Valve Status Research Articles

High performance liquid chromatographic analysis of a new proton pump inhibitor KR60436 and its active metabolite O-demethyl-KR60436 in rat plasma samples using column-switching.

A fully automated high performance liquid chromatography with column-switching was developed for the simultaneous determination of KR60436, a new reversible proton pump inhibitor, and its active metabolite O-demethyl-KR60436 from rat plasma samples. Plasma sample (50 microl) was directly introduced onto a Capcell Pak MF Ph-1 column (10 x 4 mm I.D.) where primary separation was occurred to remove proteins and concentrate target substances using acetonitrile-potassium phosphate (pH 7, 0.1 M) (2:8, v/v). The drug molecules eluted from MF Ph-1 column were focused in an intermediate column (10 x 2 mm I.D.) by the valve switching step. The substances enriched in intermediate column were eluted and separated on a Vydac 218MR53 column (250 x 3.2 mm I.D.) using acetonitrile-potassium phosphate (pH 7, 0.02 M) (47:53, v/v) at a flow rate of 0.5 ml/min when the valve status was switched back to A position. The method showed excellent sensitivity (detection limit of 2 ng/ml) with small volume of samples (50 microl), good precision and accuracy, and speed (total analysis time 24 min) without any loss in chromatographic efficiency. The response was linear (r2 > or = 0.999) over the concentration range of 5-500 ng/ml.

Narrowbore high-performance liquid chromatography for the simultaneous determination of sildenafil and its metabolite UK-103,320 in human plasma using column switching

A fully automated narrowbore high-performance liquid chromatography method with column switching was developed for the simultaneous determination of sildenafil and its active metabolite UK-103,320 in human plasma samples without pre-purification. Diluted plasma sample (100 μl) was directly introduced onto a Capcell Pak MF Ph-1 column (20×4 mm I.D.) where primary separation occurred to remove proteins and concentrate target substances using 15% acetonitrile in 20 m M phosphate solution (pH 7). The drug molecules eluted from the MF Ph-1 column were focused in an intermediate column (35×2 mm I.D.) by a valve switching step. The substances enriched in the intermediate column were eluted and separated on a phenyl-hexyl column (100×2 mm I.D.) using 36% acetonitrile in 10 m M phosphate solution (pH 4.5) when the valve status was switched back. The method showed excellent sensitivity (detection limit of 10 ng/ml), good precision (RSD≤2.3%) and accuracy (bias: ±2.0%) and speed (total analysis time 17 min). The response was linear ( r 2≥0.999) over the concentration range 10–1000 ng/ml.

Technical Status of Pressure, Flow, and Electrohydraulic Control Valves in Hydraulic Systems

Technical Status of Pressure, Flow, and Electrohydraulic Control Valves in Hydraulic Systems

Simultaneous determination of aceclofenac and diclofenac in human plasma by narrowbore HPLC using column-switching

A fully automated narrowbore high performance liquid chromatography (HPLC) with column-switching was developed for the simultaneous determination of aceclofenac and diclofenac from human plasma samples. Plasma sample (100 μl) was directly introduced onto a Capcell Pak MF Ph-1 column (20×4 mm I.D.) where primary separation was occurred to remove proteins and concentrate target substances using acetonitrile–potassium phosphate (pH 7, 0.1 M) (14:86, v/v). The drug molecules eluted from MF Ph-1 column were focused in an intermediate column (35×2 mm I.D.) by the valve switching step. The substances enriched in intermediate column were eluted and separated on the narrowbore phenyl–hexyl column (100×2 mm I.D.) using acetonitrile–potassium phosphate (pH 7, 0.02M) (33:67, v/v) when the valve status was switched back to A position. The method showed excellent sensitivity (detection limit of 10 ng ml −1) with small volume of samples (100 μl), good precision and accuracy, and speed (total analysis time 17 min) without any loss in chromatographic efficiency. The response was linear ( r 2≥0.999) over the concentration range of 50–10000 ng ml −1.

Simplified single patch technique for the repair of atrioventricular septal defect

Objective: Because of the complexity of traditional 1- and 2-patch techniques for the repair of complete atrioventricular septal defect, we modified our repair technique to avoid the use of any ventricular septal patch material. We report our prospective experience with this simplified 1-patch technique. Method: Forty-seven consecutive patients between May 1995 and August 1998 underwent repair with the use of this technique without modification. Repair was done in all patients by direct suturing of the common atrioventricular valve leaflets to the crest of the ventricular septum. No division of valve leaflets was necessary. A single pericardial patch was used to close the defect in the atrial septal component. Follow-up included electrocardiography and echocardiographic assessment of ventricular function, atrioventricular valve function, and adequacy of the left ventricular outflow tract. Results: There were 2 deaths (4%), only 1 cardiac related, in the series. There were 17 male patients and 30 female patients. Mean age at repair was 5.6 months (median, 3.4 months). Associated lesions were repaired in 19 patients (40%). Mean follow-up was 1.85 years (median, 1.9 years). There was no heart block. There were no significant residual ventricular septal defects detected and no left ventricular outflow tract obstruction seen on echocardiography in any patient to date. Mitral valve status after operation was assessed as no incompetence in 13 patients (28%), minimal in 19 patients (40%), mild in 12 patients (26%), and moderate in 3 patients (6%). Conclusion: The repair of complete atrioventricular septal defect by direct suturing of the atrioventricular valve leaflets to the crest of the ventricular septum with a single-patch technique greatly simplifies the repair and does not lead to left ventricular outflow tract obstruction nor interfere with valve function. (J Thorac Cardiovasc Surg 1999;118:642-7)

Noninvasive measurement of cardiac output: two methods compared in patients with mitral regurgitation.

In search for the origin of the less reliable cardiac output (CO) estimations by means of electrical impedance cardiography (EIC), the authors hypothesized that cardiac valve pathology might be one of the reasons. Twenty-six patients were examined by means of echo Doppler (ED) and EIC. The cardiac valve status was obtained by means of echocardiography and color Doppler flow, while CO was obtained by means of both methods. Seventeen patients had no valve pathology (nVP) while nine patients had mild to moderate mitral regurgitation (MVR). The overall correlation between the calculation of CO by means of the two methods was good (r = 0.85, p < 0.001, mean difference and standard deviation: 0.20+/-0.74 L/min), while there was no significant difference between the paired values. After division into an nVP and an MVR population, the results showed an even closer agreement between the CO values in the nVP population (r = 0.88, p < 0.001, mean difference and standard deviation: 0.15+/-0.68 L/min). Furthermore, significant differences were found in the first derivative of the impedance (dZ/dt) signals of these groups. Although the agreement between ED and EIC was slightly lower in the MVR population, EIC reliably estimated CO, even in case of MVR. The impedance signal itself gave an indication for the existence of MVR.

Quantitative detection of outlet strut separations in Björk-Shiley convexo-concave mitral valves.

As of January 31, 1995, 564 outlet strut fractures (OSFs) of Björk-Shiley convexo-concave (BSCC) heart valves had been reported to the Shiley Heart Valve Research Center, of which approximately two thirds resulted in the death of the patient. Previous studies indicate that one leg of the outlet strut separates (single-leg separation, SLS) from the valve before the second leg breaks, which results in complete OSF. To identify those valves at risk of complete OSF, an in vivo radiographic imaging technique is being developed to evaluate the strut leg integrity. The goal of the present study was to develop an objective postprocessing technique to evaluate outlet strut leg integrity quantitatively in these cineradiographic images. Twenty-two sets (12 intact valves, 10 SLS valves) of cineangiographic images were obtained from individuals whose valve status was subsequently verified ex vivo. Several quantitative measures of SLS were evaluated to identify possible loss of metal or gaps in the SLS legs. Two of these measures, decrease in pixel intensity (DIPI) ratio and gap half-width, are diagnostic metrics of SLS: i.e., the maximum likelihood estimate of the area under the receiver operating characteristic curve was 0.892 (SD, 0.066) for a model based on DIPI ratio and 0.802 (SD, 0.093) for gap half-width. We have developed a postprocessing technique that can be used to objectively evaluate outlet strut integrity in cineradiographic images of BSCC heart valves. At an estimated specificity of 1.0, the estimated sensitivity of the objective review was comparable to that of a subjective expert review panel.

CRITIQUE AND RESPONSE: Critique of “A Longitudinal Study of the Effects of Ecological Interface Design on Skill Acquisition” by Christoffersen, Hunter, and Vicente

As one of the reviewers of this article, I've been asked by the editor to write a critique describing my comments and reservations about the study. This is a new feature for Human Factors, so I undertake this task with the knowledge that many readers will not have been exposed to such explicit professional criticism. However, this type of (I hope) constructive criticism is common in our review process for journal manuscripts. The authors are to be commended for allowing the issues I will raise in this critique to be aired publicly. Before I begin my critique, let me say that the work described here contains many excellent features. First and foremost, this research was conducted over a long period with nearly continuous empirical data gathering. This, by itself, represents a unique and valuable contribution to our body of knowledge. Anyone who has ever conducted a research study using human subjects can appreciate the logistical difficulties inherent in long-term experiments. I commend both the authors and subjects for their perseverance. Also, the topic of the research is relevant to many practical situations involving process control. This publication and the human factors research community are often taken to task for the lack of practical relevance in our work. This article and the work itself directly rebuts such criticism. The review process for the present article, which has involved two other reviewers and me, along with the editor, has taken about one year. In the two revisions since the original manuscript, I believe the authors have conscientiously tried to address reviewers' concerns. What we are left with are only a few issues about which we disagree. Other reviewers have questioned the number and selection procedure for subjects. I believe these issues are related directly to the difficult nature of long-term studies, and I'm content to let readers make their own determination regarding their relevance to the results. Only one of the issues I raised during the review process has any fundamental bearing on the interpretation of the work presented here. In my opinion, this issue has not been adequately addressed in either of the revisions. My critique of this work is quite simple. I do not believe the study addresses the primary factor it was intended to address. In the study, the performance of subjects using one of two different types of process control interfaces was compared. Statistical analyses show that although overall performance levels did not vary between the two interfaces, subjects' performance was more variable with one than with the other. The authors conclude that the type of interface - more important, the principles used to develop one of the interfaces - is the determining factor in these performance differences. I believe this factor was confounded by certain elements in the design of the two interfaces used in the study. The basic hypothesis underlying this study is that presenting simple physical information about a process, such as pressure, temperature, valve status, and so on, is not necessarily the best portrayal for supporting operator tasks, such as controlling the process. To best support various types of behavior, the authors, and others, contend that information must be presented in forms that support an abstraction hierarchy, as described by Rasmussen (1985). The authors are correct in asserting that ecological interfaces have not been widely evaluated, although at least one recent study examined operator performance with a number of different types of interfaces - including ecological - in the process control domain (Edlund & Lewis, 1994). However, the idea of presenting process information according to abstraction hierarchies is certainly not new. After the Three Mile Island accident in 1979, various studies examined the information available to nuclear power plant control room operators. With the advent of symptom-based emergency procedures, there was general agreement that presenting simple physical information was not sufficient to allow operators to make certain task-related decisions. …

Reversibility of mitral regurgitation following rheumatic fever: clinical profile and echocardiographic evaluation.

The clinical disappearance of the murmur of rheumatic mitral regurgitation after period of time has been documented by many researchers. However no studies have related the disappearance of the murmur with the functional or anatomical state of the mitral valve. This study was done to elucidate the mitral valve status using doppler and color coded echocardiography among those children who have lost their apical pansystolic murmur on auscultation following a documented attack of rheumatic fever. The study sample consisted of 51 patients including 31 patients in whom the murmur has disappeared (group I), and 20 patients with persistent isolated mitral regurgitation (group II). Patients of group I had significantly lower grades of murmur intensity, lower incidence of cardiomegaly, and had no heart failure in the initial attack. They were more compliant with prophylaxis and had less recurrences than patients of group II. The murmur disappeared in patients of group I from 1/2 to 14 years after the initial attack. Echocardiography revealed that such patients had a normal mitral valve apparatus, and a normal heart size and function. Only 5 patients of this group had a significant regurgitant jet demonstrated by colour doppler. We concluded that recovery of the mitral valve and return of cardiac functions to normal is possible in patients who had mitral regurgitation following rheumatic fever. Some of them may still have an inaudible mild regurgitation. Patients who have lost their murmur may be allowed to exercise freely, yet penicillin prophylaxis should not be discontinued.

Viability studies of human valves prepared for use as allografts

The preimplantation viability status of pulmonary and aortic valves prepared for use as allografts by the methods in current use at Green Lane Hospital, Auckland was determined by autoradiography and culture. The valves were obtained from cadaver donors, disinfected in antibiotic solution and stored by cryopreservation. A group of 45 banked valves considered unsuitable for clinical use was assayed initially and very few were found to have viable fibroblasts in their leaflets. A series of 29 valves collected at postmortem examination then was assayed sequentially after each phase of the preparation procedure. Valves obtained within 24 hours of donor death usually retained considerable viability. However, in all but a minority of cases this declined markedly after antibiotic treatment and further still after cryopreservation, so that most valves were nonviable when thawed.

Development and clinical application of a next generation implantable echocardiography probe for monitoring cardiac function under assisted circulation after open heart surgery.

Post-operative cardiac function generally is monitored by electrocardiography, invasive measurement of blood pressure, and determination of hemodynamic variables, such as pulmonary pressures and cardiac output with a Swan-Ganz catheter. In recent years, transesophageal echocardiography has been introduced into clinical use, but it is not a popular method of monitoring for various reasons, including the difficulty of application to unconscious post-operative patients. Since 1991, we have been developing a small implantable echocardiography probe. This probe was tested in 15 patients who underwent open heart surgery for severe left ventricular hypofunction, and its clinical utility was demonstrated. No deaths occurred in this series. The implantable echocardiography probe allowed post-operative cardiac function to be monitored in real-time. The ejection fraction, the cardiac output, the status of valves after valvuloplasty, the presence of cardiac tamponade, and other variables could be assessed. The echocardiography probe can be positioned at any site where specific information is desired during surgery. It can be inserted as easily as a pericardial drain tube and is removed in the same manner when no longer necessary. This probe has the potential to be useful for monitoring patients on assisted circulation after cardiac surgery.

Laparoscopic Hill repair

Gastroesophageal reflux disease, with its attendant symptoms and complications of heartburn, esophagitis, dysphagia, and upper gastrointestinal bleeding, is the most common disorder of the upper gastrointestinal tract. The open Hill repair, which has been utilized in more than 2000 patients, is best defined as restoration of the anti-reflux barrier. The anti-reflux barrier includes the gastroesophageal valve, lower esophageal sphincter, and diaphragm. The Hill repair has now been done laparoscopically in 17 patients (10 men and 7 women) who have been entered into a detailed protocol, including pre-operative evaluation, intra-operative monitoring, and post-operative evaluation. Results have been excellent, with correction of reflux in all patients. Duration of follow-up ranges from 1 to 18 months, with a mean of 10.5 months. No mortality or serious complications have occurred. Extensive post-operative testing in 13 patients, including complete symptom evaluation, standard acid reflux testing, and 24-hour pH monitoring, has shown no recurrence of reflux; lower esophageal sphincter pressure has been restored to a mean of 28 mm Hg, and gastroesophageal valve status to grade 1. Because the laparoscopic procedure is similar to the open Hill repair, expectations for good long-term results are very high. (Gastrointest Endosc 1994;40:155-9.)

Aortic valve replacement with cryopreserved pulmonary allograft.

Experimental as well as clinical data support the finding of using the pulmonary valve as a systemic semilunar valve. From January 1990 to December 1992, 89 patients received pulmonary cryopreserved allografts as aortic valve replacement. Sixteen subjects suffering from native or prosthetic valve endocarditis were included. Age ranged from 10 to 74 years. Sixty-five patients received isolated aortic valve replacement and 24 patients required additional surgical measures, such as coronary artery bypass graft, mitral valve reconstruction, replacement of the ascending aorta, supravalvular patch aortoplasty, ventricular septal defect closure, or myectomy. All operations were performed with normothermic bypass and cold cardioplegic arrest. Follow-up is maintained by visits to the outpatient clinic and echocardiographic assessment of the valve status every 3 months during the first year and every 6 months thereafter. There were four early and three late deaths. Four valves had to be removed: one intraoperatively and three 2, 4, and 24 months postoperatively. Echocardiographic assessment proved that gradients across the valve were low or absent. The majority of patients showed trivial or no aortic regurgitation during follow-up. No thromboembolic events have been observed and no new endocarditis occurred. Thus, event-free survival at 3 years is 87%. The results with pulmonary allografts have shown to be comparable to aortic allografts. Even in patients with acute native or prosthetic valve endocarditis, the use of cryopreserved pulmonary allografts has shown no adverse effects. We continue to implant cryopreserved pulmonary allografts in the aortic position. The long-term function of the valve, however, must be established, making continued evaluation of postoperative patients mandatory.

Adaptation in short-bowel syndrome: Reassessing old limits

The improving survival of patients with severe short-bowel syndrome along with the advent of successful intestinal transplantation have accentuated the need to answer two questions. (1) Is there an intestinal length below which adaptation to full enteral nutrition can not be expected to occur? (2) How much time is necessary to complete intestinal adaptation? We reviewed the outcome of 21 infants with less than 50 cm of small intestine to answer these questions. Patients were divided into three groups based on intestinal length, regardless of ileocecal valve status: group I, <10 cm (n = 3); group II, 10 to 30 cm (n = 11); and group III, 30 to 50 cm (n = 7). Data were collected to assess survival, incidence of adaptation, time to adaptation, and causes of mortality. Infants in group I did not achieve intestinal adaptation to full enteral nutrition. One survived and 2 died, one from varicella pneumonia and the other after intestinal transplantation. Eight of the 11 (73%) patients in group II survived and 5 of 8 (63%) survivors achieved full intestinal adaptation after a mean interval of 320 days (range, 148 to 506 days) on parenteral nutrition. Six of the seven patients (86%) in group III survived and all survivors (100%) achieved complete enteral adaptation after an average of 376 days (range, 58 to 727 days). The overall survival was 71% ( 15 21 ), but survival in patients with > 10 cm was 78%. The incidence of fatal catheter sepsis ( 2 21 ) and fatal parenteral nutrition-associated liver failure ( 1 21 ) was low and accounted for two of the six deaths—one patient died as a consequence of both complications. The 10-cm small intestinal length appears to be a new lower limit for the length necessary to achieve enteral nutrition. Patients with > 10 cm of small intestine should be supported on parenteral nutrition with early institution of enteral feedings to promote intestinal adaptation for a minimum of 2 years before transplantation is considered.

Element structure in stenotic mitral valves

In our previous studies, 1–3 we established the major, minor and toxic element status of stenotic mitral valves. From the results of these studies, we suggested that elucidation of the element status of mitral valve calcific deposits may provide useful information in the prevention of mitral valve calcific deposits found in rheumatic heart disease. This report examines this subject.

特集 真空技術 バルブ技術の現状

特集 真空技術 バルブ技術の現状

Simulation of PVT Experiments

Summary An interactive program (PVTLAB) was written to simulate PVT experiments with a microcomputer. The simulator is a real-time representation of an actual PVT laboratory. Operations typically performed in the laboratory may also be performed with the simulator. The Peng-Robinson equation of state (PR-EOS) is used to calculate phase behavior, and the results of the calculations are displayed in color on the microcomputer monitor. The monitor graphically represents the condition of all the physical components of the PVT laboratory, including pressures, fluid levels in vessels, and the status of valves and pumps. A printed record of every action taken during a run is kept if desired. A simulated experimental error results in an appropriate termination of the run. Program structure and operation are described, and examples of simulated PVT experiments are given.

Novel automated micro batch analyzer

An automated micro batch analyzer (AMBA) system is described. The sample is introduced into an air‐tight reaction chamber (a polypropylene microcentrifuge tube) by a loop injector made from two three‐way valves by flowing gas. Reagents/diluents are introduced into the chamber from pneumatically pressurized reservoirs provided with on‐off valves. A microprocessor‐controlled timer controls valve status and thus provides control of delivered volumes. Gas bubbles are introduced through the bottom of the chamber to perform mixing; the mixed liquid is then discharged into an optical detector via a bubble gate by superincumbent pressure. The bubble gate allows the data‐acquisition system to collect data only when liquid is actually in the detection cell. For simple fast reactions, throughput rates of 210 samples/h could be obtained.

Present status of prosthetic cardiac valves

Present status of prosthetic cardiac valves

The univentricular heart: Combined 2-dimensional-pulsed Doppler (duplex) echocardiographic evaluation

Two-dimensional echocardiographic-pulsed Doppler (2D-PD) evaluation was performed in 14 patients with a univentricular heart. Accurate information on ventricular structure, atrioventricular valve status, and great vessel anatomy and function was obtained. The characteristic morphologic features were verified in each case by angiography or autopsy, or both. In several patients, 2D-PD evaluation provided more accurate anatomic and functional information than did cardiac angiography in standard views, particularly with regard to atrioventricular valve function. Four children with pulmonary atresia and 4 with pulmonary stenosis were identified prospectively. No patient had 2D-PD evidence of aortic obstruction. Four children had typical 2D-PD patterns consistent with atrioventricular valve regurgitation. Thus, 2D echocardiography coupled with a range-gated Doppler system will improve recognition of patients with a univentricular heart and permit thorough evaluation of specific anatomic details.