Intracranial Pressure Monitoring System Research Articles

Characterization of intracranial compliance in healthy subjects using a noninvasive method - results from a multicenter prospective observational study.

An FDA-approved non-invasive intracranial pressure (ICP) monitoring system enables the assessment of ICP waveforms by revealing and analyzing their morphological variations and parameters associated with intracranial compliance, such as the P2/P1 ratio and time-to-peak (TTP). The aim of this study is to characterize intracranial compliance in healthy volunteers across different age groups. Healthy participants, both sexes, aged from 9 to 74 years old were monitored for 5min in the supine position at 0º. Age was stratified into 4 groups: children (≤ 7 years); young adults (18 ≤ age ≤ 44 years); middle-aged adults (45 ≤ age ≤ 64 years); older adults (≥ 65 years). The data obtained was the non-invasive ICP waveform, P2/P1 ratio and TTP. From December 2020 to February 2023, 188 volunteers were assessed, of whom 104 were male, with a median (interquartile range) age of 41 (29-51), and a median (interquartile range) body mass index of 25.09 (22.57-28.04). Men exhibited lower values compared to women for both the P2/P1 ratio and TTP (p < 0.001). There was a relative rise in both P2/P1 and TTP as age increased (p < 0.001). The study revealed that the P2/P1 ratio and TTP are influenced by age and sex in healthy individuals, with men displaying lower values than women, and both ratios increasing with age. These findings suggest potential avenues for further research with larger and more diverse samples to establish reference values for comparison in various health conditions. Brazilian Registry of Clinical Trials (RBR-9nv2h42), retrospectively registered 05/24/2022. UTN: U1111-1266-8006.

Determining an accurate external reference point for zeroing an external ventricular drain (EVD) as an intracranial pressure monitoring system.

Determining an accurate external reference point for zeroing an external ventricular drain (EVD) as an intracranial pressure monitoring system.

Implantable Intracranial Pressure Sensor with Continuous Bluetooth Transmission via Mobile Application.

Hydrocephalus is a clinical disorder caused by excessive cerebrospinal fluid (CSF) buildup in the ventricles of the brain, often requiring permanent CSF diversion via an implanted shunt system. Such shunts are prone to failure over time; an ambulatory intracranial pressure (ICP) monitoring device may assist in the detection of shunt failure without an invasive diagnostic workup. Additionally, high resolution, noninvasive intracranial pressure monitoring will help in the study of diseases such as normal pressure hydrocephalus (NPH) and idiopathic intracranial hypertension (IIH). We propose an implantable, continuous, rechargeable ICP monitoring device that communicates via Bluetooth with mobile applications. The design requirements were met at the lower ICP ranges; the obtained error fell within the idealized ±2 mmHg margin when obtaining pressure values at or below 20 mmHg. The error was slightly above the specified range at higher ICPs (±10% from 20-100 mmHg). The system successfully simulates occlusions and disconnections of the proximal and distal catheters, valve failure, and simulation of A and B ICP waves. The mobile application accurately detects the ICP fluctuations that occur in these physiologic states. The presented macro-scale prototype is an ex-vivo model of an implantable, rechargeable ICP monitoring system that has the potential to measure clinically relevant ICPs and wirelessly provide accessible and continuous data to aid in the workup of shunt failure.

Fiber-Optic Intracranial Pressure Monitoring System Using Wi-Fi-An In Vivo Study.

Continuous invasive monitoring of intracranial pressure (ICP) is essential in neurocritical care for surveillance and management of raised ICP. Fluid-based systems and strain gauge microsensors remain the current standard. In the past few decades, several studies with wireless monitoring were developed aiming to reduce invasiveness and complications. To describe a novel Wi-Fi fiber-optic device for continuous ICP monitoring using smartphone in a swine model. Two ICP sensors (wireless prototype and wire-based reference) were implanted in the cerebral parenchyma of a swine model for a total of 120 minutes of continuous monitoring. Every 5 minutes, jugular veins compression was performed to evaluate ICP changes. The experimentation was divided in 3 phases for comparison and analysis. Phase 1 showed agreement in ICP changes for both sensors during jugular compression and releasing, with a positive and strong Spearman correlation (r = 0.829, P < .001). Phase 2 started after inversion of the sensors in the burr holes; there was a positive and moderately weak Spearman correlation (r = 0.262, P < .001). For phase 3, the sensors were returned to the first burr holes; the prototype behaved similarly to the reference sensor, presenting a positive and moderately strong Spearman correlation (r = 0.669, P < .001). A Wi-Fi ICP monitoring system was demonstrated in a comprehensive and feasible way. It was possible to observe, using smartphone, an adequate correlation regarding ICP variations. Further adaptations are already being developed.

Rapid chest compression effects on intracranial pressure in patients with acute cerebral injury

BackgroundPatients with acute brain injury often require invasive mechanical ventilation, increasing the risk of developing complications such as respiratory secretions retention. Rapid chest compression is a manual chest physiotherapy technique that aims to improve clearance of secretions in these patients. However, the rapid chest compression technique has been suggested to be associated with increased intracranial pressure in patients with acute brain injury. The aim of this work is to elucidate the effects of the technique on intracranial pressure in mechanically ventilated patients with acute brain injury. Furthermore, the effects of the technique in different volumes and flows recorded by the ventilator and the relationship between the pressure applied in the intervention group and the different variables will also be studied.MethodsRandomized clinical trial, double-blinded. Patients with acute brain injury on invasive mechanical ventilation > 48 h will be included and randomized in two groups. In the control group, a technique of passive hallux mobilization will be applied, and in the intervention group, it will be performed using the rapid chest compression technique. Intracranial pressure (main variable) will be collected with an intracranial pressure monitoring system placed at the lateral ventricles (Integra Camino).DiscussionThe safety of chest physiotherapy techniques in patients at risk of intracranial hyperpressure is still uncertain. The aim of this study is to identify if the rapid manual chest compression technique is safe in ventilated patients with acute brain injury.Trial registrationNCT03609866. Registered on 08/01/2018.

Invention of a non-invasive intracranial pressure (ICP) monitoring system – an enlightenment from a hydrocephalus study

Background Mechanical obstruction is the most common cause of shunt failure for hydrocephalic patients. However, the diagnosis is extremely challenging and often requires invasive testing methods. Thus, a simple and non-invasive technique is in urgent need to predict the intracranial pressure (ICP) of hydrocephalic patients during their post-surgical follow-up, which could help neurosurgeons to determine the conditions of the shunt system. Materials and methods Two groups of patients were enrolled in the current study. In group I, patients were enrolled as they were diagnosed with high ICP hydrocephalus and received shunt surgery. The shunt valve pressures were taken for their post-surgical ICP. Meanwhile, the participants of group II exhibited abnormally increased lumbar puncture opening pressure (LPOP; from 180 to 400 mmH2O). Both the ICP and LPOP were used to match with their corresponding tympanic membrane temperature (TMT). Results When patients’ ICP were in the normal range (group I, from 50 to 180 mmH2O), the TMT correlated with ICP in a linear regression model (R 2 = 0.59, p < 0.001). Interestingly, when patients exhibited above-normal ICP (LPOP was from 180 to 400 mmH2O), their TMT fit well with the ICP in a third-order polynomial regression (R 2 = 0.88). When the ICP was 287.98 mmH2O, the TMT approached the vertex, which was 38.54 °C. Based on this TMT-ICP algorithm, we invented a non-invasive ICP monitor system. Interestingly, a tight linear correlation was detected between the ICP data drawn from the non-invasive device and Codman ICP monitoring system (R 2 = 0.93, p < 0.01). Conclusions We believe the TMT-ICP algorithm (the Y-Jiang model) could be used for preliminary prediction of shunt malfunction as well as monitoring ICP changes.

Peak Systolic Velocity in Middle Cerebral Artery in Patients with Severe Traumatic Brain Injury as an Indicator of Detrimental Rise in Intracranial Pressure

Background Intracranial pressure (ICP) is the major concern for neurosurgeons while treating patients with severe traumatic brain injury, as any troublesome escalation in intracranial pressure heralds feared complications leading to definite morbidity or even mortality.&#x0D; Objective This study focuses on analyzing the correlation between peak systolic velocity in middle cerebral artery derived from transcranial doppler ultrasonographic spectral analysis and intracranial pressure values derived from invasive intracranial pressure monitoring system in a patient with severe traumatic brain injury.&#x0D; Method A prospective observational study was performed using a convenience sample technique including all adult patients with severe traumatic brain injury who had invasive intracranial monitors placed as part of their clinical care. Transcranial doppler ultrasonography was performed with a 2 MHz linear probe of ACUSON X300 ultrasound system while simultaneous intracranial pressure readings were obtained directly from invasive intracranial pressure monitoring. The association between peak systolic velocity in the middle cerebral artery and invasive intracranial pressure was assessed with Pearson’s correlation coefficient.&#x0D; Result One hundred one transcranial doppler ultrasound spectral analysis was performed on 26 individual patients. The mean age of the population involved in this study is 43.57 years ± S.D. 19.95 (range 18-78 years), with male preponderance in a ratio of 5.5:1. Pearson’s correlation coefficient of peak systolic velocity in middle cerebral artery and intracranial pressure was 0.715 (p &lt; 0.000) demonstrating a significant positive correlation. With further evaluation of area under curve characteristics, peak systolic velocity in middle cerebral artery of 39.6 cm/s yielded the most favorable balance of test characteristics to diagnose elevation of intracranial pressure, with a resulting sensitivity of 82.1% and specificity of 84.4%.&#x0D; Conclusion Peak systolic velocity in middle cerebral artery can be explored further as a dependable screening tool to evaluate intracranial pressure among patients with severe traumatic brain injury in settings with unavailability of invasive intracranial pressure monitoring facilities.

Design of circularly polarized implantable antenna for wireless intracranial pressure monitoring system

Monitor of intracranial pressure (ICP) system is a life-saving instrument that monitors changes in brain pressure in real time. To implement wireless data transfer, antenna is an indispensable device. In this paper, an implantable antenna is designed with circularly polarized, wideband and compact in size to adapt the application of the ICP monitoring system. First, a one-layer human skin model to verify the basic characteristics of this antenna; and then a multilayered human head model is built to demonstrate the system performance of the designed antenna. In addition, we also considered the human safety to calculate the specific absorption rate value of the proposed antenna. The antenna can transmit different rates over to 1.5 m distance verified by the wireless communication link, which proved it has a good transitions characteristic. Finally, the sample of the antenna is fabricated and tested with help of fresh minced pork. Experiment results shows the antenna with a good property in the ICP monitoring system, as well as other remote medical telemetry system.

From head micro-motions towards CSF dynamics and non-invasive intracranial pressure monitoring

Continuous monitoring of the intracranial pressure (ICP) is essential in neurocritical care. There are a variety of ICP monitoring systems currently available, with the intraventricular fluid filled catheter transducer currently representing the “gold standard”. As the placement of catheters is associated with the attendant risk of infection, hematoma formation, and seizures, there is a need for a reliable, non-invasive alternative. In the present study we suggest a unique theoretical framework based on differential geometry invariants of cranial micro-motions with the potential for continuous non-invasive ICP monitoring in conservative traumatic brain injury (TBI) treatment. As a proof of this concept, we have developed a pillow with embedded mechanical sensors and collected an extensive dataset (> 550 h on 24 TBI coma patients) of cranial micro-motions and the reference intraparenchymal ICP. From the multidimensional pulsatile curve we calculated the first Cartan curvature and constructed a ”fingerprint” image (Cartan map) associated with the cerebrospinal fluid (CSF) dynamics. The Cartan map features maxima bands corresponding to a pressure wave reflection corresponding to a detectable skull tremble. We give evidence for a statistically significant and patient-independent correlation between skull micro-motions and ICP time derivative. Our unique differential geometry-based method yields a broader and global perspective on intracranial CSF dynamics compared to rather local catheter-based measurement and has the potential for wider applications.

Correlation between Invasive Intracranial Pressure Monitoring and Optic Nerve Sheath Diameter in Patients with Traumatic Brain Injury

Background In management of patients with traumatic brain injury, intracranial pressure holds an important place. Any untoward rise in intracranial pressure portends dreaded complications. Hence, any delay in detecting the issue is considered unacceptable.&#x0D; Objective This study focuses on analyzing the correlation between ultrasound derived optic nerve sheath diameter and intracranial pressure values derived from invasive intracranial pressure monitoring system in a neurosurgical patient with severe traumatic brain injury.&#x0D; Method A prospective observational study was performed using a convenience sample technique including all adult patients with traumatic brain injury who had invasive intracranial monitors placed as part of their clinical care. Ocular ultrasound was performed with 5 - 7.5 MHz linear probe of ACUSON X300 ultrasound system while simultaneous intracranial pressure readings were obtained directly from an invasive intracranial pressure monitoring system. The association between optic nerve sheath diameter and invasive intracranial pressure reading was assessed with the Pearson’s correlation coefficient and a receiver operator characteristic curve was created to determine the optimal optic nerve sheath diameter cutoff to detect intracranial pressure &gt; 15 cm H2O.&#x0D; Result One hundred and fifteen ocular ultrasounds were performed on 30 individual patients. The mean age of the population involved in this study is 42.13 years ± 1.89 with male preponderance in the ratio of 6:1. Pearson’s correlation coefficient of optic nerve sheath diameter and intracranial pressure was found to be 0.844 (p &lt; 0.000) demonstrating a significant positive correlation. The area under the receiver operating characteristic curve was found to be 0.961 (95% confidence interval = 0.93 to 0.99). Based on analysis of the receiver operating characteristic curve, optic nerve sheath diameter &gt; 4.85 mm performed best to detect intracranial pressure &gt; 15 cm H2O with a sensitivity of 93.5% and specificity of 83%.&#x0D; Conclusion Optic nerve sheath diameter is a dependable screening tool to evaluate for elevated intracranial pressure among patients with traumatic nerve injury.

Real-Time Intraoperative Pressure Monitoring to Avoid Surgically Induced Localized Brain Injury Using a Miniaturized Piezoresistive Pressure Sensor.

Neurosurgical procedures often cause damage to the brain tissue at the periphery from surgical manipulations. Especially during retraction, a large amount of pressure could be applied on the brain surface, which can damage it, leading to brain herniation, which can be fatal for patients. To resolve this issue, we have developed a pressure sensor that can be used to monitor the applied pressure during surgery for intraoperative care. This device was tested on a rodent model to create a superficial surgically induced damage profile for three different applied pressures (30, 50, and 70 mmHg) and compared to a standard intracranial pressure monitoring system. Magnetic resonance imaging has been performed after surgical procedures to detect the herniation caused by applied pressure. To evaluate the damage to brain cells and tissue rupture, histological analysis was performed using hematoxylin and eosin staining. A scoring system was developed to understand the severity of the surgically induced brain injury, which will help neurosurgeons to limit the pressure to an optimum point without causing damage.

Wireless Passive Intracranial Pressure Sensor Based on Vacuum Packaging

This paper presents a wireless passive pressure sensor based on a pressure-sensitive capacitor specifically designed to monitor intracranial pressure (ICP) in patients with traumatic brain injuries. It is crucial that temperature will affect the accuracy of pressure detection. To improve temperature stability, the capacitor is composed of an SOI wafer as the sensing element and a glass cap for vacuum packaging. To realize reliable vacuum packaging, it is vital to transfer the electrical signal out of the vacuum cavity. The experimental results show that the proposed sensor demonstrated averaged pressure sensitivity and averaged temperature sensitivity of 0.5803 Hz/kPa and 0.024 Hz/°C. Additionally, the in-vivo test in the animal show that the proposed sensor has the similar detection effect with the commercial wired sensor, and naturally has the advantage of reducing the risk of infection, which further validated the feasibility and effectiveness of the wireless passive ICP monitoring system.

Vibrational Properties of a Hemispherical Shell With Its Inner Fluid Pressure: An Inverse Method for Noninvasive Intracranial Pressure Monitoring

Vibration due to a hammer impact on an aluminum hemisphere fully filled with water is determined to study the frequency response of the structure at different inner fluid pressures. Modal analysis techniques are utilized on the frequency response function (FRF) to extract the modal frequencies and the damping ratios at each pressure level. As fluid pressure increases, changes to the peaks of frequency response are observed. Due to this, modal frequencies will also undergo some shifts with changes in the repeated poles of frequency response. Changes can also be observed in singular bending wave modes. An inverse analysis of such changes due to inner pressure in modal frequencies of the structure can make a possible method for using vibrational stimulus and response in a noninvasive intracranial pressure (ICP) monitoring system.

Deciding on Appropriate Telemetric Intracranial Pressure Monitoring System

The clinical advantage of telemetric intracranial pressure (ICP) monitoring has previously been limited by issues with inaccuracy and zero-drift. Today, 2 comparable telemetric ICP monitoring systems are available performing adequately in these parameters. The objective of this study is to identify appropriate uses of each system. The 2 telemetric ICP monitoring systems from Raumedic (implant: Neurovent-P-tel) and Miethke (implant: Sensor Reservoir) are compared in terms of fundamental differences, sensor survival, monitoring possibilities, complications, and cost/benefit. Two illustrative cases are presented highlighting clinical advantages and disadvantages of each system. Both systems provide transdermal (telemetric) ICP measurements through external application of a reader unit cabled to a portable data sampler. Thereby, they allow several ICP monitoring sessions without multiple surgical insertions of a cabled ICP sensor. The Miethke implant has a high sampling frequency (40 Hz) and a long CE (Conformité Européenne) approval (3 years) but cannot be used for long-duration monitoring sessions. In comparison, the Raumedic implant has a lower sampling frequency (5 Hz) and shorter CE approval (90 days) but can be used for long-duration monitoring sessions. The standard 3-year cost for a patient with a Neurovent-P-tel is 17,380 €, and for the Sensor Reservoir it is 15,790 €. The Miethke system is useful in outpatient clinics where patients have sequential point measurements of ICP performed, whereas the Raumedic system is ideal for long-duration ICP monitoring outside the hospital. When choosing between the 2 systems, it must primarily be decided if the clinical situation requires long-duration monitoring sessions or continuous repeated ambulatory follow-up sessions.

Intraoperative Measuring of the Offending Vessel’s Pressure on the Facial Nerve at Root Exit Zone in Patients with Hemifacial Spasm During Microvascular Decompression: A Prospective Study

The compression of the offending vessel on the facial nerve at root exit zone is considered as the leading cause of hemifacial spasm (HFS). However, the correlation between the severity of spasm and the pressure of neurovascular compression (NVC) has not yet been investigated. The aim of this study was to investigate the clinical correlation between the severity of HFS and the pressure of NVC. A prospective study was performed, which included 52 of 151 patients who underwent microvascular decompression. We classified the preoperative spasm severity according to the Cohen scores. Codman intracranial pressure monitoring system was used to measure the NVC pressure at the root exit zone during microvascular decompression. All patients were followed up for 12-24 months. Herein, the intraoperative pressure readings of NVC were in the range of 21-63 mmHg. The means of thepressure of NVC that corresponded to the Cohen scores (1-4) were 23.00 ± 1.83, 34.91 ± 12.42, 46.50 ± 9.40, and 55.40 ± 3.03 mmHg, respectively. The Spearman's rank correlation established a strong positive correlation between the pressure and the Cohen scores (r= 0.689, P<0.0001). The simple linear analysis indicated that sex (P= 0.132), duration (P= 0.304), and delayed relief (P=0.158) were not significantly associated with the pressure. However, a substantial correlation was determined between the pressure values and the time until the complete recovery (r= 0.949, P < 0.0001) of the delayed healing population. The severity of HFS exhibited a strong positive correlation with the intraoperative offending vessel's pressure values. Thus, the neurovascular pressure is a significant factor in the pathogenesis of HFS.

Study of Intracranial Pressure Monitoring In Traumatic Brain Injury

Intracranial pressure monitoring is considered the standard of care for severe traumatic brain injury and is used frequently. However, the efficacy of treatment based on monitoring in improving the outcome has not been rigorously assessed. We conducted a trial in which we included 26 patients of all types of traumatic brain injury (TBI) and they were monitored for intracranial pressure by Conventional fluid filled system with a manometer (Group 1) and compared with the Fiber optic transducer-tipped intracranial pressure monitoring system (Group 2).The main aim of this study was to examine the relationship between Intracranial Pressure (ICP) monitoring and in-hospital mortality. The median length of stay in the ICU was similar in the two groups (12 days in the conventional pressure-monitoring group and 9 days in the new fiber optic group; P=0.25), the number of days of brain-specific treatments (e.g., administration of hyperosmolar fluids and the use of hyperventilation) in the ICU was similar in both groups. The distribution of serious adverse events was similar in the two groups. We concluded that ICP monitoring (as is any monitoring modality) is a useful guide for management. The outcomes are decided by the differences in management protocols that the knowledge of the said parameter brings about. ICP monitoring is recommended for the better management of traumatic brain injury and fiber optic ICP monitoring seems to be beneficial than using the conventional methods of ICP monitoring with manometer.Nepal Journal of Neuroscience, Volume 15, Number 2, 2018, page: 23-29

Implantable Wireless Intracranial Pressure Monitoring Based on Air Pressure Sensing

A wireless intracranial pressure (ICP) monitoring system based on the air pressure sensing is proposed in this work. The proposed system is composed of an implantable ICP sensing device and a portable wireless data recorder. The ICP sensing device consists of an air pressure sensor, an ultra-thin air pouch for pressure sensing, and a low-power dedicated system-on-a-chip (SoC) for the data acquisition control and wireless transmission. The SoC consists of a power management unit, a wake-up controller, the sensor interface, a wireless transmitter, and the workflow control logic. The SoC is fabricated in 0.18μm CMOS technology with a die area of 3.04 mm × 2 mm. Experimental results show that the prototype implantable ICP device has achieved a resolution of 0.2 mmHg and a battery lifetime of 1 week with a 3 V 50 mAh battery. The ICP device has been tested in the liquid environment. The nonlinearity error is less than ±0.4 mmHg for the full measurement range of -20 to +150 mmHg. Compared to the other implantable wireless ICP solutions in the literature, the proposed system alleviates the biocompatibility issue and increases the measurement accuracy.

Characterization of 3-D Loop Antenna to Overcome the Impact of Small Lateral Misalignment in Wirelessly Powered Intracranial Pressure Monitoring System

This communication presents a 3-D loop antenna to overcome the impact of small lateral misalignment of the order of 2 mm between the inductively coupled antennas. This communication is a continuation of our previously reported work. In our previous work, we have successfully activated the pressure monitoring sensor and performed the pressure readout for an intracranial pressure monitoring application. The pressure sensor was activated through wireless inductive near-field powering. Measurement showed that there was significant effect on pressure readout accuracy due to small lateral misalignment between the inductively coupled antennas. In this communication, we demonstrate that the structural properties of a simple 3-D loop antenna help to overcome the pressure readout error caused by small lateral misalignment. We present the design procedure, simulation results, and pressure readout measurement of the proposed 3-D loop antenna. Moreover, the pressure monitoring system shows maximum improvement of 9 mmHg in pressure readout accuracy with the proposed 3-D loop antenna.

A Novel Intracranial Pressure Readout Circuit for Passive Wireless LC Sensor.

We present a wide frequency range, low cost, wireless intracranial pressure monitoring system, which includes an implantable passive sensor and an external reader. The passive sensor consists of two spiral coils and transduces the pressure change to a resonant frequency shift. The external portable reader reads out the sensor's resonant frequency over a wide frequency range (35MHz-2.7 GHz). We propose a novel circuit topology, which tracks the system's impedance and phase change at a high frequency with low-cost components. This circuit is very simple and reliable. A prototype has been developed, and measurement results demonstrate that the device achieves a suitable measurement distance (>2 cm), sufficient sample frequency (>6 Hz), fine resolution, and good measurement accuracy for medical practice. Responsivity of this prototype is 0.92MHz/mmHg and resolution is 0.028mmHg. COMSOL specific absorption rate simulation proves that this system is safe. Considerations to improve the device performance have been discussed, which include the size of antenna, the power radiation, the Analog-to-digital converter (ADC) choice, and the signal processing algorithm.

Effect of temperature variation on remote pressure readout in wirelessly powered intracranial pressure monitoring system.

An implantable pressure monitoring system is a compelling approach to home monitoring of intracranial pressure in the long term. In our approach, an on-body unit powers a cranially concealed system where a piezoresistive element senses the pressure. A data transmission unit built in the same platform emits a signal at a pressure dependent frequency through a miniature far field antenna. In this work, we focus on assessing the impact of variable temperature on the pressure readout at an off-body unit through in-vitro experiments.