Accuracy and precision of a new, portable, handheld blood gas analyzer, the IRMA®

Objective. The accuracy and precision of the new IRMA® (Immediate Response Mobile Analysis System, Diametrics, Inc.®, St. Paul, MN) handheld blood gas analyzer was compared with that of two benchtop blood gas analyzers. The IRMA consists of a notebook-sized machine and disposable cartridges, each containing a pH, a CO 2 and an O 2 electrode, and provides bedside (point-of-care) blood gas analysis. Methods. A total of 172 samples (arterial and mined venous) were obtained from 25 informed, consenting patients undergoing cardiopulmonary bypass. The pH, PCO 2 and PO 2 of each sample was determined on four blood gas analyzers: NOVA Statlabs Profile 5 (NOVA Biomedical, Waltham, MA), the ABL-50 (Radiometer, West Lake, OH), and two IRMA machines. Linear regression and bias ± precision were determined, comparing each of the analyzers with the NOVA. Results. All three machines showed a similar, high degree of correlation with the NOVA for pH, PCO 2 , and PO 2 . The bias and precision of the IRMA machines compared with the NOVA was similar to that of the ABL compared with the NOVA for pH (NOVA:ABL −0.005 ± 0.011; NOVA: IRMA 1 = 0.0026 ± 0.025; NOVA: IRMA 2 = 0.0021 ± 0.025), for PCO 2 (NOVA:ABL = −1.4 ± 1.3 mmHg; NOVA: IRMA 1 = −1.3 ± 1.9 mmHg; NOVA: IRMA 2 = −1.2 ± 2.1 mmHg) and PO 2 (NOVA:ABL = 3.6 ± 21.1 mmHg; NOVA: IRMA 1 = 3.4 = 19.9 mmHg; NOVA: IRMA 2 = 6.3 ± 20.9 mmHg). The bias found for pH, PCO 2 , and PO 2 was not affected by extremes of temperature (range 25.5–40°C) or hematocrit (range 11–44%) for any machine. Conclusions. The new technology incorporated in the IRMA blood gas analyzer provides results with an accuracy that is similar to that of benchtop analyzers, but with all of the advantages of point-of-care analysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43058/1/10877_2005_Article_BF02221753.pd

Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake, Alaska

Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Oecologia 153 (2007): 643-652, doi:10.1007/s00442-007-0753-8.Long-term fertilization of acidic tussock tundra has led to changes in plant species composition, increases in aboveground production and biomass and substantial losses of soil organic carbon (SOC). Root litter is an important input to SOC pools, though little is known about fine root demography in tussock tundra. In this study, we examined the response of fine root production and live standing fine root biomass to short- and long-term fertilization, as changes in fine root demography may contribute to observed declines in SOC. Live standing fine root biomass increased with long-term fertilization, while fine root production declined, reflecting replacement of the annual fine root system of Eriophorum vaginatum, with the long-lived fine roots of Betula nana. Fine root production increased in fertilized plots during an unusually warm growing season, but remained unchanged in control plots, consistent with observations that B. nana shows a positive response to climate warming. Calculations based on a few simple assumptions suggest changes in fine root demography with long-term fertilization and species replacement could account for between 20 and 39% of observed declines in SOC stocks.This project was supported by National Science Foundation research grants 9810222, 9911681, 0221606 and 0528748