Cerebral blood flow response to acute hypoxic hypoxia.
Bottom Line: However, this response, particularly at the tissue level, is not well characterised.The rate constant, temporal delay and magnitude of the CBF response were characterised using an exponential model for whole-brain and regional grey matter.The delay and rate constant for changes in R2 * were 24 s (95% CI: 21 s, 26 s) and 0.0392 s(-1) (95% CI: 0.0333 s(-1), 0.045 s(-1)), respectively, for the hypoxic response, and 12 s (95% CI: 10 s, 13 s) and 0.0921 s(-1) (95% CI: 0.0744 s(-1), 0.1098 s(-1)/) during the return to normoxia, confirming rapid changes in blood oxygenation with the end-tidal forcing system.
Affiliation: CUBRIC, School of Psychology, Cardiff University, Cardiff, UK.Show MeSH
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Mentions: According to the model fitting of the group-averaged data, across grey matter, CBF increased from 76.1 mL/100 g/min (95% CI: 75.5, 76.7) to 87.8 mL/100 g/min (95% CI: 86.7, 89.6), with a rate constant of 0.0035 s–1 (95% CI: 0.0019, 0.0046) and a delay of 185 s (95% CI: 132, 230). This corresponds to a 15.4% increase in CBF. The parameters from the fitting (and the 95% CIs on these fits showing the reliability or noise in the parameter fit) across the regions are given in Table 2. The CBF and R2* time-course and model fits for all grey matter are shown in Fig. 4. The R2* response was more rapid than the CBF response, with a rate constant of 0.0392 s–1 and a delay of 24 s calculated for the transition to hypoxia (Table 3, Fig. 4).
Affiliation: CUBRIC, School of Psychology, Cardiff University, Cardiff, UK.