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Biomedical subjects

S N Hunyor

Publications and source records attributed to S N Hunyor.

At least 37 records · Page 2Linked to original sources
PubMed1992

Relationship between angiographic infarct size and left ventricular filling.

Infarct size may influence left ventricular filling after acute myocardial infarction. Pulsed Doppler transmitral flow velocities were compared in 47 patients at 7 +/- 6 days following acute myocardial infarction and 47 age-matched controls. Patients were stratified by angiographic infarct size into Groups I, II, III (corresponding angiographic hypokinetic scores less than 2; 2-2.99; greater than or equal to 3 SD/cord). Early diastolic transmitral Doppler flow velocities did not differ between infarct groups but atrial transmitral Doppler flow measurements did: peak A velocity (p = 0.001), A velocity time integral (p less than 0.001), and total velocity time integral (p = 0.001). Compared to controls atrial transmitral Doppler flow was augmented in Group I, whilst atrial and total transmitral Doppler flow were depressed in Group III. Peak A velocity and A velocity time integral were inversely related to infarct size (R = -0.44 to -0.54) and directly to left ventricular ejection fraction (R = 0.59 to 0.65). Large infarct size following myocardial infarction is associated with lower atrial and total transmitral Doppler flow velocities.

Adult↗
PubMed1992

Accuracy of Borg's ratings of perceived exertion in the prediction of heart rates during pregnancy.

When using Borg's 6-20 scale during pregnancy, ratings of perceived exertion (RPE) did not significantly correlate with exercise heart rates (HR) (P greater than 0.05). The HR predicted from RPE significantly (P less than 0.05) underestimated the exercise HR in the second trimester during walking (Group 1: mean difference 16 beats min-1, n = 11), aerobics classes (Group 4: mean 15 beats min-1, n = 48) and circuit training (Group 3: mean 18 beats min-1, n = 24); and in the third trimester during cycling (Group 2: mean 16 beats min-1, n = 12) and aerobics classes (Group 5: mean 11 beats min-1, n = 29). Maximal individual HR under-estimations were large for each physical activity during pregnancy, with values up to 54 beats min-1. Consequently, exercise intensity should not be monitored solely with RPE during pregnancy.

Exercise Test↗
PubMed1991

Voluntary blood pressure control by biofeedback: relationship to psychological characteristics.

1. Psychological characteristics were studied in 25 hypertensives (mean and standard deviation of blood pressure 150/95 +/- 12/5 mmHg), who received blood pressure (BP) biofeedback (BFB). Personality factors and success in BFB-BP modifying ability were correlated and the predictive value of psychological factors was estimated. 2. Questionnaires consisted of a Locus of Control of Behaviour (LCB) scale, the Spielberger state trait anxiety inventory and the Framingham Type A personality inventory. 3. BP was monitored continuously from the finger by volume clamp plethysmography during eight BFB sessions, each with three trials of raising, ignoring and lowering systolic blood pressure (SP). 4. SP was raised/lowered by 12 +/- 11/6 +/- 9 mmHg and heart rate (HR) increased by 10 +/- 3.9/+ 1 +/- 6.1. Ten subjects were able to lower SP by greater than or equal to 5 mmHg (15 +/- 7.5) and raise it by 17 +/- 11. The others achieved no decrease in SP and were also less successful at raising (8 mmHg, P = 0.04). 5. Changes in LCB and trait anxiety correlated with DP rise, whereas type A and pre-study state anxiety correlated with rising HR. Lowering of SP correlated weakly with change in LCB (r = 0.47, P = 0.06). 6. Combinations of psychological factors had independent predictive value for BP and HR change: trait anxiety (P = 0.03) and change in LCB (P = 0.009) with rise in diastolic blood pressure (DP); type A (P = 0.009), pre-study LCB (P = 0.02) and pre-study state anxiety (P = 0.01) with HR rise.(ABSTRACT TRUNCATED AT 250 WORDS)

Biofeedback, Psychology↗
PubMed1991

Relevance of the waterfall phenomenon in continuous finger cuff blood pressure measurements.

1. Finger cuff blood pressure monitors that provide continuous presentation of arterial pressure at the finger are available. 2. The operation of such instruments is based on 'clamping' arterial volume under a pressurized encircling cuff applied to a digit. Blood volume is detected by measuring infra-red transmission across the finger. 3. The compressed veins adopt cuff pressure and combine with the resistance of the peripheral vascular bed at the finger tip to control the blood flow. This results in waterfall behaviour in the veins under the cuff. 4. With the cuff set just 5 mmHg below the undisturbed arterial pressure, adequate flow to the distal finger is maintained. 5. Two potential sources of error affect the finger cuff blood pressure method. These are related to the increase in systolic pressure associated with moving peripherally and the variable value of occluding transmural pressure, both of which depend on muscular tone.

Blood Pressure Monitors↗
PubMed1990

The effect of exercise on circulating immunoreactive calcitonin in men.

Moderate-duration exercise increases serum catecholamine and serum calcium levels and might as a result be also expected to increase the levels of circulating serum immunoreactive human calcitonin (HCT). To explore this possibility, HCT was studied during and after moderate duration symptom-limited dynamic exercise in 13 healthy males, mean age 28 +/- 6.9 (SD) years. The mean duration of exercise using the Bruce treadmill protocol was 14.1 +/- 2.2 (SD) minutes. The mean heart rate (HR) peaked at 185 +/- 6 (SD) bpm which was 96.1% of the predicted maximal HR for age. Values for HCT, uncorrected for changes in plasma volume, showed a minimal decrease in the recovery phase, whilst HCT corrected for changes in plasma volume did not alter during exercise or recovery. The serum parathyroid hormone (PTH) also did not change. At peak exercise, uncorrected but not corrected values for plasma noradrenaline, adrenaline and dopamine had increased significantly. Corrected plasma total calcium increased during recovery. In summary, dynamic weight-bearing moderate-duration exercise did not elevate HCT in healthy males.

Adult↗
PubMed1990

Increased sensitivity to isoprenaline following digoxin pretreatment in anaesthetised and conscious dogs.

STUDY OBJECTIVE: The aim of the study was to evaluate the effect of chronic digoxin therapy on cardiac sensitivity to isoprenaline. DESIGN: Responses to isoprenaline were examined in both conscious and anaesthetised dogs pretreated with digoxin, and compared with conscious or anaesthetised controls with no digoxin pretreatment. Isoprenaline infusion (0.001-0.1 micrograms.kg-1.min-1) in pretreated groups was performed 7 d after digoxin dosing was stopped, when plasma digoxin concentrations were zero. SUBJECTS: Mongrel dogs of either sex (15-25 kg) were used in the experiments, done under anaesthetic. They were divided into three groups (n = 6 per group): group A were controls; groups B and C were pretreated with digoxin 500-750 micrograms.d-1, for 14 d (B) and 7 d (C). For the experiments in conscious animals, six mongrel dogs (25-30 kg) and two greyhounds (25-30 kg) were used; group D (n = 6) were treated with digoxin for 20-40 d; group E (n = 2) were treated for 7 d. MEASUREMENTS AND RESULTS: Heart rate, blood pressure and myocardial contractility (dP/dt: integrated isometric tension) were measured during isoprenaline infusion. Digoxin pretreatment for 14 d did not significantly change the chronotropic or depressor responses to isoprenaline in anaesthetised dogs but there was a 10-fold increase in inotropic sensitivity to isoprenaline following withdrawal. When the pretreatment period was reduced to 7 d there was no change in any of the responses to isoprenaline. In conscious dogs there was also a significant increase in inotropic sensitivity to isoprenaline after digoxin withdrawal, but this was not so marked as in anaesthetised dogs. In conscious dogs chronotropic sensitivity to isoprenaline was also increased. CONCLUSIONS: It is possible that the inotropic effect maintained during the 2 weeks of digoxin treatment may cause substantial withdrawal of sympathetic tone to the heart, with a consequent increase in beta adrenoceptor number or sensitivity, which could be detected a week after digoxin withdrawal.

Anesthesia, General↗
PubMed1988

Voluntary blood pressure control using continuous systolic blood pressure biofeedback.

1. Ability to alter blood pressure (BP) acutely with continuous systolic (SBP) BP biofeedback was assessed in volunteers using a new non-invasive finger BP monitor. 2. Reliability of finger BP measurement was demonstrated in six hypertensive subjects (21-60 years), by beat-to-beat comparison with brachial intra-arterial BP over 90 min. Wide variation of BP was achieved by physiological manoeuvres. Mean error of finger BP was -3.0/-2.2 mmHg with intra-subject s.d. of 7.2/5.4 mmHg. 3. Thirteen normotensives (21-51 years) were paid to undergo 30 trials of SBP biofeedback in six sessions over 3 weeks. The SBP trend was displayed on a monitor with appropriately 'shaped' targets; each trial consisted of BP-raising and -lowering periods of 45 and 90 s respectively with intervening 45 s baselines. 4. Nine subjects raised BP, on analysis of the last 10 trials, by an average of 18.8 mmHg while five of the 13 successfully lowered BP by an average of 10.0 mmHg. BP lowering was best achieved by diminishing respiratory rate and depth, and muscular relaxation. 5. Demonstration of large BP reductions in five of 13 normotensives using strategies applicable to longer training sessions warrants further investigations in hypertensive subjects, focusing on mediating mechanisms and transfer of effect beyond the laboratory.

Adult↗
PubMed1987

Fetal heart rate and maternal cardiovascular and catecholamine responses to dynamic exercise.

Fourteen women performed treadmill exercise for continuous 10-minute periods at levels of 2, 3 and 4 mets in the second and third trimester of pregnancy and again postpartum. The percentage increase in heart rate in response to exercise was similar during pregnancy and postpartum while systolic blood pressure was increased only during pregnancy. Maternal plasma noradrenaline levels at peak exercise increased 64% (p less than 0.005), 42% (p less than 0.005) and 29% (NS) in the 3 studies respectively compared to resting levels at these times. Ten women experienced increased uterine activity during the exercise or recovery periods. Fetal heart rate was increased (p less than 0.05) by exercise but this was independent of uterine contractions and plasma noradrenaline levels.

Adult↗
PubMed1987

Physical characteristics and clinical evaluation of a new disposable fibreoptic transducer-tipped catheter system.

A new disposable fibreoptic transducer-tipped catheter manometer system was evaluated to assess its accuracy, stability of accuracy under prolonged simulated intra-arterial conditions, and dynamic characteristics. Maximum errors observed in the measurement of static pressure using a sample of five catheters (with one display unit) were 2 mmHg at 0 mmHg reference pressure, 2 at 20 mmHg, 4 at 40 mmHg, 4 at 100 mmHg and 9 at 200 mmHg. An immersion artifact caused a shift in baseline of up to 2 mmHg. Exposure of the transducer to 24 hours of simulated intra-arterial conditions (pulsatile pressure at 40 degrees C) resulted in errors of up to 7 mmHg for pressures up to 100 mmHg, and 11 mmHg for 200 mmHg, which were largely attributable to a drift in baseline pressure (up 6 mmHg by 24 hours). Consistent overestimation by the system suggested inappropriate gain setting within the display unit which, however, is not user-adjustable. The system exhibited uniform frequency response up to 33 Hz.

Angiography↗
PubMed1985

Blood pressure variability in health, hypertension and autonomic failure.

24h intra-arterial pressure monitoring was used to examine blood pressure variability in 5 normal volunteers, 137 subjects with suspected or established essential hypertension and 9 subjects with autonomic failure. Subjects with autonomic failure showed increased short-term blood pressure variability while active but reduced values at rest. Heart rate variability was low at all times. 24h recordings were reduced to hourly mean values and two indices of variability derived - day-night difference and average hourly change. For blood pressure, subjects with autonomic failure showed negative values of the former but high values of the latter; both indices of heart rate variability were low. In the remaining group, the relationship of these indices to constitutional factors, mean blood pressure and indices of physical activity during the study was explored. Day-night difference in systolic pressure was negatively correlated with mean pressure and average hourly change positively related to age. No other relationship was significant.

Adult↗
PubMed1985

Real time detection of significant blood pressure events in ambulant subjects.

A typical twenty-four hour continuous ambulatory blood pressure (BP) record demonstrates many marked, apparently spontaneous blood pressure spikes. Awareness of such BP fluctuations may help determine their causative mechanisms and lead to improved applications of conscious learned control of BP (Biofeedback). A microprocessor device has been constructed to monitor direct arterial blood pressure in real time and to compile a profile history of the BP and heart rate (HR). When the BP level exceeds a threshold based on the BP history, an audio signal prompts the subject, who is then able to record the current physical and emotional status. Alternatively, a combination of the parameters (SBP,DBP,HR) may be used to determine the threshold criteria. A decision table determines whether each parameter should lie above, below or within the threshold region. Triggering will occur only if a predefined relationship has occurred. The device will aid in the detection and interpretation of significant BP events occurring during a 24 hour recording as well as in the application and assessment of biofeedback control of blood pressure.

Biofeedback, Psychology↗
PubMed1984

The effect of dihydroergotamine on venous distensibility and blood pressure in idiopathic orthostatic hypotension.

We report a case of severe idiopathic orthostatic hypotension (IOH) documented by direct, continuous, ambulatory blood pressure monitoring. Failure of vasoconstriction and more significantly of venoconstriction in response to upright posture was demonstrated, indicating an autonomic nervous system disorder. The venoconstrictive agent dihydroergotamine (DHE) had little effect in preventing a fall in forearm venous tone with head up tilting but caused a recumbent pressor response leading to side effects. These were noted at a time of low plasma DHE levels indicating denervation hypersensitivity. Difficulties may arise in using DHE to treat severe cases of IOH who have denervation hypersensitivity.

Aged↗