Search

BACKGROUND: Acquired immunodeficiency syndrome (AIDS) is a pandemic disease commonly associated with respiratory infections, hypoxemia, and death. Noninvasive PEEP has been shown to improve hypoxemia. In this study, we evaluated the physiologic effects of different levels of noninvasive PEEP in hypoxemic AIDS patients. METHODS: Thirty AIDS patients with acute hypoxemic respiratory failure received a randomized sequence of noninvasive PEEP (5, 10, or 15 cm H2O) for 20 min. PEEP was provided through a facial mask with pressure-support ventilation (PSV) of 5 cm H2O and an FIO2 of 1. Patients were allowed to breathe spontaneously for a 20-min washout period in between each PEEP trial. Arterial blood gases and clinical variables were recorded after each PEEP treatment. RESULTS: The results indicate that oxygenation improves linearly with increasing levels of PEEP. However, oxygenation levels were similar regardless of the first PEEP level administered (5, 10, or 15 cm H2O), and only the subgroup that received an initial treatment of the lowest level of PEEP (ie, 5 cm H2O) showed further improvements in oxygenation when higher PEEP levels were subsequently applied. The PaCO2 also increased in response to PEEP elevation, especially with the highest level of PEEP (ie, 15 cm H2O). PSV of 5 cm H2O use was associated with significant and consistent improvements in the subjective sensations of dyspnea and respiratory rate reported by patients treated with any level of PEEP (from 0 to 15 cm H2O). CONCLUSIONS: AIDS patients with hypoxemic respiratory failure improve oxygenation in response to a progressive sequential elevation of PEEP (up to 15 cm H2O). However, corresponding elevations in PaCO2 limit the recommended level of PEEP to 10 cm H2O. At a level of 5 cm H2O, PSV promotes an improvement in the subjective sensation of dyspnea regardless of the PEEP level employed. [ABSTRACT FROM AUTHOR]

Activated biocarbons (ABs) with high specific surface area were prepared by the one-step methodology using three different agricultural biomass wastes: sugarcane bagasse (SB), coconut shell (CS) and endocarp of babassu coconut (EB). These lignocellulosic precursors are generated in large quantities in Brazil (among other countries) and, due to inappropriate disposal, they can cause several damages to the environment. From these precursors, ABs samples were prepared by a single step carbonization/physical activation (with steam) heat treatment and free of chemicals. This methodology was conducted inside a horizontal furnace under a rigorous argon flow, controlled heating program and water injection rate. The results of textural analysis revealed that the ABs products were mostly microporous with some mesopores, with BET specific surface area values of 547, 991 and 1068 m2 g−1 for the products derived from SB, CS and EB, respectively. These values were superior when compared with a number of commercial ABs and to other materials prepared using similar precursors and activation methodology reported in the literature. Among the samples investigated in this work, EB was the precursor that originated the best AB in terms of porosity (BET), pointing out to promising applications of this material as a cheap precursor of highly porous adsorbents. [ABSTRACT FROM AUTHOR]