Search PubMed⌕ Search

Biomedical subjects

A Murray

Publications and source records attributed to A Murray.

At least 361 records · Page 20Linked to original sources
PubMed1983

Measurement of chest wall movement; design, performance and clinical use of a four-channel magnetometer instrument.

A four-channel magnetometer instrument is described. It has been developed to measure changes in diameters of the chest and abdomen during respiration. A linearisation correction allows for the magnetic field strength detected by the receiver being proportional to the inverse cube of the diameter being measured. Diameters and changes in diameter are measured to an accuracy of 4% (1 SD) over the working range (15-50 cm). The effects of non-ideal positioning and extraneous movements of the magnetometer coils, cross-channel interference and the influence of nearby metals are described. With minimal care in positioning the coils, these effects are negligible. The instrument has been in use for one year, assessing chest wall movement in patients with abnormal lung function. Recordings are presented illustrating typical normal and abnormal chest wall movements.

Biomedical Engineering↗
PubMed1983

Mechanisms of fixed coupled ventricular ectopic complexes.

Mechanisms of fixed coupled ventricular ectopic complexes (VECs) were studied in the monitoring ECGs of 7 patients with the aid of a special purpose computer. Over 80% of the 4500 fixed coupled VECs studied had coupling intervals restricted to a range of 120 ms. The actual coupling interval varied between subjects. No special part of diastole exhibited the property of fixation. In five patients there was evidence of parasystole despite the fixed coupling. In two of these the ectopic period was clearly different from the sinus period. In the other three a difference was evident between inter-ectopic and sinus intervals, but the ectopic period could not be determined due to absence of short inter-ectopic intervals. Absence of some intervals was due to exit block or consistent coincidence of ectopic stimuli with ventricular refractoriness. In all five patients the inter-ectopic intervals showed progressive adjustment so as to become equal to a multiple of the sinus period. The coupling interval, which indicated the preferred phase relationship of the two rhythms, was altered by small changes in the sinus period. These adjustments were greater manifestations of the synchronising effects, already described, of sinus rhythm on a ventricular parasystolic rhythm. By contrast the VECs of two other patients exhibited very different characteristics. In one, the VECs restricted to 40 ms after the T wave in early diastole were probably due to ventricular re-excitation. In the other, runs of idioventricular rhythm and VECs in late diastole were due to an escape pacemaker rhythm.

Aged↗
PubMed1983

A simple uroflowmeter tester.

A simple device for testing urine flowmeters is described. It is made from readily available components and is portable, easy to use, and requires no special care in setting up. The flow rate is accurate to within 0.5 ml/s. Nursing staff are now able to do regular calibration checks on the urine flowmeters and some flowmeter deficiencies have been exposed. Using the tester, examples of artefactual peak flow rates have been recorded.

Equipment Design↗
PubMed1982

Computer assisted M-mode echocardiogram analysis.

An analysis system has been developed to aid the quantitative interpretation of echocardiograms. A small and relatively inexpensive desk-top computer, which requires no modification is used. The analysis system enables a variety of complex continuous measurements to be made. The include left ventricular dimension changes, velocities and "work" diagrams. Using the digitiser in the system, a series of options in the operating program allow the analysis steps to be tailored to specific clinical or research requirements. Analysed waveforms can be output singly or superimposed to allow physiological and measurement variabilities to be studied. The system is now being used in several hospitals, and all report favourably on its flexibility and ease of use.

Computers↗
PubMed1982

The pathology of hepatitis A in man.

Liver biopsies from 17 patients with serologically established hepatitis A were examined by light microscopy. Biopsies were taken from 2 to 27 weeks after onset of symptoms. All showed acute hepatitis, usually with centrilobular lesions but also commonly with a striking portal and periportal inflammatory reaction, resembling that seen in chronic active hepatitis. The infiltrate was rich in plasma cells. Centrilobular cholestasis was common and occasionally severe. Neither cholestasis nor the periportal lesion appeared to be related to patient age or to the timing of liver biopsy. All patients made a full recovery and none developed chronic liver disease. The histological changes differed from those reported in children and in chimpanzees in the presence of centrilobular lesions, but resembled them in that the latter two groups also had periportal lesions. These lesions may lead to a false impression of impending chronicity if the aetiology of the hepatitis is not known at the time of liver biopsy.

Adult↗
PubMed1981

Ultrastructural features in chronic non-A, non-B (NANB) hepatitis: A controlled blind study.

Liver biopsies from 12 patients with chronic Non-A, Non-B (NANB) hepatitis, 7 with hepatitis B surface antigen (HBsAg) positive chronic liver disease, 1 HBsAg positive normal carrier, and 4 patients with non-viral liver disease, were examined by electron microscopy for cytoplasmic and nuclear changes. Aggregates of particles measuring 20-35 nm in diameter were noted in the nuclei of 8 of 12 patients with NANB chronic hepatitis, but not in the other groups. The tubular changes seen in the endoplasmic reticulum (ER) of chimpanzees with NANB hepatitis were not noted in biopsies from any of our patients.

Cell Nucleus↗
PubMed1981

Low-dose combined guanethedine 1% and adrenaline 0.5% in the treatment of chronic simple glaucoma: a prospective study.

This paper reports on the results of a prospective double-blind crossover study, comparing adrenaline 1% with adrenaline 0.5% combined with guanethedine 1% over an 8-week period with each formulation. The guanethedine/adrenaline formulation was found to be the more effective hypotensive agent of the two. This study confirms the potentiating effect of adding guanethedine to adrenaline, and suggests that this combination would be a useful alternative treatment when adrenaline 1% or adrenaline 0.25% with guanethedine 1% is insufficient.

Aged↗
PubMed1981

Short incubation non-A, non-B hepatitis transmitted by factor VIII concentrates in patients with congenital coagulation disorders.

Ten cases are reported of short incubation (one to four weeks) non-A, non-B hepatitis occurring after infusion of various preparations of factor VIII concentrates into patients with coagulation disorders. Five patients were symptomatic and, in all, serum transaminase levels were increased for at least six months. These cases of chronic hepatitis exhibited none of the features of autoimmune chronic hepatitis: autoantibodies were negative and serum immunoglobulins were normal. Hepatic histology confirmed acute hepatitis in two cases biopsied early in the illness, and chronic active hepatitis (three) of chronic persistent hepatitis (two) in five cases studied later. Lobular inflammation was a prominent feature in all cases. Other features not commonly associated with type A or B hepatitis included fatty change and damaged bile ducts.

Adolescent↗
PubMed1981

Pacemaker assessment in the ambulant patient.

A new technique for assessing implanted cardiac pacemaker function in the ambulant patient has been introduced and assessed. A modified portable electrocardiograph recorder is used to store 24 hours of electrocardiograms along with marker pulses indicating the timing of pacemaker impulses. The recorder detects this narrow impulse and records a wider marker pulse on a second channel. The false positive detection rate was estimated from recordings, each of 24 hours, taken from 10 patients. All of these patients were ambulant and none had a cardiac pacemaker. There was on average less than one false positive per 24 hours. When similar recordings were taken from a group of 15 patients with pacemakers, the average false positive rate in 13 of these patients was also less than on per 24 hours. In the two other recordings artefacts resulted in false positive rates of 28 and 960 per 24 hours. Failure to detect pacemaker pulses was confirmed in only one patient. In addition to determining the accuracy of pacemaker pulse detection, the clinical usefulness of this technique was assessed. Two patients had fixed-rate pacemakers and 13 had demand pacemakers. Of the latter, two patients had a total of three episodes of failure to sense, one patient frequently failed to capture, and six patients had episodes of inappropriate inhibition of the pacemaker, the number of episodes ranging from one to 21 in 24 hours. Paced complexes were easily identified even when they occurred as fusion complexes. The frequency of paced complexes was quantified in each patient and varied from 21 to over 100 000 impulses in the 24 hour period.

Electrocardiography↗