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Biomedical subjects

W Wieling

Publications and source records attributed to W Wieling.

At least 55 records · Page 3Linked to original sources
PubMed1997

Are portable folding chairs useful to combat orthostatic hypotension?

The effect of sitting on a derby chair (height, 48 cm), fishing chair (38 cm), and footstool (20 cm) on the improvement of postural hypotension was studied serially in 8 patients with autonomic failure. The increment in blood pressure during sitting was higher by using a lower portable chair. This was related to an increasing cardiac output at lower sitting heights. The fishing chair was, according to our patients' experience, most useful.

Aged↗
PubMed1997

The Valsalva manoeuvre as a cardiovascular reflex test in healthy children and teenagers.

The objective of this study was to determine whether the Valsalva manoeuvre is applicable as a test for neurocardiovascular control in healthy children and teenagers. Sixty-eight 6- to 16-year-old children and teenagers performed two Valsalva manoeuvres in the sitting position. They were instructed to maintain airway pressure (strain) for 15 s at 30 mmHg in the first and at 40 mmHg in the second manoeuvre. Finger arterial pressure and heart rate were monitored continuously. In three of the 68 subjects it was not possible to obtain a reliable blood pressure recording due to movements of the finger and/or hand. Only 10 subjects were able to reach a strain of 30 mmHg and to maintain this strain constant during 15 s; in the others the level or the duration of the strain varied substantially. Nine subjects kept strain at 40 mmHg during 15 s. With a Valsalva manoeuvre of 30 mmHg, control values of blood pressure and heart rate in the last 5 s prior to the manoeuvre increased in 11 subjects. Notwithstanding the large range in straining (15-55 mmHg), on visual inspection blood pressure and heart rate responses known from studies in adults could be recognized in 57 of the 65 subjects. In the other eight subjects atypical heart rate responses were observed. Forty-four of the 65 subjects could perform a Valsalva manoeuvre with a higher airway pressure compared to the first manoeuvre: range 35-55 mmHg. The higher airway pressure resulted in more pronounced blood pressure and heart rate responses. There was no correlation between age and gender versus airway pressure. It was concluded that the Valsalva manoeuvre generated blood pressure responses as found in adults. Heart rate responses were sometimes atypical, and needed underlying blood pressure measurement for full interpretation. For quantitative analysis the test was hampered by the inability of the majority of our young subjects to produce the exact strain during the 15-s period. Qualitatively, however, the Valsalva manoeuvre seems applicable as a cardiovascular reflex test to assess neurocardiovascular control in children and teenagers.

Adolescent↗
PubMed1997

Variability of near-fainting responses in healthy 6-16-year-old subjects.

1. Fainting is a common phenomenon in young subjects, but the final events before the actual faint are not well known. The aim of the present study was to study the inter-individual variability of haemodynamic events associated with near-fainting in children and teenagers. 2. Sixty-eight healthy subjects (aged 6-16 years) performed a 70 degrees tilt-up test with intravascular instrumentation for 5 min. Responses in 29 near-fainting subjects were analysed and compared with 39 non-fainting subjects. Arterial pressure was measured by Finapres. Left ventricular stroke volume was computed from the pressure pulsation waveform. 3. Inability to maintain vasomotor tone was the mechanism underlying near-fainting in the vast majority of near-fainting subjects. The three classical haemodynamic responses (vasovagal, vasodepressor and vagal) could be recognized, but large individual differences were found. After tilt back, blood pressure in near-fainters showed a mirror response to the stage before tilt-back; blood pressure gradually increased and was normal at 1 min after tilt-back. 4. The variability in haemodynamic responses on approach of an orthostatic faint is wide in the young.

Adolescent↗
PubMed1997

Pathophysiological mechanisms underlying vasovagal syncope in young subjects.

The occurrence of vasovagal fainting is common in young subjects, but the origin of the precipitating hemodynamic mechanisms involved remain a subject of considerable speculation. Vasovagal fainting is not a sudden onset phenomenon, early failure of vascular resistance responses occurs in faint-prone young subjects. The variability of hemodynamic responses during the actual faint is large, but the main mechanism operative during, is withdrawal of sympathetic outflow to blood vessels in skeletal muscle with impairment of ability to maintain vasomotor tone.

Adolescent↗
PubMed1997

Neural circulatory control in vasovagal syncope.

The orthostatic volume displacement associated with the upright position necessitates effective neural cardiovascular modulation. Neural control of cardiac chronotropy and inotropy, and vasomotor tone aims at maintaining venous return, thus opposing gravitational pooling of blood in the lower part of the body. The present concept of the vasovagal response or "common faint" implicates the development of inappropriate cardiac slowing due to sudden augmentation of efferent vagal activity, and arteriolar dilatation by sudden reduction or cessation of sympathetic activity. The venous pooling associated with lasting orthostatic stress results in development of central hypovolemia. At a certain point during the ongoing reflex adaptation to the hypovolemia in progress, a depressor reflex is set in train. The depressor reflex input along this second "peripheral" afferent pathway is postulated to originate from various sites in the cardiovascular system but remains uncertain. The common faint in humans is of both vaso- and vagal origin; the pure vagal response is less common than its vasodepressor variant. There is strong evidence for an early loss of vasomotor tone in the majority of fainting subjects. Blocking the vagus nerve or cardiac pacing is not of much help in preventing vasovagal syncope; though atropine or pacing may prevent bradycardia in vasovagal fainting, they have never been proven to prevent hypotension. Baroreflex modulation of autonomic outflow remains present during the presyncopal stages until it becomes offset by an opposing depressor reflex with relative bradycardia and relaxation of arterial resistance vessels. The nature of the vasodilatation associated with the vasovagal response has still not been settled.

Adaptation, Physiological↗
PubMed1997

Unusual recovery from acute panautonomic neuropathy after immunoglobulin therapy.

A 33-year-old woman with acute idiopathic postganglionic panautonomic neuropathy experienced prompt recovery of all dysautonomic symptoms after receiving high-dose intravenous immunoglobulin therapy. Her recovery was complete within 6 months after onset of disease. This unusually rapid and complete recovery in comparison with that of historical control subjects suggests that patients with acute, severe, and widespread autonomic failure might benefit from intravenous immunoglobulin therapy.

Acute Disease↗
PubMed1996

Circulatory response evoked by a 3 s bout of dynamic leg exercise in humans.

1. The mechanisms underlying the pronounced transient fall in arterial blood pressure evoked by a 3 s bout of bicycle exercise were investigated in twenty healthy young adults and four patients with hypoadrenergic orthostatic hypotension. 2. In healthy subjects a 3 s bout of upright cycling induced a 28 +/- 3 mmHg fall in mean arterial pressure at 12 s. The fall in mean arterial pressure was preceded by a 12 +/- 2 mmHg rise in right atrial pressure at 3 s and accompanied by a 54 +/- 7% increase in left ventricle stroke volume at 6 s. Systemic vascular resistance dropped 48 +/- 2% at 7 s after the start of the manoeuvre to remain at that level for approximately 5 s. The total response lasted about 20 s. During sustained upright cycling the initial fall in mean arterial pressure was also present, but less pronounced (17 +/- 2 vs. 26 +/- 3 mmHg). A 3 s bout of supine cycling in four patients with hypoadrenergic orthostatic hypotension also elicited a pronounced fall in mean arterial pressure (22 +/- 4 mmHg) and in systemic vascular resistance (38 +/- 4%). 3. A bout of exercise with a large muscle mass induces two main effects. First, it mechanically increases filling of the heart due to activation of the muscle pump, resulting in an increase in cardiac output. Second, it induces a drop in systemic vascular resistance. The increase in cardiac output is not sufficient to compensate fully for the pronounced fall in systemic vascular resistance and the result is a transient fall in arterial pressure at the onset of whole-body exercise. The rise in right atrial pressure evoked by 3 s cycling is abrupt and large, but the almost immediate onset and rapid fall of the systemic vascular resistance is too fast for sympathetically mediated reflex effects due to stimulation of the cardiopulmonary afferents. An important factor involved in the drop in systemic vascular resistance appears to be local, non-autonomically mediated vasodilatation in exercising muscles, since it also occurs in patients with autonomic failure.

Adult↗
PubMed1996

Blood pressure and heart rate variability in autonomic disorders: a critical review.

Spectral analysis (SA) of blood pressure (BP) and heart rate (HR) fluctuations has been proposed as a unique approach to obtain a deeper insight into cardiovascular regulatory mechanisms in health and disease. A number of studies performed over the last 15 years have shown that autonomic influences are involved in the modulation of fast BP and HR fluctuations (with a period <1 min), particularly at frequencies between 0.2 and 0.4 Hz [high frequency (HF) region or respiratory frequency] and around 0.1 Hz [mid frequency (MF) region]. In patients with secondary or primary autonomic dysfunction, SA of BP and HR signals recorded at rest or during orthostatic challenge in a laboratory environment have shown the occurrence of a reduction in the power of MF and/or HF, BP and HR components. Such a reduction is associated or may even precede the clinical manifestation of autonomic neuropathy. However, the above results collected in standardized laboratory conditions cannot reflect the features of neural cardiovascular control during daily life in ambulant individuals with autonomic failure. To investigate this issue, SA techniques have been applied to 24 h beat-to-beat intra-arterial and non-invasive finger BP recordings obtained in elderly subjects and in pure autonomic failure patients, respectively. In these conditions, HR powers displayed a reduction over a wide range of frequencies (from 0.5 to below 0.01 Hz). Conversely, BP powers underwent a complex rearrangement characterized by a reduction in the power around 0.1 Hz and by an increase in the powers at the respiratory frequency and at frequencies below 0.01 Hz. Dynamic quantification of the sensitivity of the baroreceptor-heart rate reflex by combined analysis of systolic BP and pulse interval (i.e. the interval between consecutive systolic peaks) powers around 0.1 Hz (alpha technique) has shown that in elderly subjects, and even more so in pure autonomic failure patients, baroreflex sensitivity is markedly reduced over the 24 h, and is no longer characterized by its physiological day-night modulation. In conclusion, although in some instances SA of cardiovascular signals may fail to fully reflect the features of autonomic cardiovascular control, the evidence discussed clearly demonstrates that this approach represents a promising tool for a dynamic assessment of the early impairment of neural circulatory control in autonomic failure. This is particularly the case when these analyses are performed on 24 h continuous BP and HR recordings in ambulant subjects.

Autonomic Nervous System Diseases↗
PubMed1996

Orthostatic hypotension due to suppression of vasomotor outflow after amphetamine intoxication.

Ten hours after ingestion of amphetamines, a previously healthy 17-year-old female adolescent experienced dizziness on standing. Examination revealed pronounced drowsiness and severe orthostatic hypotension. Assessment of arterial baroreflex function suggested that suppressed sympathetic vasomotor drive was the cause of the orthostatic hypotension. Within 3 days, the baroreflex failure resolved spontaneously. To our knowledge, suppressed vasomotor outflow after ingestion of amphetamines has been previously observed only in animal studies.

Adolescent↗
PubMed1995

Incidence and hemodynamic characteristics of near-fainting in healthy 6- to 16-year old subjects.

OBJECTIVES: We studied the incidence and hemodynamic characteristics of near-fainting under orthostatic stress in healthy children and teenagers. BACKGROUND: Orthostatic stress testing is increasingly used to identify young subjects with unexplained syncope. However, the associated incidence of syncope and hemodynamic responses in normal young subjects are not well known. METHODS: Eighty-four healthy subjects 6 to 16 years old performed forced breathing, stand-up and 70 degrees tilt-up tests. An intravenous line to sample blood for biochemical assessment of sympathetic function was introduced between the stand-up and tilt-up tests. Finger arterial pressure was measured continuously. Left ventricular stroke volume was computed from the pressure pulsations. RESULTS: Sixteen of the 84 subjects were excluded because of technical problems. The incidence of a near-fainting response in the remaining 68 subjects was 10% (7 of 68) for the stand-up test and 40% (29 of 68) for the tilt-up test. Baseline parasympathetic and sympathetic activity of nonfainting and near-fainting subjects was not different. Near-fainting was characterized by attenuated systemic vasoconstriction and exaggerated tachycardia that occurred as early as 1 min after return to the upright position. On tilt-up, plasma adrenaline levels increased by a factor of 2, with slightly higher increments in the near-fainting subjects. CONCLUSIONS: Inadequate vasoconstriction is the common underlying mechanism of near-fainting in young subjects. The remarkably high incidence of near-fainting during the tilt-up test after intravascular instrumentation raises serious doubts about the utility of this procedure in evaluating syncope of unknown origin in young subjects.

Adolescent↗
PubMed1995

Twenty four hour continuous non-invasive finger blood pressure monitoring: a novel approach to the evaluation of treatment in patients with autonomic failure.

Occasional sphygmomanometric readings are not an effective way of evaluating the effect of treatment in patients with hypoadrenergic orthostatic hypotension. A novel non-invasive portable device (Portapres) was used to monitor 24 hour continuous finger blood pressure before and during chronic volume expansion in a 66 year old woman with severe orthostatic hypotension. In both conditions pressures while she was standing were lowest in the morning. Her tolerance to standing and walking increased during the day and, as a consequence of a higher upright mean blood pressure, was improved after treatment. Mean blood pressure during sleep was increased after treatment. Continuous 24 hour non-invasive finger blood pressure monitoring is a promising technique for the evaluation of the effect of treatment in patients with autonomic failure. It provides information about situations in daily life that cannot be obtained by laboratory tests or conventional sphygmomanometric measurements.

Aged↗
PubMed1995

Circadian profile of systemic hemodynamics.

We determined the continuous 24-hour profile of mean arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance in eight healthy ambulatory volunteers. Beat-to-beat intra-arterial blood pressure was recorded with the Oxford system; subjects were ambulant during daytime and slept at night. Beat-to-beat stroke volume was determined by the pulse contour method from the arterial pulse wave. During the nighttime, compared with the daytime average, there was a decrease in blood pressure (9 mm Hg), heart rate (18 beats per minute), and cardiac output (29%); stroke volume showed a small decrease (7%), and total peripheral resistance increased unexpectedly by 22%. When subjects arose in the morning a steep increase in cardiac output and decrease in total peripheral resistance were found. Comparable changes were seen during a period of supine resting in the afternoon, whereas physical exercise caused opposite changes in hemodynamics. This pattern was observed in all subjects. We conclude that the circadian pattern of cardiac output and total peripheral resistance originates from the day-night pattern in physical activity: during the nighttime, blood flow to the skeletal muscles is decreased through local autoregulation, which increases total peripheral resistance and decreases cardiac output compared with the daytime.

Adolescent↗
PubMed1994

[2 Dutch travelers returning from Thailand with cholera].

Cholera is a disease rarely imported in the Netherlands. Recently a 34-year-old woman who had returned from a trip through Thailand was admitted to our hospital with complaints of vomiting, watery stools and moderate dehydration. Vibrio cholerae OI serotype Ogawa biotype El Tor was isolated from the faeces. She recovered after antimicrobial and fluid therapy. Her 29-year-old travelling companion had only mild symptoms of diarrhoea, but the bacterium was isolated from her stool also. Cholera should be considered in travellers with vomiting and diarrhoea coming back from Thailand.

Adult↗
PubMed1994

Effects of leg muscle pumping and tensing on orthostatic arterial pressure: a study in normal subjects and patients with autonomic failure.

1. The effects of leg muscle pumping (tiptoeing) and tensing (leg-crossing) on orthostatic blood pressure were investigated in six healthy adult subjects (aged 28-34 years) and in seven patients with severe hypoadrenergic orthostatic hypotension (aged 20-65 years). 2. Finger arterial pressure was monitored. Relative changes in left ventricular stroke volume were computed by a pulse contour method. 3. Tiptoeing increased mean arterial pressure (7 +/- 5 mmHg) in the healthy subjects, but not in the patients, whereas cardiac output increased in both groups, although by more in the healthy adults than in the patients (35 +/- 10% versus 20 +/- 11%, P < 0.05). Systemic vascular resistance decreased substantially in both groups while tiptoeing. Leg-crossing did not affect arterial pressure in the healthy subjects, although stroke volume had increased. In contrast, in the patients an increase in cardiac output (16 +/- 12%) and mean blood pressure (13 +/- 13 mmHg) was observed. 4. Tiptoeing and leg-crossing have different effects on orthostatic blood pressure in healthy adult subjects and in patients with autonomic failure. In normal humans, tiptoeing increases arterial pressure, whereas leg-crossing has little effect. In the patients, in contrast, tiptoeing has little effect, whereas leg-crossing increases arterial pressure considerably. Patients with autonomic failure should be instructed to apply leg-crossing to combat orthostatic dizziness.

Adult↗
PubMed1994

Effects of aging on blood pressure variability in resting conditions.

The objective of this study was to determine the effect of aging on beat-to-beat blood pressure and pulse interval variability in resting conditions and to determine the effect of aging on the sympathetic and vagal influence on the cardiovascular system by power spectral analysis of blood pressure and pulse interval. We studied three groups of healthy, normotensive subjects: young (10 to 15 years, n = 16), adult (20 to 40 years, n = 16), and elderly (70 to 90 years, n = 25). Beat-to-beat blood pressure was measured by Finapres during 20 minutes supine and 10 minutes standing. Overall systolic and diastolic blood pressures and pulse interval variability were determined as SD and as coefficient of variation. Also, relative powers of the mid-frequency (0.08 to 0.12 Hz) and high-frequency bands (0.15 to 0.40 Hz) were determined by spectral analysis. In these subjects no differences in blood pressure variability (either as SD or coefficient of variation) were found between age groups, except for the coefficient of variation of standing diastolic blood pressure, which decreased with aging. Pulse interval variability decreased with aging. Power of the mid-frequency band of systolic and diastolic blood pressures was markedly decreased in the elderly, especially in the standing position. Power of the high-frequency band of pulse interval was also decreased in the elderly. Baroreflex sensitivity calculated by fast Fourier transformation spectral analysis was decreased in the elderly subjects compared with the younger groups. In conclusion, we found no change in the overall variability of blood pressure with aging. Mid-frequency spectral power of blood pressure and mid- and high-frequency spectral powers of pulse interval variability were decreased in the elderly. These results suggest that aging does not merely influence the magnitude of blood pressure and pulse interval variability but causes a complex rearrangement of the variability pattern by changes in neurocardiovascular regulation.

Adolescent↗