Performance characteristics of 10 home mechanical ventilators in pressure-support mode: a comparative bench study

OBJECTIVE: Inspiratory pressure (Pi) support delivered by a bilevel device has become the technique of choice for noninvasive home ventilation. Considerable progress has been made in the performance and functionality of these devices. The present bench study was designed to compare the various characteristics of 10 recently developed bilevel Pi devices under different conditions of respiratory mechanics. DESIGN: Bench model study. SETTING: Research laboratory, university hospital. MEASUREMENTS: Ventilators were connected to a lung model, the mechanics of which were set to normal, restrictive, and obstructive, that was driven by an ICU ventilator to mimic patient effort. Pressure support levels of 10 and 15 cm H(2)O, and maximum were tested, with "patient" inspiratory efforts of 5, 10, 15, 20, and 25 cm H(2)O. Tests were conducted in the absence and presence of leaks in the system. Trigger delay, trigger-associated inspiratory workload, pressurization capabilities, and cycling were analyzed. RESULTS: All devices had very short trigger delays and triggering workload. Pressurization capability varied widely among the machines, with some bilevel devices lagging behind when faced with a high inspiratory demand. Cycling was usually not synchronous with patient inspiratory time when the default settings were used, but was considerably improved by modifying cycling settings, when that option was available. CONCLUSIONS: A better knowledge of the technical performance of bilevel devices (ie, pressurization capabilities and cycling profile) may prove to be useful in choosing the machine that is best suited for a patient's respiratory mechanics and inspiratory demand. Clinical algorithms to help set cycling criteria for improving patient-ventilator synchrony and patient comfort should now be developed.     

Polyanions and Glucose as Osmotic Agents in Simulated Peritoneal Dialysis

Peritoneal dialysis solutions contain glucose as an osmotic agent to obtain ultrafiltration. Due to rapid absorption, glucose does not sustain high ultrafiltration during long exchanges. Nonabsorbable polyanions might be effective as osmotic agents when suspended in electrolyte solution. Concentrations of freely diffusible ions should be in Gibbs-Donnan equilibrium with plasma electrolytes. The ideal proportion of diffusable to polymerbound cation concentrations is unknown. To obtain concentrations of free ions in equilibrium with plasma, it is assumed that the polymer solution dialyzed against a polyelectrolyte solution of the desired composition (with hydraulic pressure higher on the polymer side) will approach the same thermodynamic activity as the electrolyte solution. Subsequently, if transmembrane pressure is released, osmotic ultrafiltration will occur in proportion to the hydrostatic pressure applied during polymer solution preparation. Polyacrylate solution so prepared was compared with a commercial dextrose dialysis solution in an in vitro simulation of peritoneal dialysis. With dwell times up to 24 h, sustained ultrafiltration with polymer was observed, whereas, with dextrose, ultrafiltration ceased after 8 h. Concentrations of diffusible bivalent cations in polyacrylate were lower than intended due to avid polymer complexing; however, dextran sulfate solutions were developed to contain desired concentrations of diffusible electrolytes. The conclusion is that some polymer solutions might be useful in clinical settings when high sustained ultrafiltration is needed.     

Symptom differences in reactive psychoses and schizophrenia with poor prognosis.

Genetic and clinical studies dealing with reactive psychoses are reviewed briefly. Diagnostic criteria are defined, and patients diagnosed as reactive psychoses and schizophrenia with poor prognosis are compared for differences in cross-sectional symptomatology. Symptoms were systematically recorded in the Present State Examination. Emotional blunting, auditory hallucinations in clear consciousness, tactile hallucinations, thought broadcasting, voices commenting, and “any first-rank symptom of schizophrenia” were noted to occur more often in schizophrenia with poor prognosis. Dysphoric mood, sleep disturbance, and irritability occurred more often in reactive psychoses. These findings are considered to offer additional support for the clinical differentiation of reactive psychoses from schizophrenia.     

右旋糖酐与氟碳乳剂稀释血液对心肌缺血时全血粘度与侧支循环影响的比较

用麻醉开胸狗对比观察了低分子右旋糖酐与氟碳乳剂稀释血液对急性心肌缺血时全血粘皮与侧支血流量变化的影响。结果表明,氟碳乳剂稀释血液除具有与右旋糖酐稀释血液相同的降低全血粘度、增加侧支血流量、提高缺血区心肌供血量/需血量比值等作用外,还可使血氧分压与活性氧明显增加,因而使缺血区心肌供氧量增加。     

激光小角光散射仪测定右旋糖酐分子量

激光小角光散射仪(LALLS)由于采用了激光光源,具有光强度高、单色性强、准直性好等特点,可以在微量样品池及很低浓度的溶液中进行小角度(3°～7°)散射光强的测量,溶质的瑞利系数与其分子量有如下关系:     

Cyclosporine Versus Tacrolimus: Which Calcineurin Inhibitor Has Influence on Cytomegalovirus Infection in Cardiac Transplantation?

Introduction

Cytomegalovirus (CMV) infection is a relevant cause of morbidity and mortality in transplantation patients. Its major incidence is in the first year and viral replication is related to acute rejection, survival reduction, and graft vascular disease.

电磁脉冲辐射对原癌基因c-fos调控区的影响

目的　通过研究电磁脉冲 (electromagneticpulse ,EMP)辐射对原癌基因c fos调控区域的影响 ,探讨其诱导细胞功能改变的机制。方法　构建c fos启动区氯霉素乙酰化转移酶 (chloramphenicolacetyl transferase,CAT) ,然后转染HeLa癌细胞株 ,高场强EMP模拟源 (有界波模拟源 )辐射细胞 ,EMP场强为6× 10 4V/m ,脉冲上升时间为 2 0ns ,脉宽为 3 0 μs ,频率为 2 .5个脉冲 /min ,辐射 2min ,处理后 2 0min时观察细胞中CAT的活性。结果　EMP辐射转染的细胞后 2 0min ,转染了P50 0 ( -711～ -2 2 3bp)和P2 50 ( -3 62～-10 0 )的Hela细胞其CAT活性明显高于对照水平的活性 (P <0 .0 1)。结论　EMP辐射可引起c fos基因调控区的 -3 62～ -2 2 5明显改变。