Abstract
We have previously demonstrated that changes in preload will influence mitral flow (QM) prior to changes in aortic flow (QA), while a change in afterload will influence QA first. During spontaneous unobstructed inspiration and Mueller maneuvers, QA is minimum during inspiration and reaches a maximum in early expiration. We tested whether primary changes in QM or QA were dominantly responsible for the observed respiratory variation in QA. In 7 acutely instrumented dogs, we placed both mitral and ascending aortic flow probes, closed the pericardium and chest and allowed spontaneous respiration to resume. We evaluated preload (QM) or afterload (QA) dominance by measuring which integrated flow reached its' inspiratory minimum or expiratory maximum first during a single respiratory cycle.
These data suggest that while an afterload influence does exist, preload changes dominate over afterload changes in determining changes in LV stroke volume during respiration under our experimental conditions with small changes in pleural pressure with or without a change in lung volume.
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Robotham, J., Stuart, R., Borkon, A. et al. 131 PHASIC MITRAL FLOW DURING SPONTANEOUS RESPIRATION. Pediatr Res 19, 132 (1985). https://doi.org/10.1203/00006450-198504000-00161
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DOI: https://doi.org/10.1203/00006450-198504000-00161