A comparison of pulse oximetry and laser Doppler flowmetry in monitoring sequential vascular occlusion in a rabbit ear model

Abstract

The ultimate success of any free flap transfer depends not only on the experience of the given surgical team, but also requires constant vigilance in the perioperative period to assure continued anastomotic patency. Clinical acumen remains the 'industry' standard, but adjunctive monitoring devices are important to reinforce these subjective evaluations. We routinely use laser Doppler flowmetry in spite of known drawbacks, including expense. On the other hand, we know that pulse oximetry is a possible and readily available alternative. The efficacy of these two monitoring systems was directly compared in a New Zealand white rabbit central artery and vein ear model. Arterial occlusion was immediately recognized by a precipitous drop in flow and oxygen saturation (SaO 2 ). A rapid drop in flow after venous occlusion with a trend to zero was also noted with laser Doppler flowmetry. The SaO 2 had a very slow but steady gradual decline, but values remained in the range of normoxemia for a prolonged time. Because a minimum threshold of SaO 2 for predicting venous occlusion was elusive, the usefulness of pulse oximetry for monitoring microsurgical composite tissue transfers is limited.

Comparison of NIRS, laser Doppler flowmetry, photoplethysmography, and pulse oximetry during vascular occlusion challenges

“…The results from SpO 2 measurements are not surprising and they align with previous reported results (Hallock andRice 2003, Shafique et al 2012) However, our methodologies differ as we used intermittent occlusions separately and not increasing the occlusion pressure gradually in one single measurements. Even though the occlusions were short, this allowed us to investigate the different responses to different occlusions.…”

“…Our results confirm that significant changes in SpO 2 during venous occlusion were observed in both commercial and custom-made pulse oximeters. However, these changes are still within the normoxic range (100-96%) and tolerance range of pulse oximeters (±2 -3%), making difficult to distinguish venous occlusion from baseline values (Hallock and Rice 2003). Noteworthy changes in SpO 2 were observed only at 100 mmHg, whereas the pulse oximeters failed during both systolic and over-systolic pressure.…”

“…The parameter is calculated as the ratio of the ac component over the dc component (ac/dc) and is believed to assess the adequacy of perfusion (Lima and Bakker 2005). NIRS, LDF, PPG, and PO have been investigated singularly or in pairs, during a vascular occlusion test (VOT), in their ability to indicate changes in perfusion, oxygenation, or to differentiate between healthy and diseased (Galla et al 1999, Yuen and Fend 2000, Hallock and Rice 2003, Jarm et al 2003, Klaessens et al 2003, Gomez et al 2008, Bergkvist et al 2015. However, the results from singular studies are scattered due to different studies methodologies, applications, or populations investigated.…”

Methods of ex vivo analysis of tissue status in vascularized composite allografts

“…For this reason, methods to assess VCA tissue leverage flow dynamics to quantify microcirculation [ 136 , 137 ]. Laser Doppler imaging (LDI) has been used to dynamically visualize vasculature, blood flow, and perfusion in superficial tissues [ 138 , 139 ]. In a rat hind limb free flap transplant model, the method has been used to visualize tissue perfusion to diagnose vascular stenosis in VCA in vivo .…”

Correlation between retinal oxygen saturation and the haemodynamic parameters of the ophthalmic artery in healthy subjects

“…Secondly, there are no data up to now as to what extent the retinal oximetry measurement is influenced by the haemodynamic parameters of the ophthalmic artery circulation. Peripheral blood flow and blood oxygenation level are tightly coupled as shown in studies combining laser Doppler flowmetry with pulse oximetry during vascular occlusion challenges, both in the animal model (Hallock & Rice 2003 ) and in healthy individuals (Abay & Kyriacou 2016 ). In the ocular vessels, blood flow velocity and vascular resistance can be measured non‐invasively using the ultrasound colour Doppler imaging (CDI) of the ophthalmic artery.…”