Biomedical subjects

R B Logan-Sinclair

Publications and source records attributed to R B Logan-Sinclair.

9 recordsLinked to original sources

PubMed1995

Elevated levels of exhaled nitric oxide in bronchiectasis.

Bronchiectasis is characterized by chronic inflammation in one or more bronchi, but the extent of inflammation is difficult to monitor. The concentration of nitric oxide (NO) in exhaled air is increased in asthmatic patients, possibly as a result of the chronic inflammatory process. We have measured exhaled NO in patients with documented bronchiectasis and investigated whether the concentration of exhaled NO is related to the extent of disease as defined by computed tomography (CT) and lung function. In 20 patients with bronchiectasis who were not taking inhaled steroids, the peak concentration of NO in exhaled air, measured by a modified chemiluminescence analyzer, was significantly elevated (285 +/- 49.0 ppb) as compared with values for 79 normal subjects (89 +/- 2.7 ppb, p < 0.01) and 19 patients with bronchiectasis treated with inhaled steroids (88 +/- 13.4 ppb, p < 0.01). Thin-section CT was used to quantify the extent of bronchiectasis in the 19 patients. There was a significant correlation between the CT score and FEV1 (r = 0.73, p < 0.01). In patients not treated with inhaled steroids there was a significant relationship between CT score and peak exhaled NO (r = 0.81, n = 12, p < 0.02), but this was not the case for patients treated with regular inhaled steroids (n = 7). We conclude that untreated bronchiectasis is associated with an increase in exhaled NO, and that this is correlated with disease severity, whereas patients treated with inhaled steroids have levels of exhaled NO within the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗

PubMed1994

Peak expiratory nitric oxide differences in men and women: relation to the menstrual cycle.

OBJECTIVE: To develop a method to measure end expiratory nitric oxide concentration and to use it to determine whether there are sex related differences between healthy men and women. DESIGN: Modification of commercially available chemiluminescent analyser to allow endogenous nitric oxide (endothelium derived relaxing factor) to be measured in a single slow forced vital capacity manoeuvre with evaluation of between and within subject variability. Serial measurements in women throughout the menstrual cycle. SETTING: Specialist referral hospital. SUBJECTS: 59 healthy volunteers (40 men and 19 women). RESULTS: Mean (SD) peak expiratory concentrations of nitric oxide in men (75 (20) ppb (parts per billion)), and women (70 (37) ppb (first measurement)) were > 5 times those previously recorded. In women concentrations at midcycle (150(39) ppb) were significantly higher (mean difference 94.9(41), P < 0.001) than during menstruation (59(25) ppb). CONCLUSION: Nitric oxide production (endothelium derived relaxing factor activity) is influenced by cyclical hormonal changes in women. There was an increase of more than 100% at mid cycle. This may be pertinent to the lower risk of cardiovascular disease in premenopausal women.

Adult↗

PubMed1994

Coughing frequency in patients with persistent cough: assessment using a 24 hour ambulatory recorder.

Cough is an important symptom of many respiratory disorders. We determined the frequency and diurnal variation of cough in normal subjects and in patients with asthma or with persistent cough of unknown cause. We used a portable, solid-state, multiple-channel recorder to record cough sounds over a 24 h period. The audio-signal was recorded from a unidirectional microphone strapped over the chest wall, and electromyographic (EMG) signals from the lower respiratory muscles were simultaneously registered with surface electrodes. The recorded digital data were examined on an IBM-compatible computer, and the typical signals induced by cough (as assessed by voluntary or experimentally-induced cough) were counted. In 12 normal subjects, only 0-16 coughs were recorded over 24 h. In 21 stable asthmatics with a history of chronic cough ("asthma") the median number was 282 (ranges: 45-1,577), and in 14 patients with the predominant symptom of daily dry coughs ("chronic coughers") the median number was 794 (64-3,639). In both groups of patients, there was a diurnal variation of coughs, such that the least numbers occurred between 2 and 5 a.m. (< 3% of total). In the asthma group, there was no significant correlation between forced expiratory volume in one second (FEV1) (% predicted) or diurnal variation of peak expiratory flow and cough frequency. In the chronic coughers, there was a significant correlation between daytime cough numbers and daytime cough symptoms scores but not for the night-time values. Our data show that cough frequency is not determined by the severity of asthma in relatively stable asthmatics on inhaled steroids, and is reduced during sleep in both asthmatics and chronic cough patients. This portable cough recorder may be useful in the assessment of drug therapy for chronic cough.

Adult↗

PubMed1992

Cardiac stimulator for the study of refractory period control using current pulses of programmable duration and shape.

A programmable current stimulator has been developed that allows unipolar current pulses of complex shape, long duration and high current to be generated. The stimulator conforms to the safety requirements for devices connected directly to the heart. It incorporates additional safety features to prevent unintended current being delivered, even under fault conditions. The stimulator has been used to investigate the effects of long duration current pulses on the refractory period of cardiac tissue. The flexibility of the device suggests that it may well have uses in other fields of electrophysiology.

Electric Stimulation↗

PubMed1991

Relation between cyclic variation in echo amplitude and segmental contraction in normal and abnormal hearts.

OBJECTIVE: To study the relation between cardiac systolic activity and cardiac cycle dependent variation in the ultrasound signal arising from within the myocardium. DESIGN: Regional echo amplitude was used as a measure of the myocardial ultrasound signal. Relative echo amplitude values were assigned by standardising echo gain using the posterior parietal pericardium as an in-vivo calibration. M mode measurements of the left ventricle were used to assess cardiac systolic activity. Subjects were studied prospectively. Analysis of echo amplitude was performed by investigators who were blinded to the results of the M mode analysis. The influence of impaired left ventricular performance and abnormal wall motion were assessed. PATIENTS: 11 cardiomyopathy patients with impaired ventricular function, eight patients with severe pulmonary hypertension and reversed septal motion, and 19 healthy controls. SETTING: All subject studies were performed at Harefield Hospital. Echo amplitude analysis was performed at the Royal Brompton Hospital. MAIN OUTCOME MEASURES: Cyclic variation in echo amplitude was determined as the change in echo amplitude from end diastole to end systole. Additionally, an index of cyclic variation defined as the ratio of the cyclic change in echo amplitude to end diastolic echo amplitude was measured. Both cyclic variation and the cyclic variation index were analysed to see whether they correlated with left ventricular dimensions, fractional shortening, and systolic wall thickening. RESULTS: Stepwise regression analysis showed systolic wall thickening to be the most significant independent variable that correlated with the cyclic variation index for both the septum and posterior wall (r = 0.68, p = 0.0001, septum; r = 0.69, p = 0.0001, posterior wall). The slopes and intercepts for both regression equations were similar (y = 0.005x + 0.006, septum; y = 0.006x + 0, posterior wall). Subgroup analysis showed that the healthy controls, patients with cardiomyopathy, and patients with pulmonary hypertension had similar slopes and intercepts for their individual regression equations. CONCLUSIONS: These data support the hypothesis of a quantitative relation between the extent of cyclic variation of echo amplitude and the degree of segmental myocardial shortening, as measured by systolic wall thickening, which is not significantly influenced by location within the myocardium, left ventricular performance, or wall motion. They provide further evidence of the usefulness of quantitative analysis of myocardial echo amplitude in the study of regional myocardial function in both normal and injured myocardium.

Adult↗

PubMed1989

Quantitative effects of speckle reduction on cross sectional echocardiographic images.

Speckle is prominent on all cross sectional echocardiograms. In order to assess its effects on image quantification, frames from a sector scanner with a six bit grey scale were stored and processed off line to identify and smooth the speckle by means of an adaptive filter based on fully developed speckle. In 14 controls, 12 patients with hypertrophic cardiomyopathy, and 12 with secondary left ventricular hypertrophy, filtering significantly reduced the standard deviation of echo intensity, which was used as a measure of the scatter of pixel amplitude, in all three groups (by 52%, 46%, and 46% respectively). The mean value of back-scattered echo intensity itself, however, was reduced by only 7%, 5%, and 8% respectively, and median values were not affected at all. Mean (SD) left ventricular cavity areas on the apical four chamber view were significantly increased from 26 (15) to 30 (17) cm2. The valve dimensions in the parasternal minor axis in 10 patients with mitral stenosis were significantly increased by 11% laterally, but were unaffected anteroposteriorly. Subjective image quality was appreciably modified: endocardial boundaries in apical views were enhanced and the septal "ground glass" appearance was lost in hypertrophic cardiomyopathy. Speckle reduction therefore greatly reduced the scatter of pixel values, with little effect on the mean regional back scattered echo amplitude. It also modified the perceived image texture. Improved boundary definition consistently increased the area estimates, particularly when these depended on lateral rather than range resolution.

Cardiomegaly↗

PubMed1984

Relation between regional echo intensity and myocardial connective tissue in chronic left ventricular disease.

Cross sectional echocardiograms were recorded within one week of death in seven patients with valvular heart disease, four with coronary artery disease, and nine with congenital heart disease. Regional echo amplitude was measured from the cross sectional display by constructing histograms of pixel intensity. Parietal pericardium was used as an internal standard for setting the gain of the instrument. At necropsy myocardium was taken from the free wall of the left ventricle, the papillary muscles, and the septum. Fibrosis was assessed histologically and biochemically as hydroxyproline content. In individual samples histological and biochemical estimates were correlated. In all regions other than the septum in patients with left ventricular hypertrophy, log [collagen] correlated with median pixel intensity. The amplitude of reflected echoes from the hypertrophied septum was significantly higher than that from other samples but was similarly correlated with collagen content. Agreement between echo amplitude and histological grade was significantly less good. Thus in chronic left ventricular disease myocardial collagen content appears to be the major determinant of regional echo intensity. Reproducibility of measurements and more rigorous definition of tissue abnormalities will, however, require further study.

Adult↗

PubMed1984

Relation of regional echo amplitude to left ventricular function and the electrocardiogram in left ventricular hypertrophy.

In order to determine the relation between three manifestations of left ventricular hypertrophy--ST-T wave changes on the electrocardiogram, diastolic disturbances, and increased myocardial echo intensity--M mode and cross sectional echocardiograms were recorded in 12 normal subjects, 15 athletes, 16 patients with hypertrophic cardiomyopathy, and 42 patients with secondary left ventricular hypertrophy due to aortic stenosis (20), severe essential hypertension (8), coarctation (7), or subaortic stenosis (7). M mode echocardiograms were digitised and cross sectional echocardiograms were analysed for regional echo intensity. In patients with hypertrophy regional echo amplitude was significantly increased in mid and basal septum and posterior left ventricular wall. Patients with increased echo amplitude in any region showed a higher incidence of ST-T wave abnormalities than those without and of diastolic abnormalities--including prolongation of isovolumic relaxation time, delay in mitral valve opening with respect to minimum cavity dimension, and a reduction in peak rate of posterior wall thinning and dimension increase. There was a significant rank order correlation between median pixel count and these diastolic abnormalities. No significant differences were demonstrable in these relations between the diagnostic groups. By contrast, electrocardiographic findings, diastolic function, and pixel count were uniformly normal in athletes, although the increase in left ventricular mass was similar to that in the patients. Thus an increase in left ventricular mass alone is not responsible for repolarisation or wall motion abnormalities occurring in pathological left ventricular hypertrophy. These latter changes are, however, strongly associated with the change in myocardial properties detected as an increase in echo intensity and may be due to increased interstitial fibrosis.

Adult↗

PubMed1978

Analysis of regional left ventricular wall movement by phased array echocardiography.

Images from standard two-dimensional echocardiographs do not lend themselves to the study of regional left ventricular wall movement because of poor definition of endocardium. An alternative method, based on a wide-angle phased array sector scanner has, therefore, been devised. Once the appropriate region of the heart has been identified, the scan rate is increased, and an array of 41 M-mode scans is produced, resulting in improved frequency response and endocardial definition. Each scan is digitised separately, and since their spatial orientation is known, the left ventricular image can be reconstituted by computer, and isometric or contour displays produced. Preliminary results, based on 40 patients, are presented showing examples of left ventricular wall movement. Regional abnormalities of amplitude or timing can be displayed with results similar to those of angiography, while disturbances of septal motion or wall thickness can be observed in greater detail than with other methods.

Computers↗