Increase In Opening Pressure Research Articles

Headache and Other Factors Modifying Cerebrospinal Fluid Opening Pressure in Pediatric Patients.

Cerebrospinal fluid opening pressure values are associated with various neurologic diseases; however, numerous factors can modify this measurement. This study aims to describe factors related to modifications in opening pressure measurements in pediatric patients. Methods: A retrospective analysis of lumbar punctures in pediatric patients conducted by the neuropediatrics group with institutional standardization. Bivariate and linear regression analyses were performed to determine the association between opening pressure and variables included in the study. Results: 544 events, median age 107 months, median opening pressure 19.7 cm H2O. Bivariate analysis found no association with medication use; anesthetics that increased opening pressure were remifentanil (P = .02) and propofol (P = .05), along with a positive linear correlation between opening pressure and age (P < .0001). Multiple linear regression analysis revealed that age, BMI, male gender, and remifentanil use were associated with an increase in opening pressure, whereas corticosteroid withdrawal was associated with a reduction in opening pressure. There is an interaction between age and headache, with an association with increased opening pressure up to around 140 months. Conclusion: This study identifies factors associated with changes in opening pressure, crucial for estimating normal opening pressure values in children. Headaches, anesthetic use, and corticosteroid withdrawal are confirmed as significant factors.

Experimental study of the venting characteristics of dust explosion through a vent duct

To further understand the dynamic mechanism of dust explosion through a vent duct, we designed a small-scale cylindrical vessel connected with a vent duct and performed a dust explosion venting experiment under different opening pressures using corn starch as the explosive medium in this study. The results show that weakening effect of duct on venting is positively correlated with the opening pressure. The explosion pressure in the duct presents a three-peak-structure with time, successively caused by the membrane breaking shock wave, the secondary explosion in the tube, and the continuous combustion, and decreases gradually with the propagation distance. Meanwhile, the three pressure peaks are positively correlated with the opening pressure, while the time interval between them goes to contrary. The increase of opening pressure leads to the increase of secondary explosion intensity and reverse flow in the vessel, further accelerates the reaction rate in the vessel, and then shortens the duration of combustion in the vessel until the phenomenon of flame reignition in the vessel disappears.

CSF Pressure Change in Relation to Opening Pressure and CSF Volume Removed.

Idiopathic intracranial hypertension is a complex neurologic disorder resulting from increased intracranial pressure. Our aim was to determine whether a correlation exists between the CSF pressure-volume relationship, specifically the craniospinal elastance and pressure-volume index, in patients with idiopathic intracranial hypertension and whether opening pressure affects this relationship. Lumbar punctures performed for suspected idiopathic intracranial hypertension from 2006 to 2017 were identified. Opening and closing pressures, CSF volume removed, and clinical diagnosis of idiopathic intracranial hypertension were obtained from the medical records. The craniospinal elastance (pressure change per milliliter of CSF removed) and pressure-volume index were calculated, and the Pearson correlation coefficients between both the craniospinal elastance and pressure-volume index and opening pressure were determined. Linear regression models of craniospinal elastance and the pressure-volume index and interaction terms with opening pressure were assessed for covariate influence on this association. One hundred sixteen patients were included in the final analysis. The mean craniospinal elastance according to opening pressure group was 0.52 ± 0.18 for <20 cm H2O, 0.57 ± 0.20 for 20-29 cm H2O, 0.91 ± 0.28 for 30-39 cm H2O, and 1.20 ± 0.25 for ≥40 cm H2O. There was a positive linear association between opening pressure and craniospinal elastance with a 0.28 cm H2O/mL increase in craniospinal elastance (standard error = 0.03, P < .001) for every 10 cm H2O increase in opening pressure. Of the covariables analyzed, only age older than 50 years and total volume of CSF removed affected this association. As opening pressure increases, the craniospinal elastance increases in a linear fashion while the pressure-volume index decreases. Further studies are needed to determine whether these changes relate to the underlying pathophysiology of idiopathic intracranial hypertension or simply represent established CSF volume pressure dynamics.

Morbid Obesity Causes Chronic Increase of Intraabdominal Pressure

Intraabdominal hypertension and the abdominal compartment syndrome are known to deleteriously affect a wide array of organ systems. We retrospectively reviewed 62 women who underwent either laparoscopic gastric bypass surgery or adjustable gastric banding. Their age, body mass index (BMI), and race were known. Their opening abdominal pressure was recorded by connecting a Verress needle to a pressure monitor. Linear regression was used to assess the contribution of age, race, and BMI to the observed variation in opening abdominal pressure. Neither variation in age or race explained the variation in opening pressure (P > .05). By contrast, variation in BMI explained 8% of the observed variation in opening pressure (P < .05). For every 1 kg/mm(2) increase in BMI, there was on average a 0.07 mm Hg increase in opening pressure. Increases in BMI are associated with increases in intraabdominal pressure.

Effect of urethral compliance on the steady state p‐Q relationships assessed with a mechanical analog of the male lower urinary tract

Using a lumped parameter theoretical model of bladder outlet function, we previously explored the relationship between the tube law of the urethra and the pressure-flow characteristics during micturition [Mijailovich et al., 2004]. To validate this theoretical model, we constructed a mechanical analog of the male lower urinary tract that incorporated elements simulating all relevant parameters of the theoretical model. In addition, we determined the effect of alterations in compliance of the flow-controlling zone on these relationships. In the mechanical analog, the bladder neck and urethra were represented by a thin-walled conduit made of latex rubber and the prostate with a fluid filled cuff of variable compliance encircling the conduit. We measured in the same system steady-state pressure-flow (p-Q) and pressure-area (p-A) relationships of the flow-controlling zone. The effects of bladder outlet obstruction and prostatic compliance on these relationships were simulated by varying cuff pressure and capacitative coupling of the cuff, respectively. We demonstrated two previously described flow regimes-critical for low Q, and subcritical for higher Q. In the critical flow regime, the cross-sectional area of the collapsible conduit downstream of the cuff became narrow up to a site where the area suddenly expanded (elastic jump). Pressure losses across the cuff region decreased with increasing Q as the elastic jump approached the cuff, and the jump vanished when Q became subcritical. By altering prostatic cuff compliance and cuff pressure, we showed that an increase in opening pressures was associated with a steeper p-Q relationship. Using this mechanical analog, the measurements of p-A and p-Q relationships under various experimental conduit conditions validated our previous theoretical model of the male lower urinary tract. Both the experimental measurements and our previous theoretical model predictions indicate that an increase in opening pressure is associated with an increase in the slope of the p-Q relationship which becomes steeper with decreased cuff compliance. These data are in accordance with urodynamic findings in patients with benign prostatic hypertrophy (BPH) and suggest that a reduction in prostatic compliance exacerbates the severity of obstruction.

The effects of injector nozzle geometry and operating pressure conditions on the transient fuel spray behavior

Effects of injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure, and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details inside model nozzle and real nozzle were also investigated both experimentally and numerically. For the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.

Eustachian tube function in children after insertion of ventilation tubes.

This study was performed to assess the effect of the insertion of ventilation tubes and the subsequent aeration of the middle ear on eustachian tube (ET) function in children. Manometric ET function tests were performed repeatedly for 3 months after the placement of ventilation tubes in 83 children with otitis media with effusion (OME). Opening and closing pressures (passive tubal function) and active tubal function were measured. Analysis of the results showed a significant increase in opening pressure over time, whereas the closing pressure did not change. The active tubal function did not change and remained at the same poor level. Therefore, the opening pressure and closing pressure and, especially, the poor active tubal function, were more likely to be a causal factor of OME than a result. Certain children may have poor intrinsic ET function that makes them more susceptible to OME.

A prospective retrieval study to determine how speaking valve failure is effected by colonization

INTRODUCTION: It has been suggested that Groningen Low Resistance (GLR) valve failure is associated with biofouling of the valve's oesophageal surface and hinge areas. However, the valve edges are responsible for efficient valve function.1 Therefore, valve edge colonization should be the most important factor determining valve failure. The null hypothesis that valve edge colonization was not associated with failure was tested using 106 GLR valves retrieved, after failure, from 41 patients. METHODS: The opening pressures, reverse opening pressures and forward resistances of the new valves were determined using apparatus validated previously.2 The pressure/flow parameters were measured again after removal and the changes calculated. The degree of colonization of each valve edge, oesophageal surface, hinge area, tracheal surface and valve lumen was scored using 100-mm linear analogue scales. The changes, in pressure/flow parameters were examined for associated with colonization of the five areas described above. RESULTS: The increase in the opening pressure and resistance, and decrease in reverse opening pressure, of the retrieved valves was significant compred with new valves. The increase in opening pressure was associated with colonization of the valve edge (rs = 0.262, P = 0. 007). The decrease in reverse opening pressure was associated with colonization of the valve edge, hinge areas and oesophageal surface (rs = 0.266, P = 0.006; rs = 0.271, P = 0.005; rs = 0.271, P = 0.004, respectively). The increase in resistance was associated with colonization in all areas (rs >/= 0.367, P = 0.0005). CONCLUSION: This study demonstrated that colonization of the valve edge is associated significantly with the changes, in pressure/flow parameters of failed valves.

Introduction by Topic Editors, Peter W. Carmel, M.D., and James M. Drake, M.D.

Shunt systems with differential pressure valves are prone to the complications of overdrainage. A programmable valve permits adjustment of the opening pressure of the valve. In this paper the authors report the incidence of subdural fluid collections in a randomized trial of programmable compared with conventional valves, and they describe methodologies used in management of this complication. A multiinstitutional, prospective, randomized trial of the Codman Hakim programmable valve and conventional fixed-pressure valves was undertaken. Two classes were defined: "new" and "replacement" valves. Randomization of the type of valve in each group was performed at each study site. Clinical and radiological studies were required at fixed intervals over a 104-week period. All complications were reported. The experimental valves were required to be reprogrammed after magnetic resonance imaging studies, but all other decisions regarding pressure setting were left to each investigator. Three hundred seventy-seven patients were randomized; 194 were treated with a programmable valve and 183 with a fixed-pressure valve. The two groups were statistically similar in demographic composition, as were the "new" and "replacement" categories. The investigators made 540 valve pressure changes (five per patient; range one-41 changes). More than half of the reprogramming adjustments were made in the first 3 months postplacement; 70% were made within 6 months. More than half of all reprogramming adjustments were required in a group of 30 patients. Four treatment modalities were observed: 1) 30% of the fluid collections resolved spontaneously (25% in the patients with programmable valves and 36.3% in those with conventional valves) and were largely found to be hygromas in infants and children; 2) four subdural fluid collections were unresolved and under observation; 3) the subdural hematoma was drained and the shunt removed (in 8.3% of patients with the programmable valve and 36.3% of those with the control valve); 4) the pressure of programmable valve was raised in 58% of patients (seven of 12), and this increase in opening pressure was a feature used by investigators to affect treatment. There was no significant difference in the incidence of subdural fluid collections between the programmable and fixed-pressure valve treatment groups. The programmable feature provided a considerable advantage in treatment when subdural collections occurred.

Incidence and management of subdural hematoma/hygroma with variable- and fixed-pressure differential valves: a randomized, controlled study of programmable compared with conventional valves

Thirty-two patients with normal-pressure hydrocephalus were managed using the lumboperitoneal (LP) shunt system in which the Codman Hakim programmable valve was utilized. The initial opening pressure was set at 100 mm H(2)O in three cases, 80 mm H(2)O in two, 70 mm H(2)O in three cases, 50 mm H(2)O in 23, and 30 mm H(2)O in one case (mean pressure 57.8 mm H(2)O). In 12 patients the valve pressure required reprogramming. The final valve pressure was 30 mm H(2)O in four cases, 50 mm H(2)O in 19, 70 mm H(2)O in three, 80 mm H(2)O in one, 100 mm H(2)O in two, 130 mm H(2)O in one, 140 mm H(2)O in one, and 170 mm H(2)O in one case (mean 62.5 mm H(2)O). Lumboperitoneal shuntography was performed in five patients by injection of contrast medium into the prechamber. In two patients a shunt obstruction developed between the valve and the lumbar catheter. Complications occurred in eight patients. Low-pressure symptoms such as headache and vomiting were observed in four patients but disappeared after increasing the valve pressure. One patient, whose shunt pressure was set at 50 mm H(2)O developed a slight asymptomatic subdural effusion, which resolved after increasing the valve pressure to 100 mm H(2)O. Convulsions developed in two aged patients but were easily controlled with anticonvulsant medication. Surgery-related wound infection was observed in one patient. The major advantage in the use of this valve is the ability to modify the pressure noninvasively. Another important advantage of the LP shunt system in which this valve is incorporated is the lower pressure of 30 mm H(2)O that can improve symptoms caused by underdrainage of cerebrospinal fluid.

Response of the whole bladder‐urethra model (rabbit) to autonomic drugs

AbstractTo investigate the function of the bladder‐urethra as a continuous unit we set up an in vitro whole bladder‐urethra model (rabbit). We were able to measure the intravesical pressure at which saline infused into the bladder emptied via the urethra (“opening pressure”). Methoxamine added to the bath caused a significant increase in opening pressure, whereas phentolamine caused a significant decrease in opening pressure compared to controls. Atropine had no effect on opening pressure in the absence or presence of methoxamine. Thus, it appears that the in vitro bladder‐urethra unit has intrinsic alpha‐adrenergic tone that is of sufficient force to maintain an intravesical pressure of 7.0 cm H2O, and that this tone is not influenced by antagonism with the anticholinergic agent atropine.