A new self-adjustable glaucoma valve.

Introduction: Glaucoma, the leading cause of irreversible blindness globally, affects more than 70 million people across the world. When initial treatments prove ineffective, especially for cases with high intraocular pressure (IOP), the preferred approach involves employing glaucoma drainage devices (GDDs). Methods: This study introduces a novel self-adjustable glaucoma drainage device (SAGDD) designed to maintain IOP within the desired biological range (10 mmHg < IOP <18 mmHg) by dynamically modulating its fluidic resistance. Inspired by the starling resistor, we designed a circular valve with a thin, flexible membrane placed over the valve's inlet and outlet. To achieve the ideal design for the SAGDD and optimize its parameters, we utilized fluid-solid interaction (FSI) numerical models and conducted parametric studies, wherein simulations demonstrated the validity of the concept. Subsequently, to confirm and validate the numerical results, we fabricated a SAGDD at a 3:1 scale and subjected it to in vitro testing. Results: Our findings demonstrate that, on a 3:1 scale, a circular SAGDD with a diameter of 8.1 mm and a stainless-steel membrane with a thickness of 10 µm effectively maintained IOP within the target range when the membrane exposed to external pressures of 7.5 or 10 mmHg. Discussion: In summary, our study establishes a strong foundation for further exploration of the potential efficacy of SAGDD as a promising treatment for glaucoma. The cost-effectiveness and simplicity of its design, devoid of costly instrumentation, hold considerable promise in addressing the challenges associated with glaucoma.

Valve-Adjustable Optofluidic Bio-Imaging Platform for Progressive Stenosis Investigation.

The clinical evidence has proven that valvular stenosis is closely related to many vascular diseases, which attracts great academic attention to the corresponding pathological mechanisms. The investigation is expected to benefit from the further development of an in vitro model that is tunable for bio-mimicking progressive valvular stenosis and enables accurate optical recognition in complex blood flow. Here, we develop a valve-adjustable optofluidic bio-imaging recognition platform to fulfill it. Specifically, the bionic valve was designed with in situ soft membrane, and the internal air-pressure chamber could be regulated from the inside out to bio-mimic progressive valvular stenosis. The developed imaging algorithm enhances the recognition of optical details in blood flow imaging and allows for quantitative analysis. In a prospective clinical study, we examined the effect of progressive valvular stenosis on hemodynamics within the typical physiological range of veins by this way, where the inhomogeneity and local enhancement effect in the altered blood flow field were precisely described and the optical differences were quantified. The effectiveness and consistency of the results were further validated through statistical analysis. In addition, we tested it on fluorescence and noticed its good performance in fluorescent tracing of the clotting process. In virtue of theses merits, this system should be able to contribute to mechanism investigation, pharmaceutical development, and therapeutics of valvular stenosis-related diseases.

Non-adjustable gravitational valves or adjustable valves in the treatment of hydrocephalus after aneurysmal subarachnoid hemorrhage patients?

PURPOSE: Hydrocephalus requiring permanent CSF shunting after aneurysmal subarachnoid hemorrhage (aSAH) is frequent. It is unknown which type of valve is optimal. This study evaluates if the revision rate of gravitational differential pressure valves (G-DPVs, GAV® system (B Braun)) (G-DPV) is comparable to adjustable pressure valves (Codman Medos Hakim) (APV) in the treatment of post-aSAH hydrocephalus. METHODS: The use of a gravitational differential pressure valve is placed in direct comparison with an adjustable pressure valve system. A retrospective chart review is performed to compare the revision rates for the two valve systems. RESULTS: Within the registry from Radboud University Medical Center, 641 patients with a SAH could be identified from 1 January 2013 until 1 January 2019, whereas at the Heinrich Heine University, 617 patients were identified, totaling 1258 patients who suffered from aSAH. At Radboud University Medical Center, a gravitational differential pressure valve is used, whereas at the Heinrich Heine University, an adjustable pressure valve system is used. One hundred sixty-six (13%) patients required permanent ventricular peritoneal or atrial shunting. Shunt dysfunction occurred in 36 patients: 13 patients of the 53 (25%) of the gravitational shunt cohort, and in 23 of the 113 (20%) patients with an adjustable shunt (p = 0.54). Revision was performed at a mean time of 3.2 months after implantation with the gravitational system and 8.2 months with the adjustable shunt system. Combined rates of over- and underdrainage leading to revision were 7.5% (4/53) for the gravitational and 3.5% (4/113) for the adjustable valve system (p = 0 .27). CONCLUSION: The current study does not show a benefit of a gravitational pressure valve (GAV® system) over an adjustable pressure valve (CODMAN ® HAKIM®) in the treatment of post-aSAH hydrocephalus. The overall need for revision is high and warrants further improvements in care.

Retrospective single-center historical comparative study between proGAV and proGAV2.0 for surgical revision and implant duration.

OBJECTIVE: Cerebrospinal fluid (CSF) diversion shunt systems remain to be the most common treatment for pediatric hydrocephalus. Different valve systems are used to regulate CSF diversion. Preventing complications such as occlusions, ruptures, malpositioning, and over- or underdrainage are the focus for further developments. The proGAV and proGAV2.0 valve system are compared in this retrospective study for revision-free survival and isolated valve revision paradigms. METHODS: In the first part of the study, the shunt and valve revision-free survival rates were investigated in a retrospective historical comparison design for a period of 2 years in which each valve was used as standard valve (proGAV: July 2012-June 2014; proGAV2.0: January 2015-December 2016) with subsequent 30-month follow-up period, respectively. In the second part of the study, the implant duration was calculated by detecting isolated valve (valve-only) revisions together with another valve explantation during the entire period of the first study and its follow-up period. RESULTS: Two hundred sixty-two patients (145 male and 117 female, mean age 6.2 ± 6.1 years) were included in the cohort of revision-free survival. During the 30-month follow-up period, 41 shunt revisions, including 27 valve revisions (shunt survival rate: 72.1%, valve survival rate: 81.6%) were performed in the proGAV cohort and 37 shunt revisions, including 21 valve revisions (shunt survival rate: 74.8% and valve survival rate: 85.0%) were performed in the proGAV2.0 cohort without showing statistically significant differences. In the second part of the study, 38 cases (mean age 4.0 ± 3.9 years) met the inclusion criteria of receiving a valve-only-revision. In those patients, a total of 44 proGAV and 42 proGAV2.0 were implanted and explanted during the entire study time. In those, a significantly longer implant duration was observed for proGAV (mean valve duration 961.9 ± 650.8 days) compared to proGAV2.0 (mean length of implantation period 601.4 ± 487.8 days; p = 0.004). CONCLUSION: The shunt and valve revision-free survival rates were found to be similar among the groups during 30 month follow-up. In patients who received "valve only" revisions and a subsequent explanation, the implant duration was significantly longer in the proGAV. Although the amount of patients with valve-only-revisions are small compared to the entire cohort certain patients seem to be at higher risk for repeated valve revisions.

Clinical feature analysis of subdural effusion/hematoma after shunt use of adjustable valves in children with hydrocephalus / 中华实用儿科临床杂志

Objective:To analyze the clinical data of children with hydrocephalus suffering from subdural effusion/hematoma after shunt(SEHS) with adjustable valves, and to provide reference for postoperative follow-up.Methods:A total of 102 children with hydrocephalus treated with adjustable valves in the Department of Neurosurgery, Wuhan Children′s Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology from August 2017 to September 2021 were enrolled and studied retrospectively.There were 16 cases with SEHS, 11 of whom were male and 5 were female.The age ranged from 3 months to 13 years (median: 2.5 years). The age, clinical manifestations, the time of SEHS occurrence, treatment methods(pressure regulation only or combined with drilling and drainage), and prognosis of the patients were analyzed.The pressure adjustment treatment was to increase the by 10-20 mmH 2O (1 mmH 2O=0.009 8 kPa) each time and the patients were followed up 2-4 weeks after the adjustment.If SEHS didn′t improve according to the follow-up results, pressure regulation combined with drilling and drainage was recommended. Results:Of the 16 patients with SEHS, 3 cases were over 3 years old, and the other 13 cases were 3 years old or below.Eleven cases were treated by pressure regulation only, and 5 cases who were all aged ≤3 years received pressure regulation combined with drilling and drainage.Symptoms occurred in 2 patients, including vomiting in 1 case, and head and limb shaking in the other case.Fourteen cases were asymptomatic.The time from shunt operation to the occurrence of SEHS was ≤1 month in 5 cases, who were all cured by pressure regulation only.SEHS occurred in 5 cases >1-3 months after shunt surgery, and 2 cases of them were treated by pressure regulation combined with dri-lling and drainage.Three cases had SEHS>3-6 months after shunt surgery, and 1 case of them was treated by pressure regulation combined with drilling and drainage.SEHS occurred in 3 cases more than 6 months after shunt surgery, and 1 case of them was treated by pressure regulation combined with drilling and drainage.For the patients who received pressure regulation combined with drilling and drainage, the time from shunt operation to the occurrence of SEHS was 1 month and 21 days, 2 months and 7 days, 4.5 months, 7.5 months, and 25.0 months, respectively.The time from the occurrence of SEHS to the last reexamination with no SEHS detected was ≤1 month in 7 cases (all were cured by pressure regulation only); >1-3 months in 5 cases (3 cases were treated by pressure regulation combined with drilling and drainage); more than 3 months in 4 cases (2 cases were treated by pressure regulation combined with drilling and drainage). For the patients who received pressure regulation combined with drilling and drainage, the time from the occurrence of SEHS to the last reexamination with no SEHS detected was 1 month and 14 days, 2.0 months, 3.0 months, 7.0 months and 8.0 months, respectively.Except for 2 cases who experienced pressure regulating valve failure, all other cases were cured.Six cases were unilateral SEHS, and the SEHS volume was about 11 to 75 mL (median: 39.0 mL). Ten cases were bilateral SEHS, and the SEHS volume was about 23-380 mL (median: 158.2 mL). The 6 cases were all cured by pressure regulation, and 5 cases of them had SEHS at the shunt tube insertion side.Conclusions:SEHS in children with hydrocephalus is generally asymptomatic and rarely causes clinical symptoms.SEHS mostly occurs within 6 months after operation, especially within 3 months.SEHS found in 1 month after surgery can be cured by increasing the shunt valve pressure only.Therefore, SEHS can be cured by pressure regulation only by shortening follow-up and identifying SEHS early after shunt operation.This will also reduce the probability that patients require the drilling and drainage operation.

Paradoxical response of intracranial pressure to shunt valve setting adjustments.

BACKGROUND: The hydrodynamics of cerebrospinal fluid shunts have been described in vitro; however, knowledge on the response of intracranial pressure (ICP) to valve settings adjustments in vivo is limited. This study describes the effect of adjusting the shunt valve setting on ICP in a cohort of patients with complex symptom management. METHOD: Single-centre retrospective observational study. Patients who underwent ICP-guided valve setting adjustments during 24-h continuous ICP monitoring, between 2014 and 2019, were included. Patients with suspected shunt malfunction were excluded. Median night ICP before and after the valve adjustments were compared (Δ night ICP). The responses of ICP to valve adjustment were divided into 3 different groups as follows: expected, paradoxical and no response. The frequency of the paradoxical response and its potential predicting factors were investigated. RESULTS: Fifty-one patients (37 females, 14 males, mean age 38 years) receiving 94 valve setting adjustments met the study inclusion criteria. Patients' underlying conditions were most commonly hydrocephalus (47%) or idiopathic intracranial hypertension (43%). The response of ICP to valve setting adjustments was classified as 'expected' in 54 cases (57%), 'paradoxical' in 17 cases (18%) and 'no effect' (Δ night ICP < 1 mmHg) in 23 cases (24%). There was a significant correlation between the Δ night ICP and the magnitude of valve setting change in both the investigated valves (Miethke ProGAV, p = 0.01 and Medtronic Strata, p = 0.02). CONCLUSIONS: Paradoxical ICP changes can occur after shunt valve setting adjustments. This observation should be taken into account when performing ICP-guided valve adjustments and is highly relevant for the future development of "smart" shunt systems.

Haemodynamic evaluation of the new pulsatile-flow generation method in vitro.

Continuous-flow ventricular-assist devices are widely used to support patients with advanced heart failure, because continuous-flow ventricular-assist devices are more durable, have smaller sizes and have better survival rates for patients compared to the pulsatile-flow ventricular-assist devices. Nevertheless, continuous-flow ventricular-assist devices often cause complications such as gastrointestinal bleeding, haemorrhagic stroke, and aortic insufficiency and have a negative impact on the microcirculation for both long-time implantable and short-time extracorporeal systems. The aim of this study is the evaluation of the pulsatile-flow generation method in continuous-flow ventricular-assist device without pump speed changes. The method may be used for short-time extracorporeal continuous-flow mechanical circulatory support and long-time implantable mechanical circulatory support. A shunt with a controlled adjustable valve, that clamps periodically, is connected in parallel to the continuous-flow ventricular-assist device. We compared the continuous-flow ventricular-assist device operating with and without the shunt on the mock circulation loop. The continuous-flow ventricular-assist device-shunt system was connected according to the left ventricle-aorta circuit and worked in phase with the ventricle. Heart failure was simulated on the mock circulation circuit. Rotaflow (Maquet Inc.) was used as the continuous-flow pump. Haemolysis studies of the system for generating a pulse flow were carried out at a flow rate of 5 L/min and a pressure drop of 100 mm Hg. To compare the haemodynamic efficiency, we used the aortic pulsation index Ip, the equivalent energy pressure and the surplus haemodynamic energy. These indexes were higher in the pulsatile mode (Ip - 4 times, equivalent energy pressure by 7.36% and surplus haemodynamic energy - 10 times), while haemolysis was the same. The normalised index of haemolysis was 0.0015 ± 0.001. The results demonstrate the efficiency of the pulsatile-flow generation method for continuous-flow ventricular-assist devices without impeller rotation rate changes.

Setting pressure can change the size and shape of MRI artifacts caused by adjustable shunt valves: a study of the 4 newest models.

OBJECTIVE: Adjustable shunt valves that have been developed for the management of hydrocephalus all rely on intrinsically magnetic components, and artifacts with these valves on MRI are thus inevitable. The authors have previously reported that the shapes of shunt artifacts differ under different valve pressures with the proGAV 2.0 valve. In the present study the authors compared the size and shape of artifacts at different pressure settings with 4 new-model shunt valves. METHODS: The authors attached 4 new models of MRI-resistant shunt valve to the temporal scalp of a healthy volunteer: the proGAV 2.0; Codman Certas Plus; Polaris; and Strata MR. They set 3 different scales of pressures for each valve, depending on magnet orientation to the body axis. Artifacts were evaluated and compared among all valves on a 3.0-T GE scanner and 2 valves were also evaluated on a Philips scanner and a Siemens scanner. In-plane artifact sizes were evaluated as the maximum distance of the artifact from the expected scalp. RESULTS: The sizes and shapes of artifacts changed depending on valve pressure for all valves on the 3 different MRI scanners. Artifacts were less prominent on spin echo sequences than on gradient echo sequences. For diffusion-weighted imaging and time-of-flight MR angiography, the authors matched image numbers within the same sequence and compared appearances of artifacts. For all valves, the number of images affected by artifacts and the image number showing the largest artifact differed among valve settings. CONCLUSIONS: Artifacts of all adjustable shunt valves showed gross changes corresponding to pressure setting. Not only the maximum distance of artifacts but also the shape changed significantly. The authors suggest that changing pressure settings offers one of the easiest ways to minimize artifacts on MRI.

A double-blind randomized trial on the clinical effect of different shunt valve settings in idiopathic normal pressure hydrocephalus.

OBJECTIVE: The study aim was to examine the effect of gradually reducing the opening pressure on symptoms and signs in the shunt treatment of idiopathic normal pressure hydrocephalus (iNPH). METHODS: In this prospective double-blinded, randomized, controlled, double-center study on patients with iNPH, a ventriculoperitoneal shunt with an adjustable Codman Medos Valve was implanted in 68 patients randomized into 2 groups. In 1 group (the 20-4 group) the valve setting was initially set to 20 cm H2O and gradually reduced to 4 cm H2O over the course of the 6-month study period. In the other group (the 12 group), the valve was kept at a medium level of 12 cm H2O during the whole study period. All patients were clinically evaluated using 4 tests preoperatively as well as postoperatively at 1, 2, 3, 4, and 6 months. The test scores between the 2 groups (20-4 and 12) were compared for each clinical evaluation. RESULTS: Fifty-five patients (81%) were able to complete the study. There were no significant differences between the 2 groups (20-4 and 12) preoperatively or at any time postoperatively. Both groups exhibited significant clinical improvement after shunt insertion at all valve settings compared with the preoperative score, with the greatest improvement observed at the first postoperative evaluation. The clinical improvement was significant within the first 3 months, and thereafter no significant improvement was seen in either group. CONCLUSIONS: Gradual reduction of the valve setting from 20 to 4 cm H2O did not improve outcome compared with a fixed valve setting of 12 cm H2O. Improvement after shunt surgery in iNPH patients was evident within 3 months, irrespective of valve setting.

A Clinical Analysis of the Ventriculoperitoneal Shunt with Programmable Shunt Divice

CSF shunting procedures are widely employed in the treatment of hydrocephalus and other disturbances of the dynamics of CSF such as a rachnoid cyst and syrinx. The relative simplicity of this operation with respect to other neurosurgical procedures is matched by a high incidence of complications. Many kinds of shunt devices have been developed to reduce complications. Yet, this operation frequently requires surgical revision. Traditional shunts were primarily designed to manage hydrocephalus by regulating intracranial pressure. Those devices, in some circumstances, can cause to underdrain or overdrain CSF and may need a surgical revision to adjust the pressure Authors have treated 28 patients with the disturbaces of CSF dynamics using pressuread justable valve system (Codman-Medos p rogrammable Hakim valve system). Two patients had arachnoid cysts and the others had hydrocephalus with various etiologies. Subdural hygroma was developed in 5 patients and underdrainage was observed in 9 patients on CT scan. By adjusting the pressure, Authors achieved clinical improvements without a need for surgical revision. The optimum pressure was 97.4+17.4mmHO for the patients with hydrocephalus with various etiologies in adults. In conclusion, the incidence of shunt revision by using this shunt device for the treatment of hydrocephalus and arachnoid cysts was decreased.