Oxygen delivery and haemoglobin

McLellan, Stuart; Walsh, Timothy

doi:10.1093/bjaceaccp/mkh033

Cited by 100 publications

(83 citation statements)

References 3 publications

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“…If we indicate with [O 2 ] in and [O 2 ] out the upstream and downstream concentrations of oxygen in the blood, the rate of oxygen extraction (Ȯ 2 ) from a capillary can be expressed as the product of the convective inflow of oxygen (σ c ( c ) [O 2 ] in , where σ is the cross sectional area of the blood vessel and c ( c ) is the speed of blood flow in the capillary) times the oxygen extraction factor {([O 2 ] in − [O 2 ] out )/[O 2 ] in }. Because 97–98% of the oxygen in blood is bound to hemoglobin [McLellan and Walsh, 2004; Guyton and Hall, 2011 (Ch. 40)], [O 2 ] in ~ 4 S in ctHb, where S in is the saturation of incoming blood, ctHb is the total hemoglobin concentration in blood, and the factor 4 takes into account the four binding sites for oxygen of hemoglobin.…”

Section: Hemodynamic Modelmentioning

confidence: 99%

Dynamic model for the tissue concentration and oxygen saturation of hemoglobin in relation to blood volume, flow velocity, and oxygen consumption: Implications for functional neuroimaging and coherent hemodynamics spectroscopy (CHS)

2014

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This article presents a dynamic model that quantifies the temporal evolution of the concentration and oxygen saturation of hemoglobin in tissue, as determined by time-varying hemodynamic and metabolic parameters: blood volume, flow velocity, and oxygen consumption. This multi-compartment model determines separate contributions from arterioles, capillaries, and venules that comprise the tissue microvasculature, and treats them as a complete network, without making assumptions on the details of the architecture and morphology of the microvascular bed. A key parameter in the model is the effective blood transit time through the capillaries and its associated probability of oxygen release from hemoglobin to tissue, as described by a rate constant for oxygen diffusion. The solution of the model in the time domain predicts the signals measured by hemodynamic-based neuroimaging techniques such as functional near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI) in response to brain activation. In the frequency domain, the model yields an analytical solution based on a phasor representation that provides a framework for quantitative spectroscopy of coherent hemodynamic oscillations. I term this novel technique coherent hemodynamics spectroscopy (CHS), and this article describes how it can be used for the assessment of cerebral autoregulation and the study of hemodynamic oscillations resulting from a variety of periodic physiological challenges, brain activation protocols, or physical maneuvers.

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Section: Hemodynamic Modelmentioning

confidence: 99%

Dynamic model for the tissue concentration and oxygen saturation of hemoglobin in relation to blood volume, flow velocity, and oxygen consumption: Implications for functional neuroimaging and coherent hemodynamics spectroscopy (CHS)

2014

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“…In this context, the sO 2 information that we derived from this study has great significance in understanding the formation of PU. Normal tissue usually has an ERO 2 of 20% to 30% . However, we discovered that the I‐R tissue has a significantly higher ERO 2 (37.21 ± 10.62%) than normal tissue during reperfusion.…”

Section: Discussionmentioning

confidence: 71%

“…From the vascular sO 2 image, the local oxygen extraction ratio can be quantified. It is defined as :

{ERO}_{2} = \frac{{sO}_{2, a} - {sO}_{2, v}}{{italicsO}_{2, a}},

where ERO 2 represents extraction ratio of oxygen, sO 2, a and sO 2, v are the oxygen saturation of a pair of artery and vein, respectively. ERO 2 is a measure of the fraction of oxygen delivered to the microcirculation that is taken up by the tissues .…”

Section: Image Processingmentioning

confidence: 99%

In vivo label‐free functional photoacoustic monitoring of ischemic reperfusion

Dinish

Goh

et al. 2019

Journal of Biophotonics

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Pressure ulcer formation is a common problem among patients confined to bed or restricted to wheelchairs. The ulcer forms when the affected skin and underlying tissues go through repeated cycles of ischemia and reperfusion, leading to inflammation. This theory is evident by intravital imaging studies performed in immune cell–specific, fluorescent reporter mouse skin with induced ischemia‐reperfusion (I‐R) injuries. However, traditional confocal or multiphoton microscopy cannot accurately monitor the progression of vascular reperfusion by contrast agents, which leaks into the interstitium under inflammatory conditions. Here, we develop a dual‐wavelength micro electro mechanical system (MEMS) scanning–based optical resolution photoacoustic microscopy (OR‐PAM) system for continuous label‐free functional imaging of vascular reperfusion in an IR mouse model. This MEMS‐OR‐PAM system provides fast scanning speed for concurrent dual‐wavelength imaging, which enables continuous monitoring of the reperfusion process. During reperfusion, the revascularization of blood vessels and the oxygen saturation (sO2) changes in both arteries and veins are recorded, from which the local oxygen extraction ratios of the ischemic tissue and the unaffected tissue can be quantified. Our MEMS‐OR‐PAM system provides novel perspectives to understand the I‐R injuries. It solves the problem of dynamic label‐free functional monitoring of the vascular reperfusion at high spatial resolution.

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“…In an idealized model, global DO 2 is 1000 mL/min in normal patients, 505 mL/min in patients with anemia (hemoglobin 7.5 g/dL), and 585 mL/min in anemic patients on oxygen therapy. Anemia therefore results in a significant decrease in global DO 2 despite oxygen therapy 28. In a comparison between induced hypertension, fluid bolus, and red blood cell transfusion to augment cerebral oxygen delivery as detected by 15 O-PET imaging, although all therapies were shown to improve cerebral oxygen delivery, transfusion showed the greatest increase in cerebral DO 2 of 23% without impairing CBF compared with increases of 14% and 10% for induced hypertension and hypervolemia, respectively 29…”

Section: Discussionmentioning

confidence: 99%