Biomedical subjects

E Hoorn

Publications and source records attributed to E Hoorn.

7 recordsLinked to original sources

PubMed1999

Tendon displacement assessment by pulsed Doppler tissue imaging: validation with a reciprocating string test target.

After hand trauma and surgery, assessment of tendon excursion is important in reconstructive surgery and rehabilitation. Aimed as a more reliable alternative to traditional noninvasive methods, a colour Doppler imaging scanner was adapted to measure longitudinal tendon displacement. Displacement was quantified by integrating the velocity estimated from the zero-crossing rate of the Doppler signal. The system was tested by measuring displaced distances of a rubber string that was moved back and forth. At a determined optimal receiver gain, 1.5-cm string displacements were measured with less than +/- 0.05-cm bias throughout an echo-signal dynamic range of 22 dB; standard deviations were around 0.05 cm. Regression analysis between measured and true displacements in the range 0.5-2.5 cm resulted in a best fit straight line with slope 0.927, intercept 0.041 cm and residual standard error of 0.06 cm. A transfer technique was conceived to ensure accuracy when measuring tendons in the body. This CDI-based pulsed Doppler system merits verification for measurement of tendon excursion in patients.

Biomechanical Phenomena↗

PubMed1998

Tendon excursion measurements with colour Doppler imaging.

We assessed the applicability of tendon excursion measurement by means of Colour Doppler Imaging (CDI) on human specimens, and also assessed the correlation between values measured by Doppler and by displacement meters. Muscles were separately connected to a mass of 1 kg with a steel wire running over a pulley. This weight moved the telescopic end of a digital displacement meter up and down during passive extension and flexion of the fingers. Excursion was measured with a pulsed multi-channel CDI scanner on the same arm. Assessment of finger tendon excursion with CDI correlated well with the mechanical micro displacement meter, the latter being considered the most accurate method in cadaver studies.

Aged↗

PubMed1991

Serial lung model for simulation and parameter estimation in body plethysmography.

A serial lung model with a compressible segment has been implemented to simulate different types of lung and airway disorders such as asthma, emphysema, fibrosis and upper airway obstruction. The model described can be used during normal breathing, and moreover the compliant segment is structured according to more recent physiological data. A parameter estimation technique was applied and its reliability and uniqueness were tested by means of sine wave input signals. The characteristics of the alveolar pressure/flow patterns simulated with the model agree to a great extent with those found in the literature. In the case of absence of noise the parameter estimation routine produced unique solutions for different simulated pathologic classes. The sensitivity of the different parameters depended on the values belonging to each class of pathology. Some more simplified models are presented and their advantages over the complex model in special types of pathology are demonstrated. Noise added to the simulated flow appeared to have no influence on the estimated parameters, in contradiction to the effects with noise added to the pressure signal. In that case effective resistance was accurately estimated. Where parameters had no influence, as for instance upper airway resistance in emphysema or peripheral airway resistance in upper airway obstruction, the measurement accuracy was less. In all other cases, a satisfactory accuracy could be obtained.

Humans↗

PubMed1991

A lung function information system.

A lung function information system (LFIS) was developed for the data analysis of pulmonary function tests at different locations. This system was connected to the hospital information system (HIS) for the retrieval of patient data and the storage of the lung function variables of patients to generate follow-up reports and to support financial and administrative management. The application programs were developed in such a way that high flexibility was obtained with respect to the patient-computer-technician interaction. The sampled data are stored on a disc to correct earlier decisions, perform recalculations and reanalyse the data for research purposes. When the measurements performed on a patient are authorized, the sampled data are deleted, except for when they are needed for future research. A distributed computer system was chosen to combine the benefits of a centralized system with those of several stand-alone systems. The main tasks of the central unit are to store collected data and computer programs, generate a final lung function report on laser printer and provide a connection to the HIS. In the satellite computers, which are located close to the lung function equipment, the signals and raw data are processed. Furthermore, the satellite computers were in use for program development and several research projects, and for the offline data processing of the lung function measurements from two other hospitals by means of a modem connection. The LFIS improved the quantity and quality of data acquisition. It resulted in an increased capacity of about 50% concerning spirometry, and facilitated time-consuming complex analyses. It also avoided miscalculations and mistakes in reports previously experienced with hand calculations.

Computer Systems↗

PubMed1991

PDPS: a pulmonary data processing system for assessment of gas exchange properties by multiple gas wash-out.

A data acquisition and processing system for the analysis of inert gas wash-out tests is described. The described system is in clinical use on spontaneously breathing patients as well as on mechanically ventilated Intensive Care patients. It combines several analysis techniques with an aim to provide a deeper insight into the nature of existing ventilation inhomogeneity than the individual techniques alone can provide. The signals measured are the respiratory flow, the fractions of one or two indicator gases washing out and the fractions of the metabolic gases oxygen and carbon dioxide. Analysis of these signals provides information concerning the end-expiratory lung-volume, distribution of ventilation and perfusion in the lung, the role of diffusion in the ventilation process and the metabolic oxygen uptake and CO2 release. This article describes the algorithms used and the results that are presented.

Algorithms↗

PubMed1989

A computerized respiratory system including test functions of lung and circulation.

The design of a microcomputer-controlled ventilator for automatic performance of lung function and circulatory tests has been described. It incorporates the characteristics of normal mechanical ventilation and also allows one to perform a multitude of test procedures for lung function and circulatory studies in paralyzed animals. The major components of the setup are a pump assembly with solenoid valves to direct gas flow, an electromechanical servo system, and a MS-DOS microcomputer system. The pump assembly has been constructed as a relatively simple device. Great versatility is created by the use of a microcomputer for the control of the ventilator. The software can be easily adapted to several other types of experimental studies. Besides the keyboard input the ventilator can be controlled by a remote computer system. This allows one to run an experimental protocol automatically and to use it in closed-loop servo ventilation. The flexibility in the choice of the respiratory parameters makes the ventilator suitable for lung function and circulatory studies during artificial ventilation. The ventilator has been successfully used in different animal studies during the last 6 yr.

Animals↗

PubMed1985

Consequences of the O2-CO2 dissociation curves for gas exchange in avian and mammalian lung at various altitudes.

Gas exchange in avian and mammalian lung was studied with computer simulations using mutually dependent O2-CO2 dissociation curves. The mammalian lung was simulated with an ideal mixing unit. The model of the avian lung consisted of 25 ideal mixing units placed in series with respect to the ventilation but placed in parallel with respect to the perfusion (cross-current arrangement). The consequence of the right shift in the avian oxygen dissociation curve, if compared with the human dissociation curve, was studied by application of both dissociation curves to the avian lung model. The influence of a decreased tension of oxygen in the inspired air was studied under conditions of constant PvCO2 (48 mmHg), PvO2 (30 mmHg), RQ (0.70) and approximately constant levels of PaCO2. At sea-level the avian lung needs 80 per cent of the alveolar ventilation and 64 per cent of the cardiac output to transport the same amount of gas if compared with the mammalian lung. The difference in the need for cardiac output resulted from the right shift in the dissociation curve of avian blood. Changing PIO2 from 115 mmHg (2000 m) to 100 mmHg (3000 m) showed a dramatic difference in the performance of the two lung models. The mammalian lung model needed a more than eight fold increase in cardiac output whereas the avian lung model needed less than a three fold increase to maintain a RQ of 0.7. This difference could be ascribed to the Haldane effect in combination with the cross-current arrangement. The Haldane effect was also responsible for an end expired CO2 tension which exceeded the mixed venous CO2 tension.

Adaptation, Physiological↗