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PubMed2005

Measurements and theory of normal tracheal breath sounds.

We studied the mechanisms by which turbulent flow induces tracheal wall vibrations detected as tracheal breath sounds (TRBSs). The effects of flow rate at transitional Reynold's numbers (1300-10,000) and gas density on spectral patterns of TRBSs in eight normal subjects were measured. TRBSs were recorded with a contact sensor during air and heliox breathing at four flow rates (1.0, 1.5, 2.0, and 2.5 l/s). We found that normalized TRBSs were proportional to flow to the 1.89 power during inspiration and to the 1.59 power during expiration irrespective of gas density. The amplitude of TRBSs with heliox was lower than with air by a factor of 0.33 +/- 0.12 and 0.44 +/- 0.16 during inspiration and expiration, respectively. The spectral resonance frequencies were higher during heliox than air breathing by a factor of 1.75 +/- 0.2-approximately the square root of the reciprocal of the air/heliox wave propagation speed ratio. In conclusion, the flow-induced pressure fluctuations inside the trachea, which cause tracheal wall vibrations, were detected as TRBSs consist of two components: (1) a dominant local turbulent eddy component whose amplitude is proportional to the gas density and nonlinearly related to the flow; and (2) a propagating acoustic component with resonances whose frequencies correspond to the length of the upper airway and to the free-field sound speed. Therefore, TRBSs consist primarily of direct turbulent eddy pressure fluctuations that are perceived as sound during auscultation.

Adult↗
PubMed2006

Feature extraction for systolic heart murmur classification.

Heart murmurs are often the first signs of pathological changes of the heart valves, and they are usually found during auscultation in the primary health care. Distinguishing a pathological murmur from a physiological murmur is however difficult, why an "intelligent stethoscope" with decision support abilities would be of great value. Phonocardiographic signals were acquired from 36 patients with aortic valve stenosis, mitral insufficiency or physiological murmurs, and the data were analyzed with the aim to find a suitable feature subset for automatic classification of heart murmurs. Techniques such as Shannon energy, wavelets, fractal dimensions and recurrence quantification analysis were used to extract 207 features. 157 of these features have not previously been used in heart murmur classification. A multi-domain subset consisting of 14, both old and new, features was derived using Pudil's sequential floating forward selection (SFFS) method. This subset was compared with several single domain feature sets. Using neural network classification, the selected multi-domain subset gave the best results; 86% correct classifications compared to 68% for the first runner-up. In conclusion, the derived feature set was superior to the comparative sets, and seems rather robust to noisy data.

Aged↗
PubMed1979

Echocardiography and fetal heart sounds in the diagnosis of fetal heart block.

A 32-week fetus was demonstrated phonocardiographically and echocardiographically to have a regular atrial rate of 150 per minute and a regular ventricular rate of 39 per minute, indicating complete heart block. The diagnosis was suspected when two groups of heart sounds at two distinct rates were heard on auscultation, and was confirmed by the postnatal ECG. The maternal history was significant for the presence of systemic lupus erythematosus. The basis for the echocardiographic diatnosis of complete heart block, the presence of atrial heart sounds in complete heart block, and the relationship of maternal SLE to congenital heart block are discussed.

Adult↗
PubMed1993

Precordial ST segment depression in patients with Q wave inferior myocardial infarction: role of infarction-associated pericarditis.

To examine the diagnostic significance of precordial ST segment depression in Q wave inferior myocardial infarction, 157 consecutive patients were examined carefully by means of auscultation, ECG, and two-dimensional echocardiography. Precordial ST segment depression was transient (lasting < 72 hours from the onset of myocardial infarction) in 63 patients and persistent (> or = 72 hours) in 40. Twenty-eight patients with persistent, 19 patients with transient, and 14 patients without precordial ST segment depression had advanced asynergy (akinesia or dyskinesia) in the posterior segments, whereas 13 patients with persistent, six with transient, and six without precordial ST segment depression had pericardial rub. Patients with persistent precordial ST segment depression had a significantly higher incidence of severe wall motion abnormality (p < 0.01) and inflammation (p < 0.05) of the posterior wall than the other two groups. In 5 of 40 patients with persistent ST segment depression, pericardial rub was detected in the absence of advanced asynergy in the posterior segments. Although not highly sensitive, persistent precordial ST segment depression appeared to be a fairly specific indicator (specificity 92%) of concomitant posterior involvement with severe wall motion abnormality, inflammation, or both.

Aged↗
PubMed1980

Pseudoischemic "false positive" S-T segment changes induced by hyperventilation in patients with mitral valve prolapse.

Hyperventilation-induced S-T segment changes that simulate myocardial ischemia have previously been noted, but the origin of this electrocardiographic finding has never been defined. To investigate further the basis for this response, the records were reviewed of 1,678 consecutive patients who underwent forced hyperventilation for 90 seconds and treadmill exercise testing. Twenty-eight patients (1.7 percent) were identified in whom hyperventilation resulted in ischemic-appearing S-T segment changes, and follow-up was possible in 21 (17 women, 4 men). Of the 21 patients, 16 (76 percent), including 15 (88 percent) of the 17 women, had evidence of mitral valve prolapse, 6 on auscultation alone, 2 on echocardiography alone and 6 with a combination of studies. Ten of the 21 patients had a negative exercise test; of the 11 patients who had a positive exercise test, only 1 had angiographic evidence of coronary arterial narrowing. The finding of ischemic-appearing S-T segment changes in response to forced hyperventilation has a high predictive value for the presence of mitral valve prolapse, particularly in women. The possible association of autonomic factors and mitral valve prolapse in the pathogenesis of an abnormal response to hyperventilation is discussed.

Adult↗
PubMed1987

The efficacy of intrapartum electronic fetal monitoring.

With basic methodologic criteria as a framework, this report assesses the quality of the seven randomized controlled clinical trials conducted in five countries to compare a policy of routine electronic fetal monitoring with a policy of fetal heart rate monitoring by auscultation. One trial found a statistically significant decrease in the occurrence of neonatal seizures in the electronic fetal monitoring group. The trials demonstrated no other statistically significant benefit associated with the use of electronic fetal monitoring, but most reported significant increases in the rates of abdominal and vaginal operative deliveries associated with electronic fetal monitoring. Taken together, the seven trials provide valuable information about the routine use of intrapartum electronic fetal monitoring; they do not demonstrate that it is a useful screening procedure for all women in labor.

Australia↗
PubMed1992

The accuracy of auscultatory detection of fetal cardiac decelerations: a computer simulation.

To evaluate current practices of auscultation for the detection of decelerations, we used a computer to generate contractions and late decelerations and perform the counting. The baseline rate ranged from 110 to 180 beats/min. The duration of the deceleration ranged from 1 to 2 minutes, and the amplitude of the deceleration ranged from 10 to 90 beats/min. The onset of the decelerations ranged from 0.4 to 0.7 of the length of the contraction. Counting was begun at 80%, 100%, and 120% of the contraction length. The duration of counting varied between 15 and 60 seconds. A multicount algorithm obtained three 10-second counts separated by 5 seconds. Results were classified by the ability to detect rates below 120, 100, or 80 beats/min (threshold determination) or 20 and 25 beats/min below the baseline rate (subtraction determination). The baseline rate and deceleration amplitude had the greatest effect on accuracy. The higher the baseline rate and the smaller the deceleration amplitude, the less accurate was detection. Multiple counts were more accurate than the single-count strategy, and subtraction detection was more accurate than threshold detection. The effects of counting error are briefly described. This model, which requires clinical confirmation, nevertheless emphasizes the potential inaccuracies of many popular schemes of auscultatory surveillance, even for the detection of prolonged or sustained decelerations. Certain modifications of auscultatory practice may improve the accuracy of this technique.

Computer Simulation↗
PubMed1975

Retinal vascular lesions in two patients with prolapsed mitral valve leaflets.

Two patients with retinal vascular lesions had mid-late systolic clicks on cardiac auscultation, suggesting the diagnosis of prolapsed mitral valve. The first patient demonstrated an inferonasal arteriolar branch occlusion secondary to embolization; the second patient had a central vein occlusion with multiple hemorrhages, glial proliferative tissue, and retinal neovascularization. This report describes the association between the prolapsed mitral valve syndrome and retinal vascular lesions.

Arterial Occlusive Diseases↗
PubMed1989

Is the shunt patent?

A novel technique for auscultating an aortopulmonary shunt murmur utilizing the principle of conduction of sounds through a closed air system is described.

Anastomosis, Surgical↗
PubMed1976

Increased upper airway resistance in patients with airway narrowing.

The mean air flow resistance of the orolaryngeal (upper) airway was significantly increased in 7 of 11 patients with chronic airway obstruction, when compared with 6 controls. All the patients had noisy respiration with harsh breath sounds audible by auscultation over the larynx. The increase in resistance was greater during expiration than during inspiration. Since 4 patients had normal upper airway resistance, the signs were not invariably associated with upper airway narrowing and presumably could arise also in the chest. When increased, upper airway resistance was usually more than half the total airway resistance. It is suggested that this increase could only be due to narrowing of the glottis, probably by muscle activity. This narrowing may have had the same function as expiration through pursed lips. On the other hand, when present, the increased resistance through the upper airway during inspiration is unlikely to have had a useful function.

Adult↗
PubMed1985

Phonopneumograph possible for real-time tracing.

We constructed a new phonopneumograph that provides real-time tracing of lung sounds at a high speed without the steps of memory and playback by use of a thermal printer system. Accuracy of the recorded wave form was considered adequate even at the maximum speed of 750 mm/sec for detailed wave form analysis. The device is easily connected to a recording system for respiratory flow rate or volume. To test the clinical usefulness of this portable instrument, the difference in the interpretation of four types of basic adventitious lung sounds by different listeners was examined. The "trained" group who had experience in using this instrument interpreted adventitious lung sounds more accurately than did the "untrained" group. Even in the "trained" group, however, the accuracy of identifying certain sounds was sometimes low. These results suggest that this device is useful for bedside interpretation of adventitious lung sounds or for training of auscultation ability.

Analog-Digital Conversion↗
PubMed1994

Comparison of AR-based algorithms for respiratory sounds classification.

Respiratory sounds of pathological and healthy subjects were analyzed via autoregressive (AR) models with a view to construct a diagnostic aid based on auscultation. Using the AR vectors, two reference libraries, pathological and healthy, were built. Two classifiers, k-nearest neighbour (k-NN) classifier and a quadratic classifier, were designed and compared. Performances of the classifiers were tested for different model orders. The best classification results were obtained for model order 6.

Algorithms↗
PubMed1991

Intrauterine manometry: reapplication of an old concept.

Electronic fetal heart rate and uterine activity monitoring during labor requires expensive equipment and a source of electricity. However, it is not available to most of the women in the world. Intrauterine manometry provides a method which can be employed in underdeveloped settings to assess uterine contractions and to time auscultation. The vertical column of fluid in a standard intrauterine pressure catheter (IUPC) correlated well (R = 0.93) with the intrauterine pressure measurements obtained by a standard IUPC/pressure transducer system. Intrauterine manometry provides an alternative measure of uterine tone which may be employed in underdeveloped areas.

Catheters, Indwelling↗
PubMed1990

Devices for the diagnosis and treatment of temporomandibular disorders. Part II: Electromyography and sonography.

This second article in the three-part series on temporomandibular disorder (TMD) devices compares the claimed diagnostic usefulness of electromyography and sonography with the present scientific evidence. This review concludes that there is no evidence to support the use of either surface electromyography or silent period duration for the evaluation or diagnosis of TMD. Furthermore, in view of the available evidence, sonography and Doppler ultrasound have no particular advantage over a conventional stethoscope or direct auscultation.

Auscultation↗
PubMed1985

Maternal attitudes to fetal monitoring.

During a randomized clinical trial concerning alternative methods of intrapartum fetal surveillance (electronic fetal monitoring (EFM) and auscultation (AUS)) an investigatory interview was carried out. Out of 655 expecting mothers the antepartum preference of EFM was 39.5%, of AUS 32.3% and 28.1% were undecided (UD). EFM was especially preferred by obstetrical high-risk patients. Reasons for preference of AUS were a natural childbirth, a non-technological milieu, and the lack of supposed discomfort from sensors and belts. The pregnant women found as major advantages of EFM continuous observation and the possibility of quick intervention. Postpartum 385 patients were again interviewed. The majority upheld the original preference if that method was used. If the non-preferred method had been applied many would stick to the primary preference although a tendency to prefer the experienced method was seen. The patients who antepartum preferred AUS, but had EFM, became more positive toward the method, and a significantly increased number were positively influenced by the EFM signal/trace and found the method promoting their partner's involvement in labor. Enforced immobility, however, was a major disadvantage as well as the technical milieu. If EFM is to be accepted by a majority of women giving birth it is necessary to increase the pregnant women's knowledge of the method and to take milieu factors into consideration in order to reduce the intrinsic depersonalization of EFM.

Adult↗
PubMed1989

Cardiac gas embolism during carbon dioxide hysteroscopy: risk and management.

A relatively high number of fatal complications during hysteroscopy, where carbon dioxide was used as the uterine distension medium, plus a recent report on heart embolism during dog experiments with venous carbon dioxide infusion, audible by simple stethoscopic surveillance during the infusion, prompted the present study. Seventy women with no history of cardiac valvular disease or failure were observed during carbon dioxide hysteroscopy for the occurrence of the characteristic metallic heart sound caused by the intracardiac presence of free carbon dioxide during the heart contractions. In seven cases (10%) the typical metallic heart sounds appeared during the hysteroscopy, leading to immediate interruption of the hysteroscopy and withdrawal of the hysteroscope. This caused the pathological heart sounds to disappear, after which the hysteroscopy could continue. Heart auscultation should always be performed during carbon dioxide hysteroscopy in order to avoid serious cardiovascular complications. This simple precaution turns carbon dioxide hysteroscopy into a versatile and safe method for intra-uterine diagnosis and therapy.

Animals↗
PubMed1993

A microcomputer based lung sounds analysis.

The use of a microcomputer in lung sound-analysis is described. The system was used experimentally in order to evaluate automated auscultation as a mean for improving the sensitivity of pulmonary health mass screening. The sound signals from four custom-made piezoelectric transducers, affixed at specific locations on the chest wall, and the breathing flow signal produced by a pneumotachograph were amplified, filtered and digitized simultaneously at 4000 Hz per channel for 512 ms. The acoustic data were transformed to the frequency domain to enable the calculation of the power spectra. Those were averaged over successive runs and displayed as log power vs. frequency. The operator could assess the convergence of the spectral pattern using the on-line graphics and calculated parameters, and store the data once the noise level had reached a preset level. This procedure was repeated during expiration, inspiration and on breath arrest. The results of the off-line analysis of the lung sounds, combined with pulmonary function tests and a questionnaire, were used to identify lung pathology.

Auscultation↗