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Biomedical subjects

M Eriksen

Publications and source records attributed to M Eriksen.

At least 19 recordsLinked to original sources
PubMed1999

Development of oxygen sensitivity in infants of smoking and non-smoking mothers.

AIMS: To assess the effect of prenatal cigarette smoke exposure on the postnatal resetting of oxygen sensitivity in term infants. METHODS: 15 healthy term infants of smoking mothers (median 10 cigarettes/day) and 16 controls were studied during quiet sleep 1, 3, and 10 days and 10 weeks postnatally. Strain-gauge respiratory trace was continuously recorded. Repeated 15-s challenges with 100% O2 and 15% O2 were presented in randomised order through a face mask. A median of six hyperoxic and six hypoxic challenges per recording were obtained. Breath-by-breath ventilation in a time-window from 20 s before onset of stimulus to 60 s after was extracted. For each infant at each age, the normalised coherently averaged response to hyperoxia and hypoxia was calculated. Mean ventilation at end of the 15-s stimulus was analysed with ANOVA, as were parameters describing a function fitted to each averaged response. RESULTS: During air breathing, smoke-exposed infants had higher respiratory rates and lower tidal volumes than controls. Nicotine concentration in infant hair, measured by gas chromatography, was positively correlated with maternal level of smoking. A long-term development in oxygen sensitivity was demonstrated in both groups. However, neither the time-course nor the magnitude of O2 responses was affected by maternal smoking. Overall, hyperoxia reduced ventilation by 6.3% at day 1, 13.2% at day 3, 29.6% at day 10, and 40.0% at week 10. Transient hypoxia increased ventilation by 3.5%, 3.2%, 6.4%, and 8.8%, respectively, at the four ages studied.

Adult↗
PubMed1999

Involvement of the human splanchnic circulation in pressor response induced by handgrip contraction.

We have analysed the adjustment of blood flow and vascular conductance in the abundantly supplied splanchnic circulation to a generally released pressor reaction. Pressor responses were induced by 2-min periods of standardized, sustained handgrip in seven healthy students. The effects of handgrip tests were followed both in the fasting state and after the consumption of a substantial, mixed meal. In the first of the two sessions, changes in superior mesenteric artery blood flow were recorded and concomitant changes in local vascular conductance derived. In the other session, pressor released cardiac output changes were recorded and changes in total peripheral vascular conductance derived. Both types of flow changes were recorded using ultrasound Doppler technique. Typically, blood flow in the superior mesenteric artery increased two- to threefold after a meal. Handgrip contractions induced an initial rapid increase in heart rate, cardiac output and total peripheral conductance, followed by a gradual decline in total peripheral conductance and stroke volume and a gradual increase in heart rate and mean arterial pressure for the rest of the period. At the end of 2-min pressor periods, total peripheral conductance was only about 10% below the pre-handgrip level, whereas vascular conductance locally in the area of the superior mesenteric artery decreased by some 30%. Thus, it appears that the splanchnic vascular bed contributes markedly to the compound pressor response. Handgrips caused significantly less reduction in local vascular conductance in the post-prandial than in the pre-prandial state, indicating that blood flow to the digesting gastrointestinal tract retains a relatively high priority also in a pressor situation.

Adult↗
PubMed1999

A method of assessing ventilatory responses to chemoreceptor stimulation in infants.

Various methods of assessing infant chemoreceptor responses have been reported in the literature. However, equipment dead space, trigeminal stimulation and inherent respiratory variability may have affected the results. A method is presented which attempts to reduce the effect of these factors and thereby isolate the chemoreceptor response. Inspiratory gas was delivered into a lightweight face mask with a pliable rim, minimal dead space and a connected pneumotachograph. Ventilatory data were computed breath by breath. Computer-controlled electromagnetic valves allowed instantaneous switching between air and different gas mixtures, repeated in a randomized sequence. In 18 healthy term neonates, the mask increased ventilation by 12% (95% confidence interval 6-18%), measured by calibrated strain-gauge bands. The effect on respiratory frequency and tidal volume differed significantly between sleep states. Neonates were challenged with short-lasting hyperoxia, mild hypoxia, rebreathing and mild hypercapnia. Coherent averaging of several ventilatory responses from each sleep state reduced the variability while maintaining a high time-resolution.

Analysis of Variance↗
PubMed1998

Electrophysiological evidence of reinnervation of the transplanted human heart.

Beat-by-beat heart rate (HR) changes during exercise were studied in two young and fit heart-transplanted humans at different time intervals following transplantation. Upon the start of the exercise, a slow gradual increase in HR was seen during the early experiments after the transplantation, whereas an immediate rapid increase in HR was observed during the later experiments. From standard ECGs obtained 32 months after transplantation, two P waves at somewhat different rates could be identified in both subjects, probably arising from donor and recipient sinoatrial nodes, respectively. The two P wave rate changes during and following exercise were very similar. We conclude that these changes in the HR pattern and ECG must be due to reinnervation of the donor hearts, most likely by parasympathetic cardiac fibers.

Adult↗
PubMed1997

Effect of ultrasound contrast medium in color Doppler and power Doppler visualization of blood flow in canine kidneys.

PURPOSE: To examine the effect of an ultrasound contrast medium (UCM) in the visualization of parenchymal blood flow by means of color Doppler and power Doppler sonography. MATERIAL AND METHODS: Nonenhanced and UCM-enhanced Doppler images of canine kidneys were obtained in a transversal plane during various states of flow reduction in the anterior branch of the renal artery. The UCM consisted of air-filled shell-stabilized microballoons (half-life approximately 2 min). The images were evaluated blindly by 4 observers who rated the amount of flow signal in the cortex and medulla, and categorized the flow state (normal, reduced or no flow) in the anterior part of the kidney. RESULTS: The UCM increased the area of Doppler signals in the cortex and outer medulla during normal or reduced blood flow. The border between nonperfused and normally perfused parenchyma was more distinct with the UCM. The categorization of the regional flow state was more correct with the UCM. Improvement with the UCM was greatest when the nonenhanced Doppler images had suboptimal intensity, but positive effects with the UCM were also seen in recordings with adequate precontrast intensity. Color blooming artifacts sometimes occurred on the side of the kidney facing away from the transducer. CONCLUSION: The UCM improved the color Doppler and power Doppler visualization of the parenchymal blood flow in the canine kidney, and allowed a more correct categorization to be made of the regional blood flow state.

Air↗
PubMed1997

Local constriction of arteriovenous anastomoses in the cooled finger.

We have examined the influence of local cooling from 35 to 19 degrees C on spontaneous arterial blood velocity fluctuations in the acral skin of thermoneutral subjects. The skin temperature of one hand was gradually lowered in a water bath in two separate experimental runs. Simultaneous continuous blood velocity was measured from the third finger artery of both hands using ultrasound-Doppler. The large blood velocity fluctuations assumed to be caused by synchronous vasomotion of the arteriovenous anastomoses were invariably seen in the control finger artery throughout the two cooling periods, indicating that the subjects were in their thermoneutral zone. The velocity fluctuations on the cooled side remained nearly unchanged and closely correlated with those in the control finger artery during local cooling from 35 to approximately 21.5 degrees C. Below this temperature (range 23-20 degrees C) the velocity fluctuations ceased abruptly, and the velocity was nonfluctuating and continuously low. These results indicate a local thermal level below which there is abrupt, sustained closure of the arteriovenous anastomoses.

Adult↗
PubMed1996

Short-term control of cardiovascular function: estimation of control parameters in healthy humans.

In a previous study, we recorded short-term cardiovascular responses after a steep increase in arterial pressure in healthy humans [Am. J. Physiol. 266 (Heart Circ. Physiol. 35): H199-H211, 1994]. The aim of the present study was to develop a mathematical model of the baroreflex control of arterial pressure, to use this model with the previously recorded data to estimate unknown parameters in the reflex control loop, and then to analyze the overall open- and closed-loop performance of the system by model simulations with use of individual sets of optimal parameters. The mathematical model consists of a heart, a linear elastic arterial reservoir, and two parallel resistive vascular beds. The arterial baroreflex loop is modeled by two separate time domain processing objects, each with its own gain, time constant, and delay, to simulate the action of a sympathetic signal to the peripheral vascular bed and a parasympathetic signal to the heart. In repeated model simulations, the control parameters in the model were systematically adjusted by an automated algorithm that minimized the deviations between the time courses of the cardiovascular variables simulated by the model and the previously recorded responses in each individual. In all 10 subjects, the short-term cardiovascular responses were adequately simulated by using individual sets of parameters in the model. Open-loop transfer functions for arterial pressure control were obtained by using the individual sets of optimal model parameters in new simulation runs. Open-loop gain for arterial pressure control at nearly zero frequency (steady state) was between 0.9 and 4. Model simulations also indicated an underdampened response at 0.05-0.07 Hz in the closed-loop situation in four subjects, corresponding to peaks in the mean arterial pressor power spectra obtained from separate recordings of spontaneous variations in the resting situation.

Baroreflex↗
PubMed1995

A causal relationship between fluctuations in thermoregulatory skin perfusion and respiratory movements in man.

The relationship between regular respiration with normal tidal volume and spontaneous fluctuations in blood flow through skin arteriovenous anastomoses (AVAs) was investigated. Laser Doppler measurements from skin areas known to contain arteriovenous anastomoses, ultrasound Doppler measurements from the radial artery and respiratory movements were recorded simultaneously in 7 supine human subjects in a thermoneutral environment. The phase relationship between respiration and the onset of sudden arteriovenous anastomoses vasoconstrictions was calculated in each subject. A few seconds before a vasoconstriction, there was a clear tendency towards synchrony in the respiration recordings, indicating that some respiration-phase-dependent event precedes the vasoconstrictions. Since arteriovenous anastomoses constrictions are accompanied by specific changes in heart rate and blood pressure, our findings link respiration to low-frequency heart rate and blood-pressure variability in humans.

Adult↗
PubMed1995

The status of local smoking regulations in North Carolina following a state preemption bill.

OBJECTIVE: To determine the number and protectiveness of local smoking regulations adopted before the implementation of a preemptive statewide smoking control bill. METHOD: Review of local smoking control regulations from all 100 counties and 85 municipalities with populations greater than 5000 in North Carolina. MAIN OUTCOME MEASURES: Adoption of local smoking control regulations before and during the 3-month delay in enactment of the preemptive bill. Protectiveness of regulations was based on restrictions on smoking and requirements for separate ventilation systems at private work sites: none (smoking unrestricted); minimal (smoking restricted to designated areas); partial (smoking restricted to designated areas served by separate ventilation systems); and complete (smoking prohibited). Because some regulations would be phased in gradually over the next 5 years, we evaluated the requirements that will be in effect by January 1, 2000. RESULTS: Between July 15 and October 15, 1993, the number of local smoking regulations in North Carolina increased from 16 to 105. By the year 2000, 59% of private employees still will not be guaranteed any protection from work site environmental tobacco smoke; 19% will have minimal protection, 22% will have partial protection, and none will have complete protection. CONCLUSIONS: The 3-month delay in preemption created an unnatural time frame for communities to organize, debate, and adopt smoking restrictions. Despite the adoption of 89 new regulations, no private employees will be guaranteed complete protection from work site environmental tobacco smoke by the year 2000; new regulations can no longer be adopted. HB 957 has been a setback for public health in North Carolina.

Humans↗
PubMed1995

Spontaneous flow waves detected by laser Doppler in human skin.

The contribution of spontaneous variations in sympathetic nervous activity and perfusion pressure to the laser Doppler flux signal in human skin was studied in nine healthy subjects. Simultaneous recordings were made of laser Doppler flux, mean blood pressure, and blood flow in the radial artery. In the skin of the palm and sole, there was a significant and strong correlation between fluctuations in flux and radial artery velocity, which indicated a high degree of neural control of microcirculatory blood flow. This correlation decreased progressively toward the trunk and face. In the skin of the nose and at scattered sites on the face, trunk, and extremities, there was correlation between flux and mean blood pressure that indicated a predominantly "passive" vascular bed. At other sites, multivariate regression analysis revealed contributions of both blood pressure and sympathetic activity. In skin on the ear and forehead, a characteristic pattern of regular oscillations in flux, uncorrelated with blood pressure and sympathetic activity, was demonstrated. The laser Doppler signal from different skin sites thus contains varying contributions from variations in perfusion pressure, sympathetic nervous activity, and local, myogenic arteriolar vasomotion.

Adult↗
PubMed1995

Effect of local warming on hand and finger artery blood velocities.

The effect of local heating on blood velocities in arteries supplying the skin of hand and fingers was studied in subjects kept in their thermoneutral zone. The temperature of one hand was steadily raised from 35 to 43 degrees C in 15 min, whereas the control hand was kept in the air or immersed in a water bath at 35 degrees C. Simultaneous blood velocity recordings from the two hands were made continuously using ultrasound Doppler. In the heated hand, a general rise in blood velocity level was seen. However, the spontaneous fluctuations in blood velocity assumed to be caused by synchronous vasomotor activity of the arteriovenous anastomoses (AVAs) remained unchanged and closely correlated with those in the control hand throughout the experiment. Thus the central nervous control of AVA vasomotion seems to be unaffected by local heating. The elevation of blood velocity in the heated hand is probably due to dilatation of other parts of the vascular bed, e.g., ordinary arterioles in the skin. Earlier investigators, using venous occlusion plethysmography, have reported vasoconstriction in the locally heated human finger. No sign of such heat-induced vasoconstriction was found in this study.

Adult↗
PubMed1995

Acute effects of indometacin on cerebral blood flow in man.

Blood velocity changes in the internal carotid artery were estimated using Doppler ultrasound before, during and after injection of indometacin or placebo in 7 healthy adults. Upon injection of the active substance there was a rapid reduction in blood velocities in the internal carotid artery, increasing with increasing doses of indometacin. A fall in end-expiratory PCO2 was also observed, indicating a state of hyperventilation. The observed relative reduction in cerebral blood flow was much higher in all subjects than the expected reduction due to the accompanying drop in PCO2. Experiments in which arterial PCO2 was kept constant showed that indometacin also causes a reduction in blood velocity independent of changes in PCO2. We suggest that indometacin has both a direct effect on the cerebral microcirculation, and an additional effect mediated through induction of hyperventilation. The drug probably affects the respiratory center through an increase in intracerebral PCO2 due to reduced perfusion.

Adult↗
PubMed1994

Connection between skin arteriovenous shunt flow fluctuations and heart rate variability in infants.

Large, spontaneous fluctuations in blood flow to acral skin, caused by synchronous opening and closing of arteriovenous anastomoses (AVAs), have been demonstrated in adults in a thermoneutral environment. Individual AVA constrictions were accompanied by a diphasic heart rate (HR) response, indicating the presence of an autonomic rhythm which affected both skin AVA activity and heart rate variability. In the present study, 24 neonates were examined on day 2 (range 1-3 days) and re-examined at 14 weeks (11-17 weeks). The presence of rhythmic, synchronous fluctuations in laser Doppler flux in the palm of the hand and sole of the foot in 20 of 24 neonates strongly indicated the presence of functional skin AVA at birth. Both neonates and 3-month-old infants showed a diphasic HR response in association with cutaneous AVA constrictions. The infant response differed from the adult response mainly by the longer duration of the secondary bradycardia. This may reflect different properties of the baroreceptor reflex in infants and adults.

Arteriovenous Anastomosis↗
PubMed1994

Results of the Dutch community project "Healthy Bergeyk".

BACKGROUND: This article reports on the results of a community health project that was implemented in the Dutch municipality of Bergeyk. The major goal was to reduce four cancer-related risk behaviors: smoking, high fat consumption, excessive alcohol use, and exposure to artificial sunlight. A control community received no new intervention. Intervention methods included mass media messages, self-help materials, small group activities, lectures, and structural activities. Community organization principles such as a social network approach, community participation, and intersectoral cooperation were applied in the project. METHODS: Data were collected from both communities among cohort research samples on three occasions using telephone interviews. RESULTS: The results indicate a significant reduction in fat intake in the experimental community. No other significant behavioral effects were found. Further analysis among respondents in the experimental condition showed that those personally exposed to the project as indicated by familiarity with and discussion about the project, had a greater decrease in fat consumption between baseline survey and second post-test than those who were not. Also, the percentage of smokers who quit between baseline survey and second post-test was greater among those who knew about the project than among those who did not. Finally, discriminant analysis was used to further examine the determinants of project exposure. Community involvement, marital status, education, and sex were related to project exposure. CONCLUSIONS: It is concluded that with the time limitations of the project in mind, the findings are encouraging.

Adult↗
PubMed1994

Thermoregulatory fluctuations in heart rate and blood pressure in humans: effect of cooling and parasympathetic blockade.

The spontaneous fluctuations in acral skin blood flow, mean blood pressure (MAP), and heart rate (HR) were studied in 9 healthy supine volunteers in a thermoneutral and in a cool environment, and after parasympathetic blockade by atropine. In skin areas with a high density of arteriovenous anastomoses (AVAs), there were large, spontaneous fluctuations in blood flow in a thermoneutral environment. The fluctuations were nearly abolished in a cool environment, while they seemed unaffected by atropine administration. Power spectral analysis demonstrated a reduction in HR and MAP variability in the low- and mid-frequency (LF) (< 0.15 Hz) band after cooling, and a prominent reduction in HR variability in both the LF and the high-frequency (HF) (< 0.15 Hz) band after atropine administration. A sudden drop in skin vascular conductance was accompanied by diphasic HR changes and an increase in MAP. After atropine administration, the initial HR acceleration was delayed and reduced in magnitude. The secondary HR deceleration, which probably represents baroreceptor modulation, was abolished. Atropine administration caused a delayed, but augmented increase in MAP, which was probably related to the loss of baroreceptor control of HR. The presence of an autonomic rhythm, consisting of sympathetic vasoconstrictor impulses to skin AVAs, connected with reciprocal sympathetic and vagal impulses to the heart, is indicated. The HR changes were mainly determined by vagal activity. The rhythmic changes in skin blood flow, HR and MAP were suppressed in a cool environment.

Adult↗
PubMed1994

Priority of blood flow to splanchnic organs in humans during pre- and post-meal exercise.

Cardiac output and superior mesenteric arterial flow in five healthy young men were followed using Doppler ultrasound techniques at rest and during 4 min bouts of bicycle exercise in both a pre- and a post-meal situation. The meal given was mixed and heavy, with an energy content (related to body size) of about 1400-1600 kcal (5.9-6.9 MJ). Two levels of exercise, 50-65 W and 150-200 W (about 75% of VO2max), were tested, with the subjects cycling in a reclining position. Superior mesenteric arterial flow increased threefold, to about 1.1 l min-1, after the meal. During exercise in the fasting situation there were only modest changes in splanchnic vascular conductance, and moderate increases in superior mesenteric arterial flow were actually recorded. Exercise in the post-prandial state caused appreciable reductions in splanchnic vascular conductance, and a 38% reduction was observed during the most heavy exercise. However, not even such a decrease in conductance resulted in any definite reduction in superior mesenteric arterial blood flow, which was maintained at the pre-exercise level. Cardiac output increased by about 1.3 l min-1 after the meal. The exercise-induced increases in cardiac output were of the same order in the fasting and in the post-prandial state. Variance analyses showed the high cardiac output levels reached during post-prandial exercise to be no different from levels that would be reached by pure summation of the changes caused by eating alone and by exercise alone. It is concluded that blood flow to the splanchnic organs in reclining man retains its high pre- and post-prandial priority during short exercise bouts of up to 75% of VO2max.

Adult↗