Noninvasive diffuse optical monitoring of cerebral blood flow and oxygenation responses to intermittent hypoxia in neonatal rats.

SIGNIFICANCE: Intermittent hypoxia (IH) is common in preterm neonates and can cause hypoxic-ischemic brain injury. Simultaneous monitoring of cerebral blood flow (CBF) and oxygenation is essential to detect oxygen delivery-extraction mismatches and guide intervention.

AIM: We aimed to adapt and test an innovative diffuse speckle contrast flow oximetry (DSCFO) system for continuous monitoring of cerebral hemodynamics during IH in neonatal rats, a model approximating human neonates.

APPROACH: Two compact laser diodes and a miniature CMOS camera were integrated into a fiber-free probe for continuous monitoring of changes in relative CBF (rCBF) and oxy- and deoxy-hemoglobin concentrations (Δ[HbO2] and Δ[Hb]) in 8-day-old neonatal rats. Sham rats ( n = 6 ) underwent 10 min of normoxia, whereas IH rats ( n = 8 ) experienced 10 cycles of sequential 2-min hypoxia (8% O2) and 2-min hyperoxia (100% O 2 ).

RESULTS

Sham rats maintained stable cerebral hemodynamics under normoxia, whereas IH rats exhibited pronounced periodic fluctuations during IH. Hypoxic episodes caused instantaneous decreases in rCBF and Δ [ HbO 2 ] and increases in Δ [ Hb ] , whereas hyperoxic episodes reversed these effects, reducing hypoxic stress. However, the pronounced cerebral hemodynamic fluctuations during IH may still contribute to brain injury.

CONCLUSIONS

We demonstrate an affordable, noninvasive, wearable, fiber-free DSCFO system for continuous monitoring of rCBF, Δ [ HbO 2 ] , and Δ [ Hb ] during IH in neonatal rats. The system captured hypoxia-induced cerebral deoxygenation and hyperoxia-driven recovery, revealing episode-dependent protective and disruptive mechanisms. Future work will correlate DSCFO findings with neurological and histological outcomes to guide IH interventions in large neonatal animal models and human infants.