Although a moderate positive end-expiratory pressure (PEEP) level is widely recommended, it is unknown whether moderate PEEP during mechanical ventilation has adverse effects during severe ...hemorrhagic shock. Therefore, the purpose of our study was to evaluate the effects of 0 cm H
2O PEEP versus 5 cm H
2O PEEP versus 10 cm H
2O PEEP on short-term survival in a porcine model of severe hemorrhagic shock. Secondary study endpoints were hemodynamic variables and blood gases.
Twenty-four anesthetized pigs were bled approximately 45 mL/kg, randomized into 3 groups, and then ventilated with 0, 5, or 10 cm H
2O PEEP. Survival rates were compared using Kaplan-Meier methods with log rank (Mantel Cox) comparison of cumulative survival by treatment group.
Seven of 8 0 cm H
2O PEEP animals survived the 120-minute study period, but 8 of 8 5 cm H
2O PEEP animals died within 30 minutes, and 8 of 8 10 cm H
2O PEEP animals were dead within 20 minutes (
P<.0001). Ventilation with 0 cm H
2O PEEP prevented a further reduction of mean arterial blood pressure and cardiac output. When compared with the 0 cm H
2O PEEP group, end-tidal CO
2 declined in the 5 cm H
2O PEEP and 10 cm H
2O PEEP animals. Compared with the 0 cm H
2O PEEP animals, those ventilated with 5 or 10 cm H
2O PEEP had higher lactate levels after 10 minutes.
When compared with pigs ventilated with either 5 or 10 cm H
2O PEEP, those ventilated with 0 cm H
2O PEEP during untreated, severe hemorrhagic shock had significantly improved short-term survival.
The Community Climate System Model Blackmon, Maurice; Boville, Byron; Bryan, Frank ...
Bulletin of the American Meteorological Society,
11/2001, Letnik:
82, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The Community Climate System Model (CCSM) has been created to represent the principal components of the climate system and their interactions. Development and applications of the model are carried ...out by the U.S. climate research community, thus taking advantage of both wide intellectual participation and computing capabilities beyond those available to most individual U.S. institutions. This article outlines the history of the CCSM, its current capabilities, and plans for its future development and applications, with the goal of providing a summary useful to present and future users.
The initial version of the CCSM included atmosphere and ocean general circulation models, a land surface model that was grafted onto the atmosphere model, a sea-ice model, and a “flux coupler” that facilitates information exchanges among the component models with their differing grids. This version of the model produced a successful 300-yr simulation of the current climate without artificial flux adjustments. The model was then used to perform a coupled simulation in which the atmospheric CO₂ concentration increased by 1% per year.
In this version of the coupled model, the ocean salinity and deep-ocean temperature slowly drifted away from observed values. A subsequent correction to the roughness length used for sea ice significantly reduced these errors. An updated version of the CCSM was used to perform three simulations of the twentieth century’s climate, and several projections of the climate of the twenty-first century.
The CCSM’s simulation of the tropical ocean circulation has been significantly improved by reducing the background vertical diffusivity and incorporating an anisotropic horizontal viscosity tensor. The meridional resolution of the ocean model was also refined near the equator. These changes have resulted in a greatly improved simulation of both the Pacific equatorial undercurrent and the surface countercurrents. The interannual variability of the sea surface temperature in the central and eastern tropical Pacific is also more realistic in simulations with the updated model.
Scientific challenges to be addressed with future versions of the CCSM include realistic simulation of the whole atmosphere, including the middle and upper atmosphere, as well as the troposphere; simulation of changes in the chemical composition of the atmosphere through the incorporation of an integrated chemistry model; inclusion of global, prognostic biogeochemical components for land, ocean, and atmosphere; simulations of past climates, including times of extensive continental glaciation as well as times with little or no ice; studies of natural climate variability on seasonal-to-centennial timescales; and investigations of anthropogenic climate change. In order to make such studies possible, work is under way to improve all components of the model. Plans call for a new version of the CCSM to be released in 2002. Planned studies with the CCSM will require much more computer power than is currently available.
An overview of the computational design for the latest version of the NCAR Atmospheric General Circulation Model, designated CCM2, is presented. Parallel implementation details are driven by two ...major algorithmic classes of computation that require different patterns of data communication, the spectral transform method and the semi-Lagrangian advection technique. The organization and performance characteristics of a shared-memory parallel implementation, and an analogous distributed-memory message-passing parallel implementation are described. The advantages and limitations of this coarse-grained partitioning are discussed in the context of global climate modeling research.
The latest version of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is described. The changes in both physical and dynamical formulation from CCM2 to CCM3 are ...presented. The major differences in CCM3 compared to CCM2 include changes to the parameterization of cloud properties, clear sky longwave radiation, deep convection, boundary layer processes, and land surface processes. A brief description of each of these parameterization changes is provided. These modifications to model physics have led to dramatic improvements in the simulated climate of the CCM. In particular, the top of atmosphere cloud radiative forcing is now in good agreement with observations, the Northern Hemisphere winter dynamical simulation has significantly improved, biases in surface land temperatures and precipitation have been substantially reduced, and the implied ocean heat transport is in very good agreement with recent observational estimates. The improvement in implied ocean heat transport is among the more important attributes of the CCM3 since it is used as the atmospheric component of the NCAR Climate System Model. Future improvements to the CCM3 are also discussed.
Under the current care delivery model, persons with chronic illnesses, such as diabetes, are not receiving all recommended interventions and failing to meet targeted outcomes. The Chronic Care Model ...provides a framework for new approaches and roles for many members of the multidisciplinary team. Using the Chronic Care Model as a guide, a group of hospital-based clinics in an academic system incorporated nurse practitioners into the care model for patients with diabetes. Through use of planned visits, a patient registry, drug intensification protocols, and collaboration with other members of the team, the pilot sample improved processes of care and clinical outcomes. Use of nurse practitioners in this model of care for chronically ill patient populations has economic implications, as the payers begin to pay for performance.
