Search

Microvascular impairments are typical of several cardiovascular diseases. Near-infrared spectroscopy (NIRS) combined with a vascular occlusion test provides non-invasive insights into microvascular responses by monitoring skeletal muscle oxygenation changes during reactive hyperaemia. Despite increasing interest in the effects of sex and ageing on microvascular responses, evidence remains inconsistent. Therefore, the present study aimed to investigate the effects of sex and age on microvascular responsiveness. Twenty-seven participants (seven young men and seven young women; seven older men and six older women; aged 26 ± 1, 26 ± 4, 67 ± 3 and 69 ± 4 years, respectively) completed a vascular occlusion test consisting of 5 min of arterial occlusion followed by 5 min reperfusion. Oxygenation changes in the vastus lateralis were monitored by near-infrared spectroscopy. The findings revealed that both women (referring to young and older women) and older participants (referring to both men and women) exhibited lower microvascular responsiveness. Notably, both women and older participants demonstrated reduced desaturation (-38% and -59%, respectively) and reperfusion rates (-24% and -40%, respectively) along with a narrower range of tissue oxygenation (-39% and -39%, respectively) and higher minimal tissue oxygenation levels (+34% and +21%, respectively). Women additionally displayed higher values in resting (+12%) and time-to-peak (+15%) tissue oxygenation levels. In conclusion, this study confirmed decreased microvascular responses in women and older individuals. These results emphasize the importance of considering sex and age when studying microvascular responses. Further research is needed to uncover the underlying mechanisms and clinical relevance of these findings, enabling the development of tailored strategies for preserving vascular health in diverse populations., (© 2024 The Authors. Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

New Findings: What is the central question of this study? The role of the cerebral haemodynamic response to either normobaric or hypobaric hypoxia in people susceptible to acute mountain sickness (AMS) is still under debate. Prefrontal cortex near-infrared spectroscopy-derived parameters were monitored in normobaric hypoxia at rest and during moderate-intensity exercise in AMS-prone and non-AMS individuals. What is the main finding and its importance? The AMS-prone individuals did not increase microvascular blood volume and showed lower prefrontal cerebral oxygenation in normobaric hypoxia both at rest and during exercise compared with non-AMS subjects, suggesting that these changes might underpin later development of AMS at altitude., Abstract: The aim of this study was to evaluate changes in prefrontal cerebral oxygenation and microvascular blood volume during exercise in normobaric hypoxia and to investigate possible associations with the occurrence of acute mountain sickness (AMS) at altitude. Twenty-two healthy individuals (age, 26 ± 4 years; peak oxygen uptake, 42 ± 4 ml kg -1  min -1 ) were tested in two different conditions: normoxia (NORM) and normobaric hypoxia (fraction of inspired O 2  = 0.13; HYPO). Data were collected at rest and during submaximal constant-speed exercise. The peripheral oxyhaemoglobin saturation was measured by finger pulse oximeter. Changes in prefrontal cerebral oxygenation (ΔHbO 2 ), deoxygenation (ΔHHb) and microvascular blood volume (ΔHb tot ) were obtained by near-infrared spectroscopy. Within 2 weeks after laboratory testing, subjects rapidly ascended to 3647 m a.s.l., and AMS was evaluated using the Lake Louise scale. Eight subjects were AMS + , whereas 14 were AMS - . During NORM, near-infrared spectroscopy variables did not change from baseline values both at rest and during exercise, with similar results in AMS + and AMS - subjects. During HYPO, ΔHHb increased to a similar extent in both groups, both at rest and during exercise. The ΔHbO 2 was significantly less in AMS + compared with AMS - subjects, both at rest [-3.23 ± 5.90 versus 1.44 ± 2.14 μm, P = 0.04, effect size (ES) = 1.1, respectively] and during exercise (-6.56 ± 5.51 versus 0.37 ± 4.36 μm, P < 0.01, ES = 1.2, respectively). Total haemoglobin did not change from baseline, both at rest (-1.67 ± 9.53 μm) and during exercise (-0.96 ± 9.12 μm) in AMS + subjects, which was significantly different from the AMS - group (5.49 ± 3.99 μm, P = 0.03, ES = 1.0 and 8.17 ± 7.34 μm, P = 0.02, ES = 1.0, respectively). Individuals prone to AMS seem to be unable to increase microvascular blood volume and to maintain oxygenation at the cerebral level during exercise in acute normobaric hypoxia, suggesting that these changes might underpin later development of AMS., (© 2020 The Authors. Experimental Physiology © 2020 The Physiological Society.)