Vasovagal syncope may be due to a transient cerebral hypoperfusion that accompanies frequency entrainment between arterial pressure (AP) and cerebral blood flow velocity (CBFV). We hypothesized that cerebral autoregulation fails during fainting; a phase synchronization index (PhSI) between AP and CBFV was used as a nonlinear, nonstationary, time-dependent measurement of cerebral autoregulation. Twelve healthy control subjects and twelve subjects with a history of vasovagal syncope underwent 10-min tilt table testing with the continuous measurement of AP, CBFV, heart rate (HR), end-tidal CO2 (ETCO2), and respiratory frequency. Time intervals were defined to compare physiologically equivalent periods in fainters and control subjects. A PhSI value of 0 corresponds to an absence of phase synchronization and efficient cerebral autoregulation, whereas a PhSI value of 1 corresponds to complete phase synchronization and inefficient cerebral autoregulation. During supine baseline conditions, both control and syncope groups demonstrated similar oscillatory changes in phase, with mean PhSI values of 0.58+/-0.04 and 0.54+/-0.02, respectively. Throughout tilt, control subjects demonstrated similar PhSI values compared with supine conditions. Approximately 2 min before fainting, syncopal subjects demonstrated a sharp decrease in PhSI (0.23+/-0.06), representing efficient cerebral autoregulation. Immediately after this period, PhSI increased sharply, suggesting inefficient cerebral autoregulation, and remained elevated at the time of faint (0.92+/-0.02) and during the early recovery period (0.79+/-0.04) immediately after the return to the supine position. Our data demonstrate rapid, biphasic changes in cerebral autoregulation, which are temporally related to vasovagal syncope. Thus, a sudden period of highly efficient cerebral autoregulation precedes the virtual loss of autoregulation, which continued during and after the faint.

Global health partnerships between high-income countries and low/middle-income countries can mirror colonial relationships. The growing call to advance global health equity therefore involves decolonising global health partnerships and outreach. Through decolonisation, local and international global health partners recognise non-western forms of knowledge and authority, acknowledge discrimination and disrupt colonial structures and legacies that influence access to healthcare.Despite these well-described aims, the ideal implementation process for decolonising global health remains ill-defined. This ambiguity exists, in part, because partners face barriers to adopting a decolonised perspective. Such barriers include overemphasis on intercountry relationships, implicit hierarchies perpetuated by educational interventions and ethical dilemmas in global health work.In this article, we explore the historical entanglement of education, health and colonialism. We then use this history as context to identify barriers that arise when decolonising contemporary educational global health partnerships. Finally, we offer global health partners strategies to address these challenges.

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