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H B Boom

Publications and source records attributed to H B Boom.

At least 55 records · Page 3Linked to original sources
PubMed1990

Automatic stance-swing phase detection from accelerometer data for peroneal nerve stimulation.

The development of implantable peroneal nerve stimulators has increased interest in sensors which can detect the different phases of walking (stance and swing). Accelerometers, having a potential for implantation, are studied as detectors for the swing phase of walking to replace footswitches. Theoretically, we could show that accelerometers can be used to distinguish between stance and swing phase. Attaching accelerometers between ankle and knee joint the equivalent acceleration of the ankle joint was calculated. This resulted in a typical and reproducible signal in which the different walking phases were identified. Automatic detection algorithms, based on cross correlation calculation were developed and tested. Measurements from four healthy and four hemiplegic subjects resulted in a total of 317 and 272 steps, respectively. One of the hemiplegic subjects was considered to be a failure due to large disturbances in the acceleration signal during the swing phase of walking, which may be related to the use of crutches. Taking part of the data as a learning set and the other part as an evaluation set we found two errors in the push-off detection for both the healthy subjects and the remaining three hemiplegic subjects, out of 152 and 106 steps, respectively. In addition, we showed that when using one accelerometer closely below the knee joint almost identical results can be achieved. This could lead to a combination of sensor and stimulator into one implantable device.

Algorithms↗
PubMed1989

Multielectrode intrafascicular and extraneural stimulation.

The relationship between nerve stimulation, pulse amplitude and isometric muscle force was measured to investigate recruitment of motor units. Force addition experiments were performed to obtain insight in the intersection of motor unit groups recruited by different electrodes. Intrafascicular and extraneural multielectrode configurations were used for nerve stimulation. Experiments were performed on rats. The common peroneal nerve was stimulated and the forces of the tibial anterior and extensor digitorum longus muscles were measured isometrically. Recruitment was more stable for intrafascicular electrodes than for extraneural electrodes. Especially for intrafascicular electrodes no strict inverse recruitment was observed. Force addition experiments indicated that small overlap of recruited motor unit groups occurred more often for intrafascicular than for extraneural electrodes.

Animals↗
PubMed1989

A modeling study of nerve fascicle stimulation.

A nerve stimulation model has been developed, incorporating realistic cross-sectional nerve geometries and conductivities. The potential field in the volume conductor was calculated numerically using the variational method. Nerve fiber excitation was described by the model of McNeal. Cross-sectional geometries of small monofascicular rat common peroneal nerve and multifascicular human deep peroneal nerve were taken as sample geometries. Selective stimulation of a fascicle was theoretically analyzed for several electrode positions: outside the nerve, in the connective tissue of the nerve, and inside a fascicle. The model results predict that the use of intraneural or even intrafascicular electrodes is necessary for selective stimulation of fascicles not lying at the surface of the nerve. Model predictions corresponded with experimental results of Veltink et al. on intrafascicular and extraneural stimulation of rat common peroneal nerve and to results of McNeal and Bowman on muscle selective stimulation in multifascicular dog sciatic nerve using an extraneural multielectrode configuration.

Animals↗
PubMed1989

Deactivation in the rabbit left ventricle induced by constant ejection flow.

Pressure generated by the left ventricle after ejection with constant flow was studied for different values of the ejection flow, flow duration, time of flow arrest, and ventricular volume. It was found that pressure after ejection, normalized with respect to isovolumic pressure at the same volume, is regenerated according to a model consisting of an elastance, a resistance, a series elastance, and an additional deactivation component. Deactivation is defined as the difference between the value 1 and the plateau value of the normalized pressure after constant flow ejection. It is shown that this plateau value is constant after constant flow ejection until the minimum in isovolumic dP/dt, i.e., during physiological systole. The plateau value is uniquely related to the value of the normalized pressure at the end of a constant flow ejection. After the end of flow, the plateau is reached after an exponential increase of normalized pressure with a time constant of 10.44 +/- 0.09 ms which agrees with the series-elastance time constant of 10.35 +/- 0.26 ms. These results are discussed with respect to previously found results, and to the implication for predicting pressure generation during physiological flow patterns.

Animals↗
PubMed1987

Left ventricular internal resistance and unloaded ejection flow assessed from pressure-flow relations: a flow-clamp study on isolated rabbit hearts.

Left ventricular pressure-flow relations were studied, using excised working rabbit hearts and imposing constant flow ejections (flow-clamps) to separate the effects of flow on pressure from those of time, flow duration, starting volume, ejected volume, and volume at specified time. Pressure-flow data at given volume and time were independent of flow duration, starting volume, and ejected volume for flow-clamp durations exceeding 30 msec. Flow history independent of pressure-flow relations was linear for flow values larger than +/- 5 ml/sec. The time-varying elastance model, E(t), of the ventricle was extended with a resistive component. Transient effects of flow can be explained by including a second elastance. The resulting verified 3-component model is consistent with recent reported experimental findings. The properties of internal resistance correspond to a constant unloaded ejection flow Qmax, which was tested by extrapolating the linear pressure-flow relations to zero pressure. Qmax reached a plateau value of approximately 25 ml/sec within 50 msec after the start of contraction. In relaxation, Qmax is only slightly smaller. Qmax did not depend on volume; therefore, the following equation was adequate for the relation between pressure, p(t); volume, V(t); and flow Q(t), during the flow-clamped ejections from 30 minutes after the start of the flow: (t) = E(t).(V(t)-Vd).(1-Q(t)/Qmax)

Animals↗
PubMed1987

Lower extremity amputees with peripheral vascular disease: graded exercise testing and results of prosthetic training.

Thirty-nine subjects, mean age 72 (range 52 to 89), with a leg amputation because of peripheral vascular disease performed graded exercise testing at the start of their prosthetic training program. Their walking performance at the end of the program was assessed and compared with the test findings. They had a history and rest electrocardiogram (ECG) examination which revealed cardiac problems in 75% of the patients. The exercise test was performed on a specially designed arm ergometer permitting coordinated exercise of arm and trunk muscles. Cardiac condition was judged by the achieved peak heart rate (mean 125 +/- 3.8 beats per minute) and observed ECG abnormalities. In only three patients exercise-induced ECG abnormalities were found at peak workload. The mean peak workload was 52 +/- 1.9W. It was concluded from these results that the average physical and cardiac condition is poor in vascular leg amputees. In 34 patients (87%) the prosthetic training was successful. Fourteen patients needed a walking frame and twenty could walk without a walking frame. The probability of achieving walking without a walking frame was 70% in patients with peak workload above 45W and 30% in those with peak workload lower than 45W.

Aged↗
PubMed1985

Exercise electrocardiography using rowing ergometry suitable for leg amputees.

Patients unable to perform heavy leg exercises cannot perform standard exercise ECG tests using bicycle or treadmill ergometry. A rowing ergometer was developed to enable an electrocardiographic stress test. Sixteen ambulatory patients with documented coronary insufficiency performed graded exercises. Comparison revealed no significant differences in several areas. Eleven patients with above-knee amputations, inevitable because of peripheral vascular disease, were able to perform rowing exercise only. This can result in cardiac loads adequate for diagnosis of coronary heart disease. No patient experienced difficulties with rowing. Rowing exercise can be a suitable alternative to bicycle exercise for the evaluation of coronary artery disease.

Adult↗
PubMed1984

A three-dimensional muscle model: a quantified relation between form and function of skeletal muscles.

A three-dimensional muscle model with complex geometry is described and tested against experimental data. Using this model, several muscles were constructed. These muscles have equal optimum length but differ in architecture. The force exerted by the constructed muscles, in relation to their actual length and velocity of shortening, is discussed. Generally speaking, the constructed muscles with considerable pennation have great fiber angles, a great physiological cross section, a narrow active and steep passive length-force relation, and a low maximal velocity of shortening. The maximal power (force times velocity) delivered by the constructed muscles is shown to be almost independent of the architecture of the muscles. The steepness of the passive length-force relation is determined mainly by the shortest fibers within the group of constructed muscles, whereas maximal velocity of shortening and the width of the active length-force relation are determined mainly by the longest fibers. The validity of the three-dimensional muscle model with respect to some morphological and functional characteristics is tested. Length-force relations of constructed muscles are compared with the actual length-force relations of mm. gastrocnemii mediales and mm. semimembranosi of male Wistar rats. Moreover, actual fiber angle, fiber length, and muscle thickness of three mm. gastrocnemii mediales are compared with values found for constructed muscles. It is concluded that the three-dimensional muscle model closely approximates the actual muscle form and function.

Animals↗