Impact of a Right Ventricular Impedance Sensor on the Cardiovascular Responses to Exercise in Pacemaker Dependent Patients

Background. The evaluation of the heart rate (HR) response to exercise is important for the assessment of the rate response algorithm of sensor-controlled pacemakers. This study examined the effects of a right ventricular impedance sensor driven pacemaker on the cardiovascular responses to incremental exercise in pacemaker dependent patients. Methods. Twelve patients (70.5 ± 9.5 years; 5 Females: 7 Males) implanted with an Inos2+ closed loop stimulation (CLS) pacemaker were compared to 12 healthy age and sex matched controls (70.6 ± 4.8 years). All subjects performed the chronotropic assessment exercise protocol (CAEP). Variables of interest included HR, cardiac output (Q), oxygen uptake (Vo2) and blood pressure (BP). Data were analyzed at rest, throughout exercise and during recovery. Furthermore, patient chronotropic responses were compared to a reference chronotropic response slope for aerobic exercise. Results. There were no differences between groups for HR or Q. response throughout exercise. At peak exercise, V.o2 (mL.kg-1.min-1) was higher for the controls (p < 0.05). The patient chronotropic response slope was comparable to the CAEP reference slope from rest to both the anaerobic threshold (AT) and peak exercise. During recovery, no differences were observed between the groups for any parameters or for the HR decay slopes. Conclusions. Up to the anaerobic threshold, the right ventricular impedance sensor driven pacemaker delivered a pacing rate that contributed to an overall cardiovascular response similar to that observed in healthy age matched subjects

Classifying Generalization: Paradigm War or abuse of Terminology?

Lee and Baskerville (2003) attempted to clarify the concept of generalization and classify it into four types. In Tsang and Williams (2012) we objected to their account of generalization as well as their classification and offered repairs. Then we proposed a classification of induction, within which we distinguished five types of generalization. In their (2012) rejoinder, they argue that their classification is compatible with ours, claiming that theirs offers a ‘new language.’ Insofar as we resist this ‘new language’ and insofar as they think that our position commits us to positivism and the rejection of interpretivism, they conclude both that our classification is more restrictive than theirs and also that we embrace ‘paradigmatic domination.’ Lee and Baskerville\u27s classification of generalization is based on a distinction between theoretical and empirical statements. Accordingly we will first clarify the terms ‘theoretical statement’ and ‘empirical statement.’ We note that they find no fault with our classification of induction, we restate our main objections to their classification that remain unanswered and we show that their classification of generalizing is in fact incompatible with ours. We argue that their account of generalization retains fatal flaws, which means it should not be relied upon. We demonstrate that our classification is not committed to any paradigm and so we do not embrace ‘paradigmatic domination.

Modelling Earthquake Ground Motions by Stochastic Method

The prediction of earthquake ground motions in accordance with recorded observations from past events is the core business of engineering seismology. An attenuation model presents values of parameters characterising the intensities and properties of ground motions estimated of projected earthquake scenarios (which are expressed in terms of magnitude and distance). Empirical attenuation models are developed from regression analysis of recorded strong motion accelerograms. In situations where strong motion data are scarce the database of records has to cover a very large area which may be an entire continent (eg. Ambrasey model for Europe) or a large part of a continent (eg. Toro model for Central & Eastern North America) in order that the size of the database has statistical significance (Toro et al., 1997; Ambrasey, 1995). Thus, attenuation modelling based on regression analysis of instrumental data is problematic when applied to regions of low and moderate seismicity. This is because of insufficient representative data that has been collected and made available for model development purposes. An alternative approach to attenuation modelling is use of theoretical models. Unlike an empirical model, a theoretical model only makes use of recorded data to help ascertain values of parameters in the model rather than to determine trends from scratch by regression of data. Thus, much less ground motion data is required for the modelling. Data that is available could be used to verify the accuracies of estimates made by the theoretical model. Ground motion simulations by classical wave theory provides comprehensive description of the earthquake ground motions but information that is available would typically not be sufficient as input to the simulations. The heuristic source model of Brune (1970) which defines the frequency content of seismic waves radiated from a point source is much simpler. The model has only three parameters : seismic moment, distance and the stress parameter. Combining this point source model with a number of filter functions which represent modification effects of the wave travel path and the site provides estimates for the Fourier amplitude spectrum of the motion generated by the earthquake on the ground surface. The source model (of Brune) in combination with the various filter functions are collectively known as the seismological model (Boore, 1983). Subsequent research by Atkinson and others provides support for the proposition that simulations from a well calibrated point source model are reasonably consistent with those from the more realistic finite fault models

Understanding the implementation of interventions to improve the management of chronic kidney disease in primary care: a rapid realist review

Summary table and references for secondary search. (DOCX 204 kb

Axial Load Variation of Columns in Symmetrical RC Buildings Subject to Bidirectional Lateral Actions in Regions of Low to Moderate Seismicity

Columns in building frame systems are subjected to the combined action of bidirectional horizontal loading and axial load variation during an earthquake. Whilst the behaviour of RC columns under unidirectional and bidirectional lateral loading with constant axial load is understood well, the behaviour under bidirectional lateral loading with axial load variation is rarely studied, especially for limited ductile RC columns prevalent in regions of low to moderate seismicity. This paper begins with a numerical study that aims to obtain the generalised patterns and range of axial load variation in RC building columns. To this end, a case study building is subjected to a suite of 15 ground motions, representative of low to moderate seismic regions, in OpenSees. This is followed by an experimental study in which limited ductile high-strength RC columns are tested under bidirectional lateral loading and two different axial load variation protocols, namely synchronous and nonsynchronous variable axial loading protocols. The results of the numerical study demonstrated that axial load variation of the columns in an RC building is primarily dependent on the response spectral acceleration corresponding to the fundamental period of the structure in the two orthogonal horizontal directions and/or the vertical direction. The results of the experimental testing showed that nonsynchronous axial loading (compared to constant and synchronous axial loading) results in the lowest collapse drift capacity and energy dissipation of the RC columns.</p