Near-Infrared Spectroscopy During Reactive Hyperemia for the Assessment of Lower Limb Vascular Function

Summary

Here, we describe a non-invasive approach using near-infrared spectroscopy to assess reactive hyperemia in the lower limb. This protocol provides a standardized assessment of vascular and microvascular responsiveness that may be used to determine the presence of vascular dysfunction as well as the efficacy of therapeutic interventions.

Abstract

Vascular diseases of the lower limb contribute substantially to the global burden of cardiovascular disease and comorbidities such as diabetes. Importantly, microvascular dysfunction can occur prior to, or alongside, macrovascular pathology, and both potentially contribute to patient symptoms and disease burden. Here, we describe a non-invasive approach using near-infrared spectroscopy (NIRS) during reactive hyperemia, which provides a standardized assessment of lower limb vascular (dys)function and a potential method to evaluate the efficacy of therapeutic interventions. Unlike alternative methods, such as contrast-enhanced ultrasound, this approach does not require venous access or sophisticated image analysis, and it is inexpensive and less operator-dependent. This description of the NIRS method includes representative results and standard terminology alongside the discussion of measurement considerations, limitations, and alternative methods. Future application of this work will improve standardization of vascular research design, data collection procedures, and harmonized reporting, thereby enhancing translational research outcomes in the areas of lower limb vascular (dys)function, disease, and treatment.

Introduction

Cardiovascular disease (CVD) is the leading contributor to global mortality¹. While myocardial infarction and stroke are the most common manifestations of CVD, vascular diseases of the lower limbs, such as peripheral arterial disease (PAD) and diabetic foot disease, contribute substantially to the personal, social, and healthcare burden of CVD^2,3,4. Importantly, these disease states are characterized by microvascular and macrovascular dysfunction⁵ that contribute to symptoms (e.g., intermittent claudication), functional impairme....

Protocol

All methods described here have been approved by the human research ethics committee of the University of the Sunshine Coast. Furthermore, all participants gave their written informed consent to participate in the measurements outlined in this protocol. Please note, vascular occlusion testing in the lower limb is contra-indicated in individuals who have previously had a revascularization procedure involving a vascular graft or stenting of the femoral or popliteal arteries. After preparing the equipment, the participant is instructed to rest in a supine position for 10 min. At this point, NIRS data collection commences, with an initial 2 min period, allowing for stabil....

Results

Near-infrared spectroscopy
Continuous wave near-infrared spectroscopy devices measure relative changes in oxygenated (O₂Hb) and deoxygenated (HHb) hemoglobin, which reflect local O₂ delivery and utilization via light-emitting sources and photodetectors, set specific distances apart. Wavelengths of light between ~700 nm and 850 nm are emitted, corresponding with the peak absorbency of O₂Hb and HHb. Once near-infrared light has penetrated skeletal muscle, the s.......

Discussion

This article outlines standardized procedures for the assessment of lower limb reactive hyperemia using CW-NIRS TSI to evaluate microvascular function. This protocol has been refined by examination of cuff occlusion duration on response magnitude, NIRS test-retest reliability during reactive hyperemia, as well as the level of agreement between NIRS and other methods of microvascular evaluation such as contrast-enhanced ultrasound^23,24. A longer cuff-occlusion dur.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cuff Inflator Air Source	Hokanson	AG101 AIR SOURCE
Elastic Cohesive Bandage	MaxoWrap	18228-BL	For blocking out ambient light
OxySoft	Artinis	3.3.341 x64
PortaLite (NIRS)	Artinis	0302-00019-00
PortaSync MKII (Remote)	Artinis	0702-00860-00	For Marking milestones during measurement
Rapid Cuff Inflator	Hokanson	E20 RAPID CUFF INFLATOR
Thigh Cuff	Hokanson	CC17
Transpore Surgical Tape	3M	1527-1	For fixing probe to skin