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  • Dextran-modified poly(methyl methacrylate) latex particles  (1)
  • Inverse ratio ventilation  (1)
  • (Acremonian)
  • 1995-1999  (2)
  • 1990-1994
  • 1
    ISSN: 1432-1238
    Keywords: Key words Spontaneous variability ; Mechanical ventilation ; Arterial oxygenation ; Positive end-expiratory pressure ; Inverse ratio ventilation ; Venous admixture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: To assess the magnitude of spontaneous variability of arterial oxygenation and oxygen tension-based indices over time in medical intensive care unit (ICU) patients and to study whether high positive end-expiratory pressure (PEEP) or inverse inspiratory-to-expiratory (I:E) ratio ventilation (IRV) results in a greater variability than low PEEP with conventiona l I:E ratio ventilation. Design: Prospective study. Setting: Medical ICU in a tertiary medical center. Participants: 23 patients requiring a pulmonary artery floating catheter for hemodynamic monitoring. Intervention: After being completely sedated, patients were randomized to receive pressure-control ventilation at setting A: high PEEP (15 cmH2O) with conventional I:E ratio (1:2) and setting B: inverse I:E ratio (2:1) with low PEEP (5 cmH2O) alternately, and then at setting C: low PEEP (5 cmH2O) with conventional I:E ratio (1:2). Each ventilation setting lasted 1 h. Measurements and results: The arterial and mixed venous blood samples were measured simultaneously at baseline (time 0), and at 15, 30, 45, and 60 min thereafter. The coefficient of variation (CV) of arterial oxygen tension (PaO2) over time was 5.9 % for setting A, 7.2 % for setting B, and 6.9 % for setting C. ANOVA showed no significant differences in CVs of PaO2 between the three settings. Oxygen tension-based indices, alveolar-arterial oxygen difference (A-aDO2) and PaO2/PAO2 (alveolar oxygen tension), displayed CV s equal to that of PaO2; the CV of A-aDO2/PaO2 was significantly greater than that of PaO2. Conclusions: In critically ill medical ICU patients, despite sedation, the spontaneous variability in PaO2 over time is substantial. A high PEEP or IRV does not contribute to the increased variation in PaO2.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1536
    Keywords: Key words Isothermal equilibrium adsorption ; Concanavalin A ; Dextran-modified poly(methyl methacrylate) latex particles ; Electrostatic/affinity interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Isothermal equilibrium adsorption experiments were carried out to study the adsorption of concanavalin A (Con A) on dextran-modified poly(methyl methacrylate) (PMMA) latex particles. Three PMMA particles with various levels of dextran modification were selected for study: 0% (designated as D0), 1.24% (D20), and 2.45% (D75) based on total polymer weight. The Langmuir model is applicable to both D0 and D20 systems, although the data for the D20 system are somewhat scattered. On the other hand, the amount of Con A adsorbed per gram polymer particles (q*) versus the Con A concentration in water (c*) curve for the D75 system cannot be described by the Langmuir model. The deviation is attributed to the formation of a crosslinked network structure, caused by specific binding of the dimeric Con A molecules onto two neighboring particles with grafted dextran. The ratio of the initial number of Con A molecules to the initial number of active binding sites on the dextran-modified particle surface plays an important role in determining the structure of flocs formed. The maximum amount of Con A adsorbed on the particle surface (q max) is of the order of 10−1 μmol per gram particles and q max in decreasing order is D75 〉 D20 〉 D0. The dissociation constant of the Con A-D20 (or Con A-D75) pair is of the order of 10−1 μmol dm−3 which is 1 order of magnitude smaller than that of the Con A-D0 pair. Thus, the electrostatic interaction between Con A and D0 is much weaker than the affinity interaction between Con A and D20 (or D75). An empirical model is proposed to qualitatively explain the q* versus c* data.
    Type of Medium: Electronic Resource
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