Blood gases and oximetry: calibration-free new dry-chemistry and optical technology for near-patient testing

The first calibration-free Near-Patient-Testing instrument (NPT7) for blood gases, pH and oximetry has been developed. With cartridges of 30 single-us e cuvettes, the NPT7 needs no preparation prior to sample aspiration, no ma nual calibration, and no maintenance apart from paper and cartridge changes and regulatory quality central. Each cuvette measures pCO(2), pO(2), pH, t otal hemoglobin (ctHb), oxygen saturation (sO(2)), fractions of carboxyhemo globin (FCOHb) and methemoglobin (FMetHb) on 95 mul whole blood with a 110- s measuring cycle. The measurement principles are as follows: pCO(2)-three- wavelength infrared spectroscopy of dissolved CO2; pO(2)-measurement of O-2 -induced changes in the decay time of phosphorescence; pH-the absorbance sp ectra change of an ate-dye color indicator; and oximetry is performed with a 128-wavelength spectrophotometer. We determined the within and between in strument variations with tonometered whole blood on seven prototype instrum ents, using between one and five control levels per analyte. The 95% analyt ical performance limits: +/- (\ Bias \ + 2 x S-T) in the NPT7 instrument ma tched the analytical performance criteria for the measured quantities as de fined by AACC guidelines. The application of these optical measuring method s for blood gases, pH and oximetry in single-use devices introduces a new c oncept into point-of-care testing (POCT), where preanalytical activities ot herwise associated with instrument preparation are eliminated. (C) 2001 Els evier Science B.V. All rights reserved.