In premature infants with an extremely low gestational age (ELGA, < 29 weeks GA), dysregulated changes in cerebral blood flow (CBF) are among the major pathogenic factors leading to germinal matrix/intraventricular hemorrhage (GM/IVH). Continuous monitoring of CBF can guide interventions to minimize the risk of brain injury, but there are no clinically standard techniques or tools for its measurement. We report the feasibility of the continuous monitoring of CBF, including measures of autoregulation, via diffuse correlation spectroscopy (DCS) in ELGA infants using CBF variability and correlation with scalp blood flow (SBF, served as a surrogate measure of systemic perturbations). In nineteen ELGA infants (with 9 cases of GM/IVH) monitored for 6–24 h between days 2–5 of life, we found a strong correlation between CBF and SBF in severe IVH (Grade III or IV) and IVH diagnosed within 72 h of life, while CBF variability alone was not associated with IVH. The proposed method is potentially useful at the bedside for the prompt assessment of cerebral autoregulation and early identification of infants vulnerable to GM/IVH.

Near-infrared spectroscopy (NIRS) is an established non-invasive diffuse optical method used to quantify hemoglobin oxygen saturation (${\mathrm{SO}}_2$) and hemoglobin concentration (Hb) changes from light attenuation at different wavelengths.^1,2 Diffuse correlation spectroscopy (DCS) is a more recent optical technology that uses speckle fluctuations to measure an index for blood flow (${\mathrm{BF}}_{\mathrm{i}}$). Specifically, DCS measures the intensity temporal autocorrelation function ($g_2$), which characterizes the displacement dynamics of scattering particles in the sample under interrogation.^{3 – 5} Combining DCS with NIRS allows for calculating the cerebral metabolic rate of oxygen⁶ and furthering our understanding of the relationship between hemoglobin concentration and cerebral blood flow (CBF) changes in healthy^7,8 and pathological conditions.^9,10 More recently, our and other groups have proposed the use of DCS pulsatile CBF index signals (${\mathrm{pCBF}}_{\mathrm{i}}$) to quantify intracranial pressure (ICP), critical closing pressure (CrCP), pulsatility index (PI), and cerebrovascular resistance index (${\mathrm{CVR}}_{\mathrm{i}}$) continuously and non-invasively.^{11 – 16} Despite the encouraging results, the low signal-to-noise ratio (SNR) of current DCS devices limits ${\mathrm{pCBF}}_{\mathrm{i}}$ to source-detector separations (SDsep) of up to 2.5 cm, which reduces brain sensitivity in adults,¹⁷ and to achieve sufficient time-points within a pulsatile waveform, it requires cardiac-gated averaging of 50 arterial pulses,¹¹ which dampens the pulsatile peaks and provides CrCP and ${\mathrm{CVR}}_{\mathrm{i}}$ estimates at 0.02 to 0.07 Hz, rates that are too low to investigate the dynamic pressure-flow relationship of the cerebral vasculature.¹⁸ To overcome the DCS noise, increase SDsep, and recover ${\mathrm{pCBF}}_{\mathrm{i}}$ with much less averaging, we propose a new method based on the combination of NIRS and DCS pulsatile signals.

Capacitive proximity sensing is widespread in our everyday life, but no sensor for biomedical optics takes advantage of this technology to monitor the probe attachment to the subject’s skin. In particular, when using optical monitoring devices, the capability to quantitatively measure the probe contact can significantly improve data quality and ensure the subject’s safety. We present a custom novel optical probe based on a flexible printed circuit board which integrates a capacitive contact sensor, 3D-printed optic fiber holders and an accelerometer sensor. The device can be effectively adopted during continuous monitoring optical measurements to detect contact quality, motion artifacts, probe detachment and ensure optimal signal quality.

Impaired cerebral autoregulation (CA) in premature infants leads to Intraventricular hemorrhage (IVH). A DCS-derived index of CA has shown its association with IVH. Further stratification by hsPDA may explain the variation in the No-IVH group.