Impact of Incremental Perfusion Loss on Oxygen Transport in a Capillary Network Mathematical Model

Fraser, Graham M.; Sharpe, Michael D.; Goldman, Daniel; Ellis, Christopher G.

doi:10.1111/micc.12202

Cited by 11 publications

(15 citation statements)

References 31 publications

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“…This is consistent with prior studies that noted vasopressor use was a better surrogate for microvascular injury than MAP or cardiac index [36]. MHC power was lower for patients receiving vasopressors, and may reflect reduced oxygen delivery consistent with computational models [50]. The relationship between systemic hemodynamics and the microcirculation is disrupted in critical illness [51], and disparities often exist between macrohemodynamics and the degree of microvascular injury [37,52].…”

Section: Discussionsupporting

confidence: 86%

Dynamic tracking of microvascular hemoglobin content for continuous perfusion monitoring in the intensive care unit: pilot feasibility study

Mendelson

Rajaram

Bainbridge

et al. 2020

J Clin Monit Comput

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Purpose: There is a need for bedside methods to monitor oxygen delivery in the microcirculation. Near-infrared spectroscopy commonly measures tissue oxygen saturation, but does not reflect the time-dependent variability of microvascular hemoglobin content (MHC) that attempts to match oxygen supply with demand. The objective of this study is to determine the feasibility of MHC monitoring in critically ill patients using high-resolution near-infrared spectroscopy to assess perfusion in the peripheral microcirculation. Methods: Prospective observational cohort of 36 patients admitted within 48 h at a tertiary intensive care unit. Perfusion was measured on the quadriceps, biceps, and/or deltoid, using the temporal change in optical density at the isosbestic wavelength of hemoglobin (798 nm). Continuous wavelet transform was applied to the hemoglobin signal to delineate frequency ranges corresponding to physiological oscillations in the cardiovascular system. Results: 31/36 patients had adequate signal quality for analysis, most commonly affected by motion artifacts. MHC signal demonstrates inter-subject heterogeneity in the cohort, indicated by different patterns of variability and frequency composition. Signal characteristics were concordant between muscle groups in the same patient, and correlated with systemic hemoglobin levels and oxygen saturation. Signal power was lower for patients receiving vasopressors, but not correlated with mean arterial pressure. Mechanical ventilation directly impacts MHC in peripheral tissue. Conclusion: MHC can be measured continuously in the ICU with high-resolution near-infrared spectroscopy, and reflects the dynamic variability of hemoglobin distribution in the microcirculation. Results suggest this novel hemodynamic metric should be further evaluated for diagnosing microvascular dysfunction and monitoring peripheral perfusion.

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Section: Discussionsupporting

confidence: 86%

Dynamic tracking of microvascular hemoglobin content for continuous perfusion monitoring in the intensive care unit: pilot feasibility study

Mendelson

Rajaram

Bainbridge

et al. 2020

J Clin Monit Comput

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“…This redistribution results in a more uniform distribution of RBCs among perfused capillaries and reduces the heterogeneity of capillary hematocrits and supply rates . Less heterogeneity of RBC supply rate is sufficient to maintain tissue oxygenation as O 2 consumption rates increase, without the need for increased capillary density. De‐recruitment of perfused capillaries also occurs if the IVVM preparation is exposed to elevated O 2 levels or to pathological conditions such as sepsis …”

Section: Discussionmentioning

confidence: 99%

Hyperinsulinemia does not cause de novo capillary recruitment in rat skeletal muscle

et al. 2019

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Objective The effect of insulin on blood flow distribution within muscle microvasculature has been suggested to be important for glucose metabolism. However, the “capillary recruitment” hypothesis is still controversial and relies on studies using indirect contrast‐enhanced ultrasound (CEU) methods. Methods We studied how hyperinsulinemia effects capillary blood flow in rat extensor digitorum longus (EDL) muscle during euglycemic hyperinsulinemic clamp using intravital video microscopy (IVVM). Additionally, we modeled blood flow and microbubble distribution within the vascular tree under conditions observed during euglycemic hyperinsulinemic clamp experiments. Results Euglycemic hyperinsulinemia caused an increase in erythrocyte (80 ± 25%, P < .01) and plasma (53 ± 12%, P < .01) flow in rat EDL microvasculature. We found no evidence of de novo capillary recruitment within, or among, capillary networks supplied by different terminal arterioles; however, erythrocyte flow became slightly more homogenous. Our computational model predicts that a decrease in asymmetry at arteriolar bifurcations causes redistribution of microbubble flow among capillaries already perfused with erythrocytes and plasma, resulting in 25% more microbubbles flowing through capillaries. Conclusions Our model suggests increase in CEU signal during hyperinsulinemia reflects a redistribution of arteriolar flow and not de novo capillary recruitment. IVVM experiments support this prediction showing increases in erythrocyte and plasma flow and not capillary recruitment.

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“…Further advances were made by Japee et al, who extended the analysis to full frame images, instead of being limited to single pixel line . Many recent animal studies have relied on these methods to make measurements of SO 2 for their studies …”

Section: Introductionmentioning

confidence: 99%

Using digital inpainting to estimate incident light intensity for the calculation of red blood cell oxygen saturation from microscopy images

Sové

Drakos

Fraser

et al. 2018

Journal of Biophotonics

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Red blood cell oxygen saturation (SO ) is an important indicator of oxygen supply to tissues in the body. SO can be measured by taking advantage of spectroscopic properties of hemoglobin. When this technique is applied to transmission microscopy, the calculation of saturation requires determination of incident light intensity at each pixel occupied by the red blood cell; this value is often approximated from a sequence of images as the maximum intensity over time. This method often fails when the red blood cells are moving too slowly, or if hematocrit is too large since there is not a large enough gap between the cells to accurately calculate the incident intensity value. A new method of approximating incident light intensity is proposed using digital inpainting. This novel approach estimates incident light intensity with an average percent error of approximately 3%, which exceeds the accuracy of the maximum intensity-based method in most cases. The error in incident light intensity corresponds to a maximum error of approximately 2% saturation. Therefore, though this new method is computationally more demanding than the traditional technique, it can be used in cases where the maximum intensity-based method fails (eg, stationary cells), or when higher accuracy is required.

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Impact of Incremental Perfusion Loss on Oxygen Transport in a Capillary Network Mathematical Model

Cited by 11 publications

References 31 publications

Dynamic tracking of microvascular hemoglobin content for continuous perfusion monitoring in the intensive care unit: pilot feasibility study

Dynamic tracking of microvascular hemoglobin content for continuous perfusion monitoring in the intensive care unit: pilot feasibility study

Hyperinsulinemia does not cause de novo capillary recruitment in rat skeletal muscle

Using digital inpainting to estimate incident light intensity for the calculation of red blood cell oxygen saturation from microscopy images

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