Stability and long-term durability of raman spectroscopy
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Objective. The purpose of this study was to assess in the clinical setting the reliability and long-term stability of Raman spectroscopy as implemented in the RASCAL multiple gas analyzer, and to describe/analyze failure modes that manifest in regular use.Methods. Twenty-one RASCAL analyzers were tested for accuracy and precision. Without any prior external calibration or alignment, all gas analyzers were systematically tested over a consecutive 36-hour period with standard gas mixtures. Data were analyzed by evaluating the difference between the predicted value and observed value (bias residual) as reported by each RASCAL. All service data (29 months) also were analyzed for information on durability and failure modes.Results. The RASCAL exhibited a significant tendency to overread high concentrations of agent (isoflurane/enflurane); 4 of 16 instruments misread an agent by more than ±0.30%. Four of 16 instruments could not properly identify volatile agents in low concentrations (0.31 vol%). Inventory records show that water contamination led to the replacement of gas sample sets an average of 1.5 ± 1.2 times per case over the 29-month period. Although many instruments had not been externally calibrated for over 63 days, linearity proved acceptable for CO2, O2, N2O, and N2. A rationale for instrument behavior and major failure modes, based on the instrument design, was developed.Conclusions. The manufacturer’s suggested calibration intervals (30 days) were found to be more than adequate for reliable gas analysis using Raman spectroscopy. Without the benefit of frequent calibrations and as time passes, volatile agent quantification can be expected to drift significantly upward.
Key WordsAnesthetics gases nitrous oxide Anesthetics volatile enflurane halothane isoflurane Carbon dioxide measurement Monitoring mass spectrometry oxygen nitrogen
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- 3.Gregonis DE, Van Wagenen RA, Coleman DL, Mitchell J. A commercial anesthetic-respiratory gas monitor utilizing Raman spectroscopy. Raman and luminescence spectroscopies in technology II. Proceedings of the International Society of Optical Engineering: 1990; 1336: 247–255Google Scholar
- 4.RASCAL maintenance documents. Salt Lake City: Albion Instruments, 1989Google Scholar
- 5.Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; l: 307–310Google Scholar
- 6.Optical filter guide. Salem, NH: Andover Corporation, 1990Google Scholar