THE EFFECT OF ACUTE NORMOBARIC HYPOXIA ON LEFT VENTRICULAR FUNCTION AT REST AND EXERCISE AND THE POTENTIAL IMPACT OF ISCHAEMIC PRECONDITIONING
Cardiff Metropolitan University
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Exposure to acute normobaric hypoxia induces an increased heart rate (HR) and stroke volume alongside a decrement in left ventricular end diastolic volume (LV EDV). Exercise is also a potent cardiovascular stressor, causing an increase in cardiac output (CO), HR and ventilation (VE). Ischaemic preconditioning (IPC) has cardiac protective effects against ischaemic insults such as myocardial infarctions and blunts the hypoxia induced rise in pulmonary artery systolic pressure (PASP). However, it is currently unknown whether IPC has any attenuating effect on the cardiac responses to hypoxia, specifically of the left ventricle. To investigate this 3 young, healthy males were examined in response to normoxic exercise, hypoxic rest and exercise both before, and after, a protocol of IPC. Sub-maximal exercise was performed on a supine ergometer at 1W.kg-1 bodyweight. IPC attenuated the hypoxia associated tachycardia effectively in participant 002, reducing HR by 17.50% at rest and 13.74% during exercise. IPC also caused LV EDV in hypoxia to return close to normoxic levels in participant 003, augmenting it by 26.84% and 32.43% at rest and exercise respectively. There were high levels of inter-participant variation in response to IPC throughout the study, as was evident in the high standard deviations. The use of IPC may be beneficial in reducing the negative impacts of hypoxia on HR, CO and LV EDV, however responses to it are highly individual.
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