Lactic acidosis is commonly observed in various disease states in critical care and can be adopted as a hemodynamic biomarker, as well as a target for therapy. pH is the main biomarker for the diagnosis of acid–base disorders and is currently measured utilizing invasive blood sampling techniques. Therefore, there is a need for a non-invasive and continuous technology for the measurement of pH and lactate levels. In this work, near infrared spectroscopy is explored as a technique for investigating lactic acidosis. In-vitro studies on 20 isotonic phosphate buffer solutions of varying pH with constant lactate concentration (2 mmol/L) were performed. The whole near infrared spectrum (800–2600 nm) was then divided into four parts for analysis: (a) water absorption peaks, (b) 1000–1250 nm, (c) 1700–1760 nm, and (d) 2200–2400 nm. The water absorption peaks showed a linear variation with the changes in pH in the spectra. The range from 1700–1760 nm showed good correlation with calculated values for lactate ionization, with the changes in pH. However, the region from 2200–2400 nm showed a reverse correlation with respect to the concentration changes of lactate and a distinction could be made from pH 6–7 and 7–8. This study successfully identifies wavelengths (1233 nm, 1710 nm, 1750 nm, 2205 nm, 2319 nm, and 2341 nm) which can be directly correlated to lactic acidosis. Knowledge from this study will contribute toward the development of lactate-based pH monitoring optical sensor for critical care.

中文翻译：

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不同 pH 缓冲液中乳酸的近红外光谱研究

乳酸性酸中毒在重症监护的各种疾病状态中常见，可用作血流动力学生物标志物，以及治疗靶点。pH 值是诊断酸碱紊乱的主要生物标志物，目前使用侵入性采血技术进行测量。因此，需要一种用于测量 pH 值和乳酸水平的非侵入性和连续技术。在这项工作中，近红外光谱作为一种研究乳酸性酸中毒的技术进行了探索。对具有恒定乳酸浓度 (2 mmol/L) 的 20 种不同 pH 值的等渗磷酸盐缓冲溶液进行了体外研究。然后将整个近红外光谱（800-2600 nm）分为四个部分进行分析：（a）吸水峰，（b）1000-1250 nm，（c）1700-1760 nm，和（d）2200-2400纳米。吸水峰随着光谱中pH值的变化呈线性变化。1700-1760 nm 的范围与乳酸电离的计算值以及 pH 值的变化显示出良好的相关性。然而，2200-2400 nm 的区域与乳酸浓度变化呈负相关，pH 6-7 和 7-8 可以区分。本研究成功识别出与乳酸酸中毒直接相关的波长（1233 nm、1710 nm、1750 nm、2205 nm、2319 nm 和 2341 nm）。这项研究的知识将有助于开发用于重症监护的基于乳酸的 pH 监测光学传感器。随着 pH 值的变化。然而，2200-2400 nm 的区域与乳酸浓度变化呈负相关，pH 6-7 和 7-8 可以区分。本研究成功识别出与乳酸酸中毒直接相关的波长（1233 nm、1710 nm、1750 nm、2205 nm、2319 nm 和 2341 nm）。这项研究的知识将有助于开发用于重症监护的基于乳酸的 pH 监测光学传感器。随着 pH 值的变化。然而，2200-2400 nm 的区域与乳酸浓度变化呈负相关，pH 6-7 和 7-8 可以区分。本研究成功识别出与乳酸酸中毒直接相关的波长（1233 nm、1710 nm、1750 nm、2205 nm、2319 nm 和 2341 nm）。这项研究的知识将有助于开发用于重症监护的基于乳酸的 pH 监测光学传感器。