Aqueous humor oxygen measurements.
Aqueous humor oxygen measurements.
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房水氧测量。
DOI：
10.1097/ijg.0b013e3182a4a012
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发表时间：
2013
影响因子：
2
通讯作者：
Siegfried,CarlaJ
中科院分区：
文献类型：
--
作者：
Nguyen,Alexander;Shui,Ying-Bo;Zhang,Qianru;Beebe,DavidC;Siegfried,CarlaJ
致编辑：我们饶有兴趣地阅读了Sharifipour等人最近在《青光眼杂志》上发表的一篇文章。这些作者估计了从前房取出的样本中的房水氧分压，并使用血气分析仪进行了测量。他们得出结论，青光眼患者的前房氧分压（pO 2）低于非青光眼患者。这份文件的两个方面引起了我们的关注;一个是技术方面，一个是道德方面。我们在下文中证明，Sharifipour及其同事用于测量pO 2的方法大大高估了被测样品中的pO 2，这是他们之前注意到的问题。此外，他们排除了与他们的结果相矛盾的我们小组的研究，即使他们很清楚我们的工作，在之前提交的一篇论文中引用了它。这些问题说明如下。除血气分析仪外，还使用了各种其他仪器来评估溶液的pO 2。其他检查房水的研究已经使用极谱氧电极（Clark电极）和光纤传感器（光极）来测量体内前房内的氧。2-4 Sharifipour及其同事注意到，关于报告的房水pO 2值，研究之间存在显著差异。虽然造成这种差异的原因可能尚不清楚，但我们认为寻求解释是有价值的。已经描述了使用血气分析仪测量氧张力的复杂因素。这些问题包括空气污染和氧气的代谢消耗。5-8与空气污染特别相关的是构成用于运输样品的注射器的材料类型。塑料材料对氧气的阻隔性很差。这一点已得到各种研究的证实，这些研究检查了含有人体血液样本的塑料注射器中的pO 2水平。5-8延迟提交注射器进行分析导致记录的pO 2水平较高，可能是由于空气扩散到注射器中以及样本转移到血气分析仪中。正是由于这个原因，标准方案建议使用玻璃而不是塑料注射器来进行动脉血样，这可能需要> 30分钟的经过时间，然后才能通过血气分析仪进行分析。9从微观结构的角度来看，塑料材料中较大的孔径和增加的孔密度使其比玻璃更容易渗透氧气。10然而，并非所有比较塑料和玻璃注射器的研究都有一致的结果。这可能归因于人血液中的白细胞代谢和样本处理方法的差异（例如，样本是否置于冰上）。5，6为了解决这一潜在的误差来源，我们设计了一个小型实验，以测试采集后时间对保存在注射器内并使用血气分析仪测定的溶液中pO 2值的影响。我们首先通过用100%N2鼓泡750 mL平衡盐溶液（BSS）的玻璃瓶20分钟来对该玻璃瓶进行脱氧。预计这将使溶液的pO 2达到约0 mm Hg。使用光纤传感器（Oxylab pO 2光电二极管; Oxford Optronix，Oxford，UK）验证了这一点，其读取溶液中的pO 2为1.5 mm Hg。然后使用30-G针头将脱氧BSS从瓶中缓慢抽吸到塑料结核菌素注射器中。用脱氧BSS填充针头的死腔，以避免将外来氧气引入样品中。通过血气分析仪（Stat Profile pHOx Plus C; Nova Biomedical）连续多次读取样本。
To the Editor: We read with interest and concern a recent article in the Journal of Glaucoma by Sharifipour et al. 1 These authors estimated the oxygen tension of aqueous humor in samples withdrawn from the anterior chamber and measured using a blood-gas analyzer. They concluded that patients with glaucoma had lower oxygen partial pressure (pO2) in the anterior chamber than patients without glaucoma. Two aspects of this paper were of concern to us; one technical and one ethical. We demonstrate below that the method used by Sharifipour and colleagues to measure pO2 greatly overestimates the pO2 in the sample being measured, a problem that had been brought to their attention previously. In addition, they excluded the mention of research from our group that contradicted their results, even though they were well aware of our work, having cited it in a paper submitted previously. These issues are described below. In addition to blood-gas analyzers, a variety of other instruments have been used to assess pO2 of solutions. Other studies examining aqueous humor have used polarographic oxygen electrodes (Clark electrodes) and fiber optical sensors (optodes) to measure oxygen within the anterior chamber in vivo. 2–4 Sharifipour and colleagues noted significant variability across studies regarding the reported pO2 values in aqueous humor. Although the reasons for this variability may not be clear, we think it is valuable to seek explanations. Complicating factors have been described for measuring oxygen tension using blood-gas analyzers. These include problems with air contamination and metabolic consumption of oxygen. 5–8 Of particular relevance to air contamination is the type of material that comprises the syringes used for transporting samples. Plastic materials serve as a poor barrier to oxygen. This has been corroborated by a variety of studies examining pO2 levels in plastic syringes containing human blood samples. 5–8 Delay submitting the syringes for analysis resulted in higher recorded pO2 levels, presumably due to air diffusing into the syringe as well as transfer of the samples into the bloodgas analyzer. It is for this reason that standard protocols advise the use of glass rather than plastic syringes for arterial blood samples that may require> 30 minutes of elapsed time before being analyzed by a blood-gas analyzer. 9 From a microstructural point of view, the larger pore size and increased density of pores in plastic materials renders them more permeable to oxygen than glass. 10 However, not all studies comparing plastic and glass syringes have consistent results. This may be attributable to leukocyte metabolism in human blood and differences in the methodology of handling samples (eg, whether or not samples were placed on ice). 5, 6 To address this potential source of error, we designed a small experiment to test the effect of time after collection on the pO2 values in solutions kept inside a syringe and assayed using a blood-gas analyzer. We first deoxygenated a 750mL glass bottle of balanced salt solution (BSS) by bubbling it with 100% N2 for 20 minutes. This can be expected to bring the pO2 of the solution to approximately 0mm Hg. This was verified with the use of fiberoptic sensor (Oxylab pO2 optode; Oxford Optronix, Oxford, UK), which read the pO2 in solution as 1.5 mm Hg. A 30-G needle was then used to slowly aspirate the deoxygenated BSS from the bottle into plastic tuberculin syringes. The dead space of the needle was filled with deoxygenated BSS to avoid introducing extraneous oxygen into the sample. Samples were read by a blood-gas analyzer (Stat Profile pHOx Plus C; Nova Biomedical) successive times …