Lower Mean Pressure Research Articles

Percutaneous Transluminal Angioplasty Balloon Inflation with Syringes: Who Needs an Inflator?

High pressures are important in percutaneous transluminal angioplasty, particularly in hemodialysis access. Although many operators rely on commercially available inflators, small syringes can deliver high pressures, which might make inflators unnecessary. Recently introduced polycarbonate (PC) syringes may allow higher pressure delivery than traditional polypropylene (PP) ones, so the present study was performed to determine predictors of inflation pressures achievable with various syringe designs. Forty-two subjects participated: 12 residents, 12 interventional radiology fellows, 12 interventional radiology attending physicians, and six others. Each subject made three attempts to deliver maximum pressure with use of a calibrated gauge for each syringe type (1-, 3-, 5-/6-, 10-, and 20-mL PP and PC syringes). A control experiment was conducted to assess fatigue effects. Age, sex, grip strength measured on a dynamometer, and physical parameters (height, weight, body mass index [BMI]) were collected for each participant. Pressures of 40 atm or greater were achieved by more than 90% of subjects with 1-mL PC syringes (mean, 47 atm +/- 7 [SD]). Female subjects generated lower mean pressures with every syringe type (P value range, <.0001 to .025); this effect was least pronounced with 1-mL PC syringes. Grip strength was highly correlated with pressure generation across syringe types. Control experiments showed no significant fatigue effect. With rare exceptions, age, BMI, level of training, height, and weight did not correlate with pressure generation. Irrespective of sex, grip strength, and BMI, 1-mL PC syringes can be used to generate pressures in excess of 40 atm. High correlation between grip strength and pressure generation may make it possible to predict the pressure an individual can generate with any syringe size or design.

Introduction of a Dedicated Circulation Phantom for Comprehensive In Vitro Analysis of Intravascular Contrast Material Application

To develop a circulation phantom with physiologic circulation parameters, including a pulmonary and a body circulation for the evaluation of intravascular contrast material (CM) application. The circulation phantom consists of a low-pressure venous system into which CM is injected, a pulmonary circulation, and high-pressure body circulation with an anthropometric aorta and coronary arteries. The phantom is driven by a pulsatile Harvard heart pump. Venous and arterial pressure were set to physiologic values with heart rate (60 beats/min), stroke volume (60 mL), and ratio of diastole to systole (60/40) also were within physiologic limits. CM with different iodine concentrations (300, 370, and 400 mg iodine/mL) were injected at a flow rate of 4 mL/s (iodine delivery rate: 1.2 g, 1.48 g, and 1.6 g iodine/s, respectively; total iodine load for all protocols: 36 g). Serial computed tomography scans at the level of the pulmonary artery, the ascending and the descending aorta replica were obtained. Dynamic pressure in the phantom and true injection system parameters (flow rate, injection pressure, and CM volume) was continuously monitored. Time-enhancement curves were calculated, and pulmonary and aortic peak time and enhancement were determined. Results were compared using nonparametric unpaired Wilcoxon tests. The pressure in the phantom showed physiologic values for the low (mean pressure: 15 mm Hg) and high pressure part (125/75 mm Hg). Programmed injection values (flow rate, pressure, and volume) were reached for all injections. Using CM with 400 mg iodine/mL, the shortest pulmonary and aortic peak times and the highest pulmonary and aortic peak enhancement values were obtained compared with CM with 300 and 370 mg iodine/mL. We developed a flow phantom with physiologic circulation parameters for measurement of contrast enhancement. The phantom is suitable for further evaluation of CM injection protocols for pulmonary and aortic enhancement.

98: The Influence of the Inflow Cannula Length in Rotary Blood Pumps on the Neurological Adverse Event Rate – Results from a Multi-Center Analysis

Purpose: Right ventricular (RV) failure after left ventricular assist device (LVAD) placement is a serious complication with a poor prognosis and is difficult to predict. In the era of LVAD use as destination therapy and alternatives such as the total artificial heart, predicting post-LVAD RV failure requiring mechanical support is extremely important. Methods and Materials: We reviewed patient characteristics, laboratory values, and hemodynamic data from 266 patients who underwent LVAD placement at the University of Pennsylvania from April 1995 to June 2007. Results: Of 266 LVAD patients, 99 required RV assist device (BiVAD) placement (37%). We compared 36 parameters between LVAD (n 167) and BiVAD patients (n 99) to determine preoperative risk factors for RV assist device (RVAD) need. By univariate analysis, 23 variables showed statistically significant differences between the two groups (P 0.05). The strongest of these were female gender, low body surface area, echocardiographic evidence of severe preoperative RV dysfunction, previous cardiac surgery, preoperative mechanical ventilation, elevated creatinine, elevated INR, elevated central venous pressure, low systolic blood pressure (SBP), low pulmonary artery systolic and mean pressures, low cardiac index (CI), low mixed venous oxygen saturation, and low right ventricular stroke work index (RVSWI). By multivariate logistic regression, CI 2.3 L/min m (odds ratio [OR] 5.7), RVSWI 0.25 mmHg mL/m (OR 5.1), severe preoperative RV dysfunction (OR 5.0), preoperative creatinine 1.9 mg/dL (OR 4.8), previous cardiac surgery (OR 4.5), and SBP 96 mmHg (OR 2.9) were the best predictors of RVAD need. Conclusions: The most significant predictors for RVAD need were CI, RVSWI, severe preoperative RV dysfunction, creatinine, previous cardiac surgery, and SBP. Using these factors, we have constructed an algorithm which can predict which LVAD patients will require RVAD with greater than 80% sensitivity and specificity.

Gas/Water Flow in Porous Media in the Presence of Adsorbed Polymer: Experimental Study on Non-Darcy Effects

Summary The objective of this paper is to report some experimental investigations on the effect of polymer adsorption on gas/water flow in non-Darcy regimes in homogeneous porous media, in contrast to previously available analyses focused mainly on the Darcy regime. Our investigation concentrates on gas flow either at low mean pressure, when Klinkenberg effects (or gas slippage) must be considered, or at high flow rates, when inertial effects are significant. The experimental study reported here consists of water and nitrogen injections into various silicon carbide model granular packs having different permeabilities. Experiments are carried out at different water saturations before and after polymer adsorption over flow regimes ranging from slip flow to inertial flow. In good agreement with previous works, in the Darcy regime, we observe an increase in irreducible water saturation and a strong reduction in the relative permeability to water, while the relative permeability to gas is slightly affected. At low mean pressure in the gas phase, the magnitude of the Klinkenberg effect is found to increase with water saturation in the absence of polymer, whereas for the same water saturation, the presence of an adsorbed polymer layer reduces this effect. In the inertial regime, a reduction of inertial effects is observed when gas is injected after polymer adsorption, taking into account water-saturation and permeability modifications. Experimental data are discussed according to hypotheses put forth to explain these effects. Consequences for practical use are also put under prospect.

Auto-Adjusting Versus Fixed Positive Pressure Therapy in Mild to Moderate Obstructive Sleep Apnoea

To determine if auto-adjusting positive airway pressure (APAP) would be better tolerated on the basis of delivering a lower mean pressure in patients with mild to moderate obstructive sleep apnoea syndrome (OSAS). Patients spent 8 weeks on continuous positive airway pressure (CPAP) and 8 weeks on APAP in a randomized crossover design. Respiratory Sleep Disorders Unit in a University Hospital and the patient's home. Twenty-nine patients with newly diagnosed mild to moderate OSAS (apnoea-hypopnoea frequency of 5-30 events/hour) were studied. N/A. Overnight polysomnography and Epworth Sleepiness Scale were recorded at baseline and at the end of each treatment period in addition to patient preference for device, side effects, and objective compliance. No differences were found in polysomnographic variables or Epworth Sleepiness Scale scores between the 2 treatment modes, but all variables were significantly improved from baseline values. Mean APAP pressure levels were significantly lower than CPAP (6.3 +/- 1.4 vs 8.1 +/- 1.7 cm H2O, p < .001). Patient compliance was similar with both treatments. More patients requiring higher fixed pressure (> or = 8cm H2O) preferred APAP, whereas those requiring lower pressure (< 8 cm H2O) preferred CPAP (p = .03). Follow-up after 18 months of therapy indicated that 76% of subjects continued to be compliant, with a nightly use of 5.8 +/- 1.9 hours per night, despite high levels of minor side effects. APAP and CPAP are equally effective in managing patients with mild to moderate OSAS, but device preference may be influenced by fixed pressure requirements.

High pulse pressure and low mean arterial pressure: two predictors of death after a myocardial infarction

Although the negative prognostic implication of a clinical history of arterial hypertension in myocardial infarction (MI) survivors is well known, the predictive role of the blood pressure (BP) regimen after MI is not well defined. The aim of this study was to investigate the prognostic significance of different BP indices in post-MI. We evaluated the relationship between baseline systolic, diastolic, pulse and mean arterial pressure (MAP), measured by sphygmomanometry at discharge from hospital or within 3 months of an MI, and total and cardiovascular mortality in 11 116 patients enrolled in the GISSI-Prevenzione trial. Over 3.5 years of follow-up, 999 patients died, 657 of them from cardiovascular causes. Low mean and high pulse pressure were significantly associated with total and cardiovascular mortality after controlling for potential confounders in the multivariate analysis. As compared with patients with less extreme BP values, patients with MAP of 80 mmHg or less (n = 1241; 11.2%) had a 48% higher risk of cardiovascular death [95% confidenceinterval (CI) 1.16-1.87; P = 0.001] and those with pulse pressure greater than 60 mmHg (n = 958; 8.6%) had a 35% higher risk (95% CI 1.09-1.69; P = 0.007); only four subjects (0.04%) had both a high pulse pressure and a low MAP (relative risk of cardiovascular death 3.48; 95% CI 0.48-25.88; P = 0.218). Our results show for the first time an additional prognostic importance of two easily measurable components of BP, definitely high pulse pressure (> 60 mmHg) and low MAP (< or = 80 mmHg), in a large sample of non-selected patients surviving MI who entered a modern programme of cardiovascular prevention.

Obstructive sleep apnoea syndrome: Translating science to clinical practice

OSA syndrome is characterized by recurring episodes of upper airway (UA) obstruction during sleep. The UA is subjected to collapse when the negative airway pressure generated by inspiratory activity of the diaphragm and intercostal muscles exceeds the force produced by the UA dilating muscles. Factors that reduce UA calibre lead to increased UA resistance with the generation of a more negative pharyngeal pressure during inspiration, and thereby predispose to UA occlusion during sleep. As a consequence, UA dilating muscles must contract more forcefully to maintain a patent UA, which may predispose to fatigue. Nasal CPAP counteracts these collapsing forces and is associated with resting of the UA muscles. The more recent development of auto-adjusting CPAP (APAP) is a reflection of the understanding that the pressure required to prevent UA collapse fluctuates throughout the night and results in a lower mean pressure that may be more comfortable for some patients. The predominant morbidity of the OSA syndrome is cardiovascular and there is growing understanding of the basic mechanisms involved. Intermittent hypoxia appears to play a central role by activating transcription factors that predispose to atherogenesis, particularly NFkappaB. Sympathetic overactivity also appears to play an important role but the mechanisms involved are unclear.

Invited commentary

The ultimate test of a new heart valve prosthesis remains the implantation of the device in humans. This is not without risk, and unexpected catastrophic results can be obtained in spite of extensive pre-clinical testing. Therefore it is a relief to see the report of a first clinical trial demonstrating uneventful early results. To justify such clinical implantation of newly developed heart valves, one expects at least significant advantages on the existing and generally accepted prostheses. In case of the newly designed low-profile Medtronic Advantage valve (Medtronic, Inc, Minneapolis, MN), there could be superior hemodynamics and reduced thrombogenicity. The present study [1Guenzinger R. Eichinger W.B. Botzenhardt F. et al.Rest and exercise performance of the Medtronic advantage bileaflet valve in the aortic position.Ann Thorac Surg. 2005; 80: 1319-1326Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar] reveals that the Medtronic Advantage valve performs well hemodynamically as demonstrated by low mean pressure gradients, large effective orifice areas, and indices. Furthermore, the authors performed hemodynamic studies during treadmill exercise 1 year after valve replacement, the ultimate test of heart valve performance. They also found a low incidence of patient–prosthesis mismatch and a significant regression of left ventricular (LV) mass 1 year after valve replacement. The authors are to be congratulated not only for their carefully performed study, but also for their realistic interpretation of the results. Indeed, a mean pressure gradient ranging from 10.8 to 20.0 mm Hg across all valve sizes during treadmill exercise at 100 W workload is excellent but not superior to the results of existent bileaflet valves. The same holds true for effective orifice area index (EOAI) values between 0.93 and 1.37 cm2/m2, the low incidence of patient-prosthesis mismatch, and an 18% reduction of LV mass at 1 year. It is unquestionably true that “second generation” bileaflet heart valves perform better than their “first generation” counterparts and that actual heart valves designs did “a good job.” In a comparable series of patients for example, we observed EOAI values between 0.60 to 0.92 (across all valve sizes, including size 19) for the older St. Jude Standard bileaflet valve versus 0.91 to 1.37 cm2/m2 for the actual St. Jude Regent valve (St. Jude Medical, St. Paul, MN). We may confirm the conclusion of the present study that this new bileaflet valve has an excellent hemodynamic profile, but we feel that the advantage of the Medtronic Advantage valve on the existing second generation bileaflet heart valves remains to be elucidated.

Convexity, Jensen's inequality and benefits of noisy mechanical ventilation

Mechanical ventilators breathe for you when you cannot or when your lungs are too sick to do their job. Most ventilators monotonously deliver the same-sized breaths, like clockwork; however, healthy people do not breathe this way. This has led to the development of a biologically variable ventilator--one that incorporates noise. There are indications that such a noisy ventilator may be beneficial for patients with very sick lungs. In this paper we use a probabilistic argument, based on Jensen's inequality, to identify the circumstances in which the addition of noise may be beneficial and, equally important, the circumstances in which it may not be beneficial. Using the local convexity of the relationship between airway pressure and tidal volume in the lung, we show that the addition of noise at low volume or low pressure results in higher mean volume (at the same mean pressure) or lower mean pressure (at the same mean volume). The consequence is enhanced gas exchange or less stress on the lungs, both clinically desirable. The argument has implications for other life support devices, such as cardiopulmonary bypass pumps. This paper illustrates the benefits of research that takes place at the interface between mathematics and medicine.

10-Year Experience With the ATS Mechanical Valve in the Mitral Position

The ATS Medical Open Pivot mechanical heart valve was introduced in 1992. Previous reports have focused on the low rate of thromboembolic complications in the aortic position. The purpose of this retrospective study is to analyze the rate of midterm thromboembolic events and other valve-related complications when the ATS Open Pivot valve is implanted in the mitral position. Between June 1992 and June 2002, 177 patients (63 male and 114 female; mean age 57.5 years) underwent mitral replacement with an ATS Open Pivot mechanical heart valve. Preoperatively, 17 patients (10%) were in New York Heart Association functional class II, 117 patients (66%) in class III, and 43 patients (24%) in class IV. Seventy-four patients (42%) were in chronic atrial fibrillation. Seventy-four mitral valve replacements (42%) were associated with other cardiac procedures. Etiologies included degenerative disease (56%), rheumatic disease (38%), and endocarditis (6%). On the second postoperative day, 100 mg acetylsalicylic acid and oral acenocoumarol (Sintrom) was introduced to obtain a target INR of 2.0 to 3.0. All patients were followed up by one cardiologist and underwent annual transthoracic echocardiographic examination. Percent follow-up was 90.4%. Data represent 724 total patient-years. Mean follow-up was 48 +/- 34 months (range, 1 to 119). Operative morbidity was 15%. Overall hospital mortality was 2.8% (5 patients). At hospital discharge, the mean INR for all the patients was 2.38 +/- 0.68 (range, 1.32 to 6.44). Five early neurologic complications occurred: 3 transient cerebrovascular accidents and 2 strokes. Three late transient cerebrovascular ischemic accidents occurred at 3, 4, and 6 years, respectively. No other complications such as paravalvular leak, valve dysfunction, thrombosis, or valve explant occurred. Postoperative echocardiographic data revealed low mean pressure gradient as related to the valvular size. The ATS Medical Open Pivot mitral valve demonstrates low rates of bleeding, thromboembolic, and other valve-related complications.

Bursting Strength with Various Methods of Renal Artery Ligation and Potential Mechanisms of Failure

Vascular control is crucial during laparoscopic ligation of the renal vessels. Intracorporeal suture ligation has been replaced by easier methods, such as specialized clip appliers and automatic stapling devices; nevertheless, the optimal application and margin of safety of such devices have yet to be determined. We sought to address this question by measuring the bursting strength of arteries ligated with several standard devices. One end of an adult porcine artery (3-7-mm diameter) was occluded with a titanium clip, self-locking polymer clip, or laparoscopic linear cutting stapler. Comparisons were made with one or two clips and with different distal cuff lengths (i.e., flush or 2 mm). The open end was secured to a pulsatile infusion pump. Leak/failure pressures were measured using a digital barometer. The mean bursting pressures for the clips were above physiologic arterial pressures (1220-1500 mm Hg). However, the vessels closed with the stapler leaked at a lower mean pressure (262 mm Hg). Failure of titanium or self-locking polymer clips was the result of vessel retraction into and behind the clip, while staple- line leakage occurred between individual staples. Bursting pressures with the titanium and self-locking polymer clips was unaffected by the number of clips or length of vascular cuff. All tested methods of vascular control performed well at physiologic pressures, suggesting that safety is not increased with traditional maneuvers such as additional clips or longer cuff length.

Disposable balloon-based oesophageal motility catheters: comparison with solid-state transducers*

Current oesophageal manometry systems use either water-perfused or solid-state pressure transducers. Recently developed single-use disposable catheters use small balloons prefilled with air that transmit the pressure of oesophageal contractions to external transducers. To compare data obtained from single-use disposable balloon catheters to data from solid-state systems. Healthy volunteers, patients with ineffective oesophageal motility and nutcracker oesophagus were studied to include a broad range of pressures. A single-use disposable Clinical Innovations (CI) catheter was placed adjacent to a solid-state Konigsberg Instruments (KI) catheter with pressure transducers at 5, 10, 15 and 20 cm above the lower oesophageal sphincter (LOS). Subjects received liquid and viscous swallows at 30-s intervals. Healthy volunteers received additional sets of swallows while having only one catheter in the oesophagus. When both catheters were present in the oesophagus, no differences were noted between mean pressure measurements in the distal oesophagus and there was good correlation between pressures recorded in response to individual swallows. When present alone in the oesophagus the CI catheter recorded lower mean pressures compared with the KI catheter. Overall there was good agreement in classifying swallows as normal, ineffective and simultaneous. Single-use oesophageal manometry catheters are promising alternatives to solid-state manometry systems in measuring intra-oesophageal pressures.

Decreased sleep spindles and spindle activity in midlife women with fibromyalgia and pain.

To compare sleep-spindle incidence (number of spindles per minute of non-rapid eye movement [NREM] stage 2 sleep) and duration, spindle wave time (seconds per epoch in NREM stage 2 sleep), spindle frequency activity, and pain measures (pressure pain threshold, number of tender points, skinfold tenderness) between midlife women with fibromyalgia (FM) and moderate to high pain to a control group of sedentary women without pain. A second goal was to explore the extent to which pain pressure thresholds, age, and depression explain the variance in spindle incidence. A cross-sectional descriptive study. A university-based sleep research laboratory and a referral clinic for chronic fatigue and pain. Thirty-seven medication-free women with FM (mean age, 44.9 +/- 8 years) and 30 women with self-reported good sleep and no pain (mean age, 44.1 +/- 7.7 years) completed a psychiatric interview and the Beck Depression Inventory prior to 2 consecutive nights of polysomnography, with pain measures obtained in the morning. Time domain analysis of spindle incidence and spectral analysis of spindle frequency activity were conducted on night 2 of polysomnography recordings. NA. Women with FM had fewer mean spindles per minute of NREM stage 2 sleep and lower mean spindle time per epoch of NREM stage 2 sleep (both P values < .02), but mean spindle duration, although slightly shorter, was not statistically significantly different (P < .06) compared to control women. Women with FM had a lower mean pressure pain threshold, a higher average number of positive tender points, and higher skinfold tenderness compared to control women (all P values < .001). Group differences in spindle frequency activity were found after controlling for age, depression, and psychiatric diagnosis in a general linear model (P < .02). One-way analysis of variance revealed significantly lower spindle activity in the 3 frequency bins (12-12.5 Hz, 13-13.5 Hz, 14-14.5 Hz) at C3 (all P values < .04), Fz (all P values < .02), and Cz (all P values < .02). Finally, after controlling for age and depression, pain pressure threshold significantly predicted spindles per minute and spindle time per epoch of NREM stage 2 sleep (r2 = .26; P < .001). Women with FM and pain have fewer sleep spindles and reduced electroencephalogram power in spindle frequency activity compared to control women of similar age. These data imply that some aspect of thalamocortical mechanisms of spindle generation might be impaired in FM.

Wedge and Eggbar Shoes Change the Pressure Distribution Under the Hoof of the Forelimb in the Square Standing Horse

Summary The shoe types most commonly applied to horses with navicular disease or other forms of palmar heel pain are shoes with heel wedges and eggbar shoes, although their efficacy has been a matter of debate among veterinarians and farriers for centuries. To quantify the effect of these different types of “navicular” shoeing on static hoof pressure distribution, 6 warmblood horses were shod with 6° wedge, eggbar, and plain shoes. While standing square with weight evenly distributed across both forelimbs, the center of pressure and pressures at selected areas of interest (AOI: toe, medial and lateral toe, medial and lateral heel) were measured using a Footscan (RsScan International, Belgium) pressure plate in a Latin square design using the plain shoe as a reference. Wedge shoes did not provide a significant shift in the center of pressure. The application of eggbar shoes did not alter the relative position of the center of pressure under the hoof. However, the absolute distance from the toe to the center of pressure was significantly larger with eggbar shoes (77 + 12 mm) compared with plain and wedged shoes (70 ± 8 mm, P < .05) resulting in an absolute, caudal shift of the center of pressure. When pressure (N/cm 2) values at the five AOIs were averaged for each shoe type, the wedge and eggbar shoe recordings showed a significantly lower mean pressure than plain shoes ( P < .05). In conclusion, mean AOI pressures decreased with wedge and eggbar shoes, and eggbar shoes provided a caudal shift in the center of pressure. These effects are believed to decrease the moment of the coffin joint and reduce the pressure on the navicular bone. Thus, the findings of this study might contribute to the scientific evidence of efficacy of the use of wedge and eggbar shoes in “navicular” lame horses.

The application of critical state soil mechanics to the mechanical behaviour of porous sandstones

Abstract The mechanical properties of three cohesive sandstones of different porosities ( φ ) and average grain diameters ( R ) have been investigated. These were Tennessee sandstone ( φ =0.07), Darley Dale sandstone ( φ =0.12), and Penrith sandstone ( φ =0.25). Unconfined uniaxial compression, constant displacement rate triaxial, and hydrostatic experiments were conducted. Yield stress data produced approximately circular envelopes that decreased in size with increasing porosity or grain size when plotted in the differential stress versus effective mean stress ( Q − P ) space. Normalization of these data with respect to the hydrostatic grain crushing pressure ( P * ) resulted in a unique yield envelope for sandstone. Extending these data into the Q – P – φR space allows the principles of critical state soil mechanics to be applied. The critical state line for porous sandstone (the crestal line of the yield surface) appears to correspond to the transition from dilatant behaviour with localized faulting at low effective mean pressures ( P / P * P / P * >0.5). Post-yield, deformation progresses towards the critical state as observed by constant volume deformation. The critical state model developed for soil mechanics can be applied to make generalizations about the deformation of cohesive, porous sandstones. The expected behaviour of any porous sand appears to be predictable to a useful degree from a knowledge of P * , which can be estimated from the simple parameters of porosity and mean grain size. Sensitivity to the presence of water, attributed to sub-critical crack growth, was observed in hydrostatic and uniaxial compression tests in all rock types tested. Considerable strength and elastic anisotropy was also observed.

Predictors of Severe Right Ventricular Failure After Implantable Left Ventricular Assist Device Insertion: Analysis of 245 Patients

Insertion of an implantable left ventricular assist device (LVAD) complicated by early right ventricular (RV) failure has a poor prognosis and is largely unpredictable. Prediction of RV failure after LVAD placement would lead to more precise patient selection and optimal device selection. We reviewed data from 245 patients (mean age, 54+/-11 years; 85% male) with 189 HeartMate (77%) and 56 Novacor (23%) LVADs. Ischemic cardiomyopathy predominated (65%), and 29% had dilated cardiomyopathy. Overall, RV assist device (RVAD) support was required after LVAD insertion for 23 patients (9%). We compared clinical and hemodynamic parameters before LVAD insertion between RVAD (n=23) and No-RVAD patients (n=222) to determine preoperative risk factors for severe RV failure. By univariate analysis, female gender, small body surface area, nonischemic etiology, preoperative mechanical ventilation, circulatory support before LVAD insertion, low mean and diastolic pulmonary artery pressures (PAPs), low RV stroke work (RVSW), and low RVSW index (RVSWI) were significantly associated with RVAD use. Elevated PAP and pulmonary vascular resistance were not risk factors. Risk factors by multivariable logistic regression were preoperative circulatory support (odds ratio [OR], 5.3), female gender (OR, 4.5), and nonischemic etiology (OR, 3.3). The need for circulatory support, female gender, and nonischemic etiology were the most significant predictors for RVAD use after LVAD insertion. Regarding hemodynamics, low PAP and low RVSWI, reflecting low RV contractility, were important parameters. This information may lead to better patient selection for isolated LVAD implantation.

Improving the quality of kidneys from non-heart-beating donors, using streptokinase: An animal model1

Non-heart-beating donors (NHBD) offer a promising potential to increase the cadaveric organ donor pool, especially for kidneys. However, almost half of NHBD kidneys are discarded after viability assessment. This wastage is costly in both human and monetary terms. Intravascular thrombosis at the time of donor death is an event leading to failure in the viability assessment. We have developed an animal model to investigate the effects of the addition of streptokinase to the in situ flush medium before transplant in an attempt to redress the situation. Two groups of eight healthy young Landrace Yorkshire white pigs were entered into the study. Both groups were subjected to approximately 70 min warm ischemia. Both groups received an intravascular flush with 4 L of Marshall's solution with heparin (1000 IU/L); one group of pigs also had streptokinase (1.5 MIU/L) added. After donor nephrectomy, all kidneys were machine perfused for 4 hr. Data on perfusion characteristics were taken and samples of kidney effluent were assayed for tissue damage biomarkers, glutathione S-transferase (GST) and alanine aminopeptidase (Ala-AP). Wedge sections of porcine kidneys were taken at the end of perfusion, for histological analysis. Data on machine perfusion parameters (temperature, mean pressure index, resistance) indicate better cooling, lower resistance, and lower mean pressure index in the streptokinase-treated group of pigs. GST and Ala-AP levels were increased in the nonstreptokinase group perfusates. Histopathological analysis of porcine kidneys indicated more ischemic injury and tissue damage in the nonstreptokinase group. The use of streptokinase in this porcine NHBD model conferred benefits to donor kidneys when assessed by machine perfusion. Markers of biochemical injury indicated that less renal tissue damage occurred with the incorporation of streptokinase in the in situ flush medium.

The safety and efficacy of timolol 0.5% in xanthan gum versus timolol gel forming solution 0.5%

Purpose. To evaluate the efficacy and safety of timolol maleate 0.5% gel forming solution (TXE, Merck) versus timolol maleate 0.5% gel forming solution (TXG, Falcon) in primary open-angle glaucoma and ocular hypertension patients. Methods. Following a washout period patients were randomly begun on either TXE or TXG each given once each morning for six weeks (Period 1). Patients then were crossed over to the opposite medicine for Period 2. Following each 6-week treatment period the intraocular pressure was obtained at 08:00 trough and +2 and +8 hours post-dosing. Anterior segment staining and photography were performed to assess surface irritation. Results. Thirty-two patients were enrolled in this study; 28 completed. The diurnal intraocular pressure as well as the 08:00 trough and +2 hour post dosing pressures were statistically equal between groups, although a trend to a lower mean pressure was observed in the TXE (17.9 ± 3.2mmHg) compared to the TXG (18.6 ± 3.4mmHg) group. However, eight hours after dosing the pressure was 17.5 ± 3.2mmHg in the TXE group and 18.9 ± 3.3mmHg in the TXG group (P = 0.0019). Safety was similar between groups, including corneal and conjunctival staining, conjunctival hyperemia graded by anterior segment photography and at the slit lamp, and unsolicited and solicited side effects. Vision recovery after instillation was similar between groups. Conclusion. TXE demonstrates a lower intraocular pressure eight hours after dosing than does TXG, but safety appears similar between products.

Tender Point Sensitivity, Range of Motion, and Perceived Disability in Subjects With Neck Pain

Descriptive analysis of impairment and disability measures in subjects with neck pain. To identify discrete tender points and overall pressure sensitivity and assess relationships among palpation tenderness, active cervical range of motion, visual analog scale pain scores, and Sickness Impact Profile disability scores. Palpation tenderness and cervical range of motion are used to evaluate patients with neck pain, but their ability to predict patient-perceived pain and disability is unknown. We studied 45 women and 15 men with neck pain (mean age, 35 +/- 7 years). Group 1 included 30 persons who had not sought treatment, and group 2 included 30 persons who had just been referred for treatment. Subjects demonstrated low mean pressure pain thresholds of tender points (2.3 +/- 1.3 kg). Regression analysis showed that only neck flexion predicted pain (R2 = 0.23), with decreased flexion associated with higher pain levels. Sickness Impact Profile total score was predicted by neck rotation (R2 = 0.31), group (R2 = 0.16), tender point pressure pain threshold (R2 = 0.04), and neck retraction (R2 = 0.03). Decreased neck rotation, neck retraction, and pressure pain thresholds were associated with higher disability. Neither palpation tenderness nor cervical range of motion were strong predictors of pain and disability in subjects with neck pain.

Nanoindentation behavior of a two-dimensional carbon-carbon composite for nuclear applications

Nanoindentation tests on a carbon fiber and carbon matrix composite (C/C composite) for nuclear applications were carried out over a load range from 50 μN to 20 mN on two different crosssections, normal and parallel to the fiber axis. For reference, an isotropic nuclear graphite was also examined. Both the composite and graphite revealed a large amount of elastic recovery on the first loading-unloading indentation curves and inelastic hysteresis on the subsequent cycling curves. The analysis of mean indentation pressure data on the basis of the Weibull statistics indicates that the data on the C/C composite are separated into two groups with different Weibull moduli; the group of the lower modulus with higher mean pressure is attributed to the fiber, and the higher modulus with lower mean pressure to the matrix. The average of mean indentation pressure is obtained as 101 MPa for the fiber and 35.5 MPa for the matrix, while graphite has an intermediate value of 52.2 MPa. There is a slight dependence of mean stress p m on the applied load P in all the materials. However, the trend appears to be different between the two materials; p m decreases with increasing P for the C/C composite, while the reverse is true in graphite. Young's moduli of the graphite and the two constituents of the C/C composite are estimated from the stiffness of the unloading indentation curves at 10.7 GPa for the graphite as 6.71 GPa for the fiber and 1.97 GPa for the matrix. The values estimated for the graphite and the fiber are comparable to those of the bulk graphite and C/C composite, respectively.