M L Harris

Non-volitional assessment of skeletal muscle strength in patients with chronic obstructive pulmonary disease

Background: Although quadriceps weakness is well recognised in chronic obstructive pulmonary disease (COPD), the aetiology remains unknown. In disabled patients the quadriceps is a particularly underused muscle and may not reflect skeletal muscle function as a whole. Loss of muscle function is likely to be equally distributed if the underlying pathology is a systemic abnormality. Conversely, if deconditioning and disuse are the principal aetiological factors, weakness would be most marked in the lower limb muscles. Methods: The non-volitional technique of supramaximal magnetic stimulation was used to assess twitch tensions of the adductor pollicis, quadriceps, and diaphragm muscles (TwAP, TwQ, and TwPdi) in 22 stable non-weight losing COPD patients and 18 elderly controls. Results: Mean (SD) TwQ tension was reduced in the COPD patients (7.1 (2.2) kg v 10.0 (2.7) kg; 95% confidence intervals (CI) −4.4 to −1.4; p<0.001). Neither TwAP nor TwPdi (when corrected for lung volume) differed significantly between patients and controls (mean (SD) TwAP 6.52 (1.90) N for COPD patients and 6.80 (1.99) N for controls (95% CI −1.5 to 0.97, p=0.65; TwPdi 23.0 (5.6) cm H2O for COPD patients and 23.5 (5.2) cm H2O for controls (95% CI −4.5 to 3.5, p=0.81). Conclusions: The strength of the adductor pollicis muscle (and the diaphragm) is normal in patients with stable COPD whereas quadriceps strength is substantially reduced. Disuse may be the principal factor in the development of skeletal muscle weakness in COPD, but a systemic process preferentially affecting the proximal muscles cannot be excluded.

Quadriceps muscle weakness following acute hemiplegic stroke

Objective: To determine whether quadriceps muscle weakness develops on the side ipsilateral to the brain lesion in the first week following acute ischaemic hemiplegic stroke. Design: A prospective study of muscle strength. Setting: Acute stroke unit (ASU) in a teaching hospital. Subjects: Ten patients admitted within 48 hours of stroke onset, and 10 healthy age-matched controls. Interventions: Repeat nonvolitional measurements of quadriceps muscle strength of the unaffected limb in patients and the right leg in normal subjects using magnetic femoral nerve stimulation (MS), prospectively one week apart. In addition the level of voluntary activation was assessed during a maximum voluntary contraction (MVC) manoeuvre. The Trunk Control Test (TCT) was measured in the patients. Results: The median (95% confidence interval, (CI)) baseline quadriceps twitch tension (Tw Q) and MVC in the control group were 9.4 kg (6.1–12.5 kg) and 37.2 kg (23.8–54.6 kg), and in the stroke group were 7.6 kg (4.4–9.9 kg) and 12.15 kg (7.9–30.8 kg). The median (95% CI) change in Tw Q and MVC respectively between baseline and one week later were 1.75% (–9.8 to 8%) and 5.45% (–15.1 to 22.7%) (NS) in the control group and –16.2% (–6 to –25.9%) and –30.45% (0 to –78.6%) (p < 0.01) in the stroke patients. There was a significant correlation between the percentage fall in Tw Q and both change in TCT (rs = 0.83, p < 0.01) and percentage change in body weight (rs = 0.83, p < 0.01). Conclusion: In the first week after acute hemiplegic stroke, weakness develops in the unaffected leg.

Mapping metabolic brain activation during human volitional swallowing: a positron emission tomography study using [18F]fluorodeoxyglucose.

We have previously shown that labelled water positron emission tomography (H215O PET) can be used to identify regional cerebral blood flow (rCBF) changes in the human brain during volitional swallowing. (18F) fluorodeoxyglucose (FDG PET), by comparison, uses a glucose analogue to quantitatively measure regional cerebral glucose metabolism (rCMRglc) rather than rCBF. The main advantage of FDG PET is improved spatial resolution, and because of its pharmacodynamic properties, activation can be performed external to the scanner, allowing subjects to assume more physiologic positions. We therefore conducted a study of the brains metabolic response while swallowing in the erect seated position, using FDG PET. Eight healthy male volunteers were studied with a randomised 2 scan paradigm of rest or water swallowing at 20-second intervals for 30 minutes. Data were analysed with SPM99 using multisubject conditions and covariates design. During swallowing, analysis identified increased rCMRglc (P<0.01) in the following areas: left sensorimotor cortex, cerebellum, thalamus, precuneus, anterior insula, left and right lateral postcentral gyrus, and left and right occipital cortex. Decreased rCMRglc were also seen in the right premotor cortex, right and left sensory and motor association cortices, left posterior insula and left cerebellum. Thus, FDG PET can be applied to measure the brain metabolic activity associated with volitional swallowing and has the advantage of normal task engagement. This has implications for future activation studies in patients, especially those suffering swallowing problems after brain injury.

Rapid rate magnetic stimulation of human sacral nerve roots alters excitability within the cortico-anal pathway

Abstract  Sacral nerve root stimulation (SNS) can produce dramatic symptomatic improvement in faecal incontinence (FI). However, the physiological mechanism behind this improvement remains unknown. One hypothesis is that SNS may modulate cortico‐anal pathways and drive compensatory changes within the spinal cord or cerebral cortex that beneficially alter sphincter function. Our aim was to assess whether short‐term experimental SNS can induce changes in the human cortico‐anal pathway. Eight healthy volunteers (mean age 30 years) were studied. Subjects were investigated on three separate occasions and randomized to either active (5 and 15 Hz) or sham rapid‐rate lumbosacral magnetic stimulation (rLSMS). Anal sphincter electromyograms (EMG) were recorded from an anal probe following single‐pulse transcranial magnetic stimulation, at baseline, immediately, 30 and 60 min following rLSMS at either (i) 5 Hz for 15 min, (ii) 15 Hz for 15 min or (iii) sham stimulation for 15 min. In addition, manometry and anal sphincter sensation was measured in a subset of subjects. Interventions were compared to sham using anova. Fifteen hertz rLSMS increased cortico‐anal EMG response amplitude in the 1 h postintervention (F4, 28 = 3.2, P = 0.027), without a shift in response latency. This effect was not demonstrated with either 5 Hz or sham stimulation. rLSMS had no short‐term effect on sensation or physiology. Short‐term magnetic stimulation of the sacral nerve roots induces changes in cortico‐anal excitability which is frequency specific. These data support the hypothesis that SNS produces some of its beneficial effect in patients with FI by altering the excitability of the cortico‐anal pathway.

Central fatigue of the diaphragm and quadriceps during incremental loading

Anecdotal observations suggest that low frequency fatigue, as judged by a fall in twitch tension, is more difficult to achieve in the diaphragm than nonrespiratory muscle but this hypothesis has not previously been directly tested. We studied 7 subjects by performing incremental repetitive contraction loading protocols of the diaphragm and quadriceps. We measured twitch transdiaphragmatic pressure (Tw Pdi) and twitch quadriceps tension (Tw Q) during both muscle contraction and relaxation phases during the run. Unpotentiated and potentiated Tw Pdi and Tw Q were measured before and at 20, 40, and 60 minutes after the run. During the run, greater activation of the quadriceps was achieved; for example, at 70% of maximal voluntary effort the interpolated Tw Q was 12.5% of the relaxation phase Tw Q (implying activation of 87.5%) compared with 29.4% (i.e., 70.6% activation) for the diaphragm (p = 0.05). A significantly greater fall in Tw Q than Tw Pdi was observed (unpotentiated Tw Pdi at 20 minutes 94% baseline versus Tw Q 59% baseline, p = 0.007). Low frequency fatigue in humans is more difficult to generate in the diaphragm than in the quadriceps muscle due in part to reduced central activation.

Characterization of Corticobulbar Pharyngeal Neurophysiology in Dysphagic Patients With Parkinson's Disease

BACKGROUND & AIMS Dysphagia in patients with Parkinsons disease, persisting despite dopaminergic treatment, affects intake of nutrients and medication, and reduces quality of life (QOL). We investigated the neurophysiologic mechanisms that contribute to dysphagia in these patients, on and off L-3,4-dihydroxyphenylalanine (levodopa), using transcranial magnetic stimulation. METHODS We studied 26 patients with Parkinsons disease (age, 65 ± 9 y; 10 men). Dysphagia and QOL were first assessed with qualitative questionnaires. Twelve hours after patients were taken off levodopa, they underwent cortical transcranial magnetic stimulation mapping of the pharyngeal musculature and trigeminal (bulbar) transcranial magnetic stimulation, as well as videofluoroscopy to examine swallowing. The analyses were repeated after administration of levodopa. RESULTS Eleven patients initially reported dysphagia and reduced QOL scores. Videofluoroscopy identified 10 patients with swallowing impairments on and off levodopa, and 6 patients with swallowing impairments only on levodopa; the remaining 10 subjects showed no swallowing impairments, on or off the drug. While patients were on levodopa, those with swallowing impairments had bilateral increases in pharyngeal cortical excitability compared with those with no swallowing impairment (P < .05). By contrast, with medication, amplitudes of brainstem reflexes were altered only in patients with swallowing impairments on levodopa; these were decreased compared with when the patients were off levodopa. CONCLUSIONS In patients with Parkinsons disease, dopaminergic medications such as levodopa can negatively affect swallowing. The increased cortical excitability observed in dysphagic patients after they begin taking levodopa likely results from compensatory mechanisms, perhaps secondary to subcortical disease, because we observed associated inhibition of brainstem reflexes in patients with affected swallowing on medication. UK clinical trials registration no., 9882.

The quality of patient experience of short-stay acute medical admissions: findings of the Adult Inpatient Survey in England

Introduction of the specialty of acute medicine and of acute medical units (AMUs) in the UK have been associated with improvements in mortality, length of stay and flow, but there is no literature on the patient experience during the early phase of acute medical admissions. We analysed the Adult Inpatient Survey (AIPS) findings for short-stay unscheduled medical admissions who did not move from their first admission ward (n=3325) and therefore are likely to have been managed entirely in the AMU. We compared these with short-stay emergencies in other specialties (n=3420) and short-stay scheduled admissions (n=10,347). Scheduled admissions reported a better experience for all survey items. Scores for unscheduled admissions were worse in medical patients compared with other specialties for pain control, privacy, involvement, information, and for a number of questions relating to information on discharge. The specialty of acute medicine should work to improve future patient experience.

Modulation of human visceral sensitivity by noninvasive magnetoelectrical neural stimulation in health and irritable bowel syndrome.

Abstract Visceral pain is a particularly difficult symptom to manage in patients with irritable bowel syndrome (IBS). Our aim was to examine whether noninvasive neurostimulation applied to the motor cortex or lumbosacral region can modulate human visceral sensation. Sixteen healthy adult volunteers and 10 patients with IBS were evaluated. Single-pulse lumbosacral magnetic stimulation (LSMS) or transcranial magnetic stimulation (TMS) was used to assess spinal root and cortical excitability as well as the effect of neurostimulation on anorectal sensation and pain, which were provoked by a local electrical stimulus. Initially, healthy volunteers received 6 stimulation paradigms in a randomised order (3 repetitive LSMS [1 Hz, 10 Hz, and sham]) and 3 repetitive TMS (1 Hz, 10 Hz, and sham) to investigate the effects on neural function and visceral sensation over 1 hour. The most effective cortical and spinal interventions were then applied in patients with IBS. Only 1-Hz rLSMS altered healthy anal motor excitability, increasing spinal (58 ± 12.3 vs 38.5 ± 5.7 &mgr;V, P = 0.04) but not cortical responses. Both 1-Hz rLSMS and 10-Hz repetitive transcranial magnetic stimulation increased healthy rectal pain thresholds for up to an hour after intervention (P < 0.05). When applied to patients with IBS, rectal pain thresholds were increased across all time points after both 1-Hz rLSMS and 10-Hz repetitive transcranial magnetic stimulation (P < 0.05) compared with sham. The application of magnetoelectric stimuli to the cortical and lumbosacral areas modulates visceral sensation in healthy subjects and patients with IBS. This proof-of-concept study provides supportive evidence for neurostimulation in managing functional gastrointestinal disorders.

Assessment of the validity of the English National Health Service Adult In-Patient Survey for use within individual specialties

Background Healthcare improvement requires rigorous measurement. Patient experience is a key healthcare outcome and target for improvement. Its measurement requires psychometrically validated questionnaires. In England, the Adult In-Patient Survey (AIPS), which is validated for use across the entire acute inpatient population, is administered to unselected patients after discharge from National Health Service acute Trusts. The AIPS is reported at an organisational level, but subhospital level data are needed for local quality improvement; it is currently uncertain whether the AIPS retains validity in local specialty subgroups. Methods We analysed the results of AIPS for 2010 (n=56 931 returns) by specialty (medicine, surgery, orthopaedics, renal medicine, neurosurgery, obstetrics-gynaecology and oncology) to determine whether validity is retained at a suborganisational level. Results Criterion validity and internal consistency of AIPS were retained for most specialty subgroups. When small local samples were excluded, the results for Trust level specialty groups were similar over a 2-year period, indicating test stability. For oncology there was poor internal consistency in the ‘doctors’ domain and criterion validity, expressed as the relationship elements of experience and overall rating of care, was less than for other specialties. Conclusions The AIPS is suitable for use within many specialties, but our findings question some elements of validity for oncology inpatients. We recommend that future surveys are administered and reported by specialty, to inform local improvement and permit comparison of specialty units.

PWE-062 Can magnetic neural stimulation improve anorectal sensitivity in IBS?

Introduction Visceral pain is a major clinical problem being a primary feature of irritable bowel syndrome (IBS). Treatments for this condition are limited, but there is increasing evidence that neural stimulation may be able to alter pain thresholds in the somatic literature. By contrast, little is known about the role of neurostimulation applied to visceral pain and its ability to alter sensitivity. The aim of this study was to ascertain whether repetitive magnetic stimulation (MS) applied to the lumbosacrum and motor cortex can alter anorectal sensitivity in IBS patients. Methods Participants: 10 IBS patients (9 females, age range 22 and 54 years). All IBS patients fulfilled Rome III criteria for IBS. Anorectal electrical sensory measurements were performed via a stimulating catheter positioned in the rectum, 10 cm from the anal verge andan anal plug. Sensory and pain thresholds in the rectum and anal sphincter were determined using trains of electrical stimuli, repeated three times. Anorectal sensory and pain thresholds were performed at baseline before intervention and then immediately, 30 and 60 min after each intervention. Interventions comprised 3 neurostimulation paradigms delivered in random order over separate days: repetitive 1 Hz lumbosacral magnetic stimulation (rLSMS), repetitive 10 Hz cortical transcranial magnetic stimulation (rTMS) and sham in the form of tilted coil. Results Data (mean±SEM) were analysed by two way ANOVA (see Abstract PWE-062 tables 1 and 2) showed a significant increase in sensory (ST) and pain (PT) thresholds immediately, at 30 and 60 min in the rectum following both 1 Hz rLSMS (ST (p=0.015, 0.048 and 0.022, respectively), PT (p=0.014, 0.004 and 0.012, respectively)) and 10 Hz rTMS (ST (p=0.046, 0.041 and 0.017, respectively), PT (p=0.005, 0.02 and 0.007, respectively)). In addition, only 10 Hz rTMS increased anal sphincter pain thresholds immediately, at 30 and 60 min after the intervention (PT (p=0.032, 0.004 and 0.001, respectively)). Sham stimulation had no effect on any of the anorectal sensory parameters.Abstract PWE-062 Table 1 Rectal Baseline 0 min 30 min 60 min rLSMS 1 Hz  ST 22.6±2.8 27.1±3.4* 28.8±3.5* 29.6±3.6*  P 45.9±6.4 53.8±6.5* 53.8±7** 56.9±8.2* rTMS 10 Hz  ST 24.4±2.7 27.9±3* 29.1±3.8* 29.3±3.6*  P 44.1±5.5 53±8.7** 54.6±8.9* 57.1±9** Sham  ST 21.3±3 23.3±3 24.1±3.3 23.2±2.8  P 38.7±3.4 38.6±3.2 39.8±3.6 40.4±3.5 *p<0.05, **p<0.01.Abstract PWE-062 Table 2 Anal Baseline 0 min 30 min 60 min rLSMS 1 Hz  ST 6.3±0.7 7.3±1.2 7.1±1.1 6.7±1  P 24.3±5.2 23.6±5.1 25.2±4.9 25.6±4.7 rTMS 10 Hz  ST 5.3±0.6 5.5±0.7 5.4±0.8 6±0.7  P 23.3±5.3 25.9±6* 27±5.4** 29.4±6** Sham  ST 5.8±0.7 5.8±0.6 6.4±0.7 6.1±0.6  P 22±3.3 22.3±3.1 24±3.7 23.7±3.8 *p<0.05, **p<0.01. Conclusion The application of repetitive magnetic stimulation to lumbosacral area and motor cortex is able to modulate human visceral sensitivity in IBS patients and holds promise as a future therapeutic intervention. Competing interests None declared.