A noninvasive estimation of cerebral perfusion pressure using critical closing pressure

Abstract

T he circulation of cerebral blood flow (CBF) is driven by cerebral perfusion pressure (CPP), which is defined as the vascular pressure gradient across the cerebral bed and can be calculated as the difference between arterial blood pressure (ABP) and pressure in cortical or bridging veins. 15,24 Due to difficulties in measuring the pressure of bridging veins, invasive intracranial pressure (ICP) measurements are used instead as an approximation, defining CPP as ABP − ICP. 1,26,34,39 Cerebral perfusion pressure in clinical practice is considered an esabbreviatioNs ABP = arterial blood pressure; AUC = area under the curve; CBF = cerebral blood flow; CPP = cerebral perfusion pressure; CrCP = critical closing pressure; CVR = cerebrovascular resistance; eCPP = noninvasive estimator of CPP; FV = flow velocity; GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; ICP = intracranial pressure; IQR = interquartile range; MCA = middle cerebral artery; nICP = noninvasive estimator of ICP; ROC = receiver operating characteristic; TAU = time constant of the cerebrovascular arterial bed; TBI = traumatic brain injury; TCD = transcranial Doppler. obJect Cerebral blood flow is associated with cerebral perfusion pressure (CPP), which is clinically monitored through arterial blood pressure (ABP) and invasive measurements of intracranial pressure (ICP). Based on critical closing pressure (CrCP), the authors introduce a novel method for a noninvasive estimator of CPP (eCPP). methods Data from 280 head-injured patients with ABP, ICP, and transcranial Doppler ultrasonography measurements were retrospectively examined. CrCP was calculated with a noninvasive version of the cerebrovascular impedance method. The eCPP was refined with a predictive regression model of CrCP-based estimation of ICP from known ICP using data from 232 patients, and validated with data from the remaining 48 patients. results Cohort analysis showed eCPP to be correlated with measured CPP (R = 0.851, p < 0.001), with a mean ± SD difference of 4.02 ± 6.01 mm Hg, and 83.3% of the cases with an estimation error below 10 mm Hg. eCPP accurately predicted low CPP (< 70 mm Hg) with an area under the curve of 0.913 (95% CI 0.883-0.944). When each recording session of a patient was assessed individually, eCPP could predict CPP with a 95% CI of the SD for estimating CPP between multiple recording sessions of 1.89-5.01 mm Hg. coNclusioNs Overall, CrCP-based eCPP was strongly correlated with invasive CPP, with sensitivity and specificity for detection of low CPP that show promise for clinical use.

Prospective Study on Noninvasive Assessment of Intracranial Pressure in Traumatic Brain-Injured Patients: Comparison of Four Methods

“…14 mm Hg is ''zero compensation factor'' established in a cohort of TBI patients. 29 3) Varsos and colleagues 30 (nICP_CrCP): Similarly, this method calculates nICP based on nCPP, in this case specifically using the concept of critical closing pressure (CrCP). According to Burton's model, CrCP is equal to the sum of ICP and vascular wall tension (WT) 35,36 : CrCP = ICP + WT.…”

“…However, noninvasive ICP can be calculated based on the assumption that nICP = ABP -nCPP. 29,30 Because of the variability in the reported degree of agreement between TCD-based nICP methods and measured ICP, this study aimed to compare four TCD-based nICP methods with measured ICP in a single prospective cohort of TBI patients.…”

Non-invasive Monitoring of Intracranial Pressure Using Transcranial Doppler Ultrasonography: Is It Possible?

“…4). The equation for nCPP estimation based on CrCP is Constant coefficients (0.734, 0.266, 7.026) were derived from analysis of database of 232 TBI retrospective cases [18]. CaBV Amp represents the fundamental amplitude of the cerebral arterial blood volume.…”

“…Shadowed areas in ( a ) and ( b ) represent ICP waves of vasogenic origin. It is possible to observe that at least for trends in time, there were good correspondence between ICP and nICP methods; nICP_BB non-invasive ICP method based on mathematical black-box model [6]; nICP_FVd non-invasive ICP method based on FVd [10]; nICP_CrCP non-invasive ICP method based on CrCP [18]; nICP_PI non-invasive ICP method based on PI …”

Cerebral Vasospasm Affects Arterial Critical Closing Pressure

“…38 Advantages of Impedance-Based Critical Closing Pressure The main advantage of impedance CrCP is that its renderings in SAH patients agreed with the findings of an earlier study using two traditional CrCP methods, 24 although without presenting any negative values for this pathology, as has also been verified with this estimation method in both experimental and clinical scenarios. 26,27,31,38 Despite CrCP calculations being based on FV-derived information, the changes in CrCP during CVS were independent of changes in FV, and therefore not being artificially driven by increasing FV 24 but rather being representative of changes in the physiology of the microvasculature. Most importantly, the calculations with our method were not affected by the diameter change of the insonated vessel, as the calculation of CrCP is independent of the insonated vessel's unknown cross-sectional area (please see Appendix).…”