In vivo assessment of peripheral vascular function by tcpo2 and skin blood flow modelling

Abstract

There are multiple techniques and methods to assess peripheral vascular function in vivo but not without limitations. More discriminative, sensitive and also practical evaluation strategies are needed to fully characterize the peripheral vascular function. In the present work, a new quantitative descriptor, the 'elimination half-life time' was developed from flow-related variables as a non-invasive microcirculatory rate parameter to describe vascular dynamics. Fifty-four healthy volunteers and six type 2 diabetic patients, both genders, were submitted to a dynamical procedure consisting in the inhalation of a 100% saturated atmosphere of oxygen for 10 min. The tcpO(2) and microcirculatory blood flow [Laser Doppler Flowmetry (LDF)] were measured in a randomly selected leg with a Periflux 5000 system before, during and after the procedure. A monocompartmental model was adjusted to tcpO(2) and LDF data. The tcpO(2) constant elimination rate, expressed as the Oxygen elimination half-life, was used as an indicator of the vulnerability of peripheral tissue and compared in healthy versus non-healthy individuals. Under normal conditions, the saturated ventilation increases the tissue's O(2) availability, as an expression of the natural capacity to adjust the tissue hemodynamics to new metabolical/perfusion conditions. Diabetic patients are expected to suffer vascular impairment and ischemia. Under O(2) overloading conditions, those hypoxic territories tend to uptake all the delivered oxygen, expressed as a significant increase in the O(2) elimination half-life. This approach allows to propose 'elimination half-life time' as the first quantitative descriptive parameter combining miogenic, hemodynamic and metabolic aspects of the microcirculatory physiology and to help to identify the individual's vascular vulnerability.

Combining laser-doppler flowmetry and photoplethysmography to explore in vivo vascular physiology

“…Proporciona redes vasculares acessíveis e a fácil aquisição de vários sinais biológicos através de técnicas não invasivas [2][3][4] . A fluxometria por laser Doppler (FLD) é a técnica mais bem conhecida usada com este propósito, apesar da fotopletismografia clás-sica ter vindo a ser recentemente revisitada [7,8] .…”

“…All the responses are recorded and quantified while the discriminative power of the technique is reinforced [2,3,5] . Some provocation tests induce systemic/regional changes in perfusion, such as the limb occlusion (post occlusive reactive hyperaemia) and the limb postural changes [4,5] , while others only act at local level (topical drug challenge) [6] . Experience about the simultaneous use of both LDF and PPG techniques is scarce, so that the usefulness of this combined assessment is not established.…”

“…It provides accessible vascular networks and the acquisition of several biological signals by noninvasive techniques [2][3][4] . Laser Doppler flowmetry (LDF) is the most wellknown technique used with that purpose, although the classical photoplethysmography is recently being revisited [7,8] .…”

Exploring the oxygen challenge test as a microcirculation evaluation model

“…A microcirculação cutânea tem sido usada como um sujeito especialmente prático e acessível para o estudo da circulação periférica [1,2] incluindo os mecanismos de disfunção vascular. [3][4][5] Tem sido ainda utilizada como um modelo de investigação em vários estados patológi-cos como a diabetes do tipo II, [6] a doença vascular periférica [1] e a hipertensão [7] .…”

“…Cutaneous microcirculation has been used as a very practical accessible subject for the study of the peripheral circulation [1,2] including vascular dysfunction mechanisms. [3][4][5] It has been used as a research model in various diseases such as type II diabetes [6] peripheral vascular disease [1] and hypertension.…”