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PubMed1983

Simultaneous assessment of right ventricular ejection fraction and central haemodynamics at rest and during exercise in patients with pulmonary hypertension.

In 10 patients, aged 55-73, with pulmonary hypertension, right ventricular ejection fraction (RVEF) was measured simultaneously with central haemodynamics twice, at rest and during exercise. In the first investigation, RVEF was measured with first pass (FP) radionuclide angiocardiography using 133Xe and 99Tcm as tracers. In the second investigation after 1 h's rest, RVEF was measured with equilibrium (EQ) radionuclide angiocardiography. Significant correlations were found between RVEF and pulmonary artery pressure (r = -0.76 to -0.88) and between RVEF and right arterial pressure (r = -0.76 to -0.84) at rest and during exercise. RVEF was low or decreased during exercise in all patients with haemodynamic signs of right ventricular failure. Good correlations were found between the FP and EQ techniques for measuring RVEF both at rest, r = 0.86, and during exercise, r = 0.91. RVEF, measured with the FP technique, showed better reproducibility and better correlation to haemodynamic variables and to history of right ventricular failure than the EQ technique. Thus, the FP technique seemed to be the method of choice for assessment of RVEF.

Aged↗
PubMed1991

QRS scoring with the Mason-Likar lead system at rest and during ischaemia.

The stability of the post-infarction simplified 29-point Selvester QRS score during maximal exercise testing was studied using both standard 12 and Mason-Likar (modified standard, M-L) ECG lead systems. Thirty-eight patients participated in the standard exercise test (mean interval after single infarction 4 months) and a total of 54 patients underwent exercise 201thallium emission tomography with M-L lead system 2 months later. None had electrocardiographic features complicating the scoring. There were no significant differences between the (paired) mean QRS scores, except between the M-L score at rest (2.3 +/- 2.4) and at exercise (3.2 +/- 2.6, P less than 0.01). The correlation coefficient (r) between resting scores was 0.87, between rest and exercise 0.90 (standard leads) and 0.80 (M-L leads). In 78% nuclear imaging revealed ischaemia, but this had no significant effect on the mean scores or correlation between rest and exercise scores. It is concluded that the QRS score is relatively stable during exercise with standard leads if the limb leads are recorded immediately after the exercise. Scoring with the M-L lead system is somewhat inaccurate, especially during exercise, and is not recommended for stratification of clinical risk. The QRS score is protected against ischaemia, which emphasizes its value as an independent prognostic tool.

Adult↗
PubMed1992

Use of non-invasive finger blood pressure monitoring in the estimation of aortic pressure at rest and during the Mueller manoeuvre.

The aim of this investigation was to evaluate whether reliable estimates of aortic pressure can be derived using non-invasive finger blood pressure monitoring. Finger blood pressure (Ohmeda 2300 Finapres device; Finapres, Englewood, CO) was compared with simultaneous ascending aortic pressure measured with a catheter-transducer system both at rest and during acute negative intrathoracic pressure (the Mueller manoeuvre). Thirty-eight patients aged 17-73 years were studied. All were undergoing routine diagnostic or therapeutic cardiac catheterization. Beat-to-beat values of systolic, diastolic and mean non-invasive finger and invasive aortic blood pressure were measured at rest and factors which might have an influence on the difference between methods were examined. The mean finger-aortic difference was +5 +/- 14 mmHg for systolic, -2 +/- 7 mmHg for diastolic, -5 +/- 8 mmHg for mean and +6 +/- 13 mmHg for pulse pressure. In multivariate linear regression analysis, the difference in systolic pressure was related to aortic systolic pressure (standardized coefficient beta = -0.33, P = 0.01), heart rate (beta = 0.49, P < 0.000), age (beta = -0.29, P < 0.025) and height (beta = 0.40, P < 0.005). The linear regression equations to derive resting aortic pressures from the non-invasive finger pressure readings had correlation coefficients between 0.83 and 0.87 and standard errors of estimate between 6 and 14 mmHg. During the Mueller manoeuvre, Finapres reproduced average pressure changes reliably compared with intra-aortic pressure. Due to moderate inter-individual variation in the finger-aortic differences the correlation coefficients ranged from 0.83 to 0.93 and the standard errors of estimate from 3 to 6 mmHg. Non-invasive finger blood pressure monitoring could be used to estimate central aortic mean and diastolic blood pressure fairly reliably at rest, but with respect to systolic pressure the variance in finger-aortic difference was marked. The average intra-aortic pressure changes caused by the Mueller manoeuvre were reliably reproduced by the Finapres device.

Adolescent↗
PubMed1993

Circadian variation of cardiac autonomic regulation during 24-h bed rest.

We examined the effect of circadian variation on cardiac autonomic regulation in 11 young and middle-aged, healthy men during 24-h bed rest. Cardiac parasympathetic regulation expressed significant circadian variation: sensitivity of baroreceptor reflex, standard deviation of R-R intervals and the power of high frequency component of R-R interval variability (HFP) increased during the evening (2000-2100 h), were highest during the night (0200-0300 h), and gradually decreased again towards afternoon (1400-1500 h). Cardiac sympathetic regulation, the power of medium frequency component of R-R interval variability (MFP), did not show any significant circadian variation. The autonomic response to orthostatic stress changed after the 24-h bed rest; the sympathetic dominance in response to assuming upright position was before bed rest principally attributable to increased sympathetic activity (MFP increase), whereas after bed rest this was due to withdrawal of parasympathetic activity (HFP decrease). We conclude that the effect of circadian variation must be taken into account, while assessing cardiac autonomic regulation in patients with acute cardiovascular disorders.

Adult↗
PubMed2003

The effects of exercise on resting blood pressure in children and adolescents: a meta-analysis of randomized controlled trials.

Resting blood pressure in children and adolescents can track into adulthood. The purpose of this study was to use the meta-analytic approach to examine the effects of exercise on resting systolic and diastolic blood pressure in children and adolescents. Twelve randomized, controlled trials representing 16 outcomes in 1,266 subjects met the inclusion criteria. Reductions in blood pressure were approximately 1% and 3% for resting systolic and diastolic blood pressures, respectively. However, random-effects modeling using 5000 bootstrap confidence intervals revealed that neither result was statistically significant (systolic, x-bar (x);+/-SEM=-1+/-2; 95% bootstrap confidence intervals=-2 to 0 mm Hg; diastolic, x+/-SEM=-2+/-1; 95% bootstrap confidence intervals=-3 to 0 mm Hg). The results of this study suggest that short-term exercise does not appear to reduce resting systolic and diastolic blood pressure in children and adolescents. However, a need exists for additional studies, especially in hypertensive children and adolescents.

Adolescent↗
PubMed2006

Reproducibility of computerized measurements of QT interval from multiple leads at rest and during exercise.

BACKGROUND: Accurate measurement of the QT interval is important for diagnosing long QT syndrome (LQTS), and in research on determinants of ventricular repolarization time. We tested automatic analysis of QT intervals from multiple ECG leads on chest. METHODS: Eleven healthy volunteers and 10 genotyped LQTS patients were tested at rest and during exercise with a bicycle ergometer twice 1-31 months apart. Electrocardiograms were recorded with the body surface potential mapping system, and 12 precordial channels were selected for analysis. Averaged QT peak and QT end intervals were determined with an automated algorithm, and the difference QT end minus QT peak (Tp-e) was calculated. Repeatability was assessed by coefficient of variation (CV) between measurements. RESULTS: Within one test at rest the QT end intervals were highly repeatable with CV 0.6%. In repeated tests CV was 4.4% for QT end interval and 3.5% when the QT interval was corrected for heart rate. In exercise test at specified heart rates, mean CV was 3.0% for QT end and 2.9% for QT peak interval. The CV of Tp-e interval was 10.2% at rest, and 9.3% in exercise test. Reproducibility was comparable between healthy subjects and LQTS patients. CONCLUSIONS: The BSPM system with automated analysis produced accurate and highly repeatable QT interval measurements. Reproducibility was adequate also over prolonged time periods both at rest and in exercise stress test. The method can be applied in studying duration of ventricular repolarization time in different physiologic and pharmacologic interventions.

Adult↗
PubMedDate not supplied

Bed rest during pregnancy: implications for nursing.

Research on nonpregnant individuals reveals that bed rest produces numerous adverse physical and psychosocial effects. Evidence shows that bed rest affects pregnant women in the same manner. This article provides an overview of the history of bed rest, research on the side effects of bed rest, and a discussion of the research that has been conducted on these side effects during pregnancy. Also discussed are implications for providing antepartum, intrapartum, and postpartum nursing care.

Bed Rest↗
PubMedDate not supplied

Antepartum bed rest: effect upon the family.

OBJECTIVE: To identify the effects of antepartum bed rest upon the family. DESIGN: Descriptive, retrospective survey. PARTICIPANTS: A national random selection of 89 women who had been prescribed antepartum bed rest in the hospital or at home and who contacted a high-risk pregnancy support group for information. MAIN OUTCOME MEASURE: An open-ended questionnaire. RESULTS: Families experienced difficulty assuming maternal responsibilities, anxiety about maternalfetal outcomes, and adverse emotional effects on the children. Child care was managed by various people across time. Child care problems included negative reactions from the children, concern about the quality of the provider, and maternal worry about care. Families also experienced financial difficulties, the majority of which were not compensated by insurance or work benefits. Almost all, 96.6%, families received some type of support during bed rest. Instrumental support was the most commonly received; however, emotional support was considered the most helpful. The least helpful type of support was that which was unreliable. The primary providers of support to the family were parents and family, followed by friends. The women reported that health care providers offered minimal support to the family. CONCLUSION: Despite support, antepartum bed rest creates difficulties that affect the entire family and its finances.

Adaptation, Psychological↗
PubMed1987

Bed rest and ACTH in the treatment of exacerbations in multiple sclerosis patients.

The effect of treatment with bed rest only and bed rest combined with ACTH was studied retrospectively in 55 multiple sclerosis (MS) patients suffering from 99 relapses. No convincing arguments in favour of the combination with ATCH over bed rest alone were found. A review of the literature on the treatment of exacerbations in multiple sclerosis patients with bed rest and ATCH is given.

Adrenocorticotropic Hormone↗
PubMed1994

Effects of blood-volume distribution on the characteristics of the carotid baroreflex in humans at rest and during exercise.

Seven supine subjects were studied at rest and during mild to moderate dynamic leg exercise with and without unloading of the cardiopulmonary baroreceptors accomplished by exposing the lower portion of the body to a subatmospheric pressure of 20 mmHg (Lower Body Negative Pressure, LBNP). The function of the cardiac branch of the carotid baroreflex was studied over its full operational range by measuring R-R intervals during application of pulse synchronous graded pressures (40 to -65 mmHg) in a neck-chamber device. Raising the carotid transmural pressure (systolic arterial pressure minus neck-chamber pressure) induced increasing R-R intervals in all conditions. In conformity with previous results from our laboratories it was found that the maximal rate of change in relative R-R intervals and the corresponding transmural pressure were higher during exercise than at rest, indicating that exercise increased the carotid baroreflex sensitivity and shifted its optimal buffering range to higher arterial pressures. LBNP did not affect the characteristics of the reflex at rest nor during exercise. It is concluded that reduced central venous pressure with consequent selective cardiopulmonary receptor disengagement exerts no influence on the carotid baroreflex control of heart rate (HR), as tested over the entire arterial pressure-effector response relation, either at rest or during mild-moderate exercise.

Adult↗
PubMed1977

The variability of muscle nerve sympathetic activity in resting recumbent man.

1. Pulse synchronous bursts of multi-unit sympathetic activity was recorded from median or peroneal muscle nerve fascicles in fourteen subjects resting in the recumbent position. The neural activity was quantitated in terms of burst incidence, i.e. the number of bursts in the mean voltage neurogram/100 heart beats, during successive rest periods of 2-4 min.2. For each individual the burst incidence was fairly constant between different rest periods but the mean burst incidence varied widely between individuals, the range being from less than 10 to more than 90 bursts/100 heart beats.3. Simultaneous double nerve recordings were made on one subject from median and peroneal nerves and on eight subjects from the two peroneal nerves. There was always close similarity between the two records in such experiments regardless of which muscles the nerve fascicles innervated. When analysed separately the difference in burst incidence between the two sides ranged from 0.7 to 5.1 bursts/100 heart beats. The findings suggest that sympathetic neurones destined to skeletal muscles are subjected to a homogenous central drive and that contributions to the activity from ganglionic or segmental sources are of lesser importance.4. On seven subjects repeated recordings at rest were made with intervals of 3 weeks-21 months between recordings. In each subject mean burst incidences were similar in all recordings (range of differences 0.5-11.2 bursts/100 heart beats) suggesting an individually constant level of sympathetic activity in muscle nerves.5. For each individual the variability of burst amplitudes in the mean voltage neurogram was described by burst amplitude spectra. Most subjects had a relatively larger proportion of small than high amplitude bursts, but there was a tendency for more even amplitude distributions in subjects with high burst incidence. The finding may be an indication of interindividual differences in the average number of impulses/burst.6. It is concluded that the multi-unit recording technique can be used for comparisons of the level of muscle nerve ;sympathetic tone' between different subjects.

Action Potentials↗
PubMed1997

Identification of the site of Epstein-Barr virus persistence in vivo as a resting B cell.

Epstein-Barr (EBV) is a powerful immortalizing virus for human B lymphocytes in vitro and is associated with several human neoplasias in vivo. Previously, we have shown that the majority of EBV-infected cells in the peripheral blood of healthy, persistently infected individuals do not express the activated phenotype, e.g., high levels of cell surface CD23 and CD80 (B7), characteristically expressed on in vitro-immortalized cells. Here, we show that > or = 90% of the CD23-, virus-infected cells in the peripheral blood are in G0 and therefore resting. The remaining cells may be G1 arrested, but we were unable to detect a significant number of cells traversing the S-G2-M stages of the cell cycle. The mRNA for LMP2A, but not EBNA1 originating from Qp, was readily detected in this population, and these cells appear competent in the processing and presentation of antigen by class I major histocompatibility complex. We propose that these resting B cells are the site of long-term latent persistence for EBV. We further propose that the persistence of the virus in a resting B7- B cell provides an important mechanism to escape immunosurveillance. The demonstration that EBV can persist latently in a resting B cell means that the immortalizing functions of EBV can be down regulated in a normal B cell. This conclusion has important implications for understanding and controlling EBV-associated neoplasia.

Animals↗
PubMed2005

Changes of cartilage and bone markers after intra-articular glucocorticoid treatment with and without postinjection rest in patients with rheumatoid arthritis.

BACKGROUND: Joint immobilisation improves the therapeutic effect of intra-articular glucocorticoid injection for knee synovitis. This may be due to retarded steroid resorption by immobilisation, a procedure that also could influence cartilage and bone metabolism. OBJECTIVE: To evaluate changes in cartilage and bone turnover after intra-articular glucocorticoid treatment for knee synovitis with and without postinjection rest. METHODS: 20 patients with rheumatoid arthritis and knee synovitis were randomised to 24 hour bed rest or to normal activity after intra-articular glucocorticoid treatment. Serum and urine markers of cartilage and bone turnover were studied for two weeks. Cartilage oligomeric matrix protein (COMP) was used as a marker of cartilage turnover, osteocalcin as marker of bone formation, and deoxipyridinoline (DPD) as marker of bone resorption. RESULTS: After the glucocorticoid injection COMP levels decreased in both groups (p<0.001), but significantly more in resting patients. Serum osteocalcin levels decreased significantly (p<0.001) without any difference between the groups. DPD was unchanged in both groups. CONCLUSIONS: Intra-articular glucocorticoid treatment for knee synovitis reduced serum COMP, which suggests that such treatment may have a cartilage protective effect. The slightly larger decrease of serum COMP in the resting group may reflect a lower clearance of COMP from the joint cavity. Serum osteocalcin was temporarily reduced, indicating a reversible suppression of bone formation.

Adult↗
PubMed1981

Significance of minor ST segment and T wave changes in the resting electrocardiogram of asymptomatic subjects.

Sixteen thousand resting electrocardiograms were performed on 14000 United Kingdom professional aircrew and air traffic control officers over a two-year period; 103 asymptomatic men with minor ST segment and T wave changes at rest were assessed by exercise electrocardiography and 19 responded abnormally. Five subjects had proven coronary artery disease, one hypertrophic obstructive cardiomyopathy, and one left ventricular dilatation on echocardiography. Eleven subjects were not investigated, of whom three had strongly positive exercise responses. One subject had a false positive response and assuming a false negative response of less than 2 per cent, then a sensitivity of 80.0 per cent, a specificity of 89.1 per cent, a predictive value for the exercise electrocardiogram of 44.46 per cent and for the resting electrocardiogram of 7.8 per cent is obtained. T wave changes induced by hyperventilation were common (53.4% of all). Ten (18.2%) subjects with hyperventilation-induced T wave changes responded abnormally to exercise, three having angiographically proven coronary artery disease lending little support to the contention that the two entities rarely coexist. In spite of the low return from routine electrocardiograms in a population with a low prevalence of coronary artery disease, three-eighths of those with significant coronary artery disease presented with minor ST segment and T wave changes on their resting electrocardiograms.

Adolescent↗
PubMed1989

Physiological hypertrophy of the heart and atrial natriuretic peptide during rest and exercise.

The influence of physiological cardiac hypertrophy on the concentration of plasma atrial natriuretic peptide was studied in six male athletes and six normally active, matched control men. They were examined by echocardiography during a graded exercise test on a bicycle ergometer. Plasma atrial natriuretic peptide was measured at rest, at each workload until exhaustion, and 15 and 30 minutes after the exercise test. Echocardiography showed that the athletes had a significantly larger left atrium, left ventricular end diastolic diameter, left ventricular posterior wall, interventricular septum, left ventricular ejection fraction, and left ventricular mass than the controls. The athletes performed significantly more work than the control group--325 W v 277 W. The plasma concentration of atrial natriuretic peptide rose by a mean factor of 2.76 (range 1.78-4.28) in all men from rest to maximum exercise. There were no differences between the athletes and the controls in the concentrations of plasma atrial natriuretic peptide at rest, at any workload, or at maximum workload. Neither was there any difference in the increase in plasma atrial natriuretic peptide between the groups. There was no correlation between the plasma concentrations of atrial natriuretic peptide and any of the variables measured by echocardiography. In healthy young men plasma atrial natriuretic peptide rises by a factor of about 2.8 during maximum exercise and the size of the chambers on the left side of the heart or left ventricular hypertrophy does not seem to influence the concentration of plasma atrial natriuretic peptide at rest or during exercise.

Adult↗
PubMed2005

The spasticity paradox: movement disorder or disorder of resting limbs?

BACKGROUND: Spasticity is defined/assessed in resting limbs, where increased stretch reflex activity and mechanical joint resistance are evident. Treatment with antispastic agents assumes that these features contribute to the movement disorder, although it is unclear whether they persist during voluntary contraction. OBJECTIVES: To compare reflex amplitude and joint resistance in spastic and normal limbs over an equivalent range of background contraction. METHODS: Thirteen normal and eight hemiparetic subjects with mild/moderate spasticity and without significant contracture were studied. Reflex and passive joint resistance were compared at rest and during six small increments of biceps voluntary contraction, up to 15% of normal maximum. A novel approach was used to match contraction levels between groups. RESULTS: Reflex amplitude and joint mechanical resistance were linearly related to contraction in both groups. The slopes of these relations were not above normal in the spastic subjects on linear regression. Thus, reflex amplitude and joint resistance were not different between groups over a comparable range of contraction levels. Spastic subjects exhibited a smaller range of reflex modulation than normals because of decreased maximal contraction levels (weakness) and significant increases of resting contraction levels. CONCLUSIONS: Spasticity was most evident at rest because subjects could not reduce background contraction to normal. When background contractions were matched to normal levels, no evidence of exaggerated reflex activity or mechanical resistance was found. Instead, reduced capacity to modulate reflex activity dynamically over the normal range may contribute to the movement disorder. This finding does not support the routine use of antispastic agents to treat the movement disorder.

Adult↗
PubMed2003

Influence of intensive cycling training on heart rate variability during rest and exercise.

The current study examined whether changes in heart rate variability (HRV) following intensive cycling training contribute to the mechanism of training-induced bradycardia. Thirteen healthy untrained subjects, ages 18-27 years, underwent recordings of heart rate (HR) and VO2max before and after 8 weeks of cycling, 25-60 min/day, 5 days/week at > 80% maximum HR (HRmax). Heart rate recordings were obtained during supine rest and submaximal exercise and were analysed for the following components of HRV: low frequency (LF, 0.041-0.15 Hz); high frequency (HF, 0.15-0.40 Hz); LF/HF ratio and total power (TP, 0-0.40 Hz). At posttraining, VO2max was significantly increased while HR was significantly reduced at rest and all absolute exercise work rates. Training-induced lower HR was accompanied by significantly greater HF and TP during rest as well as LF, HF, and TP during all absolute exercise work rates. Posttraining HR and the majority of HRV measures were similar to pretraining values at the same relative exercise intensity (% HRmax). These results indicated that 8 weeks of intensive cycling training increased HRV and cardiac vagal modulation during rest and absolute exercise work rates but had little effect during relative exercise work rates. Increased vagal modulation resulting from intensive exercise training may contribute to the mechanism of training-induced bradycardia.

Adolescent↗
PubMed1996

Exercise increases fat oxidation at rest unrelated to changes in energy balance or lipolysis.

The hypothesis that exercise increases fat oxidation at rest independently of changes in energy balance, body composition, and/or lipolysis was tested in 21 volunteers. After a period of energy balance, volunteers were randomly allocated to one of four groups: control, overfed (OF), overfed and exercised (OF-EX), and exercised (EX). OF and OF-EX were overfed 50% excess of energy balance calories; OF-EX and EX spent 50% excess of energy balance calories during daily exercise sessions. Exercise increased fat oxidation at rest independently of dietary intake (OF-EX = + 22 +/- 2.4, EX = + 23 +/- 1.5 mg/min) and reduced carbohydrate oxidation (OF-EX = - 49 +/- 6.2, EX = - 46 +/- 5.4 mg/min). Volunteers in the OF group had an increase in carbohydrate oxidation (85 +/- 5.9 mg/min) and a decline in fat oxidation (- 33 +/- 1.4 mg/min). Protein oxidation did not change in any group. These changes occurred without a direct relation with changes in lipolysis and persisted even when expressed as a percentage or as an absolute equivalent of resting metabolic rate in calories. Thus exercise, independent of changes in energy intake and body composition and not related to changes in lipolysis, increases fat oxidation at rest, which may explain the beneficial effects of exercise in weight loss programs.

Adult↗