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1.
Physiol Meas ; 34(9): 991-1012, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23945151

RESUMO

We present an innovative bio-potential front-end capable of recording true unipolar ECG leads for the first time without making use of the Wilson central terminal. In addition to the convenience in applications such as continuous monitoring and rapid diagnosis, the information in unipolar recordings may yield unique diagnostic information as it avoids the need to essentially subtract data or make use of the averaging effect imposed from the Wilson central terminal. The system also allows direct, real-time software calculation of signals corresponding to standard ECG leads which achieve correlations in excess of 92% with a gold standard ECG during a parallel in vivo recording. In addition, the implemented circuit is wideband (0.05-1000 Hz), compatible with standard (Ag/AgCl) bio-potential electrodes, and dry (paste-less) textile electrodes. The circuit is also low power, requiring less than 50 mW (when powered at 12 V) per standard ECG lead (two channels required). It is therefore well suited for wearable, long-term applications.


Assuntos
Eletrocardiografia/métodos , Adulto , Cateterismo Cardíaco , Eletrocardiografia/instrumentação , Eletrodos , Humanos , Masculino
2.
Neural Netw ; 45: 94-100, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23541926

RESUMO

The last decade has seen the parallel emergence in computational neuroscience and machine learning of neural network structures which spread the input signal randomly to a higher dimensional space; perform a nonlinear activation; and then solve for a regression or classification output by means of a mathematical pseudoinverse operation. In the field of neuromorphic engineering, these methods are increasingly popular for synthesizing biologically plausible neural networks, but the "learning method"-computation of the pseudoinverse by singular value decomposition-is problematic both for biological plausibility and because it is not an online or an adaptive method. We present an online or incremental method of computing the pseudoinverse precisely, which we argue is biologically plausible as a learning method, and which can be made adaptable for non-stationary data streams. The method is significantly more memory-efficient than the conventional computation of pseudoinverses by singular value decomposition.


Assuntos
Ondas Encefálicas/fisiologia , Encéfalo/fisiologia , Aprendizagem/fisiologia , Redes Neurais de Computação , Humanos , Matemática
3.
IEEE Trans Biomed Circuits Syst ; 3(5): 332-8, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23853272

RESUMO

Electrical impedance tomography uses multiple impedance measurements to image the internal conductivity of an object, such as the human body. Code-division multiplexing is proposed as a new method that can provide simultaneous impedance measurements of the multiple channels. Code division provides clear advantages of a wide frequency range at reduced cost and reduced complexity of sources. A potential drawback is the lack of perfectly orthogonal code sets. This caused an increase of 0.62% in root-mean-square spectral error when two codes were used to record two impedance channels simultaneously on a low-pass filter network. The method described provides images and spectra which are equivalent to the conventional time-multiplexed method, with increases in frequency resolution and measurement speed which may be of benefit in some applications of electrical impedance tomography spectroscopy.

4.
IEEE Trans Biomed Circuits Syst ; 2(1): 30-43, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23852631

RESUMO

In this paper, we present an analog integrated circuit design for an active 2-D cochlea and measurement results from a fabricated chip. The design includes a quality factor control loop that incorporates some of the nonlinear behavior exhibited in the real cochlea. This control loop varies the gain and the frequency selectivity of each cochlear resonator based on the amplitude of the input signal.

5.
Int J Artif Organs ; 25(9): 844-51, 2002 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12403400

RESUMO

An association between decreased duration of hemodialysis and increased morbidity and mortality in patients has been suggested. Whether this is due only to decreased solute clearance is unclear. In this prospective randomised study the effect of reducing treatment time whilst maintaining constant solute clearance was examined in fourteen patients. The study lasted for a period of 36 weeks (3x12 week study periods) and used a crossover design. The patients dialysis prescription (KW) was not changed on entering the study and was maintained during short (150 minutes) and long dialysis (240 minutes) by varying blood flow, dialysate flow and dialyzer surface area. The delivered KW was kinetically assessed. Fractional urea clearance was also measured during each treatment period by measurement of urea concentration in spent dialysate and total body water using 3H2O. At the end of each treatment period a full biochemical and hematological profile, nutritional intake and status, 24 h ambulatory blood pressure, nerve conduction studies, and quality of life questionnaire were performed. Within patients the delivered single pool KW was uniform throughout the 3 treatment periods and fractional urea clearance did not vary. However, Kt/W assessed using equilibrated models (Daugardis and Smye) was significantly lower in the short dialysis period. No differences between short and long dialysis sessions were noted in any of the measured variables. Thus, over a 36 week period there is no evidence to suggest that hemodialysis patients are adversely affected by decreased duration of treatment provided that solute clearance is maintained.


Assuntos
Soluções para Diálise/metabolismo , Taxa de Depuração Metabólica , Diálise Renal , Ureia/metabolismo , Idoso , Análise Química do Sangue , Pressão Sanguínea/fisiologia , Estudos Cross-Over , Testes Hematológicos , Humanos , Pessoa de Meia-Idade , Morbidade , Condução Nervosa/fisiologia , Estado Nutricional , Estudos Prospectivos , Qualidade de Vida , Fatores de Tempo
6.
Ultrasonics ; 39(4): 257-61, 2001 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-11432435

RESUMO

A high power resonance tracking ultrasonic amplifier is described. The amplifier is a class D type inverter, configured as a half-bridge in which the output MOSFETs are driven into saturation when on. The resonance tracking system makes use of a new method of frequency locking; admittance locking is used to track the optimum power conversion frequency for the transducer. This new arrangement offers some advantages over phase locking and motional feedback methods. The system is capable of delivering up to 3 kW at up to 25 kHz in resonance tracking operation.


Assuntos
Ultrassom , Humanos , Transdutores
7.
Ultrasonics ; 38(1-8): 284-91, 2000 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10829675

RESUMO

A new technique for the measurement in fluids of the acoustic non-linearity parameter B/A is presented, together with measured B/A values for several fluids. The non-linearity parameter is measured by phase locking radial modes within a PZT cylinder. The system, which implements the isentropic phase technique, uses continuous wave phase locking to measure the change in sound velocity that is typically associated with a change in ambient pressure under constant entropy. The method provides a means of measuring B/A in vitro both accurately and simply without the typical problems involved in time-of-flight systems. Fluid samples can remain small due to the nature of the cavity resonator, so the system is well suited to small volume, biological samples.

9.
Nephrol Dial Transplant ; 12(8): 1615-21, 1997 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-9269638

RESUMO

BACKGROUND: Kidney donors are not adversely affected by compensatory hyperfiltration of the remaining kidney in the early years after nephrectomy, but longterm longitudinal studies are lacking. METHODS: The renal function and blood pressure of 75 donors was evaluated in 1984, 1.4-20.7 years after surgery. Forty-seven of the original cohort (23 male, age 38-80 years) underwent repeat study a decade later (12-31 years post-nephrectomy), using identical laboratory techniques. RESULTS: Glomerular filtration rates (GFR) as measured by 51Cr EDTA clearance was relatively unchanged a decade later with 41 of 47 subjects (87%) having EDTA clearance within the normal laboratory reference range at review. The change in GFR in the remaining six subjects was statistically not significant. No correlation between GFR and time after nephrectomy was detected. Albumin excretion rate (AER), on timed overnight urine collections, was increased (> 20 micrograms/min) in 16 subjects (34%), although 14 of these individuals were also hypertensive. The prevalence of hypertension was significantly increased compared with age/sex matched data from epidemiological studies of the general population (both in the UK and the US), especially in those over the age of 55 years. CONCLUSION: This study demonstrates that the function of the solitary kidney is not adversely affected by prolonged compensatory hyperfiltration, although there appears to be an increased prevalence of microalbuminuria and hypertension. Regular follow-up of kidney donors is recommended in order to manage their complications effectively and to detect hypertension and or renal impairment early in those who may develop it.


Assuntos
Transplante de Rim , Doadores de Tecidos , Adulto , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/metabolismo , Albuminúria/urina , Pressão Sanguínea , Radioisótopos de Cromo/farmacocinética , Ácido Edético/farmacocinética , Feminino , Seguimentos , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Nefrectomia , Caracteres Sexuais
10.
Nephrol Dial Transplant ; 11(1): 133-9, 1996 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-8649621

RESUMO

BACKGROUND: Termination of renal replacement therapy (RRT) is common in North America and Australia but is considered to be rare in Europe. METHODS: In order to review the phenomenon of RRT termination in all patients treated in Newcastle upon Tyne between 1964 and 1993 a retrospective study of clinical case notes was undertaken. In all RRT patients sex, age at start of RRT, renal diagnosis and history of RRT were recorded. In addition, mortality data and marital and residential status were recorded in all patients who died, and Karnofsky index, bodyweight, complications, history of bereavement, place of death, overall survival, survival after withdrawal of treatment, other medical problems, higher mental function and surgical history in all patients stopping treatment. RESULTS: 1639 patients started RRT between 1964 and September 1993 inclusive. Eighty-eight patients were identified in whom death was a result of treatment being stopped (17% of all deaths). The first was in 1985. In these patients, age was greater (62 vs 47 years, P < 0.001) and diabetes was more prevalent (15 vs 7%, P < 0.03) than in the total RRT population. The Karnofsky index was 70 at the start and 33 at withdrawal of treatment (P < 0.001). The Karnofsky index at the start of RRT was weakly related to that at withdrawal and overall survival (r = 0.36 and 0.28 respectively, P < 0.01). The Karnofsky index at treatment withdrawal correlated with the following survival (r = 0.40, P < 0.001). The median survival of patients stopping treatment was significantly lower than in all RRT patients (16 vs 74 months, P < 0.001) and the majority survived less than 2 years. After dialysis withdrawal the median survival was 8 days, 15 patients survived 3 days or less and 19 more than 10 days. The majority (80%) received terminal care in hospital. At treatment withdrawal 11 patients were demented and 34 showed signs of early dementia. Seventy-eight patients (89%) stopped treatment as a consequence of multiple medical problems. The possibility of dialysis withdrawal was raised by physicians in 50.5%, the patient in 23.8% and the patients' relatives in 21.9% of cases. Four patients (3.8%) committed suicide. CONCLUSIONS: Death from dialysis termination is a relatively common cause of death in RRT patients in Newcastle upon Tyne. These patients are older with a higher prevalence of diabetes. In 89% of cases the decision to stop treatment was related to multiple medical problems with a recent deterioration. Physicians raised the issue of withdrawal in the majority of cases and most patients subsequently received terminal care in hospital.


Assuntos
Falência Renal Crônica/mortalidade , Terapia de Substituição Renal , Suspensão de Tratamento , Tomada de Decisões , Feminino , Hospitalização , Humanos , Falência Renal Crônica/complicações , Falência Renal Crônica/terapia , Masculino , Pessoa de Meia-Idade , Seleção de Pacientes , Estudos Retrospectivos , Taxa de Sobrevida , Recusa do Paciente ao Tratamento , Reino Unido/epidemiologia
11.
BMJ ; 308(6930): 698-700, 1994 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-8142796

RESUMO

OBJECTIVES: To explore the use of rapid appraisal in defining the health and social needs of a community and to formulate joint action plans between the residents and service providers. DESIGN: Collection of data by an extended primary care team from three sources: existing documents about the neighbourhood, interviews with a range of informants, and direct observations to build a profile of the community. SETTING: Council estate of 670 homes in Edinburgh. MAIN OUTCOME MEASURES: Perceived problems of the community and suggestions for change. RESULTS: The interviews and focus groups identified six priorities for change, many of which were not health related. These changes have been or are being implemented. CONCLUSIONS: An expanded primary care team can use rapid appraisal as a first step in identifying and meeting local health needs. It facilitates a multidisciplinary approach and complements quantitative methods of assessing need.


Assuntos
Medicina de Família e Comunidade/organização & administração , Necessidades e Demandas de Serviços de Saúde , Regionalização da Saúde/organização & administração , Participação da Comunidade , Feminino , Prioridades em Saúde , Nível de Saúde , Humanos , Masculino , Escócia
15.
J Clin Pathol ; 45(9): 825-7, 1992 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-1401219

RESUMO

A case of rhabdomyolysis associated acute renal failure (RM-ARF) occurring as a result of strenuous exercise is presented. Diagnostic renal biopsy was performed. The histological appearances, combined with immunoperoxidase staining for myoglobin, allowed a positive diagnosis of RM-ARF to be made and excluded the possibility of glomerulonephritis. The patient recovered completely after a stormy clinical course.


Assuntos
Injúria Renal Aguda/etiologia , Esforço Físico , Rabdomiólise/etiologia , Injúria Renal Aguda/patologia , Adolescente , Humanos , Técnicas Imunoenzimáticas , Rim/patologia , Masculino , Mioglobina/análise
16.
J Antimicrob Chemother ; 26 Suppl F: 63-71, 1990 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-2292546

RESUMO

This report describes a prospective, randomized comparison of oral ciprofloxacin and intraperitoneal vancomycin/netilmicin in the treatment of 50 consecutive episodes of CAPD peritonitis in 35 patients. Successful cure of peritonitis was achieved in 76% of subjects taking oral ciprofloxacin and 72% of those given intraperitoneal antibiotics. Satisfactory concentrations of ciprofloxacin in dialysate were achieved in all patients. Failure of ciprofloxacin was due to persistence of an isolate of intermediate sensitivity (1), to persistence with acquisition of resistance (1), and to relapse/reinfection in the remaining four cases (with resistant or moderately sensitive strains in three cases). Ciprofloxacin was well tolerated in the majority of cases. A significant rise in serum creatinine was noted in almost all patients taking oral ciprofloxacin. The advantages of oral drug administration indicate that oral ciprofloxacin is the preferred first-line treatment of CAPD-associated peritonitis.


Assuntos
Ciprofloxacina/uso terapêutico , Netilmicina/uso terapêutico , Diálise Peritoneal Ambulatorial Contínua/efeitos adversos , Peritonite/tratamento farmacológico , Vancomicina/uso terapêutico , Administração Oral , Adulto , Idoso , Idoso de 80 Anos ou mais , Ciprofloxacina/administração & dosagem , Feminino , Humanos , Injeções Intraperitoneais , Masculino , Pessoa de Meia-Idade , Netilmicina/administração & dosagem , Peritonite/etiologia , Estudos Prospectivos , Vancomicina/administração & dosagem
17.
BMJ ; 301(6751): 535-40, 1990 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-2207426

RESUMO

OBJECTIVES: To review the experience of renal replacement treatment in diabetic patients treated in Newcastle upon Tyne and the Northern region from 1964 to 1988, and to compare the morbidity and mortality of diabetic patients treated with dialysis or transplantation with those of matched controls of non-diabetic patients. DESIGN: Retrospective study of clinical case notes. SETTING: Renal units of the Northern region, particularly that in Newcastle upon Tyne. PATIENTS: All 65 diabetic patients treated by renal replacement treatment in Newcastle upon Tyne from 1964 to 1987; 42 diabetic patients were matched with 42 non-diabetic patients according to age, sex, year of starting treatment, and type of treatment (dialysis or transplantation). MAIN OUTCOME MEASURES: Sex, age, renal biopsy findings, blood pressure, history of diabetic treatment, and plasma creatinine concentration at the start of renal replacement treatment. History of renal replacement treatments, suitability for transplantation, history of transplantation, cumulative survival, and cause of death during follow up. Survival of technique, cumulative survival of the first peritoneal catheter and history of peritonitis in patients treated with continuous ambulatory peritoneal dialysis; source of graft, histocompatibility antigens, duration of associated stay in hospital, and graft survival in patients receiving renal or pancreatic transplant. RESULTS: 1259 Patients with chronic renal failure were accepted for renal replacement treatment in Newcastle upon Tyne, of whom 65 (5%) had diabetes. The first was accepted in 1974, and between 1974 and 1980 another 15 were treated (mean age 42 years; 4% of new patients). From 1981 to 1987, 49 diabetic patients (mean age 44; 9% of new patients) were treated. Fifty patients (77%) had insulin dependent diabetes and the remaining 15 (23%) non-insulin dependent diabetes. On average, the patients were aged 25 (range 5-57) when diabetes was first diagnosed and 44 (range 24-70) at the start of renal replacement treatment. The mean age at the start of treatment was 40 for patients with non-insulin dependent diabetes and 58 for patients with non-insulin dependent diabetes. Transplantation was performed in 33 of the diabetic patients, whose mean age was lower than that of those who did not receive a transplant (41 v 48 respectively, p less than 0.05). Comparison between the 42 diabetic patients and matched controls showed that the overall survival at five years was 46% and 77% respectively. The three year survival of the diabetic patients who did not receive a transplant was poor (41% v 79% respectively). Of patients transplanted, survival at five years was 73% in the diabetic patients and 90% in the controls. However, there was no significant difference in the five year graft survival (64% v 46% respectively). CONCLUSIONS: Diabetes adversely affects morbidity and mortality in patients having renal replacement treatment, but renal transplantation seems to be the best option for treating diabetic patients with end stage renal failure.


Assuntos
Neuropatias Diabéticas/terapia , Falência Renal Crônica/terapia , Transplante de Rim , Diálise Peritoneal Ambulatorial Contínua , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Diabetes Mellitus/mortalidade , Neuropatias Diabéticas/mortalidade , Inglaterra/epidemiologia , Sobrevivência de Enxerto , Humanos , Falência Renal Crônica/mortalidade , Pessoa de Meia-Idade , Transplante de Pâncreas , Complicações Pós-Operatórias , Estudos Retrospectivos , Taxa de Sobrevida
18.
Int J Artif Organs ; 13(7): 412-5, 1990 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2401579

RESUMO

Results of treatment of end-stage renal failure (ESRF) in patients with primary hyperoxaluria have been generally poor, largely due to the inability of any treatment regime to match the endogenous overproduction of oxalate. The severity of the disease varies widely, as reflected by the differences in age at onset of ESRF. This variability may influence the results of treatment of ESRF in these patients. The longest reported survival on haemodialysis of a patient with primary hyperoxaluria is eight and a half years. We report a patient who survived for eleven years on haemodialysis after reaching ESRF due to primary hyperoxaluria, and suggest that this prolonged survival was due to relatively mild disease severity rather than exceptional treatment.


Assuntos
Hiperoxalúria Primária/terapia , Hiperoxalúria/terapia , Falência Renal Crônica/terapia , Diálise Renal , Feminino , Humanos , Hiperoxalúria Primária/genética , Falência Renal Crônica/etiologia , Pessoa de Meia-Idade
19.
Int J Artif Organs ; 12(11): 708-10, 1989 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-2599670

RESUMO

A 59 year old woman developed a mediastinal haematoma after placement of a subclavian haemodialysis catheter. Vascular perforation by the guide wire used during catheterisation was the probable cause. The use of guide wires with a flexible J-shaped terminal portion is recommended to minimise this risk.


Assuntos
Cateterismo Venoso Central/efeitos adversos , Hematoma/etiologia , Doenças do Mediastino/etiologia , Diálise Renal , Feminino , Humanos , Pessoa de Meia-Idade , Veia Subclávia
20.
Clin Sci (Lond) ; 77(4): 445-51, 1989 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-2805603

RESUMO

1. Twelve patients with the nephrotic syndrome were prescribed for 4 week periods a normal protein diet (NPD) containing 1 g of protein/kg ideal body weight. They were then prescribed for further 4 week periods in random order diets with high (HPD) and low (LPD) protein contents, respectively 2.0 and 0.5 g/kg ideal body weight. 2. Compliance was confirmed by dietary history and measurement of urinary excretion. 3. Serum albumin was the same on all diets. Twenty-four hour urinary protein excretion increased progressively with increasing dietary protein (LPD 6.1 g. NPD 8.2 g. HPD 9.2 g). Recumbent plasma renin activity and serum phosphate were significantly increased on HPD (plasma renin activity: LPD 5.7, NPD 4.6, HPD 8.2 pmol of angiotensin I min-1 1(-1); serum phosphate: LPD 1.27, NPD 1.26, HPD 1.41 mmol/l). 4. There was no evidence of protein-induced hyperfiltration or hyperperfusion: 51Cr-ethylenediaminetetra-acetate and [125I]iodohippurate clearances were similar on all three diets. 5. Since proteinuria, increased plasma renin levels and hyperphosphataemia may contribute to progression of renal failure and because HPD did not improve hypoalbuminaemia, the use of HPD in the nephrotic syndrome should be abandoned. 6. Until it can be established that LPD, which is accompanied by the least proteinuria, does not, with long-term feeding, lead to malnutrition, NPD should be used in the treatment of the nephrotic syndrome.


Assuntos
Proteínas Alimentares/administração & dosagem , Síndrome Nefrótica/dietoterapia , Adulto , Idoso , Proteínas Sanguíneas/metabolismo , Creatinina/sangue , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Síndrome Nefrótica/metabolismo , Fosfatos/metabolismo , Albumina Sérica/metabolismo , Ureia/sangue
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