Browsing by Author "Alshehri, Abdulaziz Ali H"

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Determining the cerebrovascular response to hyperventilation in health and disease
(Saudi Digital Library, 2025) Alshehri, Abdulaziz Ali H; Minhas, Jatinder S
Abstract Background: Dynamic cerebral autoregulation (dCA) and arterial carbon dioxide (PaCO₂) are vital mechanisms regulating cerebral blood flow. The physiological impact of different CO₂ modulation strategies and their integration into stroke care remain underexplored. Objectives: This thesis aimed to advance the assessment of cerebrovascular regulation by evaluating the effects of controlled PaCO₂ manipulation on dCA in healthy participants using logistic curve modelling (LCM). In parallel, multimodal monitoring techniques were applied to patients with acute and subacute ischaemic stroke to assess macro- and microvascular autoregulatory responses, supporting the development of personalised stroke management strategies. Methods: The research included a systematic review of prehospital stroke care and prospective studies involving healthy individuals and patients with mild-to-moderate ischaemic stroke. Non-invasive measurements of cerebral blood velocity (CBv), arterial blood pressure, end-tidal CO₂ and heart rate were obtained using transcranial Doppler ultrasonography (TCD), near-infrared spectroscopy (NIRS), Finometer, capnography and ECG. PaCO₂ was modulated using auditory- and visual-paced hyperventilation (PaHPV, PvHPV), and a combined hypercapnia–hypocapnia protocol. LCM was modelled to characterise cerebrovascular responses across a wide range of arterial CO₂. Results: In 53 healthy participants (29 male), PvHPV elicited stronger autoregulatory responses and reduced early dysregulation compared to PaHPV. LCM revealed non-linear, biological sex related cerebrovascular response; females demonstrating higher CBv and dCA efficiency. Stroke patients showed persistent macro- and microvascular autoregulatory impairments, particularly in subacute phase. Multimodal monitoring identified regional and temporal differences in dCA, with NIRS capturing microvascular dysfunction not detected by TCD. Conclusion: Controlled PaCO₂ manipulation significantly impacts dCA, with induction method and biological sex playing critical roles. LCM provides a robust framework for quantifying cerebrovascular reactivity. This work establishes the feasibility of CO₂-based interventions and multimodal monitoring for assessing and guiding stroke management. It proposes novel protocols and modelling approaches to characterise cerebrovascular regulation, paving the way for physiologically guided therapeutic strategies.
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