Elderly participants had a slower rate of oxygen recovery than young participants (1.5 vs 2.5 %/s) during a 5-min occlusion, but responses were similar when tissue ischaemia levels were matched.
Cross-Sectional
Does age affect NIRS-derived post-occlusion tissue oxygen saturation recovery kinetics when controlling for tissue ischemia?
NIRS is a promising tool for evaluating microvascular function, but assessing and matching tissue ischemia during cuff occlusion is essential to avoid confounding age-related differences.
Absolute Event Rate: 1.5% vs 2.5%
New Findings What is the central question of this study? Can near‐infrared spectroscopy (NIRS)‐derived post‐occlusion tissue oxygen saturation recovery kinetics be used to study age‐related impairments in microvascular function? What is the main finding and its importance? Using a previously established 5 min cuff occlusion protocol, we found that NIRS‐derived indices of microvascular function were markedly reduced in elderly compared with young participants. However, when we controlled for the absolute level of vasodilatory stimulus and matched the tissue desaturation level between groups, we found similar responses in young and elderly participants. Overall, these data highlight the important role NIRS can serve in clinical vascular biology, but also establish the need for assessing tissue ischaemia during cuff occlusion protocols. Near‐infrared spectroscopy (NIRS) has emerged as a promising tool to evaluate vascular reactivity in vivo . Whether this approach can be used to assess age‐related impairments in microvascular function has not been tested. Tissue oxygen saturation ( ) post‐occlusion recovery kinetics were measured in two distinct age groups (65 years of age) using NIRS placed over the flexor digitorum profundus. Key end‐points included the following: (i) the desaturation rate during cuff occlusion; (ii) the lowest value obtained during ischaemia ( ); (iii) reperfusion rate; (iv) the highest value reached after cuff release ( ); and (v) the reactive hyperaemia area under the curve (AUC). At first, using a conventional 5 min cuff occlusion protocol, the elderly participants achieved a much slower rate of oxygen recovery (1.5 ± 0.2 versus 2.5 ± 0.2% s −1 ), lower (85.2 ± 2.9 versus 92.3 ± 1.5%) and lower reactive hyperaemia AUC (2651.8 ± 307.0 versus 4940.0 ± 375.8% s −1 ). However, owing to a lower skeletal muscle resting metabolic rate, was also significantly attenuated in the elderly participants compared with the young control subjects (55.7 ± 3.5 versus 41.0 ± 3.4%), resulting in a much lower ischaemic stimulus. To account for this important difference between groups, we then matched the level of tissue ischaemia in a subset of young healthy participants by reducing the cuff occlusion protocol to 3 min. Remarkably, when we controlled for tissue ischaemia, we observed no differences in any of the hyperaemic end‐points between the young and elderly participants. These data highlight the important role NIRS can serve in vascular biology, but also establish the need for assessing tissue ischaemia during cuff occlusion protocols.
Rosenberry et al. (Wed,) conducted a cross-sectional in Age-related microvascular dysfunction. 5 min cuff occlusion protocol vs. Young participants (<35 years) was evaluated on Rate of oxygen recovery (% s-1). Elderly participants had a slower rate of oxygen recovery than young participants (1.5 vs 2.5 %/s) during a 5-min occlusion, but responses were similar when tissue ischaemia levels were matched.