Evaluation of a novel wireless near-infrared spectroscopy (NIRS) device in the detection of tourniquet induced ischaemia

© Author(s) (or their employer(s)) 2022. No commercial reuse. See rights and permissions. Published by BMJ. INTRODUCTION Acute limb ischaemia is a vascular emergency threatening both life and limb, with estimated mortality rates of 9%–22%, and 30day extremity amputation rates of 10%–30%. 3 Timely identification of the acutely ischaemic limb is pivotal. Conventional methods of assessing limb ischaemia rely on repeated clinical examination, serial assessment of Doppler signals and imaging technology such as duplex ultrasound, digital subtraction angiography, CT angiography and MR angiography. While able to assess arterial compromise, these technologies are limited as they provide data for only a single time point, and imaging modalities are high in cost and low in portability. The ability to noninvasively and continually monitor for limb ischaemia could enable identification of compromised tissue earlier, prompting faster revascularisation and reducing complications associated with prolonged ischaemia. A growing interest in the role of the microcirculation in tissue perfusion has led to the use of nearinfrared spectroscopy (NIRS) devices in the evaluation of limb ischaemia. 6 NIRS is a noninvasive spectroscopy method of obtaining regional tissue oxygen saturation (StO 2 ), using light wavelengths in the red and nearred range of the spectrogram. NIRSbased devices can reliably identify the ratio of oxygenated haemoglobin (HbO 2 ) and deoxyhaemoglobin (HHb) present in tissue, and as such are able to determine oxygen desaturation associated with limb ischaemia. 8 A number of commercial devices are available for clinical use. Some current limitations around using existing NIRS devices are cost and bulk around the patient bedspace. As such, they are rarely used outside the operating theatre and intensive care unit settings, where patients are relatively immobile and low nurse:patient ratios make the management of multiple wired devices in the bed space feasible for staff. The aims of this prospective study were: 1. To evaluate the feasibility of using a novel, wireless NIRS device in detecting tissue StO 2 in a tourniquetinduced model of limb ischaemia in healthy volunteers. Summary box