Gastric pacing has been investigated as a potential treatment for gastroparesis. New pacing protocols are required to improve symptom and motility outcomes; however, research progress has been constrained by a limited understanding of the effects of electrical stimulation on slow-wave activity. This study introduces high-resolution (HR) "entrainment mapping" for the analysis of gastric pacing and presents four demonstrations. Gastric pacing was initiated in a porcine model (typical amplitude 4 mA, pulse width 400 ms, period 17 s). Entrainment mapping was performed using flexible multielectrode arrays (=192 electrodes; 92 cm(2)) and was analyzed using novel software methods. In the first demonstration, entrainment onset was quantified over successive waves in spatiotemporal detail. In the second demonstration, slow-wave velocity was accurately determined with HR field analysis, and paced propagation was found to be anisotropic (longitudinal 2.6 +/- 1.7 vs. circumferential 4.5 +/- 0.6 mm/s; P < 0.001). In the third demonstration, a dysrhythmic episode that occurred during pacing was mapped in HR, revealing an ectopic slow-wave focus and uncoupled propagations. In the fourth demonstration, differences were observed between paced and native slow-wave amplitudes (0.24 +/- 0.08 vs. 0.38 +/- 0.14 mV; P < 0.001), velocities (6.2 +/- 2.8 vs. 11.5 +/- 4.7 mm/s; P < 0.001), and activated areas (20.6 +/- 1.9 vs. 32.8 +/- 2.6 cm(2); P < 0.001). Entrainment mapping enables an accurate quantification of the effects of gastric pacing on slow-wave activity, offering an improved method to assess whether pacing protocols are likely to achieve physiologically and clinically useful outcomes.
A theoretical model is developed to study the dynamic response of the respiratory system using Weibel symmetric model based on the acoustic wave approach. Both rigid and compliant walls with rigid and compliant termination are investigated separately. For each case the response (normalised input impedance against prorogation frequency) is examined for occlusion at each generation from alveolar sacs up to the distal end of the trachea systematically.
A theoretical model is developed to study the dynamic response of the respiratory system using Weibel symmetric model based on the acoustic wave approach. Both rigid and compliant walls with rigid and compliant termination are investigated separately. For each case the response (normalised input impedance against prorogation frequency) is examined for occlusion at each generation from alveolar sacs up to the distal end of the trachea systematically.
Respiratory disorders are common in both developed and developing countries. Many of these disorders are directly connected to constrictions in the airways of the human respiratory system. Asthma and bronchitis are typical examples that arise from the constriction of airways. The respiratory system consists of a series of branching tubes which become narrower, shorter and more numerous as they penetrate deeper into the lung. This branching network found within the multiple succussive bifurcation of the pulmonary tree has received theoretical attention [1]. Several attempts have been made to investigate the characteristics of healthy and unhealthy lungs. Some of them theoretical [2–5] while others are experimental [6,7]. The acoustical approach has been considered as one of the leading theoretical approaches to date. This approach is based on linking the acoustical impedance between the branches by using recursive formulae [2]. None of the available references has investigated the effect of occlusions in a branch on the behaviour of the whole respiratory system. Further, the work reported on the dynamic modelling of the respiratory system has overlooked, with the exception of [5], mechanical and physical properties of the airway walls, which are believed to have a considerable impact on the overall dynamics of the system.
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