pO2 measurements by phosphorescence quenching: characteristics and applications of an automated system

Kerger, Heinz; Groth, Gesine; Kalenka, Armin; Vajkoczy, Peter; Tsai, Amy G.; Intaglietta, Marcos

doi:10.1016/s0026-2862(02)00027-4

Cited by 70 publications

(82 citation statements)

References 22 publications

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“…Resultant time constants were applied to the Stern-Volmer equation to calculate PO 2, where the quenching constant and the phosphorescence lifetime in the absence of oxygen measured are 325 mmHg/s and 600 s, respectively. The phosphorescence decay due to quenching at a specific PO 2 yields a single decay constant, and in vitro calibration is valid for in vivo measurements (13).…”

Section: Methodsmentioning

confidence: 99%

Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons

Cabrales¹,

Tsai²,

Frangos³

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

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Intaglietta. Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons. Am J Physiol Heart Circ Physiol 287: H320 -H330, 2004; 10.1152/ajpheart.01166.2003.-The oxygen transport capacity of fluorocarbons was investigated in the hamster chamber window model microcirculation to determine the rate at which oxygen is delivered to the tissue in conditions of extreme hemodilution [hematocrit (Hct) 11%]. Hydroxyethlyl starch (HES 200; 200 kDa molecular mass) was used as a plasma expander for two isovolemic hemodilutions performed with 10% HES 200 until a Hct of 65%. A third step reduced the Hct to 75% of baseline and was performed with either HES 200 or a 60% perfluorocarbon (PFC) emulsion. Comparisons of HES 200-only-hemodiluted animals versus 4.2 g/kg PFC emulsion-hemodiluted animals were made at 21% and 100% normobaric oxygen ventilation. It was found that systemic and microvascular oxygen delivery was 25% and 400% higher in the PFC animals compared with HES 200 animals, respectively, showing that PFCs deliver oxygen to the tissue when combined with hyperoxic ventilation in the present experiments, with no evidence of vasoconstriction or impaired microvascular function. Oxygen ventilation (100%) led to a positive base excess for the PFC group (5.5 Ϯ 2.5 mmol/l) versus a negative balance (Ϫ0.8 Ϯ 1.4 mmol/l) for the HES 200 group, suggesting that microvascular findings corresponded to systemic events. hyperoxia; functional capillary density; oxygen-carrying capacity; blood substitutes; tissue oxygen delivery THE CORRECTION OF BLOOD LOSSES usually begins with the normalization of blood volume. The continued decrease of red blood cell (RBC) concentration is followed by the restoration of oxygen-carrying capacity. To date, this latter phase remains firmly within the purvey of blood transfusion medicine; however, alternative oxygen-carrying volume fluids such as modified hemoglobins (Hbs) and fluorocarbons have emerged in the past decade. Few of these materials have been objectively analyzed in terms of their transport properties at the level of the microscopic blood vessels, where the actual exchange of oxygen takes place, to determine if their properties lead to adequate transport processes at the cellular/tissue level (8).Fluorocarbons have been investigated by different approaches that extended to phase 3 clinical trials (9). These materials carry oxygen, are synthetic, and, in principle, are available in very large quantities at modest costs. This has tantalized investigators, medical practitioners, and business enterprises, because it could, in principle, lead to a convenient, largely available, and pathogen-free oxygen carrier. However, fluorocarbons only become miscible with water when emulsified with phospholipids (derived from egg yolk) and therefore are not completely synthetic. Furthermore, whereas Hb carries oxygen via a reversible chemical reaction, fluorocarbons carry oxygen as a function of their solubility; therefore, at the PO 2 s prevailing in the microcirc...

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Section: Methodsmentioning

confidence: 99%

Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons

Cabrales¹,

Tsai²,

Frangos³

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

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“…High-resolution noninvasive microvascular PO2 measurements were made by phosphorescence quenching microscopy (PQM) (23,42). PQM is based on the oxygendependent quenching of phosphorescence emitted by albumin-bound metalloporphyrin complex after pulsed light excitation.…”

Section: Blood Flow (Q) Was Calculated From the Measured Values As Q mentioning

confidence: 99%

“…PQM is independent of the dye concentration within the tissue and is well suited for detecting hypoxia because its decay time is inversely proportional to PO 2 level, causing the method to be more precise at low PO2 levels. This technique is used to measure both intravascular and extravascular PO 2 since the albumin-dye complex continuously extravasates the circulation into the interstitial tissue (23,42). Tissue PO2 was measured in tissue regions between functional capillaries.…”

Section: Blood Flow (Q) Was Calculated From the Measured Values As Q mentioning

confidence: 99%

Effects of erythrocyte flexibility on microvascular perfusion and oxygenation during acute anemia

Cabrales¹

2007

American Journal of Physiology-Heart and Circulatory Physiology

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Cabrales P. Effects of erythrocyte flexibility on microvascular perfusion and oxygenation during acute anemia. Am J Physiol Heart Circ Physiol 293: H1206-H1215, 2007. First published April 20, 2007; doi:10.1152/ajpheart.00109.2007.-Responses to exchange transfusion using red blood cells (RBCs) with normal and reduced flexibility were studied in the hamster window chamber model during acute moderate isovolemic hemodilution to determine the role of RBC membrane stiffness in microvascular perfusion and tissue oxygenation. Erythrocyte stiffness was increased by 30-min incubation in 0.02% glutaraldehyde solution, and unreacted glutaraldehyde was completely removed. Filtration pressure through 5-m pore size filters was used to quantify stiffness of the RBCs. Anemic conditions were induced by two isovolemic hemodilution steps using 6% 70-kDa dextran to a hematocrit (Hct) of 18% (moderate hemodilution). The protocol continued with an exchange transfusion to reduce native RBCs to 75% of baseline (11% Hct) with either fresh RBCs (RBC group) or reduced-flexibility RBCs (GRBC group) suspended in 5% albumin at 18% Hct; a plasma expander (6% 70-kDa dextran; Dex70 group) was used as control. Systemic parameters, microvascular perfusion, capillary perfusion [functional capillary density (FCD)], and oxygen levels across the microvascular network were measured by noninvasive methods. RBC deformability for GRBCs was significantly decreased compared with RBCs and moderate hemodilution conditions. The GRBC group had a greater mean arterial blood pressure (MAP) than the RBC and Dex70 groups. FCD was substantially higher for RBC (0.81 Ϯ 0.07 of baseline) vs. GRBC (0.32 Ϯ 0.10 of baseline) and Dex70 (0.38 Ϯ 0.10 of baseline) groups. Microvascular tissue PO2 was significantly lower for Dex70 and GRBC vs. RBC groups and the moderate hemodilution condition. Results were attributed to decreased oxygen uploading in the lungs and obstruction of tissue capillaries by rigidified RBCs, indicating that the effects impairing RBC flexibility are magnified at the microvascular level, where perfusion and oxygenation may define transfusion outcome.

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“…The resonator has advanced automatching and autotuning capabilities that correct for any slight animal movements. The EPR spectrum was acquired with a scan time of 30 s, and usually 10 scans were obtained and averaged to produce a signal-to-noise ratio of at least 5 (but typically [10][11][12][13][14][15][16][17][18][19][20], which allowed accurate fitting. The peak-to-peak line width of the spectrum was obtained via computer line-fitting, and converted to pO 2 values according to a calibration curve for the oximetry probe LiPc used in the study (see the following paragraph).…”

Section: Measurement Of Cerebral Po 2 By Epr Oximetry With Particulatmentioning

confidence: 99%

“…6 Although an adequate cerebral oxygen level is critical to neuron survival, monitoring oxygen levels in this tissue, in vivo and in real time, remains a technical challenge, especially in deeper tissue or for repetitive measurements. Several techniques can be used for oxygen level measurement including Clark-type electrodes 7 and fluorescence quenching (Oxylite) 8,9 for tissue oxygenation, phosphorescence quenching 10 and near-infrared spectroscopy 11 for blood oxygenation, 19 F MRI 12 and EPR oximetry with a particulate probes. Among these methods, EPR oximetry with particulate probes has several advantages, especially for the repetitive and highly accurate measurement of localized interstitial (or tissue) pO 2 .…”

Section: Introductionmentioning

confidence: 99%

Application of in vivo EPR in brain research: monitoring tissue oxygenation, blood flow, and oxidative stress

et al. 2004

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Although oxygen levels are critical to tissue survival, monitoring tissue oxygen levels in vivo, in real time, remains a technical challenge. This is especially so for repetitive measurements in non-superficial tissue. There currently exist several techniques that can be utilized for tissue oxygen measurement, but technical difficulties have limited their usefulness and general application. Here we describe a relatively new method, electron paramagnetic resonance (EPR) oximetry, for in vivo measurement of brain tissue oxygen, as well as information on blood flow and oxidative stress. In this paper we report experiments designed to assess and illustrate the effectiveness of this new method. Using the unique capability of this approach, we have measured both absolute values and temporal changes of pO 2 in ischemic penumbra and core during cerebral ischemia and reperfusion in a rat model. EPR oximetry with particulate probe sensitively reflected differential changes in oxygenation in the core and penumbra during ischemia, reperfusion and also hyperoxic conditions. Simultaneous two-site detection with particulate probes was also obtained with good spatial resolution. Additionally, EPR measurement of oxidative stress, EPR imaging of brain with nitroxide and triarylmethyl soluble probes are also described. These results demonstrate that EPR oximetry with particulate probe can provide accurate and reproducible measurements of localized pO 2 in the brain, and it is a versatile and useful method in the measurement of tissue pO 2 under a variety of physiological and pathophysiological conditions.

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pO2 measurements by phosphorescence quenching: characteristics and applications of an automated system

Cited by 70 publications

References 22 publications

Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons

Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons

Effects of erythrocyte flexibility on microvascular perfusion and oxygenation during acute anemia

Application of in vivo EPR in brain research: monitoring tissue oxygenation, blood flow, and oxidative stress

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