Pressure Spikes Research Articles

Prevention of intraocular pressure elevation following intravitreal injections

Determining the role of vascular endothelial growth factor (VEGF) in the pathogenesis of intraocular neovascularization prompted the development of anti-VEGF therapy. In general, these intravitreal injections (IVI) are considered relatively safe. One of the side effects that can occur after IVI of anti-VEGF agents is ocular hypertension, it can be acute or persistent. Numerous studies investigating the prevention of ophthalmic hypertension have been carried out in connection with the proven risk of short-term intraocular pressure (IOP) elevation after anti-VEGF injections. Scientific literature describes several methods of preventing intraocular pressure spikes after IVI: prophylactic medications, anterior chamber paracentesis, scleral decompression. Despite the significant number of publications, there is no universal consensus on the necessity of prevention measures for IVI of anti-VEGF drugs since the clinical benefits of slightly reducing the short-term IOP spikes remain unclear. This literature review analyzes the prospects of preventing ocular hypertension after IVI of anti-VEGF agents.

The T-Line® Hernia Mesh, A Novel Mesh Uniquely Designed to Prevent Hernia Recurrence and Occurrence.

Ventral hernia repair (VHR) fixation techniques with current meshes on the market are prone to failure from intra-abdominal pressure spikes due to coughing or lifting, for example. The T-Line® Hernia Mesh (Deep Blue Medical Advances, Durham, North Carolina) is a new mesh with a novel fixation mechanism to enhance anchoring strength addressing hernia occurrence and recurrence. Used similarly to traditional mesh, the new mesh uses incorporated mesh sutures that are 15 times the surface area of sutures for fixation rather than monofilament sutures, providing ~275% stronger anchoring strength. The increased surface area of the mesh extensions decreases tension on the mesh and tissue and increases the strength of the repair overall. There is also the likelihood that anchoring gains strength over time as the extensions undergo bioincorporation. This novel mesh specifically addresses the most common complication of VHR and has the potential to significantly improve outcomes.

Functionalized Data Operator Model for System Analysis and Forecasting

A deconvolution data processing is developed for obtaining a Functionalized Data Operator (FDO) model that is trained to approximate past and present, input-output data relations. The FDO model is designed to predict future output features for deviated input vectors from any expected, feared of conceivable, future input for optimum control, forecast, or early-warning hazard evaluation. The linearized FDO provides fast analytical, input-output solution in matrix equation form. If the FDO is invertible, the necessary input for a desired output may be explicitly evaluated. A numerical example is presented for FDO model identification and hazard evaluation for methane inflow into the working face in an underground mine: First, a Physics-Based Operator (PBO) model to match monitored data. Second, FDO models are identified for matching the observed, short-term variations with time in the measured data of methane inflow, varying model parameters and simplifications following the parsimony concept of Occam’s Razor. The numerical coefficients of the PBO and FDO models are found to differ by two to three orders of magnitude for methane release as a function of short-time barometric pressure variations. As being data-driven, the significantly different results from an FDO versus PBO model is either an indication of methane release processes poorly understood and modeled in PBO, missing some physics for the pressure spikes; or of problems in the monitored data fluctuations, erroneously sampled with time; or of false correlation. Either way, the FDO model is originated from the functionalized form of the monitored data, and its result is considered experimentally significant within the specified RMS error of model matching.

Stochastic aerodynamic analysis for compressor blades with manufacturing variability based on a mathematical dimensionality reduction method

It is essential for engineering manufacture and robust design to evaluate the impact of manufacturing variability on the aerodynamics of compressor blades efficiently and accurately. In the paper, a novel quadratic curve approximation method based on the scanning points of blade design profiles was introduced and combined with Karhunen–Loève expansion, a mathematical dimensionality reduction method for modeling manufacturing variability as truncated Normal process was proposed. Subsequently, Sparse Approximation of Moment-based Arbitrary Polynomial Chaos (SAMBA PC) and computational fluid dynamics (CFD) were applied to build a computational framework for stochastic aerodynamic analysis considering manufacturing variability. Finally, the framework was adopted to evaluate the aerodynamic variations of a high subsonic compressor cascade under the design incidence. The results illustrate that the SAMBA PC method is more efficient than the traditional methods such as Monte Carlo simulation (MCS) for stochastic aerodynamic analysis. Through uncertainty quantification, the impact of manufacturing variability on the global aerodynamic performance is primarily reflected in the fluctuation of aerodynamic losses, and the fluctuation of the total losses is mainly contributed by the fluctuation of the separation loss after the suction peak (a negative pressure spike near the leading edge (LE)) and the boundary-layer loss on the suction surface (SS). With sensitivity analysis, the most important geometric modes to aerodynamics can be revealed, which provides a useful reference for manufacturing inspection process and helps reduce computational cost in robust design.

Hypotensive Effect of Topical Brimonidine Tartarate on Intra-Ocular Pressure Spikes Following Intravitreal Injection of Ranibizumab

Hypotensive Effect of Topical Brimonidine Tartarate on Intra-Ocular Pressure Spikes Following Intravitreal Injection of Ranibizumab

Combining physics-based and data-driven modeling in well construction: Hybrid fluid dynamics modeling

This study presents a hybrid modeling approach combining physics-based and data-driven models for improved standpipe pressure prediction during well constructing. The proposed approach provides a more robust and accurate model that mitigates some of the disadvantages of using purely physics-based or data-driven models.We start with purely physics-based modeling of standpipe pressure, both steady-state and transient. The steady-state model can predict the magnitude of pressure during drilling and circulation, while the transient model can simulate dynamic behavior such as pressure spikes when flow is initiated and fluid gels in the wellbore are broken. We then evaluate several machine learning techniques including neural network, deep learning, Gaussian process, support vector machine, and random forest, which were trained with drilling time-series datasets. Finally, machine learning techniques are combined with physics-based models via a hidden Markov model, which involves a rule-based, stochastic decision-making algorithm.The results of the hybrid modeling exercise show that the proposed hybrid model can more accurately predict standpipe pressure and capture the transient events when compared to either physics-based or machine learning models used by themselves. The hybrid model also provides better interpretability of results compared to a purely data-driven black-box model. This is because purely data-driven models lack a connection to the underlying physics.Being able to accurately model and manage the pressure response during drilling operations is essential, especially for wells drilled in narrow-margin drilling environments. We demonstrate how pressure can be more accurately predicted through our proposed hybrid modeling, leading to safer, more optimized operations. The work is also presented as an example of the benefits of hybrid modeling in general, which can be applied to many areas of well construction beyond mere standpipe prediction.

Incipient sliding of adhesive contacts

A model is proposed herein to investigate the incipient sliding of contacts in the presence of both friction and adhesion, where the interfacial response is modeled based on traction-separation laws. A Maugis-like parameter is defined to characterize the response in the tangential direction. Subsequently, the model is used to investigate the contact between a smooth cylinder and a flat body, where adhesion-friction interactions are strong. A range of behaviors are observed when a tangential displacement is imposed: When the parameter is low, the contact pressure exhibits a relatively constant profile; when it is high, a pressure spike is observed at the edge of the contact. This difference is caused by a significant interface compliance in the former case, which limits the amount of slip. The results for the mid-range values of the Maugis-like parameter can qualitatively replicate various experiments performed using polydimethylsiloxane (PDMS) balls.

Oral presentationsCatThe effect of anaesthetic induction with propofol, alfaxalone or ketamine on intraocular pressure in cats

Induction may produce intraocular pressure (IOP) spikes, which can be harmful in eyes predisposed to perforation or glaucoma. Our objective was to compare the effect of propofol, alfaxalone and ketamine on feline IOP.

Professor Duncan Dowson, a source of inspiration

The current paper highlights the contribution of the Dowson and Higginson work to numerical line contact elastohydrodynamic lubrication film thickness prediction and the Hamrock and Dowson contribution to the film thickness prediction in elliptical contacts. This paper shows that, even by today’s standards, both the numerical pressure and film thickness results and the curve-fitted film thickness predictions are very accurate. As for the elliptical results, the authors show that the original predictions remain surprisingly accurate for moderately elliptical contact. For very long elliptical contacts, their prediction does not tend to a line contact asymptote. This paper then concludes that the predicted pressure spikes by Dowson, Higginson, and Hamrock are correct in shape and amplitude, at least near pure rolling conditions.

A Prospective Study of Intraocular Pressure Spike and Failure After Gonioscopy-Assisted Transluminal Trabeculotomy in Juvenile Open-Angle Glaucoma: A Prospective Study of GATT in JOAG

To identify risk factors for surgical failure after gonioscopy-assisted transluminal trabeculotomy (GATT) in juvenile open-angle glaucoma (JOAG). Prospective, interventional case series. GATT was the initial surgery in 70 eyes of 70 patients with JOAG. Surgical success was defined as a postoperative intraocular pressure (IOP) of ≤21 mm Hg with at least a 20% reduction from preoperative IOP, with or without the use of antiglaucoma medication (qualified and complete success, respectively) at each postoperative visit. IOP spike was defined as IOP >30 mm Hg and an increase of at least 10 mm Hg from IOP before the spike, and then reduced to ≤21 mm Hg. The median age at the time of surgery was 19.3 years (range, 4.9-37.5 years) with a visual field mean deviation of -17.4 ± 10.6 dB. Mean IOP decreased from 31.3 ± 9.5 mm Hg preoperatively to 15.8 ± 2.7 at 12 months postoperatively. The complete and qualified success rates were 74.3% and 91.4%, respectively. An IOP spike occurred in 52 eyes (74%), with a median spike duration of 3.5 days (range, 1-21 days). Longer duration of IOP spike (P=.009) and older age at the time of surgery (P=.025) were both associated with worse surgical outcomes. Advanced disease was associated with prolonged IOP spike (P=.007). GATT provided excellent outcomes in patients with severe JOAG. Older age and longer duration of postoperative IOP spike are risk factors for failure. Severe cases are more likely to have longer durations of IOP spike. Frequent IOP monitoring during the early postoperative period is needed to detect IOP spikes in these patients.

Delayed phacoemulsification in femtosecond laser-assisted cataract surgery

A diabetic and asthmatic patient was planned to undergo femtosecond laser-assisted cataract surgery in his left eye. At the end of femtosecond procedure, he developed breathlessness due to noncardiogenic pulmonary edema. The second procedure was postponed for 3 weeks till he received fitness for undergoing further ocular surgery. The second surgery was uncomplicated. There was no corneal decompensation, exaggerated inflammation, intraocular pressure spike, diabetic retinopathy progression, or postoperative cystoid macular edema till 6 months of follow-up. Although not recommended, such a delay may be unavoidable. The delayed surgery is unlikely to compromise the surgical outcome or increase the chances of intra- or postoperative complications.

Late-onset persistent corneal hydrops after crosslinking treated with 24% C3F8

Corneal hydrops can occur in an apparently stable cornea many years after crosslinking. This case describes the management of persistent hydrops unresponsive to conservative treatment. A 31-year-old woman presented with right acute corneal hydrops 9 years after crosslinking for keratoconus. No clear precipitant was identified, and corneal topography had been stable over the past 9 years. The right cornea demonstrated inferior hydrops with gross thickening of the stroma. The hydrops persisted and failed to resolve after 6 months, despite 2 intracameral 14% C3F8 gas injections and topical hypertonic saline. An intracameral concentration of 24% C3F8, with 65% fill of the anterior chamber was performed, with the gas partially released after day 3, resulting in resolution of the hydrops. Corneal hydrops after crosslinking is a rare phenomenon, but it is likely an underreported complication. The hydrops in this case was recalcitrant to conservative measures. An expansile concentration of intracameral C3F8 was used to achieve a full gas fill to tamponade the inferior Descemet tear. Close follow-up is required to monitor for intraocular pressure spikes and perform paracentesis as required.

Experiments on duct-vented explosion of hydrogen–methane–air mixtures: Effects of equivalence ratio

In this study, experiments on the duct-vented deflagrations of hydrogen–methane–air mixtures were performed in a cylindrical vessel connected with a relief duct, at an initial pressure of 101 kPa and an initial temperature of 290 K, to investigate the effects of equivalence ratio (ϕ), in the range of 0.6–1.8, on flame evolution and pressure buildup within and outside the venting configuration. Experimental results reveal that secondary explosion in the relief duct occurred and a pressure peak with amplitude higher than the overpressure in the vented chamber formed, which resulted in the gases in the relief duct flowing reversely to the vented chamber (reverse flow). The secondary explosion in the relief duct reduced the venting efficiency in the vented chamber and created a pressure peak there, which dominated the pressure–time histories in the vented cylindrical vessel for ϕ ranging from 0.8 to 1.4. Acoustic oscillations of the overpressure in the cylindrical vessel could be easily distinguished forϕ ≤ 1.0, and the pressure peak owing to acoustic enhanced combustion was dominant atϕ = 0.6. The maximum overpressure in the cylindrical vessel first increased and thereafter decreased as ϕ was increased from 0.6 to 1.5 and was independent of ϕ for richer mixtures. A shock wave was visualized in the tests with ϕ in a range of 1.0–1.2 when the combustible cloud outside the venting configuration was ignited, which resulted in a pressure spike in the external pressure–time histories. The maximum overpressure outside the relief duct first increased and thereafter decreased as ϕ was increased.

Treatment of Glaucoma Patients with Flammer Syndrome.

Flammer syndrome (FS) describes a phenotype characterized by the presence of primary vascular dysregulation along with a number of symptoms and signs. Although most people with FS are healthy, FS favors the occurrence of certain diseases, such as normal tension glaucoma. This is because disturbed autoregulation makes the eye more sensitive to intraocular pressure (IOP) spikes or blood pressure drops. Treatment of FS is generally appropriate when patients either suffer greatly from their symptoms or if we can assume that it has contributed to a disease. In glaucoma, this may be the case if the glaucoma damage progresses despite well-controlled IOP. Both the still sparse scientific studies and our long clinical experience suggest that FS-targeted therapy not only relieves the symptoms of FS but also slows the progression of glaucoma damage in selected cases. This description is intended not only to help affected patients but to also motivate clinicians and researchers to conduct therapy studies to confirm or refute our observations.

Acute Ischemic Priapism: An AUA/SMSNA Guideline.

Priapism is a persistent penile erection that continues hours beyond, or is unrelated to, sexual stimulation and results in a prolonged and uncontrolled erection. Given its time-dependent and progressive nature, priapism is a situation that both urologists and emergency medicine practitioners must be familiar with and comfortable managing. Acute ischemic priapism, characterized by little or no cavernous blood flow and abnormal cavernous blood gases (ie, hypoxic, hypercarbic, acidotic) represents a medical emergency and may lead to cavernosal fibrosis and subsequent erectile dysfunction. A comprehensive search of the literature was performed by Emergency Care Research Institute for articles published between January 1, 1960 and May 1, 2020. Searches identified 2948 potentially relevant articles, and 2516 of these were excluded at the title or abstract level for not meeting inclusion criteria for any key question. Full texts for the remaining 432 articles were reviewed, and ultimately 137 unique articles were included in the report. This Guideline was developed to inform clinicians on the proper diagnosis and surgical and non-surgical treatment of patients with acute ischemic priapism. This Guideline addresses the role of imaging, adjunctive laboratory testing, early involvement of urologists when presenting to the emergency room, discussion of conservative therapies, enhanced data for patient counseling on risks of erectile dysfunction and surgical complications, specific recommendations on intracavernosal phenylephrine with or without irrigation, the inclusion of novel surgical techniques (eg, tunneling), and early penile prosthesis placement. All patients with priapism should be evaluated emergently to identify the sub-type of priapism (acute ischemic versus non-ischemic) and those with an acute ischemic event should be provided early intervention. Treatment of the acute ischemic patient must be based on patient objectives, available resources, and clinician experience. As such, a single pathway for managing the condition is oversimplified and no longer appropriate. Using a diversified approach, some men may be treated with intracavernosal injections of phenylephrine alone, others with aspiration/irrigation or distal shunting, and some may undergo non-emergent placement of a penile prosthesis.

Endoplasmic reticulum stress is involved in retinal injury induced by repeated transient spikes of intraocular pressure.

Clinically, a large proportion of glaucoma patients undergo repeated intraocular pressure (IOP) spike (Spike IOP) attacks during their sleep, which may facilitate retinopathy. In this study, we established a mouse model of repeated transient Spike IOP to investigate the direct damage to the retina following Spike IOP attacks, and elucidated the underlying molecular mechanism. We analyzed the changes in the number of retinal ganglion cells (RGCs) via immunofluorescence. Thereafter, we detected retinal cell apoptosis via terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) staining, and performed RNA sequencing (RNA-seq) to reveal the underlying molecular mechanism. Finally, we validated the expression of key molecules in the endoplasmic reticulum (ER) stress pathway using quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analysis. Results revealed a time-dependent RGC loss in Spike IOP, evidenced by a reduction in the number of Brn3a-positive RGCs in experimental eyes following a 7-d continuous treatment with Spike IOP. In addition, TUNEL staining indicated that apoptosis of retinal cells started in the outer nuclear layer (ONL), and then spread to the ganglion cell layer (GCL) with time. RNA-seq analysis revealed that ER stress might be involved in Spike IOP-induced retinal injury. This result was corroborated by western blot, which revealed upregulation of ER stress-related proteins including binding immunoglobulin protein/glucose-regulated protein 78 (BiP/GRP78), phosphorylated inositol-requiring enzyme 1 (p-IRE1), unspliced X-box-binding protein 1 (XBP1-u), spliced X-box-binding protein 1 (XBP1-s), phosphorylated c-Jun N-terminal kinase (p-JNK), C/EBP-homologous protein (CHOP), and B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax). These findings indicate that repeated IOP transients are detrimental to the retina, while ER stress plays an important role in retinal cell apoptosis in this situation. Notably, repeated Spike IOP among glaucoma patients is a crucial factor for progressive retinopathy.

Experiments in Shock-Vortex Interactions

Studies of shock-vortex interactions in the past have predominantly been numerical, with a number of idealizations such as assuming an isolated vortex and a plane shock wave. In the present case the vortex is generated from flow separation at a corner. A shear layer results which wraps up into a spiral vortex. The flow is impulsively initiated by the diffraction of a shock wave over the edge. The strength of the shock determines the nature of the flow at the corner and that induced behind the diffracted wave. A wide variety of cases are considered using different experimental arrangements such as having two independent shock waves arriving at the corner at different times, to reflecting the diffracting wave off different surfaces back into the vortex, and to examining the flow around bends where the reflection off the far wall reflects back onto the vortex. The majority of studies have shown that the vortex normally retains its integrity after shock transit. Some studies with curved shock waves and numerous traverses have shown evidence of vortex breakup and the development of turbulent patches in the flow, as well as significant vortex stretching. Depending on the direction of approach of the shock wave it refracts through the shear layer thereby changing the strength and direction of both. Of particular note is that the two diffracted waves which emerge from the vortex as the incident wave passes through interact with each other resulting in a pressure spike of considerable magnitude. An additional spike is also identified.

Cross-diffusion waves resulting from multiscale, multiphysics instabilities: application to earthquakes

Abstract. Theoretical approaches to earthquake instabilities propose shear-dominated source mechanisms. Here we take a fresh look at the role of possible volumetric instabilities preceding a shear instability. We investigate the phenomena that may prepare earthquake instabilities using the coupling of thermo-hydro-mechano-chemical reaction–diffusion equations in a THMC diffusion matrix. We show that the off-diagonal cross-diffusivities can give rise to a new class of waves known as cross-diffusion or quasi-soliton waves. Their unique property is that for critical conditions cross-diffusion waves can funnel wave energy into a stationary wave focus from large to small scale. We show that the rich solution space of the reaction–cross-diffusion approach to earthquake instabilities can recover classical Turing instabilities (periodic in space instabilities), Hopf bifurcations (spring-slider-like earthquake models), and a new class of quasi-soliton waves. Only the quasi-soliton waves can lead to extreme focussing of the wave energy into short-wavelength instabilities of short duration. The equivalent extreme event in ocean waves and optical fibres leads to the appearance of “rogue waves” and high energy pulses of light in photonics. In the context of hydromechanical coupling, a rogue wave would appear as a sudden fluid pressure spike. This spike is likely to cause unstable slip on a pre-existing (near-critically stressed) fault acting as a trigger for the ultimate (shear) seismic moment release.

The pressure spike mystery

An intuitive understanding of the pressure spike appearing in the elastohydrodynamic pressure distribution is presented. This comes from my personal memories of Professor Dowson from my first encounter with his book to my final conversation with him.

Intracranial pressure spikes trigger spreading depolarizations.

Spreading depolarizations are highly prevalent and spatiotemporally punctuated events worsening the outcome of brain injury. Trigger factors are poorly understood but may be linked to sudden worsening in supply-demand mismatch in compromised tissue. Sustained or transient elevations in intracranial pressure are also prevalent in the injured brain. Here, using a mouse model of large hemispheric ischaemic stroke, we show that mild and brief intracranial pressure elevations (20 or 30 mmHg for just 3 min) potently trigger spreading depolarizations in ischaemic penumbra (4-fold increase in spreading depolarization occurrence). We also show that 30 mmHg intracranial pressure spikes as brief as 30 s are equally effective. In contrast, sustained intracranial pressure elevations to the same level for 30 min do not significantly increase the spreading depolarization rate, suggesting that an abrupt disturbance in the steady state equilibrium is required to trigger a spreading depolarization. Laser speckle flowmetry consistently showed a reduction in tissue perfusion, and two-photon pO2 microscopy revealed a drop in venous pO2 during the intracranial pressure spikes suggesting increased oxygen extraction fraction, and therefore, worsening supply-demand mismatch. These haemodynamic changes during intracranial pressure spikes were associated with highly reproducible increases in extracellular potassium levels in penumbra. Consistent with the experimental data, a higher rate of intracranial pressure spikes was associated with spreading depolarization clusters in a retrospective series of patients with aneurysmal subarachnoid haemorrhage with strong temporal correspondence. Altogether, our data show that intracranial pressure spikes, even when mild and brief, are capable of triggering spreading depolarizations. Aggressive prevention of intracranial pressure spikes may help reduce spreading depolarization occurrence and improve outcomes after brain injury.