The Effect of Ischaemic Preconditioning on Right Ventricular Function During Exercise in Hypoxia

Abstract

Exercise in hypoxia causes severe arterial hypoxemia. The acute cardiovascular responses include increases in heart rate (HR), cardiac output, and sympathetic nervous system activation. In the pulmonary system, hypoxia induces a rise in pulmonary arterial systolic pressure (PASP), but right ventricular (RV) systolic function is maintained. The rise in PASP improves the matching of perfusion to ventilation, but it creates a greater afterload for the RV. For this reason it may be partly responsible for the performance decrements reported at altitude. Whilst it is known that ischaemic preconditioning (IPC) can attenuate the hypoxic rise in PASP, it is not known whether it will reduce PASP during exercise in hypoxia or improve RV function. The aim of this present study was to assess RV function during exercise in hypoxia, and to ascertain whether IPC has the potential to reduce PASP or improve RV function. 3 healthy males (mean ± SD; aged 23 ± 4.93 years, height 173 ± 0.35 cm and body mass 66.6 ± 10.46 Kg) visited the laboratory on three separate occasions, and echocardiographic measurements were taken at rest and exercise in the following conditions: baseline normoxia, hypoxia, normoxia following IPC and hypoxia following IPC. RV areas, PASP and tricuspid annular plane systolic excursion were measured using echocardiography, whilst heart rate, blood pressure and arterial oxygen saturation (SpO2) were monitored and recorded throughout. Hypoxic exercise resulted in rises in PASP and decreases in SpO2, but it was inconclusive whether RV systolic function was maintained. IPC did not attenuate the hypoxic rise in PASP for all participants at rest or during exercise; neither did it improve RV systolic function nor oxygen delivery in hypoxia. It was concluded that the modest effect of IPC was not sufficient to improve RV function during exercise in hypoxia.