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.

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.

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.

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.

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.

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.

Statistical variability of biomedical data: part 2. The influence of serial correlations on power estimates, and on comparative testing of samples.

The effect of serial-correlation structure of biomedical data on the statistical-sampling variability of power estimates is investigated, extending a previous study of mean value estimates. The degrees of freedom content for power DFp in a k-point sample is shown to be dependent on the serial-correlation structure in a generally different way from the DFk, the corresponding measure for the mean. The sampling distribution of power is also investigated. The influence of serial correlation structure on the behaviour of traditional small-sample statistical tests is also of interest; in the case of the t-test the effects can be severe but can be compensated, leading to a new variable, ct, which for correlated data, behaves rather like t for uncorrelated data. The approach is applied to the case of long-term records of systolic blood-pressure data.

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.

Statistical variability of biomedical data: Part 1. The influence of serial correlation on mean value estimates.

Many biomedical variables are subject to large short-term fluctuations; so, measurements of the variable requires statistical improvement. Such variables also commonly exhibit longitudinal correlation due to systematic variations contributed by underlying biological mechanisms and sometimes constituting most of the variability. This correlation structure interferes with the operation of statistical procedures, such as longitudinal averaging to improve resolution of the mean value, and manipulations designed to provide objective comparative assessments of data samples. A convenient approach to evaluating and overcoming these problems can be made through the degrees of freedom concept. It is shown how the degrees of freedom content of the sample of serially correlated data is related to the correlation structure of the variable and how this affects variability of the mean in different sized samples. The approach is confirmed both by simulation and by empirical studies on several biomedical variables: various intra-arterial and left ventricular blood-pressure measurements, heart rate, and nystagmus inter-beat intervals in the stimulated electro-oculogram. The implications for measurement are discussed, specifically in respect of sampling protocols to improve resolution to a specified extent (for which a microprocessor instrument has been designed), as well as in determining the inherent longitudinal resolution of a data sequence and the effective precision displayed by the observations.

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.