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Biomedical subjects

B M Sayers

Publications and source records attributed to B M Sayers.

At least 19 recordsLinked to original sources
PubMed1997

Health-care technology transfer: expert and information systems for developing countries.

Computer-based technologies such as information systems and expert systems have an undoubted contribution to health-care development in developing countries. This paper addresses the appropriateness of these technologies for developing countries, the criteria to be used in selection of the technology to be transferred, and the need for a systematic approach to evaluation. A conceptual model for assessing transferability so as to achieve an effective transfer, has been introduced. This requires not only an attempt to amplify the role of information and expert systems in health-care improvement and for socio-economic development, but the analysis of prior experience in transferring these technologies to developing countries. Following this approach, and using operational research techniques such as the Analytic Hierarchy Process, a subjective assessment model has been described that can systematically guide decision-making about computer-based health-care technology to be transferred to developing countries.

Developing Countries↗
PubMed1997

The critique of DALYs: a counter-reply.

The DALY Review Group of the WHO Advisory Committee on Health Research (ACHR) believes that, unless they are constructed purely as an intellectual exercise, indicators should have a function--ultimately to guide decision-making about resource allocation. Disability-adjusted life years (DALYs) obscure too much and in its present stage of development the DALY approach does not solve the problem of prioritization and of resource allocation and may yet turn out to have been a side-track.

Persons with Disabilities↗
PubMed1990

Timing of deep breaths during rest and light exercise in man.

1. We used digital filtering techniques and segmental analysis to dissect a series of respiratory variables into three components: (a) outlying values, including deep breaths or sighs; (b) random variation; (c) non-stationary baseline variation. 2. Records of about 30 min breathing were obtained from normal adults at rest and at 50 W exercise. 3. Deep breaths were defined as having a tidal volume greater than 2.5 sd above the mean. 4. We related these deep breaths to preceding trends in tidal volume and end-tidal partial pressure of CO2. 5. At rest, there was no relation between deep breaths and tidal volume, but the deep breaths were significantly clustered around the troughs in end-tidal partial pressure of CO2. 6. At 50 W exercise, there was no relation between deep breaths and end-tidal partial pressure of CO2, but the deep breaths were significantly clustered around tidal volume troughs. 7. Results obtained by pneumography were concordant with those obtained by using a mouthpiece to measure ventilation.

Adult↗
PubMed1987

Spatio-temporal characterization of intercostal activity during breathing in the cat.

It is envisaged that the motor control of the intercostal musculature--an assembly of mobile structures--can be characterized in terms of a conceptual spatially continuous control function, that underlies the discretely distributed muscular activity and reflects an inferred global dynamic control of the thoracic cage during breathing. The global control function is estimated by the spatio-temporal pattern obtained by averaging in time and space and interpolation of multichannel simultaneous intercostal EMG recording in the anaesthetized cat. Different examples of the experimental preparation in the presence of stimuli of different kinds are analysed. The resultant signal patterns are found to be self-consistent and capable of exhibiting systematically differing features in systematically differing experimental conditions, thus supporting the validity of the analysis and the choice of the estimator. It is concluded that a more detailed analysis of the requirements of this approach is then warranted. Such requirements are discussed, and, specifically, results that bear on the adequacy of spatial sampling rate are presented. It is suggested that such methods offer a promising approach in the study of motor control strategies of the respiratory apparatus.

Algorithms↗
PubMed1986

A structural model of the thoracic cage in the cat.

A homogeneous shell model of the mechanical characteristics of the thoracic cage in the cat is presented. The global characterization proposed parallels the characterization--presented elsewhere--of the motor control of the intercostal musculature in terms of a conceptual spatially continuous control function, that underlies the discretely distributed muscular activity and reflects an inferred global dynamic control of the intercostal muscles during breathing. Proposing a static, homogeneous shell characterization of the thoracic cage, which is heterogeneous and composed of an assembly of mobile structures, implies assuming that other elements are indirectly giving this system features that make it resemble, from a structure analysis point of view, a homogeneous, static one. The pattern of the lines of stress along the shell structure proposed as a model compares favourably with the shape of the ribs. In agreement with previous findings, supporting the need for muscular activity to satisfy demands of purely structural character, it is suggested that this global shell-like functional character is achieved by neuromuscular global dynamic integration of the components of the rib cage by the nervous control of the intercostal muscles.

Animals↗
PubMed1983

Towards fully objective evoked response audiometry.

The amplitude spectra of the auditory brainstem potentials evoked by free-field stimuli revealed significant differences from the corresponding spectra of pre-stimulus records. This was most marked for low order harmonics and in response to high intensity stimuli. In general, however, the shape of the amplitude spectrum for pre-stimulus and post-stimulus epochs was similar and the magnitude of the differences between corresponding harmonics became progressively smaller as stimulus intensity was reduced. Given that the spectrum of each coherent grand average is a function of the amplitude and phase spectra of the response ensemble, these were separately examined. Ensemble mean amplitude of individual harmonics diminished with stimulus intensity while their phases became progressively less aggregated. Phase standard deviation, used as a parameter of this aggregation, was found to change more systemically with stimulus intensity than ensemble mean amplitude. Phase standard deviation values for threshold responses were generally significantly smaller than corresponding harmonics obtained from sub-threshold responses. By contrast the amplitude differences between populations of threshold and sub-threshold responses were generally non-significant. These findings suggested that fully objective methods of threshold determination might more successfully be based on ensemble phase measures rather than amplitude measures.

Animals↗
PubMed1981

The incidence of anencephalus in the Fylde peninsula 1956-76 and changes in water hardness.

In an area which had a high incidence of anencephalus, 3.2 per 1000 births, there was a significant drop to 1.3 per 1000, below the national average of 1.7 to 1.8, among conceptions after 1967. In the northern part of the area this drop was greater in summer than winter conceptions, providing additional evidence of a different process underlying case occurrences in the north of the area from that in the south. In 1957-61 there were significantly more births of anencephalic babies in North Fylde than in South Fylde, but both areas were supplied with soft water. From 1962 to 1969 the water changed from soft to slightly hard. Soft water does not appear to be a primary aetiological factor in anencephalus, but hard water may mitigate the effect of other factors.

Anencephaly↗
PubMed1980

Signal statistics in objective auditory evoked potential (AEP) detection by the phase spectral method.

This paper reports on statistical aspects relevant to the use of the phase spectrum of post-stimulus EEG, in objective detection of the auditory evoked potential. The sampling statistics of two statistical estimators are discussed: the mean phase vector magnitude, and the standard deviation of an ensemble of post-stimulus EEG phases. These two estimators are circular statistics, and subject to strong sample size bias. Their confidence intervals have been derived empirically for sample sizes routinely used in clinical audiometry. A trial example illustrates the use of the objective phase statistics developed here; it is noted that the method may also be more efficient than the visual scoring of averaged responses.

Adult↗
PubMed1979

A model of left ventricular function in the denervated heart.

A model has been formulated for the function of the denervated left ventricle. Using the model it is possible to generate realistic waveforms for aortic flow, aortic pressure, left ventricular volume and left ventricular pressure over a wide range of simulated haemodynamic conditions. The effect of changes in contractile state is introduced through the concept of left ventricular pumping capacity. Model results compare well with similar data obtained from denervated hearts in open-chest dogs anaesthetized with halothane under positive pressure ventilation. Simulation of changes in contractile state shows excellent agreement with data published by previous investigators.

Animals↗
PubMed1979

Implementing a computer-based electro-oculographic analysis system.

Electro-oculographic recordings of caloric-induced nystagmus were conducted in a number of normal and disordered subjects. On the basis of the results, implementation of a clinical measuring system is considered; this is based on the interbeat interval, selected in view of its favourable sensitivity and stability. Two stages of processing are involved; first, the determination of the interbeat intervals, second the analysis. The first stage has been implemented off-line on a general purpose computer and also, in on-line mode, by special purpose electronics. The second stage requires computer analysis. We have used the rank magnitude sequences of interbeat intervals as the basis of the analysis.

Adult↗
PubMed1979

Pattern analysis in the study of infantile diarrhoea and other epidemiological problems.

The patterns imposed on records of epidemiological variables by spatial, temporal, and other factors demand a special approach for their identification, characterization, and interpretation. Over the last 10 years, a methodology based on pattern analysis has been developed and put to the test in elucidating selected epidemiological problems. The aim of this approach is to link the pattern or its detailed features to factors likely to be important in understanding the origins of the disease and the mechanisms underlying its occurrence; such knowledge may in turn suggest methods that can be used to control the disease. Pattern analysis provides a battery of techniques that can greatly enhance the cost-effectiveness of epidemiological investigations. To exemplify these techniques, the applications of pattern analysis in the study of the infantile diarrhoeal complex and in elucidating the epidemic spread of wildlife rabies are described. Some other examples are mentioned briefly and comments are made on the more important techniques available.

Animals↗
PubMed1978

Analysis of the occurrence of anencephalic stillbirths in the Fylde Peninsula, 1956--1967.

Computer-based statistical signal methods have been applied to the analysis of case-occurrence time and location data from a 12-year complete series of anencephalic stillbirths in the Fylde peninsula of Lancashire. In the absence of any certainty about causative or contributory factors in these occurrences, the primary questions are if the underlying process is Poisson, or if there is evidence of a seasonal influence, and if any regional differences or communicable factors can be identified. With the limited case numbers (124) most small-sample statistical tests were not sufficiently informative. But using pattern and print-process analysis methods and simulation techniques, further elucidation is possible; for example, it is shown that a seasonally rate-modulated Poisson process is a reasonable model for case occurrences in the southern region, but not in the north, for which a different process must apply and where some evidence exists of clustering of preferred inter-event intervals. It is concluded in particular, that there is a regional dependence, with seasonal factors, of the process underlying case occurrences, and in general, that signal analysis methods are useful in the interpretation of small-sample spatio-tempered epidemiological data.

Anencephaly↗
PubMed1978

Objective specification of the incremental weight variable in weanling diarrhoeal disease of infants.

The objective specification of the second variable (body weight) measured in an epidemiological field study of weanling diarrhoeal disease of infants has been approached by computer-based pattern analysis, complementing previous studies of the diarrhoeal signal of daily defaecation count (DS). The weight data are available for 64 weeks in a subset of 50 out of 139 infants in the study. A weekly incremental weight signal (IWE) was estimated by successively differencing each new observed weight with a smoothed version of the previous value. Variable latency of the different features of this variable precludes the formation of an average-profile by coherent averaging the ensemble of records; a feature-analysis method based on statistical trend analysis was therefore developed. Features of the resulting IWE average profile can be linked to weanling events, transient diarrhoeal episodes, and typical post-neonatal shifts in level of the diarrhoeal signal. The results are consistent with the view that both nutritional and infectious factors operate in most deviations from typical behaviour seen in individual IWE records. In all the infants having an abnormally low (64 week) weight gain, a sustained abnormal DS elevation can be recognized in the 7-15 week period, with recurrent diarrhoeal episodes (type P2, as previously classified) during the 45-60 week period; both abnormalities were associated with substantial effects on weight gain. But individual P2-diarrhoeal episodes occurring before about 40 weeks of age could be linked only to small, quickly-compensated effects on incremental weight.

Body Weight↗