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Biomedical subjects

R G Charles

Publications and source records attributed to R G Charles.

13 recordsLinked to original sources
PubMed1992

Comparative evaluation of rate modulation in new generation evoked QT and activity sensing pacemakers.

Two new generation rate adaptive pacemakers, the Rhythmyx (Vitatron) using the evoked QT interval and the Legend (Medtronic) using vibration as indicators of metabolic demand, were compared for rate adaptive characteristics during different forms of exercise. While both showed improvements over previous generation pacemakers, they still show deficiencies in some aspects of rate modulation. Rhythmyx was slow to respond to changes in metabolic need and showed an "over-shoot" with increasing pacing rate on cessation of exercise. Legend was quick to adapt rate at beginning and end of exercise but showed a plateaus of rate modulation during the period of slowly increasing workload. Legend also showed only modest rate adaptation to changes in treadmill gradient and to bicycle ergometer exercise. Further developments in pacemaker technology are required if physiological rate adaptation to exercise is required.

Aged↗
PubMed1992

Growth, body composition, and plasma androgen concentration of male broiler chickens subjected to different regimens of photoperiod and light intensity.

Day-old male Hubbard broilers (960) were assigned to one of four treatments (two pens of 120 birds per treatment) to evaluate the effects of high (150 lx) versus low (5 lx) light intensity and constant 23 h light (L):1 h dark (D) versus increasing (6L:18D increasing 4 h/wk to 23L:1D) photoperiod in a 2 x 2 factorial arrangement of treatments. Birds were raised to 8 wk on a typical commercial four-diet program. Low-intensity birds were heavier than high-intensity birds from 2 to 8 wk (3.25% heavier at 8 wk). Birds raised under constant photoperiod were heavier than birds raised under increasing photoperiod from 2 to 5 wk and at 7 wk of age (1.71% heavier at 7 wk). High-intensity bird carcasses had lower percentage body fat, weight of fat, and higher percentage body protein at 8 wk compared with low-intensity bird carcasses (7.77, 10.76, and 1.77%, respectively). High-intensity birds had smaller abdominal fat pads (weight and percentage of body weight) at 8 wk compared with low-intensity birds (15.46 and 12.17%, respectively). Photoperiod did not affect body composition. Birds treated with increasing photoperiod had larger testes (weight and percentage of body weight) at 8 wk compared with birds under the constant photoperiod (29.36 and 30.51%, respectively). Birds treated under increasing photoperiod had higher plasma androgen concentrations at 7 wk compared with birds under constant photoperiod (testosterone, .270 versus .188 ng/mL; androstenedione, .632 versus .494 ng/mL).(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗
PubMed1992

Effect of feed allowance during rearing and breeding on female broiler breeders. 2. Ovarian morphology and production.

The influence of feed allowance during rearing (4 to 18 wk) and breeding (18 to 62 wk) on ovarian morphology and egg production was examined. During rearing, beginning at 4 wk of age, 400 Indian River pullets that had been full-fed from 1 day of age either continued to be full-fed (F, n = 200) or were feed restricted (R, n = 200), following commercial practice. At 18 wk of age, 100 birds (within +15% of the mean BW) in each of F and R rearing groups were further assigned to be full-fed (n = 50) or feed restricted (n = 50) during breeding. Thus, based on feed allowance during rearing and breeding, four treatment groups were formed (FF, FR, RF, and RR). Feed restriction during rearing significantly delayed oviduct development and age at sexual maturity (age at first egg). Compared with feed restriction during both rearing and breeding (RR), ad libitum feeding beginning at 18 wk of age (RF) significantly increased the weight of the ovary and the number of large follicles at sexual maturity but did not significantly affect the age at sexual maturity. Feed restriction during rearing, breeding, or both significantly reduced the incidence of erratic ovipositions, defective eggs, and multiple ovulations. The incidence of erratic ovipositions was positively correlated (r = .692, P less than or equal to .001) with the laying of soft-shelled and shell-less eggs and negatively correlated (r = -.508, P less than or equal to .001) with the production of settable eggs to 62 wk of age. Compared with ad libitum feeding, controlled feeding during breeding significantly improved both settable and total egg production. Among the four feeding regimens, Treatment RR resulted in the highest fertility and hatchability.

Aging↗
PubMed1988

Beta-blockade by sotalol in early myocardial infarction decreases ventricular arrhythmias without increasing left ventricular volume.

Although early beta-blockade in acute myocardial infarction (AMI) may have potential benefits owing to an anti-arrhythmic effect and limitation of infarct size, the haemodynamic effects are not well characterised. Accordingly, we studied the effects of intravenous beta-blockade by sotalol in AMI, commencing a mean of 6 hours after the onset of chest pain, with particular reference to systemic haemodynamic changes and left ventricular (LV) volumes. Thirty patients were randomised to a control group or to sotalol therapy starting with 40 mg and increasing to 120 mg, followed by the maximal dose tolerated every 6 hours for 72 hours. Sotalol reduced heart rate and mean blood pressure without elevating pulmonary wedge pressure or increasing enzymatic infarct size. Sotalol also decreased the incidence of ventricular tachycardia (P less than 0.001). An important new finding was that there was no increase in the LV volume measured by radionuclide techniques. Therefore intravenous sotalol safely achieved its beneficial effects without causing LV dilatation.

Adult↗
PubMed1987

Holter monitoring in patients with mitral stenosis and sinus rhythm.

To determine the type and frequency of supraventricular arrhythmias in patients with mitral stenosis and sinus rhythm we studied 63 such patients, mean (sd) age 48.8 (8.2) years, by 24 hour ambulatory ECG monitoring. Thirty-five patients (55.6%) had supraventricular tachyarrhythmias. Twenty-five (39.7%) had paroxysmal atrial tachycardia, 14 (22.2%) atrial fibrillation, 8 (12.7%) multifocal atrial tachycardia and 5 atrial flutter. Ninety-five per cent (101) of episodes were asymptomatic and 96% non-sustained. Supraventricular premature beats occurred in 59 patients with couplets and triplets in 40 (63.5%) and 28 (44.4%), respectively. Frequent supraventricular premature beats, couplets, triplets and episodes of paroxysmal arrhythmias were commoner in patients greater than 50 years. Ectopic atrial rhythms with varying P wave morphology occurred in 12 patients (19%). Nine patients (14.3%) had suffered systemic embolic episodes. We conclude that supraventricular ectopic and tachyarrhythmias occur frequently in patients with mitral stenosis and sinus rhythm and that most paroxysms are non-sustained and asymptomatic.

Adult↗
PubMed1985

Rate-responsive ventricular pacing: clinical experience with the RS4-SRT pacing system.

Eighteen patients (11 men and 7 women) with symptomatic second or third degree atrioventricular block underwent implantation of the rate-responsive RS4-SRT pacing system. Exercise tolerance in RS4 mode was compared to that in VVI mode by randomized double-blind treadmill stress testing. Following hospital discharge, RS4 function was assessed by repeat exercise testing and 24-hour Holter monitoring. Difficulty in obtaining satisfactory P-wave amplitudes at implantation (mean 3.1 +/- 1.5 mV) resulted in prolonged implantation times (mean 79.4 +/- 26.4 minutes). Following implantation, 10 patients (58%) showed a significant ventricular rate response to exercise, seven did not, and one remained in sinus rhythm. For responders, peak ventricular paced rate and double product were significantly greater in RS4 than in VVI mode, being 101.8 +/- 5.8 vs. 74.3 +/- 0.4 beats per minute and 20.1 +/- 2.9 vs. 15.5 +/- 3.7 beats per minute X mmHg X 10(-3), respectively (p less than 0.001). However, treadmill times (10.5 +/- 2.6 vs. 9.7 +/- 3.3 minutes) and work done (5.51 +/- 2.01 vs. 4.97 +/- 2.33 joules X 10(-5] were not significantly different (p = 0.22). Following hospital discharge, repeat exercise testing and 24-hour Holter monitoring demonstrated RS4 function in 11 of 16 and 15 of 18 patients, respectively. We conclude that, due to unreliable atrial sensing, the RS4-SRT pacing system does not provide the reliable rate-responsiveness required to improve exercise tolerance.

Aged↗
PubMed1978

Spontaneous mid-oesophageal rupture.

The clinical presentation and management of spontaneous rupture of the middle third of the oesophagus is described in two patients. Early presentation and treatment in one case led to uncomplicated recovery. In the other patient late presentation and diagnosis resulted in delayed surgical intervention with an unsuccessful outcome. The nature of this rare lesion is discussed and nine previously described cases are reviewed.

Adult↗
PubMed1977

Endocardial pacing electrode design and rate of displacement.

In a series of 184 patients with a permanent endocardial pacing system the rate of electrode displacement was 3-0 per cent using the Devices L120SR electrode, and 23-1 per cent using the Devices S120 electrode. The technique and pacing team were unchanged during the period of study. It is suggested that the design and mechanical characteristics of the elctrodes were responsible.

Electrodes, Implanted↗
PubMed1977

Polyradiculoneuritis and Mycoplasma pneumoniae infection.

A patient with severe Mycoplasma pneumonia developed polyradiculoneuritis and respiratory failure. The acute phase of the illness was complicated by a myocarditis, and recovery of neurological function was slow. Residual left hemidiaphragmatic paralysis was present 1 year after onset of the illness.

Acute Disease↗