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PubMed1976

Korotkoff sound filtering for automated three-phase measurement of blood pressure.

Under rest conditions, changes in the Korotkoff sounds at phases I, IV, and V can be correlated with specific frequencies within the bandpass of the stethoscope. A filter capable of detecting the changes in Korotkoff sounds at phases I, IV, and V is described together with the frequency changes that characterize these phases. The importance of frequency components outside the bandpass of the stethoscope is stressed, especially in terms of the possibility of yielding more clinical information and, perhaps, additional clues above the origin of the Korotkoff sounds themselves.

Auscultation↗
PubMed1986

Pseudomonas cepacia in the hospital setting: lack of transmission between cystic fibrosis patients.

Possible mechanisms of transmission of Pseudomonas cepacia in hospitalized patients with cystic fibrosis were examined. Twelve patients were colonized with P. cepacia prior to admission (group 1), and 15 patients were not (group 2). Daily contact occurred between both groups. Sputum cultures were obtained from all patients at admission and discharge, and 3 and 6 months after discharge in group 2 patients. Environmental cultures included cough plates, settle plates, spirometry tubing, stethoscopes, sinks, wall outlets, and hands of patients, physicians, nurses, and respiratory therapists. Specimens were plated on a P. cepacia-selective medium. All group 1 patients remained colonized with P. cepacia at discharge. None of the group 2 patients acquired P. cepacia during hospitalization or follow-up. P. cepacia was recovered from three of 151 environmental cultures; two of these were presumably patient related. P. cepacia contamination of pulmonary function equipment, wall outlets, hands, and stethoscopes was not documented. We conclude that transient aerosol environmental contamination is uncommon and restricted to the immediate patient environment.

Adolescent↗
PubMed1992

A simplified form of cardiotocography for antenatal fetal assessment.

Antenatal cardiotocography has become the primary method of evaluation of fetal wellbeing, and the relationship between the presence of fetal heart rate accelerations in response to fetal movement and subsequent good fetal outcome has been demonstrated. However, in areas where electronic monitors are few or not available it would be useful if such accelerations could be demonstrated using the Pinard stethoscope. A prospective study involving 200 women with a singleton pregnancy of more than 34 weeks gestation was performed at Harare Maternity Hospital, Harare, Zimbabwe, when a 6 min electronic trace using an external transducer was compared with simultaneously performed 6 min manual record using the Pinard stethoscope. The findings showed that the manual record has a sensitivity of 75% and although traces with excessive base line variability would show an acceleration on the manual record, in no case with a flat trace was an acceleration noted on the manual record. This acceptable degree of sensitivity would allow for a significant decrease in the number of women being referred for electronic tracing and would be a more appropriate use of limited resources in terms of manpower and equipment.

Auscultation↗
PubMed1990

[A device for monitoring respiration during anesthesia: the para-tracheal monitor].

The paratracheal audible respiratory monitor (PTARM) was assessed in anaesthetized patients who were not intubated. Its working principle is simple: the sound generated by the passage of air between the vocal cords is picked up by a microphone placed on the patient's neck; the electronic signal is then amplified and changed into an audible one. It can also be recorded. This monitor was compared to others already available, Transcor, which monitors breathing sounds using a stethoscope as transducer, and Thermistor, which monitors the changes in air temperature due to air movement during breathing. The PTARM does not tie the anaesthetist down to the patient's bed, as do the precordial or oesophageal stethoscopes. Its usefulness in detecting aspiration is under investigation. It is a reliable, noninvasive and cheap breath-to-breath respiratory monitor, which can also be used in intubated patients.

Anesthesia, General↗
PubMed1991

Analysis of breath sounds in normal and asthmatic children and adults using computer digitized airway phonopneumography (CDAP).

Analysis of breath sounds using the stethoscope is a major part of physicians evaluation of their patients. However, the use of a stethoscope is often inadequate to give quantitative measurements of the clinical state of the individual. In this study a modification of a previously described computer analysis of breath sounds was used to measure sound intensity levels in both normal and asthmatic children who, in most cases, were unable to perform pulmonary function. The intensity levels were derived using a microcomputer-based program that digitizes audio signals and calculates energy values at 25-ms intervals throughout each signal. There were statistical differences between mean intensity levels for normal breath sounds in children between 2 and 6 years and the mean intensity levels for wheezing sounds in the same age group, as well as wheezing sounds in asthmatic patients over the age of 8 years (P less than 0.002). Also, the mean intensity levels for normal breath sounds could be clearly differentiated from intensity levels for other sounds from the chest, including heart sounds and voice sounds. Thus, computer digitized airway phonopneumography (CDAP) proved to be a reproducible, quantifiable method for demonstrating airway obstruction in those children and patients unable to perform pulmonary function testing.

Adolescent↗
PubMed2003

Acoustic transmission in normal human hips: structural testing of joint symmetry.

An acoustical technique has been developed for the measurement of structural symmetry of the hip joints. A mild vibratory force was applied to the sacrum and sound signals were picked up at both hips by a pair of microphones installed in two stethoscopes. These stethoscope-microphone assembles were calibrated to achieve a difference in relative sensitivity of less than 0.2 dB. The relative transmission of sound signals was analysed and compared between both hips by a dual-channel signal analyser. Twenty-seven healthy adults, 20 healthy pre-school children and 19 normal neonates were tested. Results from these three groups showed high coherence of the sound signals and that the discrepancy between both hips was smallest in the frequency range of 200-315 Hz. For normal neonates, the sound signals maintained a high coherence (gamma2>0.97) and small discrepancy (D<1.25 dB) between both hips. This study has shown that the acoustical technique provides a practical structural testing for bony symmetry of the hips and the results offer a baseline for further investigation into developmental dysplasia of the hip (DDH) in neonates. Clinical screening for DDH is still problematic in developing countries.

Acoustic Stimulation↗
PubMed1995

Korotkoff's sounds in pregnancy.

Korotkoff described the sequence of vascular sounds heard with a stethoscope over the brachial artery during deflation of a pneumatic cuff. The initial sounds are produced by vibrations of the vessel wall, although the sequence of vascular sounds has frequently been ascribed to 'turbulence' of flow in the vessel. This study has been performed to determine the relationship between the vascular sounds (Korotkoff I-V) produced during blood pressure cuff deflation and specific changes in the brachial artery waveform. Ten nulliparous women admitted to hospital in the third trimester of pregnancy have been studied by means of concurrent Doppler ultrasound and phonocardiography. Changes in the brachial artery waveform during blood pressure cuff deflation were recorded using Doppler ultrasound (7.5 MHz) with concurrent objective demonstration of phases I-V of the vascular sounds using a phonocardiography microphone. Characteristic features of the brachial artery waveform were associated with phases I-IV of the vascular sounds in all patients (10/10). No consistent features of the brachial artery waveform were associated with phase V of the vascular sounds. Phases I-IV of the vascular sounds are associated with specific changes in the pattern and direction of flow within the brachial artery in normotensive primigravid women. The vascular sounds produced by vibration of the vessel wall are modulated by changes in blood flow to produce the characteristic sequence of vascular sounds detected with a stethoscope during blood pressure cuff deflation.

Adolescent↗
PubMed2001

Evaluation of transesophageal atrial pacing in the prone and lateral positions.

OBJECTIVE: To develop recommendations for positioning the second-generation pacing esophageal stethoscope for transesophageal atrial pacing in patients positioned prone (P), right lateral decubitus (RLD), and left lateral decubitus (LLD). DESIGN: Prospective; patients assigned consecutively. SETTING: Tertiary and university hospitals. PARTICIPANTS: Thirty (10 in each position group) adult patients undergoing surgery. INTERVENTIONS: The optimal depths of insertions (DOI) where pacing current threshold was minimal (THmin) were determined first when supine, then after positioning. MEASUREMENTS AND MAIN RESULTS: Transesophageal atrial pacing was successful in all patients supine and after positioning. The optimal DOI varied from 2 cm less deep to 4 cm deeper in positioned patients compared with supine patients. Patients positioned P required equal or up to 8 mA greater current outputs to achieve transesophageal atrial pacing; LLD and RLD patients may require up to 8 mA greater or lesser current compared with supine patients. CONCLUSION: Transesophageal atrial pacing can be used safely and effectively in patients positioned P, RLD, and LLD. Recommendations are presented for positioning the pacing esophageal stethoscope. Emphasis is given to using the lowest DOIs and smallest currents to reduce the chance of transesophageal ventricular pacing.

Adolescent↗
PubMed2001

[Hygiene status of ambulances and equipment in rescue services].

PURPOSE: Focus on hygienic management in ambulances is presented based on findings from hygienic microbiological sampling. METHODS: In 44 ambulances, the handwashing area, equipment for artificial respiration, insufflation, intubation, aspiration, intravasal catheterisation, blood-pressure measurement, and sterile materials storage were examined hygienically and microbiologically using the following methods: water sampling, imprint technique, and swab technique with subsequent cultivation on blood-, endo-, and Sabouraud agar. RESULTS: The highest contamination was found in the hand-washing area and on insufflation equipment (up to > or = 100,000 cfu/ml), where proof of the potential pathogens Pseudomonas, Acinetobacter, and Alcaligenes spp. was found. The second highest contamination level was found on the sphygmomanometer cuffs, stethoscopes, and respirator masks (e.g., Enterococci and S. aureus were identified). Apparently, the germs chiefly originate from the drinking water at the handwashing station, from the environment and mucous membranes from the skin, and intestines of the ambulance personnel. The predominant hygienic deficiensies were found in the equipment of the handwashing areas, and in the storage of resuscitation equipment and sterile materials. CONCLUSIONS: Based on the results of hygienic microbiological analysis, the main focus of hygienic measures--besides hand disinfection--should be on spray disinfection of the sphygmomanometer cuffs and stethoscopes as well as disinfection of ambulance equipment and storage areas for sterile devices, supplemented by dust protection of ready-to-use materials and devices. Stationary dispensers for hand disinfection possessing at least midlength levers must become the standard in ambulances, and conventional handwashing basins with plastic drinking-water containers and pump must be eliminated entirely.

Ambulances↗
PubMed1995

Recovery of vancomycin-resistant enterococci on fingertips and environmental surfaces.

OBJECTIVE: To determine the recovery of vancomycin-resistant enterococci (VRE) on fingertips, gloved fingertips, and environmental surfaces commonly encountered in the healthcare setting, and to examine the importance of handwashing on the removal of these organisms. DESIGN: Two clinical isolates of VRE (Enterococcus faecalis and Enterococcus faecium) were inoculated onto the hands of healthy human volunteers and the following environmental surfaces: countertops, bedrails, telephones, and stethoscopes. Following inoculation, samples were obtained at various time intervals to determine rates of recovery of organisms. To evaluate the effects of handwashing on enterococcal recovery, two different soap preparations were tested. Hands were washed with water alone or with one of the soaps and water. The soap and water studies were performed with a 5-second and a 30-second wash. RESULTS: Both enterococcal strains survived for at least 60 minutes on gloved and ungloved fingertips. The E faecalis was recoverable from countertops for 5 days; the E faecium persisted for 7 days. For bedrails, both enterococcal species survived for 24 hours without significant reduction in colony counts. The bacteria persisted for 60 minutes on the telephone handpiece and for 30 minutes on the diaphragmatic surface of the stethoscope. A 5-second wash with water alone resulted in virtually no change in recovery of enterococci; a 30-second wash with water plus either soap was necessary to eradicate the bacteria from hands completely. CONCLUSION: VRE are capable of prolonged survival on hands, gloves, and environmental surfaces. Hands should be washed thoroughly and gloves removed following contact with patients infected or colonized with these multidrug-resistant bacteria. Finally, environmental surfaces may serve as potential reservoirs for nosocomial transmission of VRE and need to be considered when formulating institutional infection control policies.

Drug Resistance, Microbial↗
PubMed1999

Percussion--a new way to diagnose a pneumothorax.

We describe a new clinical sign in a case series of three patients who developed pneumothoraces during mechanical ventilation in the intensive care unit. All three patients were in the supine position. Two patients had x-rays that were inconclusive before insertion of chest drains and the third had a pneumothorax diagnosed on clinical findings alone. On each occasion we were able to diagnose pneumothorax using sternal percussion and simultaneous auscultation. The method relies on percussion of the sternum while simultaneously ausculating the anterior (superior) chest on the side of the suspected pneumothorax. The stethoscope is then placed on the other side of the chest. The percussion sound on the affected side has an exaggerated, resonant and booming quality. The percussion note is exaggerated partly because a stethoscope is used and partly because, in the supine patient, air localizes upwards to the anterior thorax.

Female↗
PubMed1985

Left ventricular performance monitored by radionuclide cardiography during induction of anesthesia.

Radionuclide cardiography with 99mTc-labeled erythrocytes was carried out in three different studies comprising 20 female patients without heart or lung diseases. Left ventricular ejection fraction (LVEF) and other hemodynamic variables were measured immediately before and during induction of anesthesia (thiopental, N2O/O2, succinylcholine, laryngoscopy + oral intubation, halothane). In study 1, serial measurements of LVEF, left ventricular volume, and derived variables were obtained by gamma camera in seven patients using 3-min sampling periods. In Studies 2 and 3, LVEF was monitored serially in seven and six patients, respectively, by a portable, nonimaging probe (nuclear stethoscope) at 1-min intervals or less. The induction period was prolonged to last 24 min in studies 1 and 2, against 9 min in study 3. In studies 1 and 2 there was an increase in blood pressure and heart rate after thiopental and after laryngoscopy and intubation. In study 3 a similar increase was observed after intubation. In the gamma camera study LVEF decreased from 0.72 to 0.53 after thiopental, with no further decrease during intubation. This decrease was accompanied by an increase in end-systolic volume and a decrease in the ratio: systolic cuff pressure/end systolic volume, whereas end-diastolic volume and cardiac index remained unchanged. In the nuclear stethoscope studies, LVEF decreased both after thiopental and after intubation, in study 2 from 0.68 to 0.38 and from 0.53 to 0.41, respectively; in study 3 from 0.69 to 0.53 and from 0.57 to 0.44, respectively. Our observation, in healthy, female individuals, provide an impetus for further noninvasive radionuclide studies during anesthesia in patients with cardiovascular disease.

Adult↗
PubMed1998

Signs of depth and danger. 1962.

A large proportion of the serious complications that occur during pediatric anesthesia are caused by failure to recognize early signs of danger. The greatest dangers include excessive anesthetic depth, respiratory obstruction and depression, acid-base derangement, shock, myocardial depression, and extreme alterations in body temperature. Simple monitoring devices, including the anesthetic chart, stethoscope, blood pressure cuff, and thermometer, are essential in all major pediatric procedures. Use of the stethoscope should never be omitted in any case. Signs of cardiorespiratory and neuromuscular activity characteristic of infants and children should be familiar to all anesthetists who engage in pediatric work.

Anesthesia↗
PubMedDate not supplied

Cardiovascular responses to an active coping challenge as predictors of blood pressure patterns 10 to 15 years later.

To assess the long-term predictive importance of high cardiovascular reactivity in relation to subsequent blood pressure, 51 men from a pool of 204 men originally tested at age 18 to 22 years were recruited for blood pressure assessment 10 to 15 years later. Initial testing uniformly involved monitoring of systolic pressure, diastolic pressure, and heart rate during a reaction time task involving threat of shock. In 30 of the 51 men who participated at follow-up, initial testing had also included separate visits to obtain relaxation-only baseline levels of the cardiovascular indices. At follow-up, in addition to clinic-type stethoscopic determinations, blood pressure and heart rate were assessed during work and social and leisure activities via ambulatory monitoring. Men with higher levels of systolic pressure during the task showed higher stethoscopic and ambulatory systolic pressure at follow-up. Likewise, men with higher levels of diastolic pressure during the task showed higher diastolic levels at follow-up. In the 30 men with both good task and baseline data from initial testing, those with high heart rate reactivity (task minus baseline) showed higher systolic, diastolic, and heart rate levels at follow-up than low heart rate reactors, even though their baseline blood pressures had not differed at initial testing. Similarly, men with high systolic reactivity showed higher diastolic pressure at follow-up than low systolic reactors. Multiple regression analyses also demonstrated that systolic, diastolic, and heart rate reactivity improve prediction of follow-up blood pressure when added to models incorporating the standard risk factors, baseline blood pressure, and parental history of hypertension.

Adaptation, Psychological↗
PubMed2006

Design, construction, and evaluation of a bioacoustic transducer testing (BATT) system for respiratory sounds.

Many different transducers are employed for recording respiratory sounds including accelerometers and microphones in couplers. However, there is no standard lung sound transducer or any device to compare transducers so that measurements from different laboratories can be determined to be of physiologic origin rather than technical artifacts of the transducers. To address this problem, we designed and constructed a prototype of a device that can be used to compare accelerometers, microphones enclosed in couplers, and stethoscopes. The prototype device consists of a rigid chamber containing a loudspeaker that opens to an antechamber covered by a viscoelastic material with mechanical properties similar to human skin and subcutaneous tissue. When driven by a white noise source, we found the sound output at the surface to be useful to comparatively evaluate sensors between 100 and 1200 Hz where lung sounds have most of their spectral energy. We compared the viscoelastic layer to similar thicknesses of fresh meat and fat and found them to produce similar acoustic spectra. This device allows air-coupled transducers, accelerometers, and stethoscopes used in respiratory sounds measurements to be compared under physical conditions similar to their intended use.

Acoustics↗
PubMed1976

Venous air embolism during neurosurgery. A comparison of various methods of detection in man.

A comparison of the various methods available for the detection of air embolus has been carried out in patients undergoing posterior fossa exploration in the sitting position. A group of 17 patients (Group A) was comprehensively monitored by a central venous catheter, an infra-red carbon dioxide analyser and a Doppler ultrasonic flow transducer in addition to more traditional clinical methods. Group B (19 patients) was monitored by commonly used clinical methods consisting of continuous palpation of the radial pulse, intermittent blood pressure measurement, the use of an oesophageal stethoscope and the electrocardiograph. In Group A the detection of air embolus varied from 6% using an oesophageal stethoscope to 58% by the Doppler method. In Group B air embolus was diagnosed in 10% of patients. One patient in each group died from air embolus; one patient had a paradoxical embolus to the coronary arteries. It is concluded that comprehensive monitoring for air embolus, including the use of Doppler ultrasound, is an essential part of the management of these patients, for both diagnosis and treatment.

Adult↗
PubMed2006

Comparison of lung sound transducers using a bioacoustic transducer testing system.

Sensors used for lung sound research are generally designed by the investigators or adapted from devices used in related fields. Their relative characteristics have never been defined. We employed an artificial chest wall with a viscoelastic surface and a white noise signal generator as a stable source of sound to compare the frequency response and pulse waveform reproduction of a selection of devices used for lung sound research. We used spectral estimation techniques to determine frequency response and cross-correlation of pulses to determine pulse shape fidelity. The sensors evaluated were the Siemens EMT 25 C accelerometer (Siemens); PPG 201 accelerometer (PPG); Sony ECM-T150 electret condenser microphone with air coupler (air coupler; with cylindrical air chambers of 5-, 10-, and 15-mm diameter and conical air chamber of 10-mm diameter); Littman classic stethoscope head (Littman) connected to an electret condenser microphone; and the Andries Tek (Andries) electronic stethoscope. We found that the size and shape of the air coupler chamber to have no important effect on the detected sound. The Siemens, air coupler, and Littman performed similarly with relatively flat frequency responses from 200 to 1,200 Hz. The PPG had the broadest frequency response, with useful sensitivity extending to 4,000 Hz. The Andries' frequency response was the poorest above 1,000 Hz. Accuracy in reproducing pulses roughly corresponded with the high-frequency sensitivity of the sensors. We conclude that there are important differences among commonly used lung sound sensors that have to be defined to allow the comparison of data from different laboratories.

Acoustics↗
PubMed1982

The prevalence and character of crackles (rales) in young women without significant lung disease.

Although some investigators have reported that crackles are present only in persons with lung disease, others say they also occur in normal persons. In order to clarify this difference of opinion, we determined the prevalence of crackles in 56 women without significant lung disease. The subjects ranged from 19 to 33 yr of age (mean, 21.3). They all had a FVC greater than 80% predicted and a FEV1/FVC ratio greater than 75%. None had a history of acute or chronic lung disease. During slow inspirations from residual volume, midinspiratory fine crackles were heard at the anterior bases in 35 of 56 subjects by a physician using an acoustic stethoscope, whereas a bioengineer using an 800 Hertz high pass filtered stethoscope heard crackles in 53 subjects. Crackles during tidal breathing were heard in 2 subjects. It is postulated that the crackles noted after expiration to residual volume are nonpathologic, and occur when basilar airways, which close at the end of a forced expiration, suddenly open during inspiration. Examination of the quality, timing, and anatomic distribution of the crackles in apparently normal subjects suggests that they can often be distinguished from those resulting from diseases such as bronchitis, interstitial fibrosis, and congestive heart failure.

Adult↗