Critical Closing Pressure: Comparison of Three Methods

Abstract

Critical closing pressure (CCP) is an arterial pressure threshold below which small arterial vessels collapse. Our aim was to compare different methods to estimate CCP in the cerebrovascular circulation using the relationships between transcranial Doppler flow velocity (FV), laser-Doppler flux (LDF), and arterial blood pressure (ABP). A total of 116 experiments in rabbits were analyzed retrospectively. At the end of each recording, cardiac arrest (CA) was induced. Arterial blood pressure in femoral artery, basilar artery FV, cortical blood LDF, intracranial pressure (ICP) was recorded. Critical closing pressure was estimated using linear regression between decreasing mean ABP values, FV, and LDF during CA. In addition, CCP was calculated from FV waveform just before CA. The correlation between CCP evaluated using LDF and FV during CA was 0.98 (P < 0.0001). The correlation between CCP measured during CA and CCP estimated from the transcranial Doppler ultrasonography (TCD) waveform was weaker (R = 0.39; P < 0.001), with CCP calculated from waveform being significantly greater than CCP from CA (median difference 9 mm Hg; P < 0.003). Critical closing pressures obtained from FV waveform and CA correlated with mean ICP before CA (R = 0.40; P = 0.001). In conclusion strong correlation exists between CCP values obtained by means of FV and LDF during cardiac arrest. However, predictions of CCP using TCD waveform analysis show substantial differences from values of CCP recorded during cardiac arrest.

Cerebrovascular reactivity and cerebral autoregulation in normal subjects

“…This physiological phenomenon has been reported in several studies using different techniques to assess dynamic cerebral autoregulation [13,14]. Hypercapnia induces a decrease in vascular tone reflected by a decrease in cerebral arterial resistance but also in the critical closing pressure (CCP), which reflects the arterial pressure threshold below which small arterial vessels collapse [14,15,18]. This reduction in vascular tone and change in physiological properties of arterial walls may be responsible for this inability for the cerebral arteries to regulate adequately the cerebral blood flow under conditions of hypercapnia.…”

Doppler Non-invasive Monitoring of ICP in an Animal Model of Acute Intracranial Hypertension

“…ABP, CPP, and FV were continuously recorded, converted into digital samples using an analog-to-digital converter fitted into an IBM compatible personal computer [27] and saved on hard disk in digital form, with sampling frequency 50 Hz.…”

Role of sympathetic nervous system in activity-induced cerebral perfusion

“…However, investigation of CCP also has its limits, as it has recently been shown that predictions of CCP with TCD waveform analysis show substantial differences from values of CCP recorded during cardiac arrest [30], suggesting that these differences will need to be understood before indirect calculations of CCP can be reliably used in clinical practice. Since we did not investigate cerebral autoregulation, but sympathetic influence in cortical activation, we think it is also valid for intra-and interindividual comparison to use ABP/CBFV to show relative changes of cerebrovascular resistance.…”