Analysis of Intracranial Pressure Pulse-Pressure Relationship: Experimental Validation.

The slope of linear relationship between the amplitude of pulsations in intracranial pressure (ICP) versus mean ICP has recently been suggested as a useful guide for selecting patients for shunt surgery in normal pressure hydrocephalus (NPH). To better understand how the pathophysiology of cerebral circulation influences this parameter, we aimed to study the relationship between mean pressure and pulsation amplitude in a wide range of conditions affecting cerebrovascular tone and ICP in experimental conditions.We retrospectively analysed experimental material collected previously.

A comparison of the time constant of the cerebral arterial bed using invasive and non-invasive arterial blood pressure measurements.

Objective: The time constant of the cerebral arterial bed (τ), which is an index of brain haemodynamics, can be estimated in patients using continuous monitoring of arterial blood pressure (ABP), transcranial Doppler cerebral blood flow velocity (CBFV) and intracranial pressure (ICP) if these measures are available. But, in some clinical scenarios invasive measurement of ABP is not feasible. Therefore, in this study we aimed to investigate whether invasive ABP can be replaced with non-invasive ABP, monitored using the Finapres photoplethysmograph (fABP).

Critical closing pressure during experimental intracranial hypertension: comparison of three calculation methods.

: The critical closing pressure (CrCP) defines arterial blood pressure below which cerebral arteries collapse. It represents a clinically relevant parameter for the estimation of cerebrovascular tone. Although there are few methods to assess CrCP, there is no consensus which of them estimates this parameter most accurately.

Cerebral arterial time constant calculated from the middle and posterior cerebral arteries in healthy subjects.

The cerebral arterial blood volume changes (∆CBV) during a single cardiac cycle can be estimated using transcranial Doppler ultrasonography (TCD) by assuming pulsatile blood inflow, constant, and pulsatile flow forward from large cerebral arteries to resistive arterioles [continuous flow forward (CFF) and pulsatile flow forward (PFF)]. In this way, two alternative methods of cerebral arterial compliance (C) estimation are possible. Recently, we proposed a TCD-derived index, named the time constant of the cerebral arterial bed (τ), which is a product of C and cerebrovascular resistance and is independent of the diameter of the insonated vessel.

Assessment of cerebral hemodynamic parameters using pulsatile versus non-pulsatile cerebral blood outflow models.

Background: Prior methods evaluating the changes in cerebral arterial blood volume (∆CBV) assumed that brain blood transport distal to big cerebral arteries can be approximated with a non-pulsatile flow (CFF) model. In this study, a modified ∆CBV calculation that accounts for pulsatile blood flow forward (PFF) from large cerebral arteries to resistive arterioles was investigated. The aim was to assess cerebral hemodynamic indices estimated by both CFF and PFF models while changing arterial blood carbon dioxide concentration (EtCO) in healthy volunteers.

Critical Closing Pressure During a Controlled Increase in Intracranial Pressure.

Objectives: The objectives were to compare three methods of estimating critical closing pressure (CrCP) in a scenario of a controlled increase in intracranial pressure (ICP) induced during an infusion test in patients with suspected normal pressure hydrocephalus (NPH).

Methods: We retrospectively analyzed data from 37 NPH patients who underwent infusion tests. Computer recordings of directly measured intracranial pressure (ICP), arterial blood pressure (ABP) and transcranial Doppler cerebral blood flow velocity (CBFV) were used.

Critical Closing Pressure During Controlled Increase in Intracranial Pressure-Comparison of Three Methods.

Goal: Critical closing pressure (CrCP) is the arterial blood pressure (ABP) threshold, below which small arterial vessels collapse and cerebral blood flow ceases. Here, we aim to compare three methods for CrCP estimation in scenario of a controlled increase in intracranial pressure (ICP), induced by infusion tests performed in patients with suspected normal pressure hydrocephalus (NPH).

Methods: Computer recordings of directly-measured ICP, ABP, and transcranial Doppler cerebral blood flow velocity (CBFV), from 37 NPH patients undergoing infusion tests, were retrospectively analyzed.