Intracranial Pressure Waveform Analysis Research Articles

Non-invasive Intracranial Pressure Waveform Analysis in Chiari Malformation Type 1: A Pilot Trial

This pilot study aimed to investigate the role of Posterior Fossa Decompression (PFD) on the intracranial pressure (ICP) waveform in patients with Chiari Malformation type 1 (CM1). It also sought to explore the relationship between symptom improvement and ICP waveform behavior. This exploratory cohort study evaluated adult patients diagnosed with CM1. The patients underwent PFD using a standard technique at our institution, which involved a 3× 3 cm posterior craniectomy and excision of the posterior arch of C1. The ICP waveform was measured using an external strain-gauge device connected to a pin attached to the skull. Measurements were collected pre- and post-PFD, and the P2/P1 ratio was calculated pre- and postoperatively. The pilot study comprised 6 participants, 3 men and 3 women, with ages ranging from 39 to 68years. The primary symptoms were cerebellar ataxia and typical headaches. The study found that most patients who showed clinical improvement, as judged by the Gestalt method, had a postoperative decrease in the P2/P1 ratio. However, 1 patient did not show an improvement in the P2/P1 ratio despite a good clinical outcome. This study suggests that the P2/P1 ratio may decrease after PFD. However, we highlight the need for further research with a larger sample size to confirm these preliminary results.

Analysis of intracranial pressure waveform using a non-invasive method in individuals with craniosynostosis.

Craniosynostosis can lead to symptoms resulting from cranial compliance (CC) changes and intracranial hypertension (ICH), which may cause cognitive and visual impairment. Non-invasive methods have emerged, including a new device that captures and processes the intracranial pressure waveform (ICPw) by the skull's oscillation. The present study evaluates ICPw obtained non-invasively (NIICPw) in patients with craniosynostosis. This prospective, cross-sectional, and descriptive study was conducted at a single center. Patients diagnosed with craniosynostosis and who provided informed consent were included. A US Food and Drug Administration-approved mechanical extensometer device (Brain4Care Corp.) was used to obtain a NIICPw. An ophthalmologist did a point-of-care retinography to check the optic nerve papilla. The P2/P1 ratio and the morphology of the NIICPw were analyzed, as well as the retinography. Thirty-five patients were evaluated, and 42 registers were obtained because seven were assessed before and after the surgery. The two patients who presented papilledema had low CC (NIICPw shape Class 3 or 4). There was a significant association between NIICPw and papilledema. The ratio P2/P1 and the NIICPw morphology provided by a non-invasive monitor are related to CC changes before papilledema occurs. This is especially useful in patients with craniosynostosis because invasive ICP monitoring is not always feasible. Further studies are warranted to establish the clinical utility of NIICPw in patients with craniosynostosis.

A Precision Medicine Approach to Cerebral Edema and Intracranial Hypertension after Severe Traumatic Brain Injury: Quo Vadis?

Standard clinical protocols for treating cerebral edema and intracranial hypertension after severe TBI have remained remarkably similar over decades. Cerebral edema and intracranial hypertension are treated interchangeably when in fact intracranial pressure (ICP) is a proxy for cerebral edema but also other processes such as extent of mass lesions, hydrocephalus, or cerebral blood volume. A complex interplay of multiple molecular mechanisms results in cerebral edema after severe TBI, and these are not measured or targeted by current clinically available tools. Addressing these underpinnings may be key to preventing or treating cerebral edema and improving outcome after severe TBI. This review begins by outlining basic principles underlying the relationship between edema and ICP including the Monro-Kellie doctrine and concepts of intracranial compliance/elastance. There is a subsequent brief discussion of current guidelines for ICP monitoring/management. We then focus most of the review on an evolving precision medicine approach towards cerebral edema and intracranial hypertension after TBI. Personalization of invasive neuromonitoring parameters including ICP waveform analysis, pulse amplitude, pressure reactivity, and longitudinal trajectories are presented. This is followed by a discussion of cerebral edema subtypes (continuum of ionic/cytotoxic/vasogenic edema and progressive secondary hemorrhage). Mechanisms of potential molecular contributors to cerebral edema after TBI are reviewed. For each target, we present findings from preclinical models, and evaluate their clinical utility as biomarkers and therapeutic targets for cerebral edema reduction. This selection represents promising candidates with evidence from different research groups, overlap/inter-relatedness with other pathways, and clinical/translational potential. We outline an evolving precision medicine and translational approach towards cerebral edema and intracranial hypertension after severe TBI.

B-waves revisited

Abstract Reduced intracranial compliance is a key manifestation common to a number of pathological conditions of the brain. It is encountered in, but not limited to, traumatic brain injury, cerebral edema, and hydrocephalus. There are no clinically accepted methods to measure intracranial compliance available to date. Intracranial pressure (ICP) waveform analysis is seeing a revival driven by advances in our understanding of cerebrospinal fluid and pressure dynamics. Its translation to widespread clinical use is dependent on the possibility to derive relevant metrics such as intracranial compliance reliably and non-invasively. The B-wave is one of the features of the ICP waveform, reflecting vasogenic activity of cerebral autoregulation. B-waves were originally defined to occupy the 0.5 to 2 cycles per minute frequency range. Recently renamed and redefined as slow waves with an extended range of 0.33 to 3 cycles per minute, specific changes in their pattern of occurrence are considered to be indicative of reduced intracranial compliance. With the still unmet need for a clinically acceptable method for acquiring intracranial compliance, and the revival of ICP waveform analysis, B-waves are moving back into the research focus. Herein we provide a concise review of the literature on B-waves, including a critical assessment of non-invasive methods for obtaining B-wave surrogates.

Intraspinal pressure and spinal cord perfusion pressure after spinal cord injury: an observational study.

In contrast to intracranial pressure (ICP) in traumatic brain injury (TBI), intraspinal pressure (ISP) after traumatic spinal cord injury (TSCI) has not received the same attention in terms of waveform analysis. Based on a recently introduced technique for continuous monitoring of ISP, here the morphological characteristics of ISP are observationally described. It was hypothesized that the waveform analysis method used to assess ICP could be similarly applied to ISP. Data included continuous recordings of ISP and arterial blood pressure (ABP) in 18 patients with severe TSCI. The morphology of the ISP pulse waveform resembled the ICP waveform shape and was composed of 3 peaks representing percussion, tidal, and dicrotic waves. Spectral analysis demonstrated the presence of slow, respiratory, and pulse waves at different frequencies. The pulse amplitude of ISP was proportional to the mean ISP, suggesting a similar exponential pressure-volume relationship as in the intracerebral space. The interaction between the slow waves of ISP and ABP is capable of characterizing the spinal autoregulatory capacity. This preliminary observational study confirms morphological and spectral similarities between ISP in TSCI and ICP. Therefore, the known methods used for ICP waveform analysis could be transferred to ISP analysis and, upon verification, potentially used for monitoring TSCI patients.

External ventricular drains: Management and complications.

Background:Insertion of an External Ventricular Drain (EVD) is arguably one of the most common and important lifesaving procedures in neurologic intensive care unit. Various forms of acute brain injury benefit from the continuous intracranial pressure (ICP) monitoring and cerebrospinal fluid (CSF) diversion provided by an EVD. After insertion, EVD monitoring, maintenance and troubleshooting essentially become a nursing responsibility.Methods:Articles pertaining to EVD placement, management, and complications were identified from PubMed electronic database.Results:Typically placed at the bedside by a neurosurgeon or neurointensivist using surface landmarks under emergent conditions, this procedure has the ability to drain blood and CSF to mitigate intracranial hypertension, continuously monitor intracranial pressure, and instill medications. Nursing should ensure proper zeroing, placement, sterility, and integrity of the EVD collecting system. ICP waveform analysis and close monitoring of CSF drainage are extremely important and can affect clinical outcomes of patients. In some institutions, nursing may also be responsible for CSF sampling and catheter irrigation.Conclusion:Maintenance, troubleshooting, and monitoring for EVD associated complications has essentially become a nursing responsibility. Accurate and accountable nursing care may have the ability to portend better outcomes in patients requiring CSF drainage.

Abstract W MP26: Intracranial Pressure Waveforms Indicate Vasodilation During Remote Ischemic Conditioning

Introduction: Remote ischemic conditioning is a powerful phenomenon where brief periods of ischemia and reperfusion in a tissue such as the leg or arm can confer protective benefits from ischemic injury to distant tissues. Our previous work using intracranial pressure (ICP) waveform analysis has identified trends in the waveform shape that suggest transient cerebral vasodilation occurs as an effect of the procedure. We present a more rigorous analysis using data prospectively collected as part of our phase I clinical trial of RIC for aneurysmal subarachnoid hemorrhage (aSAH). Methods: During the RIC procedure ICP was measured using intraventricular monitors simultaneously recorded with ECG (Fs = 400 Hz). ICP analysis was performed using the Morphological Clustering and Analysis of Intracranial Pulse (MOCAIP) algorithm which extracts 128 metrics from the ICP pulse-waveform (Figure 1A). Previous studies in patients undergoing CO2 inhalation identified a template of 72 metrics that consistently increase or decrease during vasodilation of the cerebral vasculature. The proportion of metrics that match this template (VDI) was found for each session and compared with VDIs from a control set of normal pressure hydrocephalus (NPH) patients using a Mann-Whitney test. Results: Fifteen aSAH patients had ICP monitored during 29 RIC sessions of approximately 40 minutes. ICP segments of the same length were collected for 8 NPH patients. The median VDI was significantly higher in the RIC patients (0.79, 0.42, p<0.01) (Figure 1B) Conclusion: Pulse-waveform changes observed during the RIC procedures indicate vasodilation when compared to control patients. Intracranial pressure waveform analysis is a useful tool to detect real time changes in the state of the cerebrospinal circulatory system, providing additional insight into the mechanism and effects of RIC.

Intracranial Pressure Waveform Analysis During Rest and Suctioning

Cerebral compliance is a measure of cerebral adaptability to increases in volume within the intracranial space and an indicator of risk for neurological deterioration. However, no direct measurement of compliance exists in clinical practice to guide nursing care or treatment decisions. Current use of mean intracranial pressure (MICP) and gross morphological intracranial pressure waveform (ICPW) analysis have great variability in predicting outcomes. The purpose of this review and pilot study was to evaluate the effects of suctioning on MICP and other measures estimating cerebral compliance derived from analysis of ICPW on patient outcome. We analyzed arterial blood pressure waveforms (ABPWs), ICPWs, and respiratory cycle variations using Fourier Transform analysis, to explore the potential benefits of studying ICPWs across single cardiac and respiratory cycles using linear modeling and calculation of correlation coefficients. ABPWs, ICPWs, and MICP were measured over individual cardiac cycles across multiple respiratory phases in five critically ill neurological patients. Both direct and derived ICP measures, including Fourier analysis of ABP and ICP and the cross-transform between ABP and ICP, were correlated with patient outcome. This more complex waveform analysis of individual ABPW and ICPW together, and derived measures during both single cardiac and respiratory cycles, may provide information relevant to cerebral compliance and patient outcomes. Pending confirmation with additional data sets, this technique may be a useful real-time clinical tool to provide a measure of compliance and risk of neurological deterioration for clinicians.

Is Intracranial Pressure Waveform Analysis Useful in the Management of Pediatric Neurosurgical Patients?

Background: We have reported casuistic observations that intracranial pressure (ICP) waveform analysis may be useful in the management of pediatric patients. Method: We here report our whole patient material of 65 children undergoing ICP monitoring with storage of their ICP raw data files during the years 2002–2005. We retrospectively explored the clinical symptoms/findings and radiological cerebral ventricular size before ICP monitoring. Mean ICP was the actively treated ICP parameter. Using an algorithm for identification of cardiac-beat-induced pressure waves we retrospectively determined the mean ICP wave amplitude and latency, in addition to mean ICP. Outcome with regard to change in symptoms/findings during a 1-year period was determined in 55 children. Results: The material includes children with hydrocephalus, craniosynostosis, shunt failure, benign intracranial hypertension and others. The ICP recordings gave wrong diagnostic information due to bad signal quality in 5 of 65 patients (7.7%). The mean ICP wave amplitude was increased in those with papilledema, lethargy and nausea. The main observations were that the mean ICP wave amplitude (not mean ICP) was increased in those that improved from clinical symptoms/findings after treatment and in those that were unchanged/worse after not being treated. Conclusions: Waveform analysis with computation of the mean ICP wave amplitude was more useful by providing information about the quality of the ICP recording, by comparing better with the symptoms/findings at the time of ICP monitoring and by best predicting outcome. Most significantly, 14 of 55 patients (25%) with high amplitudes and left untreated did not recover spontaneously.

Intracranial pressure waveform analysis: clinical and research implications.

Assessment of intracranial adaptive capacity is vital in critically ill individuals with acute brain injury because there is the potential that nursing care activities and environmental stimuli to result in clinically significant increases in intracranial pressure (ICP) in a subset of individuals with decreased intracranial adaptive capacity. ICP waveform analysis provides information about intracranial dynamics that can help identify individuals who have decreased adaptive capacity and are at risk for increases in ICP and decreases in cerebral perfusion pressure, which may contribute to secondary brain injury and have a negative impact on neurologic outcome. The ability to identify high-risk individuals allows nurses to initiate interventions targeted at decreasing adaptive demand or increasing adaptive capacity in these individuals. Changes in the ICP waveform occur under various physiologic and pathophysiologic conditions and may provide valuable information about intracranial adaptive capacity. Simple visual assessment of the ICP waveform for increased amplitude and P2 elevation is clinically relevant and has been found to provide a rough indicator of decreased adaptive capacity. Advanced ICP waveform analysis techniques warrant further study as a means of dynamically assessing intracranial adaptive capacity.

New monitors of neurological functions — part 2

This article is the second of two parts. In this section, techniques for monitoring cerebral oxygenation, cerebral biochemistry, intracranial elastance and spinal cord integrity are described. The developments of certain of the new monitors including near-infrared spectroscopy, brain tissue oxygen tension measurement, intracerebral microdialysis, monitors of compliance and techniques for measuring motor evoked potential are discussed in detail. New applications for some established monitors (jugular bulb venous oximetry, intracranial pressure waveform analysis) are also described.

Intracranial pressure waveform analysis: Computation of pressure transmission and waveform shape indicators

We studied transmission of arterial blood pressure to intracranial pressure by observing how the two pressure waveforms varied from baseline conditions to after postural change or jugular compression. Such experiments may lead to pressure waveform-based estimates of intracranial compliance. Using a single database of arterial blood pressure, central venous pressure! and intracranial pressure waveforms collected during baseline, jugular compresison! and head-elevated conditions from six Yucatan minipigs, we computed several numerical indicators of waveform shape to find an estimator of intracranial compliance. Of these indicators, two were based on the Fourier-decomposition of all three waveforms, and one was based on a new method for approximating the systolic slope of the intracranial pressure waveform. We computed amplitude transfer functions for the first six harmonics of the Fourier spectrum! treating intracranial pressure as system output and independently treating arterial blood pressure and central venous pressure as system inputs. Using these same inputs and outputs, we computed a single quotient based on the Fourier coefficients of the first six harmonics of the input and output waveforms. Finally, applying a Gaussian high-pass filter, we computed systolic slope approximations for all intracranial pressure wave cycles contained in a single respiratory cycle. Our third indicator was the mean-normalized variation of the slope approximations over a respiratory cycle. We studied how each composite at baseline varied with baseline mean intracranial pressure and how each composite changed from baseline as a result of a physical manipulation. Our analysis suggests that the composite based on respiratory variation of systolic slope approximations was positively correlated with mean intracranial pressure during baseline. The quotient based on Fourier coefficients with arterial blood pressure input seemed to increase from baseline to jugular compression. Composites that treated central venous pressure as input were both less correlated with mean intracranial pressure during baseline and exhibited less predictable changes from baseline to a physical manipulation than their counterparts that used arterial blood pressure as input. However! none of these apparent trends was statistically significant. The lack of statistically significant results may be due to the nature of the composites and/or the small sample size (n = 6). However, we hope this study stimulates further investigation of both central venous pressure-to-intracranial pressure (in addition to arterial blood pressure-to-intracranial pressure) transfer and automated computation of intracranial pressure waveform systolic slope. Such research may lead to noninvasively determined estimators of intracranial compliance. [Neural Res 1998; 20: 533-541]

Significance of intracranial pressure waveform analysis after head injury.

The authors have investigated the relationships between the amplitude of the ICP pulse wave, the mean values of ICP and CPP, and the outcome of 56 head injured ventilated patients. The ICP was monitored continuously using a Camino transducer (35 patients) or subdural catheter (21 patients). The mean Glasgow Coma Score was 6 (range 3-13; 5 patients had a GCS > 8 after resuscitation). Patients were grouped according to their Glasgow Outcome Score assessed at 12 months after injury. The amplitude of ICP pulse waveform was assessed using the fundamental harmonic of the pulse waveform (AMP) to avoid distortion caused by different frequency responses of the pressure transducers used in the study. Statistical analysis revealed that in patients with fatal outcome the ICP pulse amplitude increased when the mean ICP increased to 25 mmHg and then began to decrease. The upper breakpoint of the AMP-ICP relationship was not present in patients with good/moderate outcome. The moving correlation coefficient between the fundamental harmonic of ICP pulse wave and the mean ICP (RAP: R-symbol of correlation between A-amplitude and P-pressure) was introduced to describe the time-dependent changes in correlation between amplitude and mean ICP. The RAP was significantly lower in patients who died or remained in the vegetative state. In 7 patients who died from uncontrollable intracranial hypertension RAP was oscillating or decreased to 0 or negative values well before brain-stem herniation. The combination of an ICP above 20 mmHg for a period longer than 6 hours with low correlation between the amplitude and pressure (RAP < 0.5) was described as an predictive index of an unfavourable outcome.

Analysis of intracranial pressure.

Methods for the acqusition and analysis of intracranial pressure (ICP) signals are reviewed from clinical and technical perspectives. The clinical importance of ICP monitoring is presented, and methods for ICP transduction are briefly discussed. These methods include intraventricular catheters, subarachnoid screws, epidural techniques, and the new fiberoptic ICP measurement systems. Approaches to the visual analysis of the ICP waveform are presented, with special emphasis on the relationship between the ICP waveform and the arterial blood pressure signal. Methods of computer-based ICP analysis are also reviewed, including histogram and "systems analysis" methods. Methods to predict ICP pressure rises and to estimate intracranial compliance are also discussed. Finally, ICP monitoring is reviewed from the point of view of patient outcome. It is concluded that advanced ICP waveform analysis methods warrant further clinical evaluation to demonstrate their clinical usefulness.

Analysis of intracranial pressure waveform during infusion test

An analysis of intracranial pressure (ICP), based on an examination of the temporary correlation between the changes in amplitude of the pulse wave and the mean ICP level, is presented. The paper contains a discussion of the preliminary results of the method when applied to the analysis of ICP as monitored during infusion tests in a group of 24 children. Infusion of a certain volume of CSF is a good example of an uncompensated volume process, introduced externally into the intracranial space. Results allow an interpretation of the short term correlation coefficient RAP (correlation coefficient between ICP and variations of the amplitude of fundamental component of the pulse wave AMP), as a steady state index. According to this interpretation, the presented analysis enables the observation of a loss of equilibrium during the test. Other phenomena can also be observed, for instance a recovery to equilibrium after the test, nonlinearities of amplitude-pressure relationship, vasomotor reflexes etc.