Continuous monitoring of internal physiological parameters is essential for critical care patients, but currently can only be practically achieved via tethered solutions. Here we report a wireless, real-time pressure monitoring system with passive, flexible, millimetre-scale sensors, scaled down to unprecedented dimensions of 1 × 1 × 0.1 cubic millimeters. This level of dimensional scaling is enabled by novel sensor design and detection schemes, which overcome the operating frequency limits of traditional strategies and exhibit insensitivity to lossy tissue environments. We demonstrate the use of this system to capture human pulse waveforms wirelessly in real time as well as to monitor in vivo intracranial pressure continuously in proof-of-concept mice studies using sensors down to 2.5 × 2.5 × 0.1 cubic millimeters. We further introduce printable wireless sensor arrays and show their use in real-time spatial pressure mapping. Looking forward, this technology has broader applications in continuous wireless monitoring of multiple physiological parameters for biomedical research and patient care.

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Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care

Measurement of intracranial pressure (ICP) can be invaluable in the management of critically ill patients. Cerebrospinal fluid is produced by the choroid plexus in the brain ventricles (a set of communicating chambers), after which it circulates through the different ventricles and exits into the subarachnoid space around the brain, where it is reabsorbed into the venous system. If the fluid does not drain out of the brain or get reabsorbed, the ICP increases, which may lead to brain damage or death. ICP elevation accompanied by dilatation of the cerebral ventricles is termed hydrocephalus, whereas ICP elevation accompanied by normal or small ventricles is termed idiopathic intracranial hypertension. Objective We performed a comprehensive literature review on how to measure ICP invasively and noninvasively. Approach This review discusses the advantages and disadvantages of current invasive and noninvasive approaches. Main results Invasive methods remain the most accurate at measuring ICP, but they are prone to a variety of complications including infection, hemorrhage and neurological deficits. Ventricular catheters remain the gold standard but also carry the highest risk of complications, including difficult or incorrect placement. Direct telemetric intraparenchymal ICP monitoring devices are a good alternative. Noninvasive methods for measuring and evaluating ICP have been developed and classified in five broad categories, but have not been reliable enough to use on a routine basis. These methods include the fluid dynamic, ophthalmic, otic, and electrophysiologic methods, as well as magnetic resonance imaging, transcranial Doppler ultrasonography (TCD), cerebral blood flow velocity, near-infrared spectroscopy, transcranial time-of-flight, spontaneous venous pulsations, venous ophthalmodynamometry, optical coherence tomography of retina, optic nerve sheath diameter (ONSD) assessment, pupillometry constriction, sensing tympanic membrane displacement, analyzing otoacoustic emissions/acoustic measure, transcranial acoustic signals, visual-evoked potentials, electroencephalography, skull vibrations, brain tissue resonance and the jugular vein. Significance This review provides a current perspective of invasive and noninvasive ICP measurements, along with a sense of their relative strengths, drawbacks and areas for further improvement. At present, none of the noninvasive methods demonstrates sufficient accuracy and ease of use while allowing continuous monitoring in routine clinical use. However, they provide a realizable ICP measurement in specific patients especially when invasive monitoring is contraindicated or unavailable. Among all noninvasive ICP measurement methods, ONSD and TCD are attractive and may be useful in selected settings though they cannot be used as invasive ICP measurement substitutes. For a sufficiently accurate and universal continuous ICP monitoring method/device, future research and developments are needed to integrate further refinements of the existing methods, combine telemetric sensors and/or technologies, and validate large numbers of clinical studies on relevant patient populations.

https://iopscience.iop.org/article/10.1088/1361-6579/aa7256/pdf

Invasive and noninvasive means of measuring intracranial pressure: a review.

Although cerebrospinal fluid (CSF) shunt placement is the most common procedure performed by pediatric neurosurgeons, shunts remain among the most failure-prone life-sustaining medical devices implanted in modern medical practice. This article provides an overview of the mechanisms of CSF shunt failure for the 3 most commonly employed definitive CSF shunts in the practice of pediatric neurosurgery: ventriculoperitoneal, ventriculopleural, and ventriculoatrial. The text has been partitioned into the broad modes of shunt failure: obstruction, infection, mechanical shunt failure, overdrainage, and distal catheter site-specific failures. Clinical management strategies for the various modes of shunt failure are discussed as are research efforts directed towards reducing shunt complication rates. As it is unlikely that CSF shunting will become an obsolete procedure in the foreseeable future, it is incumbent on the pediatric neurosurgery community to maintain focused efforts to improve our understanding of and management strategies for shunt failure and shunt-related morbidity.

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Cerebrospinal Fluid Shunting Complications in Children.

Endoscopic Third Ventriculostomy: Outcome Analysis of 100 Consecutive Procedures

An adjuvant is a substance that enhances the antigen-specific immune response, induces the release of inflammatory cytokines, and interacts with Toll-like receptors and the NALP3 inflammasome. The immunological consequence of these actions is to stimulate the innate and adaptive immune response. The activation of the immune system by adjuvants, a desirable effect, could trigger manifestations of autoimmunity or autoimmune disease. Recently, a new syndrome was introduced, autoimmune/inflammatory syndrome induced by adjuvants (ASIA), that includes postvaccination phenomena, macrophagic myofasciitis, Gulf War syndrome and siliconosis. This syndrome is characterized by nonspecific and specific manifestations of autoimmune disease. The main substances associated with ASIA are squalene (Gulf War syndrome), aluminum hydroxide (postvaccination phenomena, macrophagic myofasciitis) and silicone with siliconosis. Mineral oil, guaiacol and iodine gadital are also associated with ASIA. The following review describes t...

Autoimmune/inflammatory syndrome induced by adjuvants (Shoenfeld's syndrome): clinical and immunological spectrum.

Telemetric Intracranial Pressure Monitoring with the Raumedic Neurovent P-tel

The objective was to evaluate the qualification of the new telemetric intracranial pressure (ICP) measurement (t-ICP) device Raumedic® NEUROVENT P-Tel and S-Tel. The proof of concept was examined in a pilot animal study measuring intraperitoneal pressure with a telemetric and a conventional ICP measurement probe at five rates for 1 h each. Moderate external pressure load allowed measuring values between 0 and 40 mmHg. To estimate long-term performance 18 t-ICP devices were implanted subdurally or intraparenchymally into minipigs. Reference measurements were performed regularly using conventional ICP probes. From the short-term as well as from the long-term perspective t-ICP proved to have excellent dynamic ICP signal components perception (e.g. pulse amplitude). Some zero drift of static ICP was found, ranging between 5 and 8 mmHg. While all telemetric, intraparenchymal probes kept their functionality throughout the follow-up, 33% of the subdurals failed for reasons detailed in another paper. Raumedic’s NEUROVENT® P-Tel/S-Tel proved to provide reliable data over periods of up to 18 months. Minor zero drift can be well tolerated as the dynamic ICP signal is measured with excellent stability. Clinicians should focus more on such ICP dynamic signal information than on static ICP when using the device over longer follow-up periods.

Telemetric ICP Measurement with the First CE-Approved Device: Data from Animal Experiments and Initial Clinical Experiences

Despite progress in shunt valve technology, CSF overdrainage is still one of the most frequent complications in shunt-treated hydrocephalus. Particularly with regard to young and adolescent patients, treatment of manifest overdrainage is complicated by several hardly influenceable factors such as increasing height and mobility. Therefore, the aim of this study was to evaluate the therapeutic efficiency of the new adjustable gravitational valve, proSA. Sixty-four shunt-treated young hydrocephalus patients aged 1.8–41.4 years (15.5 ± 10.5 years) suffering from clinical and/or radiological overdrainage underwent shunt revision surgery with the implantation of the new proSA valve. Clinical outcome after a 1-year follow-up period, pumping function of the valve chambers as well as the number of necessary postoperative valve adjustments were examined. Fifty-five patients completed the study as planned. All reported a significant improvement of their clinical condition; 91 % described a complete resolution in symptoms related to overdrainage. Preoperatively, more than 85 % of the valve chambers showed no or very slow refilling with CSF. After a year of proSA treatment, more than 90 % exhibited a normal valve chamber function. During the follow-up period, a total of 136 valve adjustments were necessary. None of the proSA valves had to be surgically revised. The postoperative adjustability of the opening pressure level is the advantage of the new gravitational valve. The good clinical outcome is attributed to the new valve technology. The proSA appears to be a promising shunt valve to overcome overdrainage in adolescent and adult hydrocephalus patients.

Overcoming CSF overdrainage with the adjustable gravitational valve proSA

Intracranial Pressure–Guided Shunt Valve Adjustments with the Miethke Sensor Reservoir

Background
Advantages of telemetric devices for long-term intracranial pressure (ICP) measurement have been mentioned several times in the literature. However, descriptions of associated complications are lacking. Therefore, the presented observational study focused on clinical and radiological findings after insertion of an intraparenchymal telemetric ICP monitor.

Sebastian Antes

Papers

Telemetric Intracranial Pressure Monitoring with the Raumedic Neurovent P-tel

Telemetric ICP Measurement with the First CE-Approved Device: Data from Animal Experiments and Initial Clinical Experiences

Overcoming CSF overdrainage with the adjustable gravitational valve proSA

Intracranial Pressure–Guided Shunt Valve Adjustments with the Miethke Sensor Reservoir

Clinical and radiological findings in long-term intracranial pressure monitoring