Biomedical subjects

R Kingma

Publications and source records attributed to R Kingma.

9 recordsLinked to original sources

PubMed2006

Intracranial penetration of a halo pin causing an epileptic seizure.

A 71-year-old man with ankylosing spondylitis and an unstable fracture of the 6th and 7th cervical vertebrae was managed with a halo vest. Eight weeks following application the halo had shifted because of a loose pin. The patient's only complaint at the time was a headache but this was followed two days later by a seizure. An MR scan of the brain showed a swollen cortex under the right dorsal pin as a result of a perforation of the internal lamina by the pin. The halo was removed and anti-epileptic medication commenced. The patient had no further seizures.

Aged↗

PubMed2003

Measures of cardiovascular autonomic nervous function: agreement, reproducibility, and reference values in middle age and elderly subjects.

AIMS/HYPOTHESIS: Currently, three categories of cardiovascular autonomic nervous function measures are used: classic Ewing-test measures, measures of heart-rate variability (HRV), and measures of baroreflex sensitivity (BRS). Little is known about the agreement between these measures, and reference and reproducibility values for these measures have not been reported within the same group. METHODS: As part of the Hoorn Study, 631 subjects aged 50 to 75 participated in a study of autonomic nervous function. Cardiac cycle duration (RR interval) and continuous finger arterial pressure were measured under three conditions: during spontaneous breathing, during six deep breaths over 1 min, and during an active change in position from lying to standing. From these readings, ten measures of autonomic function were assessed (mean heart rate, three Ewing test measures, five HRV measures and one BRS measure). RESULTS: Regression analysis in a healthy subgroup (n=191) showed sex differences for two of the ten measures and seven measures decreased with age. Therefore, appropriate age-specific and sex-specific reference values were calculated. Reproducibility (n=39) of most measures was moderate, with a reliability coefficient of around 50%. Agreement between the measures of autonomic nervous function varied greatly, between 0% and 87%. The HRV-power ratio measure and the blood pressure changes in the lying-to-standing test showed the lowest agreement with all other measures. CONCLUSION/INTERPRETATION: This study provides age-specific and sex-specific reference values for a wide range of different autonomic function measures in an elderly population. Agreement among the different measures varied widely and reproducibility was only moderate.

Aged↗

PubMed2000

A baroreflex model of short term blood pressure and heart rate variability.

Parameters based on heart rate variability alone or on both heart rate and blood pressure variability (baroreflex sensitivity) are becoming increasingly clinical relevant. Nevertheless a complete insight in physiological mechanisms underlying these parameters is still lacking. A computer model may help to fill up some of the gaps. We present a model which consists of a simple beat-to-beat hemodynamic part (Starling heart and Windkessel) linked to a detailed continuous modelled neural control part. The intermediate between continuous and beat-to-beat part is an integral pulse frequency modulator (IPFM) acting as cardiac pacemaker. Input for the IPFM is a "sympathovagal" balance signal, with different dynamics for sympathetic and vagal branches. Low-frequency variability is supposed to arise from resonance of existing noise, while high-frequency variability (respiration) is assumed to enter the closed loop at the hemodynamic (blood pressure) site. Results of three studies have been used for validation: (1) spontaneous variability in heart rate and blood pressure (baroreflex transfer functions), (2) vagal blockade with atropine, (3) a modified Valsalva manoeuvre performed in normal and quadriplegic man. Steady state as well as dynamic properties of the model reasonably well fitted to these experimental data.

Autonomic Nervous System↗

PubMed1998

Evaluation of catheter-mounted transducers for intra-oesophageal pressure recording in respiratory function tests.

Oesophageal pressure measurements in respiratory function tests are commonly performed using a balloon-catheter system. This study investigates the usefulness of catheter-mounted pressure transducers as an alternative to balloon-catheter systems. Calibration related physical properties of the catheter mounted pressure transducers are evaluated in vitro. The behaviour of these transducers in vivo is evaluated in ten volunteers by relating pressures measured in the oesophagus to airway opening pressures and by comparing these relationships with those sequentially obtained by a balloon-catheter system. The catheter-mounted pressure transducers show no drift after a proper preparation procedure. These catheters, with integrated pressure transducers, are tolerated significantly better by the subjects than are balloon catheters. The catheter-mounted pressure transducers are found to give an equivalent performance compared with the balloon-catheter system, if relative pressures are of interest. However, unpredictable and uncontrollable shifts in offset occur during the in vivo measurements, disturbing absolute pressure readings. Possible explanations for these shifts are the presence of bubbles and adhesion of mucus to the transducers, exerting Van der Waals forces, and contact with the tissue of the oesophageal wall. These shifts are found to be quite stable throughout a period of measurement and therefore of minor disturbance to relative pressure measurements, for instance in assessing the elastic properties of lungs.

Adult↗

PubMed1995

On the quantification of heart rate changes in autonomic function tests: relations between measures in beats per minute, seconds and dimensionless ratios.

1. Disorders of the autonomic nervous system are frequently diagnosed by measuring heart rate changes in response to deep-breathing and lying-to-standing manoeuvres. The heart rate changes in these manoeuvres are quantified in measures using various units, like beats per minute, seconds and dimensionless ratios. 2. In the present study we mathematically derived relationships between the measures which quantify heart rate changes in beats per minute, seconds and dimensionless ratios. The theoretical outcomes were experimentally confirmed by the results of the deep-breathing and the lying-to-standing test in 525 healthy and diabetic subjects. The measures were found to be non-equivalent, because the mean RR interval duration influenced the measures in different ways. 3. It is argued that measures in seconds are preferable to measures in beats per minute or ratios, because the physiological interpretation of this measure is easier, and the sensitivity of measures in seconds is expected to be greater. 4. Finally, we recommend that measures of heart rate variation in the deep-breathing and lying-to-standing manoeuvre are accompanied by information on the mean RR interval duration or mean heart rate to allow correct interpretation of the measures.

Autonomic Nervous System↗

PubMed1995

Effects of ketanserin on heart rate and blood pressure variability: implications for the effect on the baroreflex mechanisms.

Ketanserin is an antihypertensive drug with affinity to both serotonin S2- and alpha 1-adrenoceptors. The specific effects of ketanserin on the baroreflex are not fully understood. We, therefore, studied baroreflex regulation based on blood pressure (BP) and heart rate (HR) responses to several maneuvers before and after the administration of 2 x 5 mg of ketanserin i.v. both in supine and in standing posture. Seven young healthy volunteers were investigated. We measured spontaneous variability in HR and BP (Finapres), and performed deep inspiration, Valsalva, and lying-to-standing tests. We also used a modified Valsalva maneuver that consist of Deep Inspiration Breath-holding with closed glottis and EXpiration: DIBEX maneuver. From the BP recordings, peripheral resistance (TPR) and stroke volume (SV) were estimated by the Modelflow method. Thirty minutes after the administration of ketanserin, there was no significant change in mean HR, BP, spectral power of HR and BP variability, baroreflex sensitivity, or Valsalva ratio. Thus ketanserin did not affect the cardiac baroreflex mechanism. However, in standing position, SV increased and TPR decreased under the influence of ketanserin, and BP overshoot after the Valsalva and DIBEX maneuver was significantly decreased as well. There was also no reflex recovery of BP during the DIBEX maneuver in three volunteers, who felt faint. These observations indicate that there is a lack of vasoconstriction. We conclude that ketanserin is not a vasodilator but seems to inhibit vasoconstriction.

Adult↗

PubMed1994

Comparison of two techniques to measure the motor nerve refractory period distribution.

The techniques introduced by Ingram et al. and by Kimura to assess the motor nerve refractory period distribution were compared in the peroneal nerve of 28 healthy subjects. Twenty of these subjects were examined twice with an interval of 6-20 days. Results obtained with Ingram's technique yielded a narrower refractory period distribution, displayed less inter-individual variability, and were more reproducible than those obtained with Kimura's technique. The mean refractory period for the 5% slowest recovering fibres (MRP95) was 1.51 msec (S.D. 0.14) for Ingram's technique and 2.15 msec (S.D. 0.72) for Kimura's technique. The coefficient of variation of the MRP95 was 8% for Ingram's technique, and 22% for Kimura's technique. The present data do not allow a definite conclusion concerning the association of refractory period with age, gender and height. Ingram's technique would be favoured for practical application over Kimura's technique on the basis of this study.

Action Potentials↗

PubMed1993

Comparison of two techniques to measure the motor nerve conduction velocity distribution.

Hopf's technique to measure the distribution of motor nerve conduction velocities (DMCV) has been compared with the technique introduced by Ingram et al. in the peroneal nerve of 28 healthy subjects 41.2 (S.D. 8.4) years. Twenty subjects were examined twice. Both techniques yielded an equal DMCV and equally reproducible results. Group mean velocities for the slowest examined (MNCV95) motor nerve fibres were 39.0 m/sec (S.D. 3.3) for Ingram's technique and 38.6 (S.D. 3.6) for Hopf's technique. The conventional MNCV was always slower than the velocity of the 5% fastest fibres estimated from the DMCV. Ingram's technique may have a number of merits which may have been obscured by measurement in the peroneal nerve, which may be of advantage in shorter nerve segments or faster nerve fibres. On the basis of our data in the peroneal nerve of healthy subjects no preference can be given for either of the techniques.

Action Potentials↗

PubMedDate not supplied

Revising death education.

Current nursing education approaches toward death and dying are outdated and need revision. Inadequate preparation in this critical area causes problems for students after they graduate. Practicing nurses report they are unprepared academically to cope with the stresses of working with dying clients and their families. The author reviews the role of formalized death education programs for students in lowering personal anxiety and discomfort while teaching skillful interventions for professional practice.

Adaptation, Psychological↗