Biomedical subjects

Helen Carter

Publications and source records attributed to Helen Carter.

16 recordsLinked to original sources

PubMed2005

Somatotopic organization of the human periventricular gray matter.

The periventricular gray (PVG) matter is an established anatomical target for chronic deep brain stimulation (DBS) in the treatment of certain intractable pain syndromes. Data relating to the representation of pain and other somatosensory modalities within the PVG in humans are negligible. We examined the character and location of somatosensory responses elicited by electrical stimulation along the length of the PVG in a patient who underwent unilateral DBS for intractable nociceptive head pain. Consistent responses were obtained and indicated the presence of a somatotopic representation in this region. The contralateral lower limb was represented cranially, followed by the upper limb and trunk, with the face area located caudally, near the level of the superior colliculi. Bilateral representation was only observed in the forehead and scalp.

Adult↗

PubMed2005

Deep brain stimulation for phantom limb pain.

Phantom limb pain is an often severe and debilitating phenomenon that has been reported in up to 85% of amputees. Its pathophysiology is poorly understood. Peripheral and spinal mechanisms are thought to play a role in pain modulation in affected individuals; however central mechanisms are also likely to be of importance. The neuromatrix theory postulates a genetically determined representation of body image, which is modified by sensory input to create a neurosignature. Persistence of the neurosignature may be responsible for painless phantom limb sensations, whereas phantom limb pain may be due to abnormal reorganisation within the neuromatrix. This study assessed the clinical outcome of deep brain stimulation of the periventricular grey matter and somatosensory thalamus for the relief of chronic neuropathic pain associated with phantom limb in three patients. These patients were assessed preoperatively and at 3 month intervals postoperatively. Self-rated visual analogue scale pain scores assessed pain intensity, and the McGill Pain Questionnaire assessed the quality of the pain. Quality of life was assessed using the EUROQOL EQ-5D scale. Periventricular gray stimulation alone was optimal in two patients, whilst a combination of periventricular gray and thalamic stimulation produced the greatest degree of relief in one patient. At follow-up (mean 13.3 months) the intensity of pain was reduced by 62% (range 55-70%). In all three patients, the burning component of the pain was completely alleviated. Opiate intake was reduced in the two patients requiring morphine sulphate pre-operatively. Quality of life measures indicated a statistically significant improvement. This data supports the role for deep brain stimulation in patients with phantom limb pain. The medical literature relating to the epidemiology, pathogenesis, and treatment of this clinical entity is reviewed in detail.

Adult↗

PubMed2005

Effect of prior exercise above and below critical power on exercise to exhaustion.

PURPOSE: The aim of the present study was to ascertain whether the intensity of prior exercise altered the time to exhaustion at critical power (CP). METHODS: Eleven participants volunteered to take part in the study (mean +/- SD: VO2max 4.1 +/- 0.5 L x min(-1); age 30.1 +/- 7.2 yr; body mass 74.6 +/- 9.1 kg) and completed three trials to exhaustion at their CP under differing prior exercise conditions: 1) a control trial (CON); 2) a trial preceded by three 60-s efforts at 110% CP (severe); and 3) a trial preceded by three 73-s efforts at 90% CP (heavy). All trials followed a 5-min baseline at 50 W. RESULTS: Time to exhaustion was significantly lengthened after prior heavy exercise (1071 +/- 18 s) when compared with CON (973 +/- 16 s, F = 9.53, P = 0.006). However, there was no effect on TTE after prior severe exercise (967 +/- 16 s). Oxygen deficit was significantly reduced from that in CON (3.8 +/- 0.2 L) after prior heavy (3.2 +/- 0.3 L) and prior severe exercise (3.1 +/- 0.3 L, F = 10.95, P = 0.001). Concurrently, there was a significant reduction in the magnitude of the VO2 slow component (SC) in the trials with prior exercise (197 +/- 34 and 126 +/- 19 mL x min(-1) after heavy and severe exercise, respectively) when compared with CON (223 +/- 31 mL x min(-1), F = 9.62, P = 0.006). CONCLUSION: Prior heavy exercise does appear to improve the time to exhaustion at CP by approximately 10% and is associated with a reduction in the VO2 SC. However, the reduction in the SC, with no change in performance after prior severe exercise, suggests that a reduced SC may not necessarily lead to improved TTE.

Adult↗

PubMed2004

Living with a terminal illness: patients' priorities.

BACKGROUND: Our understanding of terminal illness and its consequences has been predominantly based on models derived from expert definition, rather than the patient's perspective. More recently, quality of life tools have been developed to enable patient choice in responses. However, an even broader approach may be needed to help identify goals for care for patients who are terminally ill. AIM: The aim of this paper is to report on an exploratory, qualitative study exploring what people living with terminal illness considered were the areas of priority in their lives. METHODS: Ten people living with terminal cancer were interviewed. Analysis of the interviews incorporated principles of narrative analysis and grounded theory. FINDINGS: Over 30 categories were identified and collated into five inter-related themes (personal/intrinsic factors, external/extrinsic factors, future issues, perceptions of normality and taking charge) encompassing the issues of importance to all participants. Each theme focused on 'life and living' in relation to life as it was or would be without illness. Practical issues of daily living and the opportunity to address philosophical issues around the meaning of life emerged as important areas. The central theme, 'taking charge', concerned with people's levels of life engagement, was integrally connected to all other themes. CONCLUSIONS: The findings suggest that the way in which health professionals manage patients' involvement in matters such as symptom relief can impact on existential areas of concern. Understanding patients' perspectives in relation to each theme may assist health professionals to develop management strategies appropriate to their needs. The findings challenge some aspects of traditional 'expert-defined' outcome measures. As this was an exploratory study, further work is needed to test and develop the model presented.

Activities of Daily Living↗

PubMed2004

Partnership working in the production of clinical guidelines.

This article describes a working partnership between the Cairns Clinical Librarian Service, Health Care Libraries, University of Oxford and the Emergency Department (ED) at the John Radcliffe Hospital, Oxford. This collaboration resulted in the establishment of a guideline development group in June 2002. The aim of the group is to produce a set of easily accessible, user-orientated, evidence-based guidelines for the use of clinicians in the Emergency Department, within a realistic timescale. The Cairns Clinical Librarian Project was built on previous models of clinical librarianship and incorporated an evaluation of previous programmes. The objective was to provide information to clinicians at the time and point of need. Consultation with the ED from the outset determined the approach adopted by the Cairns team. Clinical guidelines have been shown to improve clinical practice. Pending the introduction of nationally available protocols, we have begun to establish a collection of evidence-based guidelines using web-based architecture in conjunction with the Oxford Radcliffe Hospitals NHS Trust's IT department. A piece of diagnostic analysis was undertaken to ensure a coherent strategy was developed for the guideline project. An 'intermediate approach' was adopted, where existing valid guidelines were modified to fit local circumstances. We strove to be transparent at all times about all aspects of the guideline development process. Formative evaluation has shown how the application of evidence-based health care needs adequate resources and requires people with appropriate knowledge and skills. This article charts the progress of the project and highlights how the partnership between the clinical team and the Clinical Librarian has been deemed to be essential to the success of the project.

Cooperative Behavior↗

PubMed2004

Muscle glycogen depletion alters oxygen uptake kinetics during heavy exercise.

PURPOSE: To test the hypothesis that muscle fiber recruitment patterns influence the oxygen uptake (VO2) kinetic response, constant-load exercise was performed after glycogen depletion of specific fiber pools. METHODS: After validation of protocols for the selective depletion of Type I and II muscle fibers, 19 subjects performed square-wave exercise at 80% VT (moderate) and at 50% of the difference between VT and VO2max (heavy) without any prior depleting exercise (CON), after HIGH (10 x 1-min exercise bouts at 120% VO2max), and after LOW (3 h of exercise at 30% VO2max) exercise. RESULTS: Differences in VO2 kinetic parameters were only observed in heavy exercise AFTER HIGH: the VO2 primary component was higher (1.75 +/- 0.12 L x min) compared with CON (1.65 +/- 0.11 L x min, P < 0.05), and the VO2 slow component was lower (0.18 +/- 0.03 L x min) compared with CON (0.24 +/- 0.04 L x min, P < 0.05). CONCLUSIONS: The results indicate that the VO2 response to heavy constant-load exercise can be altered by depletion of glycogen in the Type II muscle fibers, lending support to the theory that muscle fiber recruitment influences both the VO2 primary and slow component amplitudes during heavy intensity exercise.

Glycogen↗

PubMed2003

Oxygen uptake kinetics during moderate, heavy and severe intensity "submaximal" exercise in humans: the influence of muscle fibre type and capillarisation.

The purpose of the present study was to test the hypothesis that muscle fibre type influences the oxygen uptake (.VO(2)) on-kinetic response (primary time constant; primary and slow component amplitudes) during moderate, heavy and severe intensity sub-maximal cycle exercise. Fourteen subjects [10 males, mean (SD) age 25 (4) years; mass 72.6 (3.9) kg; .VO(2peak) 47.9 (2.3) ml kg(-1) min(-1)] volunteered to participate in this study. The subjects underwent a muscle biopsy of the vastus lateralis for histochemical determination of muscle fibre type, and completed repeat "square-wave" transitions from unloaded cycling to power outputs corresponding to 80% of the ventilatory threshold (VT; moderate exercise), 50% (heavy exercise) and 70% (severe exercise) of the difference between the VT and .VO(2peak). Pulmonary .VO(2) was measured breath-by-breath. The percentage of type I fibres was significantly correlated with the time constant of the primary .VO(2) response for heavy exercise (r=-0.68). Furthermore, the percentage of type I muscle fibres was significantly correlated with the gain of the .VO(2) primary component for moderate (r=0.65), heavy (r=0.57) and severe (r=0.57) exercise, and with the relative amplitude of the .VO(2) slow component for heavy (r=-0.74) and severe (r=-0.64) exercise. The influence of muscle fibre type on the .VO(2) on-kinetic response persisted when differences in aerobic fitness and muscle capillarity were accounted for. This study demonstrates that muscle fibre type is significantly related to both the speed and the amplitudes of the .VO(2) response at the onset of constant-load sub-maximal exercise. Differences in contraction efficiency and oxidative enzyme activity between type I and type II muscle fibres may be responsible for the differences observed.

Adaptation, Physiological↗

PubMed2003

Anemia at the end of life: prevalence, significance, and causes in patients receiving palliative care.

While data exist on the prevalence and causes of anemia in defined groups of the elderly, information on palliative care patients is limited. Compared to actively treated oncology patients, for whom anemia treatment has demonstrated improved quality of life and symptom alleviation, studies of treatment outcomes in palliative care patients are limited. Knowledge of the extent and causes of anemia in palliative care patients is needed, as correction of anemia in these patients could potentially improve their physical, emotional, and cognitive functioning. In the present study, clinical data and blood test results of 105 patients meeting specific eligibility criteria were examined to estimate the prevalence of anemia and investigate its causes. Ninety-five (90.5%) patients had advanced cancer. Based on World Health Organization criteria, anemia was found in 77% of men (Hb <130 g/l) and 68.2% of women (Hb <120 g/l). The diagnosis was anemia of chronic disease in 76.7% of women and 46.8% of men. Patients with prostate cancer had a significantly lower mean Hb level (P=0.007) and more evidence of bone metastases (P=0.0007) than those with other cancers. Neutrophil hypersegmentation, suggesting occult folate deficiency, was present in 28.6% of patients, being more common in those with major weight loss (58.3%) than those with moderate (37%) or mild/no weight loss (26%) (P=0.019). The findings suggest that anemia is highly prevalent in the palliative care setting. Although anemia of chronic disease is most common, occult folate deficiency may be more prevalent than previously suspected. The findings suggest that a low serum folate level is an insensitive marker of occult folate deficiency. A randomized controlled trial of folic acid treatment is proposed.

Adult↗

PubMed2003

Thalamic field potentials in chronic central pain treated by periventricular gray stimulation -- a series of eight cases.

Chronic deep brain stimulation (DBS) of the periventricular gray (PVG) has been used for the treatment of chronic central pain for decades. In recent years motor cortex stimulation (MCS) has largely supplanted DBS in the surgical management of intractable neuropathic pain of central origin. However, MCS provides satisfactory pain relief in about 50-75% of cases, a range comparable to that reported for DBS (none of the reports are in placebo-controlled studies and hence the further need for caution in evaluating and comparing these results). Our experience also suggests that there is still a role for DBS in the control of central pain. Here we present a series of eight consecutive cases of intractable chronic pain of central origin treated with PVG DBS with an average follow-up of 9 months. In each case, two electrodes were implanted in the PVG and the ventroposterolateral thalamic nucleus, respectively, under guidance of corneal topography/magnetic resonance imaging image fusion. The PVG was stimulated in the frequency range of 2-100 Hz in alert patients while pain was assessed using the McGill-Melzack visual analogue scale. In addition, local field potentials (FPs) were recorded from the sensory thalamus during PVG stimulation. Maximum pain relief was obtained with 5-35 Hz stimulation while 50-100 Hz made the pain worse. This suggests that pain suppression was frequency dependent. Interestingly, we detected low frequency thalamic FPs at 0.2-0.4 Hz closely associated with the pain. During 5-35 Hz PVG stimulation the amplitude of this potential was significantly reduced and this was associated with marked pain relief. At the higher frequencies (50-100 Hz), however, there was no reduction in the FPs and no pain suppression. We have found an interesting and consistent correlation between thalamic electrical activity and chronic pain. This low frequency potential may provide an objective index for quantifying chronic pain, and may hold further clues to the mechanism of action of PVG stimulation. It may be possible to use the presence of these slow FPs and the effect of trial PVG DBS on both the clinical status and the FPs to predict the probable success of future pain control in individual patients.

Adult↗

PubMed2003

Percutaneous endoscopic gastrostomy. Procedure in practice.

Percutaneous endoscopic gastrostomy (PEG) is a relatively common procedure used in the treatment of children. As with all procedures, it must be used with care and only after taking careful account of circumstances and likely responses of the individual patient. This first of two articles on the procedure discusses the indications and contraindications for PEG insertion in children and then focuses on the procedure itself. The second article will discuss the role of the nurse as surgeon's assistant in the application of this procedure to children.

Child↗

PubMed2002

Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise.

We hypothesized that a higher pedal rate (assumed to result in a greater proportional contribution of type II motor units) would be associated with an increased amplitude of the O(2) uptake (Vo(2)) slow component during heavy-cycle exercise. Ten subjects (mean +/- SD, age 26 +/- 4 yr, body mass 71.5 +/- 7.9 kg) completed a series of square-wave transitions to heavy exercise at pedal rates of 35, 75, and 115 rpm. The exercise power output was set at 50% of the difference between the pedal rate-specific ventilatory threshold and peak Vo(2), and the baseline power output was adjusted to account for differences in the O(2) cost of unloaded pedaling. The gain of the Vo(2) primary component was significantly higher at 35 rpm compared with 75 and 115 rpm (mean +/- SE, 10.6 +/- 0.3, 9.5 +/- 0.2, and 8.9 +/- 0.4 ml. min(-1). W(-1), respectively; P < 0.05). The amplitude of the Vo(2) slow component was significantly greater at 115 rpm (328 +/- 29 ml/min) compared with 35 rpm (109 +/- 30 ml/min) and 75 rpm (202 +/- 38 ml/min) (P < 0.05). There were no significant differences in the time constants or time delays associated with the primary and slow components across the pedal rates. The change in blood lactate concentration was significantly greater at 115 rpm (3.7 +/- 0.2 mM) and 75 rpm (2.8 +/- 0.3 mM) compared with 35 rpm (1.7 +/- 0.4 mM) (P < 0.05). These data indicate that pedal rate influences Vo(2) kinetics during heavy exercise at the same relative intensity, presumably by altering motor unit recruitment patterns.

Adult↗

PubMed2002

Oxygen uptake kinetics during horizontal and uphill treadmill running in humans.

The aim of this study was to examine the effect of increasing the ratio of concentric to eccentric muscle activation on oxygen uptake (VO(2)) kinetics during treadmill running. Nine subjects [2 women; mean (SD) age 29 (7) years, height 1.77 (0.07) m, body mass 73.0 (7.5) kg] completed incremental treadmill tests to exhaustion at 0% and 10% gradients to establish the gradient-specific ventilatory threshold (VT) and maximal oxygen uptake (VO(2max)). Subsequently, the subjects performed repeated moderate intensity (80% of gradient-specific VT) and heavy intensity (50% of the difference between the gradient specific VT and VO(2max)) square-wave runs with the treadmill gradient set at 0% and 10%. For moderate intensity exercise, there were no significant differences between treadmill gradients for VO(2) kinetics. For heavy intensity exercise, the amplitude of the primary component of VO(2) was not significantly different between 0% and 10% treadmill gradients [mean (SEM) 2,940 (196) compared to 2,869 (156) ml x min(-1), respectively], but the amplitude of the VO(2) slow component was significantly greater at the 10% gradient [283 (43) compared to 397 (37) ml x min(-1); P < 0.05]. These results indicate that the muscle contraction regimen (i.e. the relative contribution of concentric and eccentric muscle action) significantly influences the amplitude of the VO(2) slow component.

Adult↗

PubMed2002

Oxygen uptake kinetics during treadmill running across exercise intensity domains.

The purpose of the present study was to examine comprehensively the kinetics of oxygen uptake (VO2) during treadmill running across the moderate, heavy and severe exercise intensity domains. Nine subjects [mean (SD age, 27 (7) years; mass, 69.8 (9.0) kg; maximum VO2, VO2max, 4,137 (697) ml x min(-1)] performed a series of "square-wave" rest-to-exercise transitions of 6 min duration at running speeds equivalent to 80% and 100% of the VO2 at lactate threshold (LT; moderate exercise); and at 20%, 40%, 60%, 80% and 100% of the difference between the VO2 at LT and VO2max (delta heavy and severe exercise). Critical velocity (CV) was also determined using four maximal treadmill runs designed to result in exhaustion in 2-15 min. The VO2 response was modelled using non-linear regression techniques. As expected, the amplitude of the VO2 primary component increased with exercise intensity [from 1,868 (136) ml x min-( 1) at 80% LT to 3,296 (218) ml x min-(1) at 100% delta, P < 0.05]. However, there was a non-significant trend for the "gain" of the primary component to decrease as exercise intensity increased [181 (7) ml x kg(-1) x km(-1) at 80% LT to 160 (6) ml x kg(-1) x km(-1) at 100% delta]. The time constant of the primary component was not different between supra-LT running speeds (mean value range = 17.9-19.1 s), but was significantly shorter during the 80% LT trial [12.7 (1.4) s, P < 0 .05]. The VO2 slow component increased with exercise intensity from 139 (39) ml x min(-1) at 20% delta to 487 (57) ml x min(-1) at 80% delta (P < 0.05), but decreased to 317 (84) ml x min(-1) during the 100% delta trial (P < 0.05). During both the 80% delta and 100% delta trials, the VO2 at the end of exercise reached VOmax [4,152 (242) ml x min(-1) and 4,154 (114) ml x min(-1), respectively]. Our results suggest that the "gain" of the primary component is not constant as exercise intensity increases across the moderate, heavy and severe domains of treadmill running. These intensity-dependent changes in the amplitudes and kinetics of the VO2 response profiles may be associated with the changing patterns of muscle fibre recruitment that occur as exercise intensity increases.

Adult↗

PubMed2002

The effect of interdian and diurnal variation on oxygen uptake kinetics during treadmill running.

The aim of this study was to examine the variability of the oxygen uptake (VO2) kinetic response during moderate- and high-intensity treadmill exercise within the same day (at 06:00, 12:00 and 18:00 h) and across days (on five occasions). Nine participants (age 25 +/- 8 years, mass 70.2 +/- 4.7 kg, VO2max 4137 +/- 697 ml x min(-1); mean +/- s) took part in the study. Six of the participants performed replicate 'square-wave' rest-to-exercise transitions of 6 min duration at running speeds calculated to require 80% VO2 at the ventilatory threshold (moderate-intensity exercise) and 50% of the difference between VO2 at the ventilatory threshold and VO2max (50% delta; high-intensity exercise) on 5 different days. Although the amplitudes of the VO2 response were relatively constant (coefficient of variation approximately 6%) from day to day, the time-based parameters were more variable (coefficient of variation approximately 15 to 30%). All nine participants performed replicate square-waves for each time of day. There was no diurnal effect on the time-based parameters of VO2 kinetics during either moderate- or high-intensity exercise. However, for high-intensity exercise, the amplitude of the primary component was significantly lower during the 12:00 h trial (2859 +/- 142 ml x min(-1) vs 2955 +/- 135 ml x min(-1) at 06:00 h and 2937 +/- 137 ml x min(-1) at 18:00 h; P < 0.05), but this effect was eliminated when expressed relative to body mass. The results of this study indicate that the amplitudes of the VO2 kinetic responses to moderate- and high-intensity treadmill exercise are similar within and across test days. The time-based parameters, however, are more variable from day to day and multiple transitions are, therefore, recommended to increase confidence in the data.

Adult↗

PubMed2002

Effect of creatine supplementation on oxygen uptake kinetics during submaximal cycle exercise.

The purpose of this study was to test the effect of oral creatine (Cr) supplementation on pulmonary oxygen uptake (VO(2)) kinetics during moderate [below ventilatory threshold (VT)] and heavy (above VT) submaximal cycle exercise. Nine subjects (7 men; means +/- SD: age 28 +/- 3 yr, body mass 73.2 +/- 5.6 kg, maximal VO(2) 46.4 +/- 8.0 ml. kg(-1). min(-1)) volunteered to participate in this study. Subjects performed transitions of 6-min duration from unloaded cycling to moderate (80% VT; 8-12 repeats) and heavy exercise (50% change; i.e., halfway between VT and maximal VO(2); 4-6 repeats), both in the control condition and after Cr loading, in a crossover design. The Cr loading regimen involved oral consumption of 20 g/day of Cr monohydrate for 5 days, followed by a maintenance dose of 5 g/day thereafter. VO(2) was measured breath by breath and modeled by using two (moderate) or three (heavy) exponential terms. For moderate exercise, there were no differences in the parameters of the VO(2) kinetic response between control and Cr-loaded conditions. For heavy exercise, the time-based parameters of the VO(2) response were unchanged, but the amplitude of the primary component was significantly reduced with Cr loading (means +/- SE: control 2.00 +/- 0.12 l/min; Cr loaded 1.92 +/- 0.10 l/min; P < 0.05) as was the end-exercise VO(2) (control 2.19 +/- 0.13 l/min; Cr loaded 2.12 +/- 0.14 l/min; P < 0.05). The magnitude of the reduction in submaximal VO(2) with Cr loading was significantly correlated with the percentage of type II fibers in the vastus lateralis (r = 0.87; P < 0.01; n = 7), indicating that the effect might be related to changes in motor unit recruitment patterns or the volume of muscle activated.

Administration, Oral↗

PubMed2002

Impact of a hospital palliative care service: perspective of the hospital staff.

The first New Zealand hospital palliative care support service was established in 1985. Different service models have now been adopted by various major hospitals. In 1998, a palliative care service, funded by Mary Potter Hospice, was piloted at Wellington Public Hospital. Twelve months post-implementation, the hospital staff's views of the service were evaluated. It was found that referrals to palliative care from hospital specialities outside the Cancer Centre increased. While most doctors, nurses and social workers strongly agreed or agreed that the service positively influenced patients' care and effectively addressed their symptom management needs, spiritual needs were less often met. Over 90 percent of each discipline strongly agreed or agreed that the service had assisted them in caring for patients, but, only about a half agreed that useful discharge planning advice and staff support was provided. Significant differences in responses were found between different disciplines and specialities. One fifth of the staff identified palliative care education needs. Recommendations are made concerning the development of a future hospital palliative care service.

Attitude of Health Personnel↗