PubMed Health⌕ Search

Biomedical subjects

R Chua

Publications and source records attributed to R Chua.

At least 19 recordsLinked to original sources
PubMed2006

Comparison and validation of three measures of quality of life in patients with pulmonary hypertension.

BACKGROUND: Pulmonary hypertension, when advanced, markedly limits exercise capacity, activities of daily living and quality of life (QoL). No measure of QoL has yet been validated for the assessment of pulmonary hypertension. The aim of the study was to compare the validity of the Minnesota Living with Heart Failure (MLwHF) questionnaire, the Short Form-36 (SF-36) questionnaire and the Australian Quality of Life (AQoL) measure for assessing pulmonary hypertension treatment. METHODS: Eighty-three patients were enrolled in three studies of pulmonary hypertension treatment (treprostinil, bosentan and sildenafil). They were assessed at baseline and 3 months with the MLwHF questionnaire. Treprostinil and bosentan groups also had 6 and 12 months' data. Twenty-one patients in the sildenafil trial completed concurrently, the SF-36 and AQoL measures at baseline and 3 months. QoL scores were correlated with the 6-min walk test distance, New York Heart Association functional class and right heart catheter-derived haemodynamic parameters of the disease for all matching time points and for changes in scores and clinical measurements over time. RESULTS: The MLwHF and SF-36 scores correlated well with the 6-min walk test distance and New York Heart Association functional class, but did not correlate with haemodynamic measurements. MLwHF and SF-36 scores also correlated with the rate of change of the 6-min walk test distance and New York Heart Association functional class over time. CONCLUSION: The MLwHF questionnaire and SF-36 are useful tools for the assessment of QoL in pulmonary hypertension and may be useful in the ongoing evaluation of QoL in the treatment and study of pulmonary hypertension.

Activities of Daily Living↗
PubMed2006

Will "no blood" kill Jehovah Witnesses?

A 46-year-old Indonesian woman presented with signs and symptoms suggestive of an ovarian tumour and was advised to have surgery with exploratory laparotomy and removal of the mass. She agreed but refused blood transfusion any time in the course of her treatment or procedure, as she was a Jehovah Witness. As there was a high risk of intraoperative haemorrhage, steps were taken to reduce any consequent complications due to the surgery. The ethical conflict is between respecting patient autonomy and compromising standards of care, arising from the refusal of a standard therapy. The latest developments in the blood transfusion doctrine policy for the Jehovah Witnesses are also discussed in this case study.

Advance Directives↗
PubMed2005

Touch noise increases vibrotactile sensitivity in old and young.

Stochastic resonance (SR) occurs when the detection of a subthreshold signal is aided by the presence of random energy fluctuations in the signal modality, commonly called noise. SR is counterintuitive because such noise usually worsens performance. Nonetheless, SR has been demonstrated both theoretically and experimentally in human sensory systems. Using a psychophysically sophisticated paradigm, we show that SR aids the detection of vibrating touch stimuli presented to the foot soles of both healthy elderly people with elevated vibrotactile thresholds and healthy young people with normal vibrotactile thresholds. The results also suggest that it is possible to know a priori the amount of noise needed for optimal SR effects given the degree to which the signal is subthreshold. Thus, SR may be practical as a rehabilitative aid for individuals with elevated sensory thresholds.

Adult↗
PubMed2004

A cohort study of early neurological consultation by telemedicine on the care of neurological inpatients.

OBJECTIVES: To find out the effect of early neurological consultation using a real time video link on the care of patients with neurological symptoms admitted to hospitals without neurologists on site. METHODS: A cohort study was performed in two small rural hospitals: Tyrone County Hospital (TCH), Omagh, and Erne Hospital, Enniskillen. All patients over 12 years of age who had been admitted because of neurological symptoms, over a 24 week period, to either hospital were studied. Patients admitted to TCH, in addition to receiving usual care, were offered a neurological consultation with a neurologist 120 km away at the Neurology Department of the Royal Victoria Hospital, Belfast, using a real time video link. The main outcome measure was length of hospital stay; change of diagnosis, mortality at 3 months, inpatient investigation, and transfer rate and use of healthcare resources within 3 months of admission were also studied. RESULTS: Hospital stay was significantly shorter for those admitted to TCH (hazard ratio 1.13; approximate 95% CI 1.003 to 1.282; p = 0.045). No patients diagnosed by the neurologist using the video link subsequently had their diagnosis changed at follow up. There was no difference in overall mortality between the groups. There were no differences in the use of inpatient hospital resources and medical services in the follow up period between TCH and Erne patients. CONCLUSIONS: Early neurological assessment reduces hospital stay for patients with neurological conditions outside of neurological centres. This can be achieved safely at a distance using a real time video link.

Adult↗
PubMed2004

Email triage of new neurological outpatient referrals from general practice.

OBJECTIVES: To determine whether an email triage system between general practitioners and a neurologist for new outpatient referrals is feasible, acceptable, efficient, safe, and effective. METHODS: This was a prospective single cohort study on the interface between primary care practitioners and the neurology clinic of a district general hospital. Seventy six consecutive patients with neurological symptoms from nine GPs, for whom a specialist opinion was deemed necessary, were entered in the study. The number of participants managed without clinic attendance and the reduction in neurologist's time compared with conventional consultation was measured, as was death, other specialist referral, and change in diagnosis in the 6 months after episode completion. The acceptability for GPs was ascertained by questionnaire. RESULTS: Forty three per cent of participants required a clinic appointment, 45% were managed by email advice alone, and 12% by email plus investigations. GP satisfaction was high. Forty four per cent of the neurologist's time was saved compared with conventional consultation. No deaths or significant changes in diagnosis were recorded during the 6 month follow up period. CONCLUSIONS: Email triage is feasible, acceptable to GPs, and safe. It has the potential for making the practice of neurologists more efficient, and this needs to be tested in a larger randomised study.

Adolescent↗
PubMed2003

Influence of terminal action requirements on action-centered distractor effects.

Tipper (1985; Q J Exp Psychol A 37:571-590) has suggested that competing responses programmed to distracting stimuli are inhibited based on their relationship to the action being performed. The present paper reports two experiments designed to examine the influence of the terminal action of a task on the allocation of visual attention. Taken together the results suggest that when engaging targets in an environment, which includes distracting stimuli, competing responses are likely to be programmed in parallel and that the relationship between competing responses can include both spatial position and action characteristics.

Adult↗
PubMed2001

Influence of operator orientation on relative organizational mapping and spatial compatibility.

Following up on a study by Worringham and Beringer (1989) that examined the influence of operator orientation on visual-motor performance, Experiment 1 employed a choice reaction time paradigm in which participants had to make rapid, discrete movements with a lever in response to a discrete stimulus. In Experiment 2, participants had to synchronize rhythmic movements with an oscillating visual display. Operator orientation with respect to stimulus display and response array locations was varied to examine the influence of global spatial relations. Display orientation was varied to examine the influence of spatial configuration. Mapping rules were varied to examine the effects of spatial mapping. In Experiment 1, the spatial mapping that yielded faster responses was dependent upon the stimulus display-response array configuration and the global relation. Under a parallel configuration, participants appeared to code the spatial aspects of the stimulus display and response in a manner that was unaffected by the global spatial relation. Under an orthogonal configuration, spatial mapping effects were dependent upon the global relation. In Experiment 2, the global spatial relation did not have an impact on the uniformity of co-ordination under different configuration or mapping conditions. Spatial configuration influenced whether or not differences between spatial mapping rules emerged. Together, the results speak to the relative nature of stimulus-response coding that underlie compatibility phenomena. In addition, the results have potential importance for the design of human-machine systems that allow flexibility in operator orientation.

Canada↗
PubMed2001

Human interlimb reflexes evoked by electrical stimulation of cutaneous nerves innervating the hand and foot.

There is some discrepancy over the extent to which reflex pathways from different cutaneous nerves in the hand and foot link the cervical and lumbar spinal cord in neurologically intact humans. The present experiments were designed to determine whether stimulation of a cutaneous nerve in the foot or in the hand evoked reflexes in the non-stimulated limbs (interlimb reflexes). Reflexes were elicited by stimulating (5x1-ms pulses at 300 Hz) the superficial peroneal (SP; innervates the foot dorsum) or superficial radial (SR; innervates the dorsolateral portion of the hand) nerve while subjects (n=10) performed focused contractions of different upper and lower limb muscles. Reflex responses were divided into early (<75 ms), middle (75-120 ms), and late (>120 ms) epochs as determined from averages of 50 sweeps of stimulus-locked electromyographic activity. Significant interlimb reflexes were found at the early latency in 44/106 and 44/103 muscles sampled after SP and SR nerve stimulation, respectively. At the middle latency, significant interlimb reflexes were seen in 89/106 and 87/103 muscles sampled after SP and SR nerve stimulation, respectively. Interlimb reflexes were seen when stimulating at the wrist (i.e. SR nerve) and when stimulating at the ankle (i.e. SP nerve) with an equal probability. The results show that interlimb cutaneous reflexes are widely distributed in humans. The mean latency of the earliest response was quite short and may be mediated by a propriospinal pathway. Functionally, these pathways may provide a substrate for transferring information to coordinate movements between the limb segments.

Action Potentials↗
PubMed2001

Eye-hand coordination in goal-directed aiming.

In a number of studies, we have demonstrated that the spatial-temporal coupling of eye and hand movements is optimal for the pickup of visual information about the position of the hand and the target late in the hand's trajectory. Several experiments designed to examine temporal coupling have shown that the eyes arrive at the target area concurrently with the hand achieving peak acceleration. Between the time the hand reached peak velocity and the end of the movement, increased variability in the position of the shoulder and the elbow was accompanied by a decreased spatial variability in the hand. Presumably, this reduction in variability was due to the use of retinal and extra-retinal information about the relative positions of the eye, hand and target. However, the hand does not appear to be a slave to the eye. For example, we have been able to decouple eye movements and hand movements using Müller-Lyer configurations as targets. Predictable bias, found in primary and corrective saccadic eye movements, was not found for hand movements, if on-line visual information about the target was available during aiming. That is, the hand remained accurate even when the eye had a tendency to undershoot or overshoot the target position. However, biases of the hand were evident, at least in the initial portion of an aiming movement, when vision of the target was removed and vision of the hand remained. These findings accent the versatility of human motor control and have implications for current models of visual processing and limb control.

Adult↗
PubMed2001

A century later: Woodworth's (1899) two-component model of goal-directed aiming.

In 1899, R. S. Woodworth published a seminal monograph, "The Accuracy of Voluntary Movement." As well as making a number of important empirical contributions, Woodworth presented a model of speed-accuracy relations in the control of upper limb movements. The model has come to be known as the two-component model because the control of speeded limb movements was hypothesized to entail both a central and a feedback-based component. Woodworth's (1899) ideas about the control of rapid aiming movements are evaluated in the context of current empirical and theoretical contributions.

Acceleration↗
PubMed2001

Visual awareness and the on-line modification of action.

An influential theory of visually guided action proposes that (a) conscious perception of target displacement disrupts on-line action and (b) small target perturbations are inconsequential, provided the participant is unaware of them. This study examined these claims in a study of rapid aiming movements to targets. Novel features included on-line verbal reports of target displacement, and the factorial combination of small versus large displacements occurring near peak saccadic velocity or 100 ms later. Although awareness of target displacement had no effect on movement kinematics, even small target displacements near peak saccadic velocity affected kinematic measures. These results support both a strong view of visual stream separation in the on-line control of action and richer spatial coding by unconscious processes than has previously been acknowledged.

Awareness↗
PubMed2001

Randomised controlled trial of telemedicine for new neurological outpatient referrals.

OBJECTIVE: To test the hypothesis that telemedicine for new patient referrals to neurological outpatients is as efficient and acceptable as conventional face to face consultation. METHODS: A randomised controlled trial between two groups: face to face (FF) and telemedicine (TM). This study was carried out between a neurological centre and outlying clinics at two distant hospitals linked by identical medium cost commercial interactive video conferencing equipment with ISDN lines transmitting information at 384 kbits/s. The same two neurologists carried out both arms of the study. Of the 168 patients who were suitable for the study, 86 were randomised into the telemedicine group and 82 into the face to face group. Outcome measures were (1) consultation process: (a) number of investigations; (b) number of drugs prescribed; (c) number of patient reviews and (2) patient satisfaction: (a) confidence in consultation; (b) technical aspects of consultation; (c) aspects surrounding confidentiality. Diagnostic categories were also measured to check equivalence between the groups: these were structural neurological, structural non-neurological, non-structural, and uncertain. RESULTS: Diagnostic categories were similar (p>0.5) between the two groups. Patients in the telemedicine group had significantly more investigations (p=0.001). There was no difference in the number of drugs prescribed (p>0.5). Patients were generally satisfied with both types of consultation process except for concerns about confidentiality and embarrassment in the telemedicine group (p=0.017 and p=0.005 respectively). CONCLUSION: Telemedicine for new neurological outpatients is possible and feasible but generates more investigations and is less well accepted than face to face examination.

Adolescent↗
PubMed2001

Differential regulation of cutaneous and H-reflexes during leg cycling in humans.

Reflexes undergo modulation according to task and timing during standing, walking, running, and leg cycling in humans. Both cutaneous and Hoffman (H-) reflexes are modulated by movement and task. However, recent evidence suggests that the modulation pattern for cutaneous and H-reflexes may be different. We sought to clarify this issue by reducing the effect of movement phase and altering the level of background muscle activation (low and high) in static and dynamic (leg cycling) conditions. Electromyography was recorded from the ankle extensors soleus and medial gastrocnemius (MG) and the knee extensor vastus lateralis (VL). Reflexes were evoked during the downstroke of stationary leg cycling. Cutaneous reflexes were evoked with trains of 5 x 1.0 ms pulses at 300 Hz delivered to the distal tibial nerve, whereas H-reflexes were evoked in soleus by stimulation with single 1.0-ms pulses. There were two main observations in this study: 1) middle latency cutaneous reflexes were facilitatory during static contraction but were dramatically attenuated or reversed to suppressive responses during cycling (task-dependent modulation); 2) soleus H-reflexes were larger in the high muscle activation condition but were unaffected by task (no task-dependent modulation). Thus opposite results were obtained in the two reflex pathways. It is concluded that cutaneous and H-reflexes are modulated by different mechanisms during active locomotor-like movements.

Adult↗
PubMed2001

Cost implications of outpatient teleneurology.

A randomized controlled trial was conducted to compare the costs of realtime teleneurology with the cost of conventional neurological care. Two district hospitals in Northern Ireland were equipped with videoconferencing units and were connected to the regional neurological centre by ISDN at 384 kbit/s. Of 168 patients randomized to the study, 141 kept their appointments (76 male, 65 female). Sixty-five patients were randomized to a conventional consultation while 76 were randomized to a teleconsultation. The average age was 44 years of those seen conventionally and 42 years of those seen by telemedicine. The groups had similar diagnoses. The telemedicine group required more investigations and reviews than the conventional group. The average cost of the conventional consultation was 49 pounds sterling compared with 72 pounds sterling for the teleconsultation. Realtime teleneurology was not as cost-effective as conventional care.

Adolescent↗
PubMed2000

Retinoids as ligands and coactivators of protein kinase C alpha.

Whereas retinoic acids control nuclear events, a second class of retinol metabolites, that is, the hydroxylated forms exemplified by 14-hydroxy-retro-retinol (HRR), operate primarily in the cytoplasm. They function as regulatory cofactors for cell survival/cell death decisions. In accordance with these biological aspects, we demonstrate that these retinoids bound protein kinase C (PKC) alpha with nanomolar affinity and markedly enhance the activation of PKC alpha and the entire downstream MAP kinase pathway by reactive oxygen species. HRR was 10 times more efficient than retinol, and the optimum doses are 10-7 and 10-6 M, respectively. PKC alpha activation was reversed rapidly by imposition of reducing conditions. The retinoid binding site was mapped to the first cysteine-rich region in the regulatory domain, C1A, yet was distinct from the binding sites of diacylglycerol and phorbol esters. The C1B domain bound retinoids poorly. The emerging theme is that retinoids serve as redox regulators of protein kinase C.

3T3 Cells↗
PubMed2000

The cysteine-rich regions of the regulatory domains of Raf and protein kinase C as retinoid receptors.

Vitamin A and its biologically active derivatives, the retinoids, are recognized as key regulators of vertebrate development, cell growth, and differentiation. Although nuclear receptors have held the attention since their discovery a decade ago, we report here on serine/threonine kinases as a new class of retinoid receptors. The conserved cysteine-rich domain of the NH(2)-terminal regulatory domains of cRaf-1, as well as several select domains of the mammalian protein kinase C (PKC) isoforms alpha, delta, zeta, and mu, the Drosophila and yeast PKCs, were found to bind retinol with nanomolar affinity. The biological significance was revealed in the alternate redox activation pathway of these kinases. Retinol served as a cofactor to augment the activation of both cRaf and PKC alpha by reactive oxygen, whereas the classical receptor-mediated pathway was unaffected by the presence or absence of retinol. We propose that bound retinol, owing to its electron transfer capacity, functions as a tag to enable the efficient and directed redox activation of the cRaf and PKC families of kinases.

3T3 Cells↗
PubMed2000

Modulation of human cutaneous reflexes during rhythmic cyclical arm movement.

The organization and pattern of cutaneous reflex modulation is unknown during rhythmic cyclical movements of the human upper limbs. On the assumption that these cyclic arm movements are central pattern generator (CPG) driven as has been suggested for leg movements such as walking, we hypothesized that cutaneous reflex amplitude would be independent of electromyographic (EMG) muscle activation level during rhythmic arm movement (phase-dependent modulation, as is often the case in the lower limb during locomotion). EMG was recorded from eight muscles crossing the human shoulder, elbow, and wrist joints while whole arm rhythmic cyclical movements were performed. Cutaneous reflexes were evoked with trains of electrical stimulation delivered at non-noxious intensities (approximately 2 x threshold for radiating paresthesia) to the superficial radial nerve innervating the lateral portion of the back of the hand. Phasic bursts of rhythmic muscle activity occurred throughout the movement cycle. Rhythmic EMG and kinematic patterns were similar to what has been seen in the human lower limb during locomotor activities such as cycling or walking: there were extensive periods of reciprocal activation of antagonist muscles. For most muscles, cutaneous reflexes were modulated with the movement cycle and were strongly correlated with the movement-related background EMG amplitude. It is concluded that cutaneous reflexes are primarily modulated by the background muscle activity during rhythmic human upper limb movements, with only some muscles showing phase-dependent modulation.

Adult↗