaned their stethoscopes and which cleaning agents were used. We then cultured each stethoscope by pressing the diaphragm on mannitol agar and incubating the culture aerobically for 48 hours. Staphylococcus aureus was identified by means of standard measures. We examined the effects of different cleaning agents on 24 stethoscopes. The numbers of colony-forming units (CFUs) before and after cleaning with alcohol, nonionic detergent, and antiseptic soap were noted. RESULTS: Overall, 48% of health care providers (74 of 150) cleaned their stethoscopes daily or weekly, 37% monthly, and 7% yearly; and 7% had never cleaned their stethoscopes. No significant differences were found in the hygiene routines of the three groups of providers surveyed. Use of an alcohol swab was the preferred method of cleaning. One hundred thirty-three stethoscopes (89%) grew staphylococci; 25 (19%) yielded S aureus. Mean staphylococcal bacterial counts ( +/- SD) were 52 +/- 78 CFUs per stethoscope among physicians, 46 +/- 92 CFUs among emergency medical service personnel, and 13 +/- 21 CFUs from the nursing staff (ANOVA, P = .01). Cleaning the stethoscope diaphragm resulted in immediate reduction in the bacterial count: by 94% with alcohol swabs, 90% with nonionic detergent, and 75% with antiseptic soap. CONCLUSION: Our results confirm that stethoscopes used in emergency practice are often contaminated with staphylococci and are therefore a potential vector of infection. This contamination is greatly reduced by frequent cleaning with alcohol or nonionic detergent.

Auscultation↗
PubMed1995

[Frequency analysis of crackles recorded with a stethoscope-equipped recorder].

Crackles were recorded with one of two systems in a total of 58 cases and compared. In one system a stethoscope was attached to a microphone; in the other system no stethoscope was used (see reference 9). Coarse crackles were recorded with the stethoscope system in 11 patients, and with the microphone-only system in 12 patients. Most patients with coarse crackles had bronchiectasis. Fine crackles were recorded with the stethoscope system in 13 patients, and with the microphone-only system in 22 patients. Most patients with fine crackles had idiopathic pulmonary fibrosis. Each record was examined visually, and all crackles recorded during one inspiration were selected. Power spectra were estimated with the maximum entropy method and peak frequencies were determined with the damped least-squares method. Type-I crackles were defined as those with all peak frequencies below 800 Hz; these low-pitched sounds may correspond to coarse crackles. Type-II crackles were defined as those with peak frequencies over 800 Hz regardless of the existence of peaks below 800 Hz; these high-pitched sound may correspond to fine crackles. The "%Type II" was defined as the percentage of the total crackles that were Type-II crackles. The %Type II value among coarse crackles was 10 +/- 16% with the stethoscope and 3 +/- 7% with the microphone. Among fine crackles, the values were 65 +/- 22% with the stethoscope and 79 +/- 23% with the microphone. For both kinds of equipment, the %Type II differed significantly between coarse and fine crackles (p < 0.01). The stethoscope-transmitted sound had components that could be used to differentiate fine crackles from coarse crackles. For clinical purposes, crackles recorded with a stethoscope are as useful as those recorded with a microphone only.

Auscultation↗
PubMed1985

Accuracy of left ventricular ejection fraction using the nuclear stethoscope in left ventricular aneurysm.

Although the nuclear stethoscope, a nonimaging probe, accurately determines left ventricular (LV) ejection fraction (EF), its reliability in patients with LV aneurysm has not been established. Accordingly, LVEF was determined using the nuclear stethoscope and compared with that determined by equilibrium gated blood pool scanning in 29 patients, 1 studied on 2 separate occasions, for a total of 30 patient studies. Patient studies were separated into 2 groups. Patients in group I (n = 20) had no gated blood pool evidence for aneurysm, and those in group II (n = 10) had discrete focal akinesia or dyskinesia. Nineteen patients (13 in group I and 6 in group II) had 2 separate nuclear stethoscope acquisitions. In group I, EF determined by gated blood pool scanning (53 +/- 4%, mean +/- standard error) did not differ from that determined by nuclear stethoscope (51 +/- 4%). EF determined using either gated blood pool scanning (32 +/- 6%) or nuclear stethoscope (35 +/- 5%) was significantly lower in group II than in group I, although nuclear stethoscope and gated blood pool scanning did not differ. Reproducibility was excellent (r = 0.96). Overall, nuclear stethoscope and gated blood pool EFs correlated closely (r = 0.93), and the correlation coefficients were similar in groups I (r = 0.92) and II (r = 0.92). The slopes of the regression curves for group I (0.97) and group II (0.92) were not statistically different. These results confirm the accuracy and reproducibility of LVEF determination by nuclear stethoscope and specifically demonstrate its reliability in patients with LV aneurysm.

Adult↗
PubMed1986

[Reliability of the ejection fraction determined with the nuclear stethoscope. Comparison with angiocardiography].

The purpose of this investigation was to compare the Ejection Fraction values simultaneously obtained with the Nuclear Stethoscope and with Cineangiography, in 25 patients (17M-8W) subjected to diagnostic cardiac catheterization. In all patients the determination of Ejection Fraction with the Nuclear Stethoscope always preceded the Cineangiography. Ejection Fraction values obtained with Nuclear Stethoscope change from 32 to 75%; those calculated with Cineangiography, between 18 and 88%. The average Ejection Fraction values obtained with Nuclear Stethoscope (59 +/- 13%) doesn't differ significantly from Cineangiography (59 +/- 21%). There was a direct relationship between Ejection Fraction determined by the Nuclear Stethoscope and Cineangiography (r = 0.93; p less than 0.001). In the obtained results the Authors point out that the Ejection Fraction with Nuclear Stethoscope gives assurance in most patients, although in some particular conditions Nuclear Stethoscope provides Ejection Fraction values which differ from those obtained with Cineangiography. They conclude that Nuclear Stethoscope, for its safe, repeating and simple application, is a methodology of useful employment for Ejection Fraction determination in the single patient, which allows a correct definition of the prognosis and a conforming therapeutic strategy.

Adolescent↗
PubMed1993

The Australian Incident Monitoring Study. The stethoscope: applications and limitations--an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS) were analysed with respect to the role of the oesophageal or precordial stethoscope as a continuous monitor. There were 1099 of the 1256 incidents during general anaesthesia in which one might have been used in this way, but use was reported in only 65 cases (5%), predominantly during paediatric cases. In only one report, a cardiac arrest, was the stethoscope the first to detect the incident. In a theoretical analysis it was considered that the stethoscope, used on its own for continuous monitoring, could have detected 54% of the 1256 incidents (almost 25% before any potential for organ damage), had they been allowed to evolve. However, AIMS data suggest that the actual yield using a stethoscope as a continuous monitor may be much lower than this, and that even the use of a "mobile" stethoscope can not be relied upon to detect oesophageal or endobronchial intubation. These reports confirm that there is limited use of the stethoscope for continuous monitoring in current anaesthetic practice in Australia; it has been superseded by the sophisticated electronic monitors now available. However, in areas with limited resources continuous auscultation with a stethoscope remains a basic requirement.

Accidents↗
PubMed1996

[Level of stethoscope contamination in the hospital environment].

The aim of this study was to determine the extent of the contamination of stethoscopes and their possible role in transmission of microorganisms. The stethoscopes of the medical doctors of the hospital of La Chaux-de-Fonds, Switzerland, were cultured and the date of the last cleaning recorded. 38 of the 62 stethoscopes surveyed were contaminated with microorganisms (61%). The majority of isolated organisms were gram-positive bacteria, primarily Staphylococcus species (89%). The cleaning of the stethoscopes was frequent for 32% of the doctors, rare for 46% and non-existent for 22%. After more than one day without cleaning of the stethoscope, the level of contamination rose from 0% to 69%. Stethoscope use may be an important factor in the spread of infectious agents, so that regular disinfection should be carried out (once a day at the very least).

Bacteriological Techniques↗
PubMed1988

Blinded comparison of an "ultrasound stethoscope" and standard echocardiographic instrument.

We evaluated blinded readings by a physician using a miniature real-time "ultrasound stethoscope" compared with a "standard" echo instrument used by an independent physician. Size of all four cardiac chambers, wall motion, all four valves, thickness of interventricular septum and left ventricular posterior wall, and pericardial effusion were assessed in 66 patients. Each physician estimated whether he had answered the referring question and gave a final diagnosis. The physician using the ultrasound stethoscope correctly assessed chamber size in 87 percent of cases, segmental left ventricular wall motion in 71 percent of segments studied, and wall thickness in 88 percent of cases, and the diagnosis by the ultrasound stethoscope agreed with that made by the standard instrument in 68 percent of cases. The physician with the ultrasound stethoscope detected structural valvular problems (eg, stenosis) in 70 percent of cases but only detected flow abnormalities (eg, regurgitation) in 14 percent of cases. We conclude that (1) an experienced echocardiographer using an ultrasound stethoscope can detect most structural abnormalities found by a standard echocardiographic instrument; (2) chamber size, valvular stenosis, and pericardial effusions were accurately assessed; (3) the ultrasound stethoscope cannot be used to detect valvular regurgitation; and (4) limitations include the lack of freeze-frame, M-mode, hard copy, and Doppler.

Adult↗
PubMedDate not supplied

[Measurement of the frequency response of several stethoscopes in common use. Consequences for cardiac and pulmonary auscultation].

We measured the frequency response of eight stethoscope membranes and of thirteen types of stethoscopes. Measurements were made in an anechoic chamber calculating the ratio between the intensity of a sinusoidal sound coming from a loud speaker and the intensity of the transmitted sound through the membrane of the stethoscope. Small membranes have a bandwidth (without attenuation or amplification) between 10 and 600 Hz while large membranes have a bandwidth twice the size (10-1200 Hz). This good result does not appear in the case of stethoscopes showing increasing attenuation versus frequency, with a mean value from -2.5 to -10.5 dB and variations of 10 dB in the range 50-1200 Hz which is the useful bandwidth for cardiac and pulmonary auscultation. By contrast, fidelity of the measured stethoscopes was good. Discussion of the results suggests modification of stethoscope design to eliminate faults of sound transmission and to elaborate a microphone sensor allowing an electric transmission.

Auscultation↗
PubMed1993

[Assessment of the background count to measure the left ventricular ejection fraction with a nuclear stethoscope].

The nuclear stethoscope is a newly developed device for monitoring left ventricular ejection fraction (EF) with a pair of cadmium telluride detector for both left ventricular count (first channel) and background count (second channel). Although it is useful for evaluating the cardiac function during exercise, the methodology of the calculation for distinguishing the net ventricular blood count from the background count has not been established yet. In order to establish a reasonable method to calculate EF, we measured EF using a nuclear stethoscope and conventional gated blood pool scintigraphy in 20 healthy volunteers. All subjects underwent two supine ergometer exercise tests consisting of the 3 stages for the nuclear stethoscope and blood pool scintigraphy. The EF was determined with the following three method for the nuclear stethoscope; 1) Cut-off level was fixed at 70% of first channel, 2) Cut-off level at 75%, 3) Cut-off level was determined by the background count obtained from second channel. There was a poor relationship between the EFs obtained from gated blood scintigraphy and the EFs from the nuclear stethoscope calculated by any of these method. Regarding the EF calculated using the background count, however, the delta values of EF between rest and any of the 3 stages during exercise correlated closely to those EF from blood scintigraphy. When we apply the EF-at-rest value obtained from blood pool scintigraphy to analysis with the nuclear stethoscope, the EFs of 3 stages indicated good correlation (Stage I r = 0.91, Stage II r = 0.82, Stage III r = 0.69).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Comparison of the acoustic properties of six popular stethoscopes.

This study evaluated stethoscope acoustics by using a sound frequency generator and an active artificial ear. Six popular, currently available stethoscopes were compared in their various modes involving bells, diaphragms, etc.: Littmann Classic II, Littmann Cardiology II, Littmann Master Cardiology, Hewlett-Packard Rappaport-Sprague, Tycos Harvey Triple Head, and Allen Medical Series 5A RPS Binaural. The transfer function was measured from 37.5-1000 Hz, the range where nearly all heart and lung sounds are found. Sound in the low-frequency range (37.5-112.5 Hz) was in most cases amplified by the bells and attenuated by the diaphragms; however, there were no significant differences. Both bells and diaphragms attenuated sound transmission in the high range, and this increased with frequency. The Tycos Harvey Triple Head ribbed diaphragm attenuated sound transmission to a significantly greater extent than the other diaphragms (P less than 0.01). The results show that the bell and diaphragm for a given stethoscope usually have different transmission characteristics, particularly at low frequencies. The Littmann Classic II is an exception. The Hewlett-Packard and Tycos Harvey stethoscopes showed the greatest differences in low frequency response between the bell and the diaphragm. While the differences found in sound transmission between stethoscopes were in most cases small, the Littmann Cardiology II, bell and diaphragm, appears to possess the best overall performance by this study design.

Acoustics↗