Patients requiring emergency airway management may be at greater risk of acute hypoxemic events because of underlying lung pathology, high metabolic demands, insufficient respiratory drive, obesity, or the inability to protect their airway against aspiration. Emergency tracheal intubation is often required before complete information needed to assess the risk of procedural hypoxia is acquired (i.e., arterial blood gas level, hemoglobin value, or chest radiograph). During pre-oxygenation, administering high-flow nasal oxygen in addition to a non-rebreather face mask can significantly boost the effective inspired oxygen. Similarly, with the apnea created by rapid sequence intubation (RSI) procedures, the same high-flow nasal cannula can help maintain or increase oxygen saturation during efforts to secure the tube (oral intubation). Thus, the use of nasal oxygen during pre-oxygenation and continued during apnea can prevent hypoxia before and during intubation, extending safe apnea time, and improve first-pass success attempts. We conducted a literature review of nasal-cannula apneic oxygenation during intubation, focusing on two components: oxygen saturation during intubation, and oxygen desaturation time. We performed an electronic literature search from 1980 to November 2017, using PubMed, Elsevier, ScienceDirect, and EBSCO. We identified 14 studies that pointed toward the benefits of using nasal cannula during emergency intubation.
Groundwater is a critical resource not only for human communities but also for many terrestrial, riparian, and aquatic ecosystems and species. Yet groundwater planning and management decisions frequently ignore or inadequately address the needs of these natural systems. As a consequence, ecosystems dependent on groundwater have been threatened, degraded, or eliminated, especially in arid regions. There is growing acknowledgment that governmental protections for these ecological resources are necessary, but current legal, regulatory and voluntary provisions are often inadequate. Groundwater management premised on "safe yield," which aims to balance human withdrawals with natural recharge rates, typically provides little to no consideration for water needed by ecosystems. Alternatively, the "sustainable yield" concept aims to integrate social, economic and environmental needs for groundwater, but the complexity of groundwater systems creates substantial uncertainty about the impact that current or future groundwater withdrawals will have on ecosystems. Regardless of the legal or regulatory framework, guidance is needed to help ensure environmental water needs will be met, especially in the face of pressure to increase human uses of groundwater resources. In this paper, we describe minimum provisions for planning, managing, and monitoring groundwater that collectively can lower the risk of harm to groundwaterdependent ecosystems and species, with a special emphasis on arid systems, where ecosystems and species may be especially reliant upon and sensitive to groundwater dynamics.
Phase-conjugate fiber-optic gyros (PCFOG’s) use phase conjugation to compensate for reciprocal phase changes due to thermal and mechanical effects on the fiber, while at the same time. allowing for the measurement of the nonreciprocal phase shift produced by rotation.1,2 Where the best standard fiber-optic gyros require polarization-preserving fibers and couplers to avoid polarization scrambling that is a source of noise and signal fading, the PCFOG can avoid this problem by using polarization-preserving phase conjugation.3 This has the advantage of allowing for the use of inexpensive nonpolarization preserving, and even multimode fibers and components.3-5 Our first objective was to demonstrate that the PCFOG is sensitive to the nonreciprocal phase shift produced by the Sagnac effect and can be used to sense rotation. A proof of concept experiment was set up for this objective using an externally-pumped crystal of barium titanate as the phase conjugator. This experiment, reported in Ref. 6, provided the first demonstration of rotation sensing with a PCFOG. In this proof of concept demonstration the length of the fiber-optic coil, and therefore the sensitivity of the gyro, was limited by the coherence length of the laser. To solve this problem we set up a PCFOG consisting of a Michelson interferometer in which the light beams from two arms travel as clockwise and counterclokwise beams respectively, in the same fiber optic coil and reflect from the same self-pumped phase-conjugator. We reported the demonstration of rotation sensing with this PCFOG in Ref. 7. Again, since phase conjugation can correct for modal scrambling, a PCFOG can use multimode fibers. However, complete correction of modal scrambling requires a polarization-preserving conjugator,5 and the corresponding experimental setup of a PCFOG is complicated. To solve this problem we set up a PCFOG using a multimode fiber coil, a nonpolarization-preserving conjugator,4 and a spatial filter to discriminate against the portion of the light reflected by the conjugator that does not correct for modal scrambling. This experiment, reported in Ref. 8, provided the first demonstration of rotation sensing with a PCFOG using multimode fiber.
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