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PubMedDate not supplied

Yield of the screening review of systems: a study on a general medical service.

STUDY OBJECTIVE: To determine the usefulness of screening reviews of the cardiopulmonary and gastrointestinal systems during medical admissions. DESIGN: Case series. SETTING: General internal medicine ward of a university hospital. PATIENTS: 550 consecutive medical patients were initially screened at admission. The authors excluded 265 patients with life-limiting medical conditions, and they studied 98 patients with no known cardiopulmonary disease and 207 patients with no known gastrointestinal disease. INTERVENTIONS: Positive responses to screening systems review questions were evaluated using a standardized testing algorithm. MAIN OUTCOME MEASURES: Numbers of new diagnoses; potential for patient benefit. MAIN RESULTS: The authors made 26 new diagnoses for 25 patients (95% confidence limits, 16 to 37 patients), two of whom may have gained years of life as a result. CONCLUSIONS: The absolute yield of the screening cardiopulmonary and gastrointestinal reviews of systems of 550 patients admitted to an internal medicine service of a university hospital was a new diagnosis in about 5% of patients. An estimate of the cost-effectiveness compares favorably with those of other accepted screening practices.

Adult↗
PubMed1991

Noninvasive cerebral optical spectroscopy for monitoring cerebral oxygen delivery and hemodynamics.

OBJECTIVE: To present an algorithm for noninvasive measurement of cerebral oxygen saturation (cerebral oximetry) and cerebral hemodynamics with near infrared spectroscopy. DESIGN: In vitro correlation of oximetry measurements with reference measurements; illustrative cases of hemodynamic and oximetric recordings. SETTING: Tertiary care neuroscience ICU. PATIENTS: Brain-injured patients with a prolonged, decreased level of consciousness chosen as illustrative examples. INTERVENTIONS: Two-channel multiple wavelength diffuse infrared transmission spectroscopy was interfaced with the scalp using adhesive. Transmission data were collected with gross superficial-to-deep spatial resolution. Saturation calculation based on the deep signal was observed longitudinally in the patient. With the same technology, arterial input and cerebral response functions, generated by iv tracer bolus, were deconvoluted to measure mean cerebral transit time. MEASUREMENTS AND MAIN RESULTS: A positive linear regression fit between diffuse transmission oximetry and measured blood oxygen saturation over the range 23% to 99% (r2 = .98, p less than .001) was noted. CONCLUSIONS: The approach used overcomes previously identified difficulties with cerebral oximetry, and demonstrates excellent in vitro correlation. The technique can be performed clinically without difficulty. A simultaneous measure of mean cortical transit time is possible.

Brain↗
PubMed1989

Estimating lung mechanics of dogs with unilateral lung injury.

Extended least-squares algorithms using transpulmonary pressure and airway flow data from ventilatory waveforms were studied for their ability to track parameters of one- and two-compartment models of lung mechanics. A recursive extended least-squares algorithm with discounted measures estimated parameters of discrete-time models during synchronized intermittent mandatory ventilation. In tests on seven dogs developing oleic acid-induced unilateral hemorrhagic pulmonary edema, the one-compartment estimator responded rapidly and appropriately to changes in mechanics: compliance fell to 0.55 +/- 0.15 of its initial value and resistance rose by a factor of 1.8 +/- 0.5 in 3 h following injection of oleic acid. One-compartment parameter estimates revealed a difference between the airway resistance of inspiration and expiration. Two-compartment estimates were seldom physiologically plausible. The difference between inspiratory and expiratory resistance may have caused the two-compartment estimator to fail when applied to data from the entire respiratory cycle; when only expiratory data were used for estimation, the two-compartment estimates were meaningful. These estimates demonstrated increasing lung inhomogeneity after oleic acid was injected; at the end of 3 h, the ratio of the time constants of the two compartments ranged from 5 to 20 in six of the seven dogs. We conclude that the one- and two-compartment estimates may be combined to provide a meaningful assessment of lung mechanics.

Animals↗
PubMedDate not supplied

Computer-assisted measurement of peripheral blood flow.

An automated system for the measurement of peripheral blood flow using venous occlusion plethysmography based on the low-cost Apple II microcomputer, together with purpose-built compressor unit and data acquisition interface, has been developed. The computer performs the dual role of controlling the timing of inflation and deflation of the occluding cuffs and recording the resulting increase in limb circumference. Ten 8 s epochs of data are acquired and analysed per session. Flow rate is computed using a least squares fit between 0.5 and 4.0 s after cuff inflation, giving on-line indication of blood flow. Venous capacitance and digital systolic pressure may be measured using additional algorithms. The system has been used for the investigation of circulatory disorders and in the assessment of drugs acting on the peripheral circulation.

Blood Pressure↗
PubMed1987

Diabetes mellitus and exercise.

The study deals with the subject of exercise in diabetic patients, with particular emphasis on acute physical stress in type--I and type--II diabetics. The principal task was to define metabolic changes as they occur in the diabetic subjected to acute stress induced by exercise, in comparison with non-diabetics; metabolic changes during prolonged stress as well as during the period of rest; and finally, to propose, on the basis of authors' experimental results and detailed literature research, appropriate rules of procedure for prescriptive exercise for the individual patient. There were 120 subjects divided into 8 groups. Using primarily a bicycle ergometer, the members of the individual groups were subjected to physical stress of various intensity and duration. A detailed analysis of each subject's metabolic response was performed, involving an assessment of 35 physiological and biochemical parameters, with main focus on determining biochemical changes. The study results are presented in detail both with respect to the metabolic response to a given stress in individual groups and comparatively for individual parameters with regard to specific stress rates and groups. Significant differences were found in the metabolic responses concerning the following parameters: acid-base balance, potassium, triglycerols, glucose, cholesterol, FFA, free glycerol, lactate, uric acid. On the basis of the results of experimental measurements, the following algorithm has been designed for prescribing exercise to diabetics: appropriate motivation; determination of the type of exercise; determination of the intensity of exercise; determination of the duration of exercise; respecting related contraindications and complications. A conclusion has been made that provided all possible risks and contraindications as well as prescription guidelines are respected, exercise is to be considered one of the basic principles of diabetes management.

Acid-Base Equilibrium↗
PubMed1991

Structural interpretation of fluorescence resonance-energy transfer measurements.

Fluorescence resonance-energy transfer (FRET) has been widely used to determine distance information in macromolecular systems. However, little has been written about methods for combining FRET distances into coherent structural models. I argue that the methods used so far are inappropriate. This paper describes an algorithm specifically tailored for finding structures from FRET measurements. This algorithm finds structures which fit the experimentally measured parameter, the efficiency of energy transfer, rather than derived distances. The algorithm was implemented in Mathematica and applied to FRET distances obtained for the contractile protein actin. The approach used is applicable to other experimental techniques which measure distances between a relatively small number of loci.

Energy Transfer↗
PubMed1988

Heart rate correlation, response time and effect of previous exercise using an advanced pacing rate algorithm for temperature-based rate modulation.

A temperature-based algorithm to produce pacing rate that resembles chronotropic response to activity was developed. Measurement criteria for the algorithm included workload dependent rate increases with activity and response time within 60 seconds of exercise onset. To evaluate the algorithm, right ventricular blood temperature was recorded during rest and treadmill exercise in 25 patients with implanted Kelvin 500 pacemakers (Cook Pacemaker). Patients included 16 males and nine females, ages 44-81 (mean 72). Indications for pacing were sinus node disease, atrioventricular block and atrial fibrillation with slow ventricular response. Temperature changes reflected physical activity as well as emotional stress. The algorithm was based on the rate of change (dT/dt), the relative change (delta T) and the baseline history (T) of temperature. At exercise onset, a rapid, brief drop in temperature (dT/dt) typically occurred due to peripheral vasodilation, causing prompt increase in pacing rate. As exercise continued, the increase in metabolic rate caused dT/dt as well as delta T to increase, further increasing pacing rate. After exercise, temperature returned to resting level which correspondingly decreased the pacing rate. Sensitivity of the algorithm to temperature variations, and the upper and lower pacing rate limits were programmable to adapt to individual patient needs. The rates produced by the algorithm mimicked intrinsic rate response for various activity levels and produced a mean response time of 16 seconds from exercise onset. Previous exercise had no significant effect on response time. Correlation between normal chronotropic response and simulated pacing rate from five exercise tests was 0.92. These results show good specificity and refute the statement that blood temperature yields a slow response.

Adult↗
PubMed1985

Reproducibility of left ventricular area and volume measurements using a computer endocardial edge-detection algorithm in normal subjects.

The variability of serially recorded 2-dimensional echocardiograms in normal subjects was determined. During a 2-week period, 10 normal subjects underwent echocardiography 5 times, in 2 laboratories, with use of different ultrasonographs. The video recordings were analyzed using a computer image analysis system (Quantic 1200) to provide standardized left ventricular short-axis areas and area ejection fraction (EF). Left ventricular volumes and volume EF were calculated. The 95% confidence limits of the percent difference for end-diastolic area and volume between 2 samples in a given subject were +/- 16.8 and +/- 16.7%, respectively. The limits for end-systolic area and volume were +/- 15.8 and +/- 17.0%, respectively. The 95% confidence limits for differences of area and volume EF between 2 recordings were +/- 12.8 and +/- 9.7%, respectively. No correlation was found between clinical grade (image quality) and the variability of area measurements. A good correlation (r = 0.98) was found between area and volume EF for any given subject over the 5 observations. These confidence limits are narrower than those previously recorded.

Adult↗
PubMed1987

Gait reaction reconstruction and a heel strike algorithm.

A mathematical model of gait ground loading is presented. The model allows the ground reactions produced by any particular single- or multiple-footfall pattern to be constructed, given a sufficient variety of other measured ground reactions. An algorithm which uses center of vertical pressure data only to determine the instants of successive heel strikes on a large force plate is then presented. Experiments show the high accuracy of the heel strike algorithm and show that reconstructions of the vertical component of ground reactions are typically within 3% of corresponding measured reactions. The techniques presented allow certain problems associated with small force plates and other problems associated with large force plates to be largely overcome.

Algorithms↗
PubMed1985

Reconstruction algorithm for incomplete projections in the framework of linear operators in normed linear spaces.

Based on the linearity of the Radon transform and the convolution-backprojection reconstruction algorithm, a new linear-vector space notation is introduced that is of general use in computed tomography (CT). Using this notation, a consistency condition for the completion of incomplete projection data is described. This consistency condition leads to singular or ill-conditioned systems of linear equations for the unknown projection data. Using regularization methods, an algorithm for the consistent projection completion is presented that can exploit symmetries of the missing data region. The performance of the new algorithm is documented with simulated and actualy measured CT-projection data. The algorithm quantitatively improves CT reconstructions with realistic amounts of data and noise and can be used for the completion of arbitrary regions of missing projections.

Fourier Analysis↗
PubMedDate not supplied

Towards the estimation of three-dimensional temperature fields from noisy temperature measurements during hyperthermia.

The temperatures at most locations are unknown during clinical hyperthermia because temperature data are obtained at only a few discrete locations. In an attempt to further develop a technique for possibly solving this problem, the feasibility of using state and parameter estimation methods to predict three-dimensional temperature fields during hyperthermia treatments is investigated. Previous studies attempting to solve this problem have been limited to only one or two spatial dimensions. This paper investigates some conditions for which an estimation method can predict the complete three-dimensional temperature field for controlled numerical experiments with additive measurement noise. For the range of perfusion patterns considered, results show that the steady-state temperature field can be estimated to within 1 degree C if there is no measurement noise, no model mismatch, and as few as three measurement locations for seven perfusion zones. The addition of measurement noise degrades the performance of this estimation algorithm, especially when the number of measurement locations is small. Use of Tikhonov regularization of order zero significantly improves the performance of the algorithm for these cases. It was found that there is an optimal regularization parameter which maximizes the algorithm performance. This optimal value is a function of the perfusion magnitude and pattern. The present numerical results indicate that the approach used to solve this difficult and ill-posed problem could potentially be extended to estimate the complete temperature field in more realistic clinical conditions, but considerably more progress must be made before that goal can be reached.

Algorithms↗
PubMed1990

An algorithm for the interpretation of cardiopulmonary exercise tests.

We have developed and are using an algorithm for the interpretation of cardiopulmonary exercise tests that are performed in our Pulmonary Diagnostic Service Department. As its decision points, this algorithm uses routinely obtained measurements from the results of these exercise tests, such as VO2, VCO2, VE, SaO2, HR, and AT. Using the algorithm results in an objective determination of limitation to exercise and allows for the differentiation between pulmonary and cardiac or circulatory limitation. This straightforward technique for arriving at an interpretation of these tests has resulted in a more consistent approach to interpretation and an excellent teaching guide for physicians and technicians.

Algorithms↗
PubMed1989

In vivo evaluation of a noninvasive method to measure the retinal thickness in primates.

To diagnose certain macular diseases earlier and monitor their therapy more sensitively, we are developing a noninvasive method to measure the retinal thickness. The new instrument, which is an extension of slit-lamp biomicroscopy, was used to obtain the data, which were analyzed with an algorithm to yield thickness measurements. The measurements performed in monkeys indicated that the retinal thickness can be visualized in a region extending from the optic disc to the fovea and that quantitative results can be obtained. The retinal thickness reproducibility was 6% for the same location on the same day, 15% for the same location on different days, and 12% for the same location in different eyes. The average retinal thickness in these areas was 335 microns, indicating that the reproducibility was between 20 and 50 microns. Measurements across the foveola illustrated that retinal thicknesses as low as 80 microns could be obtained.

Animals↗
PubMed1986

Morphological measurement of the SEP using a dynamic time warping algorithm.

A dynamic time warping technique was created to align the components of digitally high-pass (300 Hz-2500 Hz) filtered somatosensory evoked potentials evoked by median nerve stimulation recorded with a bipolar cephalic montage. A cost function was assigned related to the amount of warping necessary to match a standard wave derived from 24 normal subjects. Its value ranged from 0.525 to 2.456 (mean 1.305 +/- 0.501). This contrasted with a mean of 5.089 +/- 4.277 (range 0.701-13.972) derived from 25 patients with definite (n = 24) or possible (n = 1) multiple sclerosis chosen on the basis of having few or no clinical abnormalities at the time of testing. Fourteen (56%) of the patients had cost functions that were 3 or more S.D.s above the normal mean as compared to 3 (12%) having prolonged latency of the N19 peak. When used in combination, the cost function and latency yielded 60% abnormalities; 5 times higher than latency measurement alone.

Adult↗
PubMed1989

Automated determination of the magnitude and time delay ("phase") of the cardiac cycle dependent variation of myocardial ultrasonic integrated backscatter.

An algorithm for quantitative description of cardiac cycle dependent variation of integrated backscatter (cyclic variation) has been developed and is shown to be suitable for analysis of nonsinusoidal data typical of ultrasonic tissue characterization measurements from myocardium in vivo. The algorithm produces estimates of the magnitude of variation and of the time delay relative to the electrocardiographically recorded QRS-complex. To validate the algorithm, 246 integrated backscatter measurements were analyzed both manually and by the automated method. The magnitude and time delay estimates from the two methods correlated closely. With a separate set of data, the algorithm produced reasonable descriptions of the cyclic variation for 89 of 101 integrated backscatter measurements. Only modest computational power is required for effective implementation of this algorithm, facilitating inclusion of online automated analysis capabilities in quantitative ultrasonic tissue characterization systems.

Algorithms↗
PubMedDate not supplied

A method of calculating peripheral dose distributions of photon beams below 10 MV.

The radiation dose outside the radiotherapy treatment field can be of clinical concern and, therefore, a method of accurately predicting the peripheral doses received by tissues would be beneficial. This paper describes a semiempirical method developed for calculating the peripheral dose received at points outside the collimated field edge for incident photon beams with energies below neutron production thresholds (less than 10 MV). The dependence of the peripheral dose upon depth, distance, field shape and size, azimuthal angle about the central axis, external contour variations, and tissue heterogeneities are accounted for by this calculation. Predictions by this algorithm are compared with measurements and it is shown that the method is capable of reproducing the measured peripheral dose values usually to within the statistical uncertainties of the data.

Algorithms↗
PubMed1991

Noninvasive measurement of transmural gradients in myocardial strain with MR imaging.

A method is presented for performing high-resolution strain measurements by using magnetic resonance (MR) tagging. Multispectral radiofrequency pulses are used to produce tagging grids from which strain estimates are obtained with a resolution of 2 mm. A tag detection algorithm is presented that measures the center of a tag line with a precision that ranges from 0.1 to 0.2 mm over the systolic interval. With this method, a transmural gradient in the strain of a normal dog heart was detected.

Animals↗
PubMed1988

Wideband external pulse recording during cuff deflation: a new technique for evaluation of the arterial pressure pulse and measurement of blood pressure.

Analysis of the external brachial pulse recorded during standard blood pressure cuff deflation with use of a transducer with a wide frequency response has revealed a reproducible pattern with three distinct components that we have labeled K1, K2, and K3. K1 is a low-amplitude, low-frequency signal that is present with cuff pressures above systolic pressure. K2 is a triphasic signal appearing at systolic pressure and disappearing at diastolic pressure, which approximately corresponds to the audible Korotkoff sound. K3 appears with cuff pressure between systolic and diastolic pressure and continues to be present below diastolic pressure. Intra-arterial pressure recordings made with a high-fidelity Millar catheter-tip manometer revealed K2 and K3 analogs. K3 resembles the intra-arterial pressure waveform and when calibrated according to the pulse pressure, noninvasive dK3/dt determinations correlated well with intra-arterial dP/dt measurements. The appearance/disappearance property of K2 was designated as the "K2 algorithm" and represents a new, objective noninvasive method for measurement of blood pressure. The K2 algorithm compares favorably with intra-arterial measurements, is more accurate than the auscultatory technique, and may be especially useful in clinical situations in which the auscultatory technique does not work well.

Adolescent↗