Relationship between brain tissue haemodynamics, oxygenation and metabolism in the healthy human adult brain during hyperoxia and hypercapnea.

This study investigates the relationship between changes in brain tissue haemodynamics, oxygenation and oxidised cytochrome-c-oxidase ([oxCCO]) in the adult brain during hyperoxia and hypercapnea. 10 healthy volunteers were studied. We measured the mean blood flow velocity of the right middle cerebral artery (Vmca) with transcranial Doppler (TCD) and changes in concentrations of total haemoglobin ([HbT]=[HbO2]+[HHb]), haemoglobin difference ([Hbdiff]=[HbO2]-[HHb]) and [oxCCO] with broadband near-infrared spectroscopy (NIRS). We also measured the absolute tissue oxygenation index (TOI) using NIR spatially resolved spectroscopy. During hyperoxia there was an increase in TOI (2.33 +/- 0.29%), [Hbdiff] (4.57 +/- 1.27 microM) and in the oxidation of [oxCCO] (0.09 +/- 0.12 microM); but a reduction in Vmca (5.85 +/- 4.85%) and HbT (1.29 +/- 0.91 microM). During hyperoxia there was a positive correlation between [oxCCO] and TOI and [Hbdiff] (r=0.83 and r=0.95) and a negative association between [oxCCO] and Vmca and [HbT] (r=-0.74 and r=-0.87). During hypercapnea there was an increase in TOI (2.76 +/- 2.16%), [Hbdiff] (7.36 +/- 2.64), [HbT] (2.61 +/- 2.7 microM), Vmca (14.92 +/- 17.5%) and in the oxidation of [oxCCO] (0.25 +/- 0.17 microM). Correlation analysis shows that there was association between [oxCCO] and TOI, [Hbdiff] and [HbT] (r=0.83, r=0.93 and r=0.82) but not with Vmca (r=0.33). We conclude that an increase in [oxCCO] was seen during both challenges and it was highly associated with brain tissue oxygenation.

[1]  A Villringer,et al.  Changes in blood flow velocity and diameter of the middle cerebral artery during hyperventilation: assessment with MR and transcranial Doppler sonography. , 1997, AJNR. American journal of neuroradiology.

[2]  D T Delpy,et al.  Oxidation and reduction of cytochrome oxidase in the neonatal brain observed by in vivo near-infrared spectroscopy. , 1998, Biochimica et biophysica acta.

[3]  D. Delpy,et al.  Performance comparison of several published tissue near-infrared spectroscopy algorithms. , 1995, Analytical biochemistry.

[4]  B. Ludwig,et al.  Cytochrome c oxidase--structure, function, and physiology of a redox-driven molecular machine. , 2003, Reviews of physiology, biochemistry and pharmacology.

[5]  D T Delpy,et al.  Near-infrared spectroscopy of the brain: relevance to cytochrome oxidase bioenergetics. , 1994, Biochemical Society transactions.

[6]  I Tachtsidis,et al.  Investigation of in vivo measurement of cerebral cytochrome-c-oxidase redox changes using near-infrared spectroscopy in patients with orthostatic hypotension , 2007, Physiological measurement.

[7]  P. Brzezinski,et al.  Cytochrome c oxidase as an electron-transport-driven proton pump: pH dependence of the reduction levels of the redox centers during turnover. , 1988, Biochemistry.

[8]  C. Giller,et al.  Cerebral arterial diameters during changes in blood pressure and carbon dioxide during craniotomy. , 1993, Neurosurgery.

[9]  Yukio Kobayashi,et al.  Tissue oxygenation monitor using NIR spatially resolved spectroscopy , 1999, Photonics West - Biomedical Optics.

[10]  David T Delpy,et al.  The oxygen dependency of cerebral oxidative metabolism in the newborn piglet studied with 31P NMRS and NIRS. , 2003, Advances in experimental medicine and biology.

[11]  Ilias Tachtsidis,et al.  Near-infrared spectroscopic quantification of changes in the concentration of oxidized cytochrome c oxidase in the healthy human brain during hypoxemia. , 2007, Journal of biomedical optics.

[12]  S. Arridge,et al.  Estimation of optical pathlength through tissue from direct time of flight measurement , 1988 .

[13]  D. Delpy,et al.  Use of the water absorption spectrum to quantify tissue chromophore concentration changes in near-infrared spectroscopy. , 1994, Physics in medicine and biology.