PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Transducers, Pressure”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1984

[Histomorphological findings in the ascending aorta and inferior vena cava following implantation of ultrasonic Doppler flow transducers and pressure transducers in long-term experiments with rabbits and cats].

We investigated the histological changes of the vessel walls of the carotis dextra, the aorta ascendens and the vena cava inferior following implantation of flow- and pressuretransducers of 17 rabbits and 4 cats. Following correct adaptation of the vessel volumen the implantates were all well tolerated over a prolonged period (up to 58 weeks) and encapsulated by connective tissue. The histological processes are descripted in detail and lesions produced by ultrasound are shown.

Animals↗
PubMed1999

Evaluation of micro tip pressure transducers for the measurement of intracerebral pressure transients induced by fluid percussion.

We describe the application of MIKRO TIP miniature pressure transducers (MPT) for the in vivo measurement of intracerebral stresses induced by traumatic brain injury (TBI). In order to test the linearity of these transducers pressure pulses of different amplitudes (duration approximately 10ms) were generated in a closed calibration chamber. A piezoelectric pressure transducer (PPT) served as the reference measure. A linear correlation was found within the pressure range between 0.57 and 5.09 bar (R2 = 0.998). The frequency transmission characteristics of the MPTs are comparable to the PPT. In three juvenile swines (6 weeks of age) pressures within the brain tissue were induced by fluid percussion (FP) and were measured in the anterior, middle, and posterior cranial cavity as well as in the extracranial part of the medulla oblongata. The data obtained in our experiments agree with the basic biomechanics of FP known from studies in cats and rabbits. Due to their small size, MPTs can be applied in living animals. Stereotaxic positioning of these catheters at any site of the brain and spinal cord requires only minimal surgery. Therefore, MPTs are useful in evaluating animal models of brain injury and in generating input data for computational models of head injury as well as to validate the mathematical results of such models with experimental data.

Animals↗
PubMed1996

Accuracy and reliability of disposable pressure transducers coupled with modern pressure monitors.

OBJECTIVE: To determine the bedside accuracy of direct patient pressure monitoring when used with new and clinically used disposable blood pressure (BP) transducers. DESIGN: Prospective study. SETTING: Laboratory bench and critical care units in an adult and children's hospital. SUBJECTS: Seventy-five bedside patient monitors (25 Marquette Electronics, 25 Spacelab Medical, and 25 Hewlett-Packard), and 100 disposable transducers (50 from Utah Medical Products and 50 from Abbott Critical Care Systems [25 new, 25 clinically used of each manufacturer]) were tested. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A +/- 2% accuracy requirement for bedside monitors and the +/- 3% American National Standards Institute accuracy standard for disposable BP transducers were used. To test the accuracy of the bedside monitors, a certified transducer simulator was used to apply 100 mm Hg to each bedside monitor. To test the accuracy of the disposable BP transducers, a very accurate (+/- 0.05%) pneumatic dead weight tester was used to apply pressures to the transducer. A digital power supply and a 6 1/2 digit voltmeter were used. The average output of the bedside monitors when 100 mm Hg was applied was 99.90 +/- 0.83 mm Hg, with the worst cases being 98 and 103 mm Hg. For all 100 disposable pressure transducers, the average output was 100.03 +/- 0.55 mm Hg, with the worst cases being 98.53 and 101.36 when 100 mm Hg was applied. There was no important difference in the accuracy of the transducers obtained from the two vendors nor whether the transducers had been used clinically. CONCLUSIONS: All disposable BP transducers tested were much more accurate than the American National Standards Institute standard for accuracy. Even the worst case transducers were twice as accurate as required by the American National Standards Institute standard. Only one bedside monitor was outside the +/- 2% accuracy range (103 mm Hg). Based on these findings, this author recommends that fixed calibration disposable transducers and fixed calibration bedside pressure monitoring systems be used. The clinical risks of air embolism and infection from the calibrating mercury manometer and the complexity of the calibration task are the overriding factors for making these recommendations.

Adult↗
PubMed1988

Use of fiber-optic pressure transducer for intracranial pressure measurements: a preliminary report.

Invasive monitoring of intracranial pressure (ICP) is becoming the standard of care for management of acute neurologic and neurosurgical patients. As a result of improved fiber-optic technology, a new disposable 4 French fiber-optic transducer-tipped catheter (FTC) has been introduced for facilitating measurement of intracranial pressure. Placement of the FTC can be intraventricular, subarachnoid, subdural, or intraparenchymal. Sensitivity and linearity of each catheter are manufacturer calibrated and not adjustable. Zero or atmospheric balance is done only once before insertion. Because the transducer is the catheter tip, no leveling to an anatomic point is necessary. The system appears to eliminate some of the difficulties inherent in fluid-filled catheter monitoring. In clinical trials, the comparison of FTC with subdural and ventriculostomy waveforms and pressures showed essentially no difference. Pressure recordings tracked well except during transient periods of increased ICP, when FTC showed higher peak pressures. Use of the FTC requires education regarding placement and maintenance techniques. Although staff experience with the catheter can practically eliminate the problem, the FTC catheters need special handling because of potential for fiber breakage.

Catheterization↗
PubMedDate not supplied

ICP measurement control: laboratory test of 7 types of intracranial pressure transducers.

Intracranial pressure (ICP) monitoring has become an important parameter in the assessment of comatose patients, with raised intracranial pressure. The transducers in use have to fulfill the criteria of measurement accuracy, practicability and cost-effectiveness. However, these requirements are not always met in clinical practice. The need for ongoing quality control through independent laboratories remains. We have developed a laboratory set-up for the evaluation of intracranial pressure probes. Seven different types of currently used transducers have been tested for measurement accuracy. Under in vitro conditions 3 parameters were assessed: measurement accuracy, a 24 h drift and 10 day drifts. Tests for measurement accuracy were performed at increasing pressure levels of up to 80 mmHg. They were repeated 10 times per probe. This test allowed the simultaneous assessment of 5 different ICP probes. Drift was evaluated for 24 h and 10 days, at 6 pressure levels between 0 and 50 mmHg. Seven different types of ICP probes were tested (HanniSet, Camino, Codman, Spiegelberg, Medex, Epidyn and Gaeltec). Measurement accuracy was best with HanniSet probes. The maximum errors with this transducer were 3 mmHg. Camino and Codman showed similar results. Spiegelberg had slightly larger deviations. With Epidyn and Gaeltec the highest error were noted, up to 10 mmHg in the high pressure range. The 24 h drift was lowest with HanniSet (0.2 mmHg) and Camino (0.8 mmHg). The largest drifts were seen with Medex, Spiegelberg and Gaeltec (1.8 mmHg). Ten day drift was lowest with HanniSet (0.1 mmHg/day) and Codman (0.2 mmHg/day). The highest long-term drifts were found with Epidyn and Gaeltec (1.5 mmHg/day). Drift did not exhibit a linear pattern. After an initial rise in drift during the first 24-72 h, it decreased slowly during the next 7 days. Most ICP probes revealed measurement inaccuracy and drift. These results emphasize the necessity for ongoing evaluations of ICP probes. Therefore, tests for quality assurance are essential to establish a consistent standard of proficiency of ICP transducers.

Intracranial Pressure↗
PubMed1987

Arthroscopic measurement of chondromalacia of patella cartilage using a microminiature pressure transducer.

A microminiature pressure transducer was constructed to measure chondromalacia of the medial patellar facet under arthroscopic control. Normal and abnormal values were established. Among a group of 58 knees with no patellofemoral symptoms or signs, 30 knees measured "soft" using this instrument. Among a group of 107 knees with patellofemoral symptoms and signs, 98 knees measured "soft." Of these 98 knees, 55 had no observable change in the articular surface of the patella.

Adult↗
PubMed1980

[Chronic blood pressure measurements in the rabbit aorta using a novel implantable pressure transducer].

A novel implantable pressure pickup is described for chronical blood pressure measurement at the rabbit aorta, which transmits the intravasal pressure via a short liquid column in a closed foil catheter transmurally to an extravasal pressure transducer. With a natural frequency of 250 Hz, the pressure slope steepness is 1834 kPa/sec. The pickups operate up to 40 kPa linearly with deviation of 2% of the whole scale. The pressure hysteresis is at 3% of the whole scale, the temperature coefficient at 93 Pa/degrees C. The pickups are well tolerated by the tissue; their manufacture is relatively simple, and they are much cheaper than the intravasal pressure transducers.

Animals↗
PubMed1987

[Clinical experiences with a new reusable pressure transducer].

Invasive blood pressure monitoring is increasing in anesthesia and intensive care. Compared to noninvasive methods, it has some decisive advantages: (1) blood pressure trends can be assessed beat by beat, which is important especially in situations of cardiac arrhythmia; (2) respiratory changes in blood pressure as one sign of hypovolemia can be detected easily; and (3) pressure changes induced by the autonomic nervous system become apparent. We studied a new, reusable pressure transducer system, the Medex Novatrans-MX800 in routine intra- and postoperative monitoring of patients undergoing cardiac surgery using the following criteria: (1) handling; (2) accuracy of measurement; (3) durability; and (4) costs. The system is easy to use and has a low susceptability to breakdown. In 29 of 31 transducers tested, the error of measurement over a range of 0-150 mmHg was less than 2% as reported by the manufacturer. Two transducers showed errors of measurement over 5% after 60 times of reuse. The mean reusability rate until the transducer became defective was 75.8 +/- 17.3 in the operating room (19 transducers tested) and 59.7 +/- 29 in the intensive care unit (12 transducers tested, 11 still in use). A comparison of costs shows that the Novatrans-MX800 system is the cheapest system for invasive pressure monitoring available at this time.

Blood Pressure Determination↗
PubMedDate not supplied

Laboratory evaluation of pressure transducer domes containing a diaphragm.

Pressure transducers are being used with increasing frequency in patient care. The recent availability of sterile transducer domes containing a diaphragm provides a means for reducing the risk of bacteremia when using these devices. The present studies measured the effect of diaphragm domes on the accuracy of pressure measurement. The sensitivity and frequency responses of 5 pressure transducers utilizing diaphragm and nondiaphragm domes were compared. The results indicate that the type of dome utilized and the method of dome application can significantly modify pressure transducer performance. The data are useful in providing optimal accuracy and reliability of pressure measurments when using a diaphragm dome, pressure transducer combination.

Blood Pressure Determination↗
PubMed1989

Intrapartum uterine activity: evaluation of an intrauterine pressure transducer.

A newly available intrauterine pressure transducer was evaluated clinically in 100 patients. Successful insertion was accomplished in 95%. There were no significant intrapartum maternal or fetal complications. Partial dehiscence of a surgically scarred uterus did occur in one patient who received the device, but a clear relationship between its attempted insertion and the dehiscence was not apparent. Early in the clinical trial, a number of devices malfunctioned; the manufacturer defined and remedied the problem. The intrauterine transducer required no maintenance and appeared to be practical in laboring women. We suggest that the utility of the intrauterine pressure transducer might be enhanced with several modifications, including the addition of a re-zeroing mechanism and a reduction in the device's length.

Evaluation Studies as Topic↗
PubMed1995

Monitoring of pulmonary arterial diastolic pressure through a right ventricular pressure transducer.

Pulmonary arterial diastolic pressure is an important parameter for hemodynamic monitoring in congestive heart failure. It is traditionally obtained through a pulmonary arterial catheter. If it could be obtained from a sensor in the right ventricle, chronic monitoring would be possible without the use of a pulmonary arterial catheter. This study is based on the hypothesis that pulmonary valve opening and pulmonary arterial diastolic pressure occur at the time of maximum positive rate of pressure development (dP/dt) in the right ventricle, when the pressures should be equal. Thus, right ventricular pressure at the time of maximum dP/dt (PAD index) should be a reasonable estimate of pulmonary arterial diastolic pressure. Eight patients with heart failure were catheterized and exposed to hemodynamic stress. Right ventricular and pulmonary arterial pressures were simultaneously recorded from a Millar (Houston, TX) catheter with two pressure transducers. The distal transducer was positioned in the bifurcation of the pulmonary artery and the proximal transducer was placed in the right ventricle. Pulmonary arterial diastolic pressure and PAD index were stored beat by beat on a bed-side computer. Acceptable recordings were obtained in all patients. Recordings from the individual patients showed a good covariation between PAD index and pulmonary arterial pressure during different hemodynamic manuevers, except during infusion of dobutamine, when the correlation was not as good. Pulmonary arterial diastolic pressure may be estimated from a transducer in the right ventricle, thus eliminating the need for a permanent pulmonary arterial catheter in an implantable hemodynamic monitoring system. Further studies are needed to verify the correlation on a long-term basis.

Aged↗
PubMed1975

A catheter-tip capacitance pressure transducer.

A simple miniature capacitance pressure transducer is described. The operational characteristics of the device when mounted on the tip of a 6.3 F catheter are discussed and results of in vivo trials illustrated, using a commercially available catheter-tip pressure transducer for comparison.

Blood Pressure Determination↗
PubMed1988

Disposable pressure transducers.

We evaluated twelve disposable pressure transducers from eleven manufacturers. All were rated Acceptable and were ranked in four groups. The first two groups had similar performance characteristics. Groups three and four were ranked primarily according to the effect of fluid spills and the ease of achieving accurate dynamic response.

Disposable Equipment↗
PubMed1988

Disposable pressure transducers.

We evaluated 12 disposable pressure transducers from 11 manufacturers. All are rated Acceptable and are ranked in four groups. The first two groups have similar performance characteristics. Groups three and four are ranked primarily according to the effect of fluid spills and the ease of achieving accurate dynamic response. Although list prices are somewhat high, negotiated prices are usually lower. Users should weigh advantages and disadvantages against clinical preference and price.

Disposable Equipment↗
PubMed1995

Accuracy of disposable blood pressure transducers used in the critical care setting.

OBJECTIVES: To assess the initial accuracy, drift in calibration over several hours, and decline in accuracy over daily use of blood pressure transducers used in the critical care setting. DESIGN: Prospective, criterion standard. SETTING: Three critical care units in a university hospital. SUBJECTS: Twenty-seven consecutively available high-pressure transducers were used to measure intra-arterial blood pressures, and 11 consecutively available low-pressure transducers were used to measure central venous and pulmonary arterial blood pressures. INTERVENTIONS: High-pressure transducers were compared with a mercury column manometer, and low-pressure transducers were compared with a water column manometer at three pressure levels. Data were collected initially after installation of the pressure transducer, at 3 hrs, and at 6 hrs. Data collections were repeated on subsequent days. MEASUREMENTS AND MAIN RESULTS: a) The majority of pressure transducers are accurate; b) there is no drift in the accuracy of pressure transducers over several hours; c) the accuracy of pressure transducers does not decline over subsequent days. Some transducers over-estimated standard pressures by 10 mm Hg and/or underestimated standard pressure by 17 mm Hg. CONCLUSIONS: The majority of pressure transducers used in the critical care setting are accurate, although there are some transducers that may compromise patient care. Blood pressure transducers should be checked against a standard manometer upon installation, and daily during use.

Blood Pressure Determination↗
PubMed1989

Analysis of the dynamic characteristics of pressure transducers for studying respiratory mechanics at high frequencies.

Differential pressure transducers are commonly used to study respiratory mechanics at physiological frequencies as well as during external forcing at high frequencies. In the latter condition, measuring errors could occur if the input impedance of the pressure transducers is not sufficiently large with respect to that of the respiratory system. In this work we analysed the input impedance Z and the transfer function H of two common pressure transducers (Validyne MP-45 and Celesco LCVR) equipped with membranes of different sensitivities and with connecting tubes of different lengths. Z was measured by the tube method and H was measured by comparison with a flat-response pressure transducer. In agreement with the predictions based on a simple lumped-parameters model, we found that Z reached very low values, especially at the frequencies where H had a resonance peak. For instance, for the widespread Validyne MP-45 transducer (200 Pa) with connecting tubes of 16 cm length and 3.8 mm internal diameter a minimum of Z of 8300 Pa s litre-1 at 96 Hz was measured; at that frequency the amplitude of H attained a value of 3.1. Using the above transducer model we simulated the measurement of a rat input impedance up to 128 Hz using Validyne and Celesco transducers. With the Validyne MP-45 (200 Pa), equipped with the same connecting tubes as above, the computed error reached up to 50 per cent for the real part and 140 per cent for the imaginary part.

Animals↗