Heterogeneity and Stability of Local PO2 Distribution within the Brain Tissue

Lübbers, D. W.; Baumgärtl, H.; Zimelka, W.

doi:10.1007/978-1-4615-2468-7_75

Cited by 51 publications

(31 citation statements)

References 12 publications

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“…Therefore, our electrodes measure CBF and PO 2 in a region containing B1,000 microvessels. We confirmed that CBF and PO 2 are recorded from the same brain region in initial experiments in which both Pt electrodes in one hemisphere recorded only PO 2 or only CBF (Figures 1C and 1B).In the PO 2 distributions around microvessels found by others using polarographic microelectrodes (typically o25 mm in diameter), values near zero coexist with those near that of arterial blood (Feng et al, 1988;Lü bbers et al, 1994;Erecinska and Silver, 2001). Our 100 mm diameter electrodes however, with conical sensing surfaces of about 0.9 mm 2 , integrate PO 2 measurements from all sites in a tissue volume of 0.58 mm 3 .…”

supporting

confidence: 86%

“…In the PO 2 distributions around microvessels found by others using polarographic microelectrodes (typically o25 mm in diameter), values near zero coexist with those near that of arterial blood (Feng et al, 1988;Lü bbers et al, 1994;Erecinska and Silver, 2001). Our 100 mm diameter electrodes however, with conical sensing surfaces of about 0.9 mm 2 , integrate PO 2 measurements from all sites in a tissue volume of 0.58 mm 3 .…”

Section: Advantages and Limitations Of Cerebral Blood Flow-oxygen Tenmentioning

confidence: 85%

“…This led us to attempt quantitative measurements of the contribution of rCBF to changes in brain PO 2 during HBO 2 , which can only be assessed in the same brain region, because CBF and brain PO 2 may differ in adjacent microregions (see Kuschinsky and Paulson, 1992;Lü bbers et al, 1994). We used collocated hydrogen clearance and oxygen microelectrodes to measure these two variables.…”

Section: Introductionmentioning

confidence: 99%

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Cerebral Blood Flow and Brain Oxygenation in Rats Breathing Oxygen under Pressure

Demchenko

Luchakov

Moskvin

et al. 2005

J Cereb Blood Flow Metab

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Hyperbaric oxygen (HBO 2 ) increases oxygen tension (PO 2 ) in blood but reduces blood flow by means of O 2 -induced vasoconstriction. Here we report the first quantitative evaluation of these opposing effects on tissue PO 2 in brain, using anesthetized rats exposed to HBO 2 at 2 to 6 atmospheres absolute (ATA). We assessed the contribution of regional cerebral blood flow (rCBF) to brain PO 2 as inspired PO 2 (PiO 2 ) exceeds 1 ATA. We measured rCBF and local PO 2 simultaneously in striatum using collocated platinum electrodes. Cerebral blood flow was computed from H 2 clearance curves in vivo and PO 2 from electrodes calibrated in vitro, before and after insertion. Arterial PCO 2 was controlled, and body temperature, blood pressure, and EEG were monitored. Scatter plots of rCBF versus PO 2 were nonlinear (R 2 ¼ 0.75) for rats breathing room air but nearly linear (R 2 ¼ 0.88-0.91) for O 2 at 2 to 6 ATA. The contribution of rCBF to brain PO 2 was estimated at constant inspired PO 2 , by increasing rCBF with acetazolamide (AZA) or decreasing it with N-nitro-L-arginine methyl ester (L-NAME). At basal rCBF (78 mL/100 g min), local PO 2 increased 7-to 33-fold at 2 to 6 ATA, compared with room air. A doubling of rCBF increased striatal PO 2 not quite two-fold in rats breathing room air but 13-to 64-fold in those breathing HBO 2 at 2 to 6 ATA. These findings support our hypothesis that HBO 2 increases PO 2 in brain in direct proportion to rCBF. IntroductionThe O 2 content of blood is the mathematical product of hemoglobin concentration and arterial hemoglobin O 2 saturation, the latter being a nonlinear function of arterial oxygen partial pressure (PaO 2 ). The small amount of O 2 dissolved in plasma is usually negligible. However, breathing hyperbaric oxygen (HBO 2 ), that is oxygen at pressures greater than 1 atmosphere absolute (ATA), raises PaO 2 beyond the point at which hemoglobin is fully saturated, so that the dissolved fraction becomes the main source of O 2 available to cells. But this does not assure enhanced O 2 delivery to brain, because tissue PO 2 also depends on regional blood flow.Tissue oxygen tension (PO 2 ) is a dynamic balance between O 2 delivery and consumption. Many authors have reported increased brain PO 2 in HBO 2 (Jamieson and Van Den Brenk, 1962;Bennett, 1965;Bean et al, 1971;Torbati et al, 1978;Hunt et al, 1978), and reviews are available (Jamieson, 1989;Camporesi et al, 1996;Dean et al, 2003). It is also known that total or regional cerebral blood flow (rCBF) decreases in HBO 2 as a function of pressure and time. But the contribution of CBF to brain PO 2 had never been quantified. Cerebral vasoconstriction and decreased total or rCBF have been shown in healthy volunteers and patients breathing O 2 at 3.5 ATA for brief periods (Lambertsen et al, 1953;Visser et al, 1996;Omae et al, 1998). In animals, in which HBO 2 is maintained for longer times and at higher pressures, the rCBF response is biphasic: the initial decrease in rCBF is followed by a secondary rise to www.jcbfm.com control leve...

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supporting

confidence: 86%

Section: Advantages and Limitations Of Cerebral Blood Flow-oxygen Tenmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cerebral Blood Flow and Brain Oxygenation in Rats Breathing Oxygen under Pressure

Demchenko

Luchakov

Moskvin

et al. 2005

J Cereb Blood Flow Metab

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“…This fell to about 40 mm Hg when the arterial oxygen pressures were decreased to about 90 mm Hg (low normal). Both oxygen extraction and the resulting vascular oxygen pressures were similar to those found, for example, in brain cortex (Silver, 1977;Lubbers, 1994;Olano et al 1995). The oxygen pressures measured by phosphorescence quenching were more consistent with those of Whalen and Nair (1977;1983) as the extravascular oxygen pressures might be expected to be below those in the microcirculation by 5-10 mm Hg.…”

Section: 2supporting

confidence: 71%

Intracellular PO2 of the Carotid Body

et al. 2002

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“…Thus, it was possible to study oxygen transport and consumption in tissue by determining local p o 2 in vivo. Measurements of this kind have been performed, e.g., in brain [7], heart [8], kidney [9], liver, eye, ear [10]. Another example of application of the oxygen needle electrode is the investigation of the effect of cancer inhibitors on oxygen transport in tumors.…”

Section: Applications In Physiology and Medicinementioning

confidence: 99%

Measurement of Hydrodynamics and Dissolved Oxygen with a Polarographic Microelectrode

Onken

Hainke²

1999

Chem. Eng. Technol.

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Besides for electrochemical analysis, polarographic electrodes can be used for the determination of hydrodynamic parameters in aqueous media. For this latter application, a three-segment microelectrode has been developed with which vectorial hydrodynamic parameters (liquid velocity and turbulence intensity) can be determined via electrodiffusion. With oxygen instead of the normally used ferri-/ferrocyanide system, the microelectrode can be employed for hydrodynamic measurements in aerated aqueous solutions independent on coalescence behavior. Experiments show that in contrast to Laser-Doppler Anemometry and Hotfilm Anemometry the electrodiffusion electrode can also be used in aerated solid suspensions. Moreover, using the probe with oxygen as the depolarizer, it is possible to measure hydrodynamic parameters and dissolved oxygen concentration at the same time. As an example, the simultaneous determination of hydrodynamics and oxygen in aerobic batch fermentation (Erwinia herbicola) is presented.

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Heterogeneity and Stability of Local PO2 Distribution within the Brain Tissue

Cited by 51 publications

References 12 publications

Cerebral Blood Flow and Brain Oxygenation in Rats Breathing Oxygen under Pressure

Cerebral Blood Flow and Brain Oxygenation in Rats Breathing Oxygen under Pressure

Intracellular PO2 of the Carotid Body

Measurement of Hydrodynamics and Dissolved Oxygen with a Polarographic Microelectrode

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