Search PubMed⌕ Search

Biomedical subjects

J Sparrow

Publications and source records attributed to J Sparrow.

46 records · Page 3Linked to original sources
PubMed1990

Circadian variation of heart rate is affected by environment: a study of continuous electrocardiographic monitoring in members of a symphony orchestra.

Twenty four hour ambulatory ST segment monitoring was performed on 48 members (43 players and five members of the management/technical team) of the British Broadcasting Corporation (BBC) symphony orchestra without a history of cardiac disease. This period included final rehearsals and live performances (for audience and radio) of music by Richard Strauss and Mozart at the Royal Festival Hall (n = 36) and Rachmaninov and Tchaikovsky at the Barbican Arts Centre (n = 21). During the period of monitoring one person (2%) had transient ST segment changes. Mean heart rates were significantly higher during the live performances than during the rehearsals. Mean heart rates during the live performance of Rachmaninov and Tchaikovsky were significantly higher than during Strauss and Mozart in those (n = 6) who were monitored on both occasions. Mean heart rates in the management and technical team were higher than those of the players. The recognised circadian pattern of heart rate, with a peak in the morning waking hours, was altered similarly during both concert days, with a primary peak occurring in the evening hours and a lesser peak in the morning for both musicians and management/technical staff. This study showed that environmental factors are of primary importance in defining the circadian pattern of heart rate. This has important implications when identifying peak periods of cardiovascular stress and tailoring drug treatment for patients with angina pectoris.

Adult↗
PubMed1989

Ischemia in the ambulatory setting--the total ischemic burden: relation to exercise testing and investigative and therapeutic implications.

To establish the relation between treadmill exercise testing and ambulatory St segment monitoring in the detection of ischemia in patients with coronary artery disease, and to assess whether standard medical therapy affects any such relation, 277 patients with stable angina and angiographically documented coronary artery disease were studied with treadmill exercise testing and 48 h ambulatory ST segment monitoring. One hundred forty-six patients (52%) were studied while receiving no routine antianginal therapy, and 131 (48%) while receiving standard medical therapy. In 187 patients (67%) the exercise test was positive for ischemia. During 11,964 h of ambulatory monitoring, 881 episodes of ischemia (645 [73%] silent) were recorded, of which 809 (92%) occurred in patients with a positive exercise test. The mean heart rate at the onset of ischemic episodes during ambulatory monitoring was significantly less than that at the onset of 1 mm ST segment depression during exercise testing (94.5 versus 105.9 beats/min, p less than 0.0001). However, the frequency of ambulatory ischemic episodes was strongly related to a positive exercise test (p less than 0.001), and this relation was similar for both silent and painful ischemia (p less than 0.0001 for both) and in patients who were and were not receiving therapy (p less than 0.0001 for both). The total duration of ischemia was similarly related to a positive exercise test (p less than 0.0001). Only one patient with a negative exercise test had frequent (greater than 5/day) episodes of ischemia on ambulatory monitoring and had documented coronary artery spasm. Thus, exercise testing identifies the majority of patients likely to have significant ischemia during their daily activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Immunoelectron microscopical examination of the surface distribution of opsin in rat rod photoreceptor cells.

The distribution of the visual pigment protein opsin in postnatal day 8 and adult rat retinal photoreceptor cells was studied using several well characterized monoclonal antibodies against rhodopsin and a sensitive, modified colloidal gold technique. Distribution of opsin was studied in intact tissue, explant cultures and freshly dissociated cell preparation. At PN8 labeling was seen in the plasma membrane overlying the cell body, inner and outer segment. Adult retinas still showed heavy labeling of the cell body and outer segment, but reduced labeling of the inner segment surface. Semi-quantitative estimates of colloidal gold particles bound indicated a ratio of 3-20 times more particles per unit length in the outer vs. the inner segment, depending on tissue age, preparation and antibody. Together with the subcellular localization of other photoreceptor plasma membrane proteins, these data reveal a complex system of membrane domains into which different protein components are segregated.

Animals↗
PubMed1989

Unpredictable zero drift in intravascular micromanometer tipped catheters during long term pulmonary artery pressure recording: implications for catheter design.

Zero drift may be a cause of imprecision when micromanometer tipped catheters are used for intravascular pressure measurement over long periods of time. Drift of only a few mm Hg may represent a significant error when accurate recording of low vascular pressures is required. To overcome this problem a micromanometer tipped catheter has been modified so that it can be calibrated easily while it is in the circulation. Laboratory testing has demonstrated that when zero drift occurs this intravascular "reference calibration" is a valid linear function of true zero (r = 0.999). As the sensitivity of the catheter is unaffected by zero drift, it is possible to measure pressure accurately by compensating for this zero drift. During dynamic testing of two catheters, there was a mean net drift over 24 h of -0.54 mm Hg. Clinical evaluation of the catheter was undertaken in the human pulmonary circulation in eight patients (two for 48 h, five for 24 h and one for 8 h). In contrast to the laboratory findings, over the first 4 h after catheterisation there was a phase of rapid zero drift: the net drift was -1.9 (SD 3.3) mm Hg with a range of drift of 5.5 (7.4) mm Hg. Subsequently there was gradual drift: the net drift between 4 and 24 h was -0.44 (2.1) mm Hg with a range of drift of 2.8(1.0) mm Hg; and the net drift between 24 and 48 h was 3.7(2.1) mm Hg with a range of drift of 4.1(1.9) mm Hg. During long term intravascular pressure measurement with micromanometer tipped catheters, zero drift may occur unpredictably and should be quantified.

Ambulatory Care↗
PubMed1989

Ambulatory ST segment monitoring in the assessment of patients following PTCA.

In this article we discuss the place of ambulatory ST-segment monitoring in the investigation of the patient following coronary angioplasty. Particular attention is focused on the relationship between the results of exercise testing (the standard technique in the evaluation of the post-angioplasty patient) and ambulatory ST-segment monitoring, in order to assess whether ST-segment monitoring might contribute further information in the identification of residual or recurrent ischaemia.

Angioplasty, Balloon, Coronary↗
PubMed1989

A new exercise test for the assessment of heart failure: use of a self powered treadmill.

Time limited exercise on a self powered treadmill was evaluated as a method of assessing functional capacity in patients with mild heart failure. The characteristics of the treadmill were established by exercising 11 controls at three speeds and two inclinations and comparing oxygen consumption with that on a motorised treadmill under the same conditions. Oxygen consumption on the self powered treadmill at an equivalent speed and inclination was significantly higher because of the work needed to overcome the friction of the belt. Unlike a conventional treadmill, increasing the gradient on the self powered treadmill did not increase oxygen consumption. The distance walked in 12 minutes on the self powered treadmill was measured in eight patients with mild heart failure and ten controls. Maximal oxygen consumption was measured in the same group on a conventional treadmill by a mass spectrometer. There was a significant correlation between the distance walked and maximum oxygen consumption. In patients with mild heart failure the distance travelled in 12 minutes on a self powered treadmill provides a practical, inexpensive, and sensitive method of assessing functional capacity.

Aged↗
PubMed1989

Silent myocardial ischaemia in patients referred for coronary bypass surgery because of angina: a comparison with patients whose symptoms were well controlled on medical treatment.

The frequency and characteristics of silent ischaemia were prospectively studied in 114 patients with confirmed coronary artery disease and angina. Fifty seven patients who had angina that was not adequately controlled by standard medications were referred for elective coronary artery bypass surgery (group 1). Fifty seven other patients had symptoms that were well controlled on medical treatment (group 2). Patients underwent treadmill exercise testing (n = 109) and 48 hours of ambulatory ST segment monitoring (total 5125 hours). Patients in group 1 had more severe coronary artery disease and a shorter time to 1 mm ST segment depression and maximal exercise. Twenty two patients in group 1 (38%) and 16 in group 2 (28%) had greater than or equal to 1 episode of silent ischaemia during 48 hours of ST monitoring. There was no significant difference in the mean frequency of silent ischaemic episodes in 24 hours between the two groups (group 1 0.72 v group 2 0.64); however, the mean frequency of painful ischaemic episodes in 24 hours was greater in group 1 patients (0.51) than in group 2 (0.11). In both groups the frequency of silent ischaemia was significantly related to a positive exercise test, as was the total duration of silent ischaemia. The circadian variation of silent ischaemia showed a peak of episodes in the evening in both groups. The frequency of silent ischaemia in patients with coronary artery disease and angina receiving standard antianginal medications was not related to the severity of symptoms, but was significantly related to a positive exercise test. Thirty three percent of the patients studied had evidence of silent ischaemia during 48 hours of ambulatory ST segment monitoring; however, only four patients (3.5%) had frequent (>/=5) daily episodes of silent ischaemia.

Adult↗
PubMed1987

The objective assessment of cataract.

The objective assessment of cataract is central to any epidemiological or therapeutic study of cataract. The objective methods consist of: 1: A resolution target projection ophthalmoscope (Acuity scope) for the estimation of potential visual acuity. 2: The Oxford Clinical Cataract Classification and Grading System, which records and quantifies the features of the lens that are visible at the slit-lamp microscope. This system is essential since photographic methods cannot define the morphology of cataract. 3: Two photographic methods; slit-lamp photography and retro-illumination photography are needed to give a comprehensive statement about the amount of cataract. The negatives are measured by computerised image analysis systems.

Cataract↗
PubMedDate not supplied

The costs involved in running a fully computerized primary care system for a district.

In 1971 Exeter Community Health Services Computer Project (ECHSCP) embarked upon a scheme to produce a fully integrated patient record system. By 1975 many of its original objectives had been achieved and systems were operational in the areas of hospital administration, nursing records for patients and in primary care. The primary care system enabled general practitioners to dispense with the previously maintained manual record and replace it with a computer-based system, with the GP entering and retrieving data from a terminal located in his own surgery. Because of its original research nature, the ECHSCP has only implemented the full system in two health centres with respectively five and seven GPs in each. The computer system could provide the service on a District-wide basis serving a population of around 285 000 patients. This paper identifies the present costs of the system and uses them to extrapolate and estimate the costs per patient in running a fully computerized District-based primary care system, on equipment ordered originally in 1971 but still operational in 1980.

Catchment Area, Health↗