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Biomedical subjects

R Vincent

Publications and source records attributed to R Vincent.

18 recordsLinked to original sources
PubMed1992

Fast ECG data compression algorithms suitable for microprocessor systems.

ECG data compression techniques have received extensive attention in ECG analysis. Numerous data compression algorithms for ECG signals have been proposed during the last three decades. We describe two algorithms based on the scan-along polygonal approximation algorithm (SAPA) that are suitable for multichannel ECG data reduction on a microprocessor-based system. One represents a modification of SAPA (MSAPA) which adopts the method of integer division table searching to speed up data reduction; the other (CSAPA) combines MSAPA and TP, a turning-point algorithm, to preserve ST segment signals. Results show that our algorithms achieve a compression ratio of more than 5:1 and a percent rms difference (PRD) to the original signal of less than 3.5%. In addition, the maximum execution time of MSAPA for processing one data point is about 50 microseconds. Moreover, the CSAPA algorithm retains all of the details of the ST segment, which are important in ischaemia diagnosis, by employing the TP algorithm.

Algorithms↗
PubMed1992

Intracerebral haemorrhage after thrombolytic therapy for acute myocardial infarction.

Seven cases of intracerebral haemorrhage were identified following the use of thrombolytic therapy in a total of 710 patients with acute myocardial infarction. Each case was reviewed in detail with particular attention to the presenting symptoms. A confusional state was the commonest initial feature. Increased age and male sex were associated with increased risk of cerebral bleed. The possible role of intravenous heparin in increasing risk and the management of affected cases is discussed. Early recognition and action is emphasized.

Age Factors↗
PubMed1991

Quantitative analysis of signal-averaged P waves in idiopathic paroxysmal atrial fibrillation.

Detailed analysis of the QRS complex can identify patients at risk from ventricular arrhythmias, but similar techniques applied to the atria have been disappointing. This study attempts to quantitate differences in the fine morphology of P waves in a group of 9 patients with paroxysmal atrial fibrillation (AF) versus 15 control subjects. Atrial triggered signal-averaging was combined with a detailed investigation of P-wave duration, high-frequency spatial voltage and spatial velocity. Signal-averaged P-wave duration was significantly increased in patients with paroxysmal AF (135 +/- 8 vs 126 +/- 4 ms, p less than 0.05). The root-mean-square voltage at frequencies greater than 35 Hz in these patients was also significantly greater (16 +/- 3 vs 12 +/- 1 microV, p less than 0.05). Similar observations were made at frequencies greater than 40 Hz (10 +/- 3 vs 7 +/- 1 microV, p less than 0.05). These differences appeared to be confined to the third quarter of the P wave (third quarter root-mean-square voltage at greater than 40 Hz expressed as a ratio of total P-wave root-mean-square voltage, 1.4 +/- 0.1 vs 1.2 +/- 0.1, p = 0.005). Spatial velocity was also increased in the paroxysmal AF group (peak spatial velocity 6.4 +/- 1.8 vs 4.6 +/- 0.5 mV/s, p less than 0.05). These observations support previous intracardiac data that implicate delay and fragmentation of intraatrial conduction in the pathogenesis of paroxysmal AF.

Adult↗
PubMed1990

Reduction in hospital time to thrombolytic therapy by audit of policy guidelines.

Despite the importance of early thrombolysis in the treatment of acute myocardial infarction, unacceptable delays in drug administration still occur in hospital. From March 1989 we decided to monitor our performance, and thereby to reduce avoidable in-hospital delay to a minimum. Potential candidates for thrombolytic therapy were identified by paramedic ambulancemen whenever this was feasible. Rapid check-lists were used for inclusion and exclusion criteria in the Accident and Emergency Department. A target of 15 min was set for time to treatment, and reasons for any gross deviation (greater than 30 min) were explored in each instance. As a result of these strategies, we achieved a median time from admission to initiation of thrombolysis in 50 consecutive patients of 17 min. The 39 patients treated with injections of APSAC as opposed to infusions of streptokinase had a median in-hospital delay to treatment of only 13 min.

Aged↗
PubMed1990

The European Community and dental education.

This paper traces the impact of the Rome Treaty of March 1957 on the countries of the European Economic Community relative to dental education. It also reviews the studies that have been conducted to help determine how best to implement the freedom of movement of dentists throughout the Community.

Education, Dental↗
PubMed1988

Transcutaneous pacing for cardiac emergencies.

Transcutaneous cardiac pacing using the Pace-Aid (Cardiac Resuscitator Corporation) was assessed in 32 emergency patients presenting with profound bradycardia or asystole who had failed to recover with advanced life support including the use of epinephrine. Pacing stimuli, pulse width 20 ms at 50, 100, or 200 mA, were delivered through two 8 cm gel-pad electrodes placed antero-posteriorly on the chest. By ECG criteria, definite electrical capture was achieved in a total of five patients and possible capture in a further 16. Of the 21 patients presenting in asystole 11 showed possible electrical capture only. No evidence of capture was seen in one third of the patients studied. Use of the Pace-Aid resulted in a palpable pulse in a total of seven patients. Four of the 11 patients with profound bradycardia survived to receive temporary transvenous pacing; two were eventually discharged. None in the asystolic group survived. Difficulties in using the Pace-Aid resulted from electrical overload by the pacing impulse that obscured the evidence for electrical capture, and intense muscle contraction that hindered reliable palpation of the arterial pulse. Transcutaneous pacing can occasionally be of value even at a late stage in the emergency treatment of profound bradycardia but is unlikely to be worthwhile in complete asystole.

Aged↗
PubMed1979

Low voltage electrical activity preceding right atrial depolarisation in man.

Electrical recordings were made in the high right atrium in 28 patients undergoing cardiac catheterisation and in 3 healthy volunteers. After filtering and amplification by 3 to 10 million times, the signals were passed through a signal averaging process in a digital computer. Of the 28 subjects who had technically satisfactory recordings, 23 showed low voltage electrical activity preceding the conventionally-recorded atrial depolarisation. The low voltage activity started 50 to 200 ms before the atrial deflection and was variable in shape. These early signals may be the result of activity in the region of the sinus node.

Arrhythmia, Sinus↗
PubMed1979

Epileptiform seizures with maprotiline hydrochloride.

Two cases are described who developed epileptic seizures whilst taking maprotiline hydrochloride in therapeutic dosage. In both cases the electroencephalogram was normal and the fits stopped on withdrawal of the drug.

Adult↗
PubMed1978

Aldosterone in myxoedema.

Ten patients with severe myxoedema were treated with regular increments of thyroxine. The urine aldosterone excretion rate and plasma-aldosterone level increased with each increasing dose of thyroxine. Two patients in whom the serum-aldosterone rose to abnormally high levels had cardiac failure which resolved when the thyroxine dose was reduced.

Aldosterone↗
PubMed1978

Aryl hydrocarbon hydroxylase in persons with lung or laryngeal cancer.

To test whether the distribution of AHH inducibility is shifted toward the high end of the range in patients who had lung and laryngeal cancer, we measured this trait in 59 patients (32 lung and 27 laryngeal) who had resectable tumors and had been disease-free for a period of time. The advantage of selecting patients who were free of clinical disease was that measurement of their AHH inducibility should not have been affected by the disease state. Patient and control populations showed no difference in basal and induced AHH activity of AHH inducibility. The mean AHH inducibility in patients who had lung cancer was 3.20 +/- 0.20; in patients who had laryngeal cancer 2.96 +/- 0.18, and for all controls 3.29 +/- 0.04 (no significant difference at p = 0 05). Further analysis of the distribution of AHH inducibility in the patient group compared to controls showed no suggestion of a shift toward the higher end of the range in patients who had lung and laryngeal cancer.

Adenocarcinoma↗
PubMed1977

Questionable relation of aryl hydrocarbon hydroxylase to lung-cancer risk.

To test whether the genetically determined trait, aryl hydrocarbon hydroxylase inducibility, affects susceptibility to lung cancer, we measured this trait in cultured lymphocytes from a normal population, patients with lung cancer and progeny of such patients. We found very low aryl hydrocarbon hydroxylase activity (19 per cent of normal) in about half the patients with lung cancer. Only part of this activity can be accounted for by reduced cell growth and by reduced protein synthesis. In an indirect assessment of inducibility, both 57 progeny and 27 matched controls had a mean inducibility of 2.95 and a similar distribution into low, intermediate and high groups (chi-square = 0.3 P = 0.9). No differences in basal or induced activity were observed. Thus, if patients with lung cancer possess altered aryl hydrocarbon hydroxylase inducibility or activity these characteristics are not transmitted to their progeny.

Adult↗
PubMed1977

Distribution of aryl hydrocarbon hydroxylase inducibility in cultured human lymphocytes.

We measured aryl hydrocarbon hydroxylase (AHH) in cultured human lymphocytes. A striking seasonal variation in AHH activity was observed with induced AHH activity levels from January through May measuring approximately 20% of the values during the remainder of the year. AHH inducibility was determined by comparing lymphocytes from the same person cultured with and without the inducer 3-methylcholanthrene. If measurements are limited to the summer and fall seasons when AHH activity is high, AHH inducibility is reproducible for most persons with repeat determinations on the same person averaging 11% from the mean. The values of AHH inducibility in 53 persons ranged from 0.9 to 5.0, but the distribution of values did not fall into three distinct, nonoverlapping classes as reported by others. We were not able to determine the distribution of AHH inducibility in lung cancer patients since lymphocytes from less than half of the patients tested could be successfully cultured.

Aryl Hydrocarbon Hydroxylases↗
PubMedDate not supplied

[Monitoring the air in the workplace. Vapors and gases].

In order to control occupational exposure to gases and vapors, the industrial Hygienist use different sampling instruments and analytical procedures to measure directly or indirectly the gas and vapor concentrations in working atmospheres. The main techniques employed are here described.

Environmental Monitoring↗