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Biomedical subjects

R Völker

Publications and source records attributed to R Völker.

18 recordsLinked to original sources
PubMed1993

Influenza vaccines: the effect of vaccine dose on antibody response in primed populations during the ongoing interpandemic period. A review of the literature.

Health authorities tend to favour an increase of the antigen dose in inactivated influenza vaccines from < or = 10 micrograms haemagglutinin (HA) per vaccine strain to 15 micrograms HA/strain. The increased dose is expected to yield a meaningful increase in the number of subjects to be protected after vaccination. To verify this expectation, we have reviewed 20 published reports (1978-1991) of serological studies in which anti-HA-IgG antibody after different doses was measured. In the review, stratification groups of previously primed subjects were formed and the antibody response was estimated for doses of 10 and 15 micrograms HA by linear k*2-chi 2 model. Despite a considerable heterogenicity of study populations, study designs, vaccine types and strains, and antibody assays, the results were consistent in revealing high protection rates (> or = 75%) for a 10 micrograms HA dose of influenza A vaccine components. For both response and protection rates, an increase of the antigenic load from 10 to 15 micrograms HA was not associated with a meaningful increase of seroresponse: in 38 out of 39 stratification groups, the increase of response and/or protection rate varied between -9% and +8%, with a median of 1.5%. These results do not justify the expectation that a vaccine dose of 15 micrograms HA per strain would be clinically superior to a dose of 10 micrograms HA. Only in a group of immune-compromised patients on chronic intermittent haemodialysis were results in favour of a higher dose found, which may justify further evaluation in this special population.

Adolescent↗
PubMed1992

[Gonadotropin release and course of diseases after administration of a GnRH-analog in cattle with follicular-thecal cysts].

Twenty-five heifers and cows with follicular cysts (high level of total oestrogens, low level of progesterone in plasma) were treated with 20 or 50 micrograms buserelin i.m. 5-84 weeks after parturition. Two hours after medication an increased LH release was observed in all animals. In contrast to LH, FSH concentration was not increased in all cows. Twelve days after treatment a high progesterone concentration in plasma could be determined in 17 of 25 treated animals. Twenty cows showed oestrous symptoms 23.5 +/- 9.6 days after medication. The oestrous cycle was prolonged in 10 cows. Nineteen cows were inseminated and 14 cows became pregnant after 1-4 (phi 1.7 +/- 0.9) inseminations (73.6% of all inseminated cows and 56% of all treated cows). The differences in conception rate and in services per conception after treatment with 20 or 50 micrograms buserelin in favour of the higher dosage cannot be attributed to the medication.

Animals↗
PubMed1991

[Changes in the ultrasound power spectrum due to concentric stenoses of the femoral artery of the dog].

An artificial stenosis model consisting of a revolving centric cylinder with six boreholes (10-60% diameter reduction) was implanted in the superficial femoral artery of anaesthezised beagles (n = 10). Range gated pulsed Doppler signals were recorded at 7 sites between three diameters upstream to ten diameters downstream the Angle corrected parameters derived from the contour of spectral lines between 3 and 21dB on both sides of mode frequency were calculated for different time windows. Two groups of dogs could be distinguished. Group A showed marked downstream power spectrum changes which did not correlate to the degree of stenosis. In Group B, in contrast, the degree of power spectral disturbances correlated to the degree of stenosis. It was suggested that partial thrombosis of the stenoses during measurement provides an acceptable explanation for the missing correlation in Group A.

Animals↗
PubMed1990

Effect of different body-exercise modes on the rate response of the temperature-controlled pacemaker Nova MR.

In order to evaluate the effect of different modes of physical exercise on the rate response of the temperature-controlled Nova MR, parameters such as temperature behaviour and correlation of work load to pacing rate were investigated using different types and protocols of stress testing. This study considered 21 patients (age: 66 +/- 12 y). The indications for the Nova MR were AV block (n: 14) and sick sinus syndrome (n: 7). The patients performed two different types of exercise (treadmill n: 13, bicycle n: 14) based on different protocols. We registered the surface ECG, pacing rate, exercise time, and (via data transmission by the RX 2000 programmer) blood temperature and pacing rate. An adequate rate response could be achieved with all the different types of exercise and protocols using more sensitive program settings. The type of stress testing used to adjust or evaluate the Nova MR seems to be secondary, although cycling as compared with treadmill exercise resulted in a slightly weakened reaction of temperature and pacing rate. Our investigations revealed a good correlation between work load and pacing rate independent of the type of stress testing. The initial DIP (48%) is not a constant phenomenon and showed inter- and intraindividual variations. Impressive psychological influences also exhibited an effect on temperature and pacing rate, sometimes preventing a DIP response. During exercise at lower work loads (under 50 watts, shorter than 3-4 min) the rate response of the Nova MR--without any detected DIP--is often delayed due either to a decrease or to a late and flat increase in temperature. An additional fast-reacting sensor could be advantageous in triggering the initial rate response in such cases.

Aged↗
PubMed1988

[Cardiopulmonary stress test in variable frequency stimulation: a comparison of Activitrax and Nova-MR pacemakers in VVI/AAI stimulation].

In seven patients with implanted intermedics NOVA MR pacemakers, we examined the cardiopulmonary effects of maximum bicycle ergometer exercise for three types of pacing in a randomized sequence: VVI or AAI at 70/min (SSI 70), rate adaptive temperature controlled with the implanted NOVA MR, and rate adaptive activity controlled by means of a Medtronic Activitrax pacemaker taped to the chest wall, which triggered the implanted Nova MR in the VVT or AAT mode via skin electrodes. The maximum exercise tolerance was 67 W with SSI 70, 71 W with Activitrax and 91 W with Nova MR. The maximum oxygen uptake was accordingly 17.6 ml/min/kg with SSI 70, 19.5 ml/min/kg with Activitrax, and 21.5 ml/min/kg with Nova MR. The highest heart rate reached was 81 beats/min with SSI 70,98 beats/min with Activitrax and 118 beats/min with Nova MR. The rate increase from rest to maximum exercise was 11 beats/min with SSI 70,29 beats/min with Activitrax and 47 beats/min with Nova MR. An increase in exercise tolerance and maximum heart rate could be achieved with both rate adaptive types of pacing, but significantly more clearly with the temperature controlled Nova MR than with the activity controlled Activitrax. However, using a different form of exercise, e.g. treadmill ergometry, the rate response of the Activitrax would presumably have been somewhat clearer.

Aged↗
PubMed1988

First clinical results with a new temperature-controlled rate-responsive pacemaker. Comparison of Activitrax and Nova MR pacemakers with VVI/AAI pacing.

We examined the cardiopulmonary effects of maximum bicycle ergometer exercise in seven patients with implanted Intermedics Nova MR pacemakers for three types of pacing in a randomized sequence: VVI or AAI at 70 beats/min (SSI 70), rate-adaptive temperature-controlled pacing with the implanted Nova MR, and rate-adaptive activity-controlled pacing with a Medtronic Activitrax pacemaker taped to the chest wall, which triggered the implanted Nova MR in the VVT or AAT mode by skin electrodes. The maximum exercise tolerance was 67 W with SSI 70, 71 W with Activitrax pacing, and 91 W with Nova MR pacing; the maximum oxygen uptake as 17.6, 19.5, and 21.5 ml/min/kg, respectively. The highest heart rate achieved was 81 beats/min with SSI 70, 98 beats/min with the Activitrax, and 118 beats/min with the Nova MR on average; the mean rate increase from rest to maximum exercise was 11, 29, and 47 beats/min, respectively. With both rate-adaptive types of pacing (Nova MR and Activitrax), an increase in exercise tolerance and maximum heart rate could be achieved, but this increase was significantly more obvious with the temperature-controlled Nova MR than with the activity-controlled Activitrax. However, with a different form of exercise, for example, treadmill ergometry, the rate response of the Activitrax would presumably have been somewhat clearer.

Aged↗
PubMed1987

Lead fracture in pacemaker patients.

We studied the incidence of lead fractures in 2,226 patients with a total follow-up period of 8,558 patient years. Lead fractures occurred in 100 out of 2,563 implanted leads (3.9%). This corresponds to an average rate of 1.2% per patient year. We found 62 out of 881 singlefilar coil leads fractured (7.0%), 20 out of 809 Siemens Elema 588 leads (2.5%) and only 6 out of 630 multifilar soil leads (1.0%). Lead fractures occurred at a significantly (p less than 0.05) higher rate in singlefilar coil leads than in Simens Elema 588 leads or in multifilar coil leads. Independent of the type of lead, a significantly (p less than 0.05) higher fracture rate was found with leads implanted through the internal jugular vein. Most fractures occurred either inside the pacemaker pocket or on the way from the connector to the venous entry. Only 7% of all fractures occurred within the vascular system. Patients with a second or third degree AV-block and a multifilar coil lead implanted showed a significantly (p less than 0.05) better survival rate compared to those with a singlefilar coil or a Siemens Elema 588 lead. In pacemaker-dependent patients a replacement of singlefilar coil leads might be considered.

Equipment Design↗
PubMed1985

Survival and follow-up after pacemaker implantation: a comparison of patients with sick sinus syndrome, complete heart block, and atrial fibrillation.

The number of patients receiving cardiac pacemakers for sick sinus syndrome (SSS) has increased considerably in recent years. The literature has suggested that patients with sick sinus syndrome have a shorter life expectancy with pacemaker therapy than patients with total heart block or atrial fibrillation. We studied the survival rate of 1,049 patients with complete heart block, 592 with sick sinus syndrome and 447 with atrial fibrillation. After 10 years we found a survival rate of 54.5% for patients paced for SSS, 34.4% for those with complete heart block, and 24.7% for those with atrial fibrillation (statistical significance: SSS--heart block: p less than 0.05; SSS--atrial fibrillation: p less than 0.01; heart block--atrial fibrillation: NS). Considering the calculated survival rates of a comparable normal population (i.e., 56.5%; 41.2%; 47.8%), the differences in survival expectancy are even more pronounced (SSS-normal: NS; heart block-normal p less than 0.05; atrial fibrillation-normal: p less than 0.05). For patients with sick sinus syndrome, the life expectancy parallels that of the general population, while that of patients with complete heart block or atrial fibrillation have a life expectancy that is considerably lower.

Adolescent↗
PubMed1981

[The Bonn Cooperative Tumor Aftercare Model. A contribution to the amelioration of tumor patient care in the practitioner's office (author's transl)].

Problems of aftercare of tumor patients are so involved that one doctor cannot cope with them single-handed. Every doctor who has care of tumor patients is dependent on the cooperation of doctors of various faculties as with scarcely any other disease. The experience of a specialized multidisciplinary medical team is as indispensable in aftercare as the general medical supervision of the family doctor. In an action financed by the Federal Minister of Health a cooperative model was worked out intended to enable a qualitatively high level of aftercare for tumor patients over a wide field, making full use of the existing medical welfare structure.

Aftercare↗