Epidural oscillating cardiac-gated intracranial implant modulates cerebral blood flow

BACKGROUND: We have previously reported a method and device capable of manipulating ICP pulsatility while minimally effecting mean ICP. OBJECTIVE: To test the hypothesis that different modulations of the intracranial pressure (ICP) pulse waveform will have a differential effect on cerebral blood flow (CBF). METHODS: Using an epidural balloon catheter attached to a cardiac-gated oscillating pump, 13 canine subjects underwent ICP waveform manipulation comparing different sequences of oscillation in successive animals. The epidural balloon was implanted unilaterally superior to the Sylvian sulcus. Subjects underwent ICP pulse augmentation, reduction and inversion protocols, directly comparing time segments of system activation and deactivation. ICP and CBF were measured bilaterally along with systemic pressure and heart rate. CBF was measured using both thermal diffusion, and laser doppler probes. RESULTS: The activation of the cardiac-gate balloon implant resulted in an ipsilateral/contralateral ICP pulse amplitude increase with augmentation (217%/202% respectively, P <.0005) and inversion (139%/120%, P <.0005). The observed changes associated with the ICP mean values were smaller, increasing with augmentation (23%/31%, P <.0001) while decreasing with inversion (7%/11%, P =.006/.0003) and reduction (4%/5%, P <.0005). CBF increase was observed for both inversion and reduction protocols (28%/7.4%, P <.0001/P =.006 and 2.4%/1.3%, P <.0001/P =.003), but not the augmentation protocol. The change in CBF was correlated with ICP pulse amplitude and systolic peak changes and not with change in mean ICP or systemic variables (heart rate, arterial blood pressure). CONCLUSION: Cardiac-gated manipulation of ICP pulsatility allows the study of intracranial pulsatile dynamics and provides a potential means of altering CBF.