Lawson D, Samanta S, Magee P T, Gregonis D E
Department of Anesthesiology, University of Virginia Health Sciences Center, Charlottesville 22908.
J Clin Monit. 1993 Sep;9(4):241-51. doi: 10.1007/BF02886694.
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.
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.
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.
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.
本研究旨在评估RASCAL多气体分析仪中所采用的拉曼光谱技术在临床环境中的可靠性和长期稳定性，并描述/分析在常规使用中出现的故障模式。
对21台RASCAL分析仪进行准确性和精密度测试。在没有任何预先外部校准或校准的情况下，所有气体分析仪均使用标准气体混合物在连续36小时内进行系统测试。通过评估每个RASCAL报告的预测值与观测值之间的差异（偏差残差）来分析数据：还分析了所有服务数据（29个月）以获取有关耐用性和故障模式的信息。
RASCAL在读取高浓度药剂（异氟烷/安氟醚）时存在明显的高估倾向；16台仪器中有4台对药剂的误读超过±0.30%。16台仪器中有4台无法正确识别低浓度（0.31 vol%）的挥发性药剂。库存记录显示，在29个月的时间里，水污染导致每个案例平均更换气体样本组1.5±1.2次。尽管许多仪器超过63天未进行外部校准，但二氧化碳、氧气、一氧化二氮和氮气的线性度仍被证明是可接受的。基于仪器设计，阐述了仪器行为和主要故障模式的原理。
发现制造商建议的校准间隔（30天）对于使用拉曼光谱进行可靠的气体分析来说绰绰有余。在没有频繁校准的情况下，随着时间的推移，挥发性药剂的定量预计会显著向上漂移。
