Noninvasive Multiple Inert Gas Elimination Technique

描述（由申请人提供）：血液氧合不足（低氧血症）是ICU患者的常见症状，可能由四种不同病理共同引起：1)肺泡通气减少（低通气），2)氧气扩散受限，3)通气/灌注不均匀，4)分流。低氧血症可通过以下任何生理参数进行评估：1)动脉PO2和PCO2, 2)肺泡和动脉PO2的差异，3)静脉混合（称为生理分流），4)生理死腔。然而，虽然这些参数在临床上是有用的，但它们提供的信息相当有限，并且在基本假设不满足时容易被误解。在大多数情况下，使用目前可用的工具很难区分任何给定患者低氧血症的确切原因。多重惰性气体消除技术（MIGET）是在20世纪70年代初引入的，它克服了上述经典方法所带来的许多限制。MIGET的独特之处在于它使用惰性气体数据来量化急性疾病中O2和CO2气体交换的许多病理特征。MIGET利用应用于惰性气体（与O2和CO2相比）的更简单的气体交换模型，提供了关于V& / Q&比率的通风和血流的定量分布。正是这些分布的获取构成了MIGET提供的许多O2和CO2气体交换参数计算的基础。重要的是，MIGET的一个特殊优势是它区分了低V& a / Q&比区域和不通气区域（分流），以及高V& a / Q&比区域和未灌注肺。MIGET还可以进一步了解气体交换，包括1)确定O2扩散限制的存在，以及2)量化肺外因子对动脉PO2和PCO2气体交换限制的作用。然而，MIGET从未从研究工具演变为临床管理工具，原因是：1)测量时间延迟；2)操作复杂性；3)实质性的侵入性。这项工作的目标是开发和验证仪器和方法，这些仪器和方法提供了复杂的V& / Q&分布和MIGET分析，但没有引用的缺点。

DESCRIPTION (provided by applicant): Insufficient oxygenation of the blood (hypoxemia) is a common symptom in ICU patients, and may be caused by a combination of four different pathologies: 1) decreased alveolar ventilation (hypoventilation), 2) oxygen diffusion limitation, 3) inequality in ventilation/perfusion, and 4) shunts. Hypoxemia can be assessed by any of the following physiological parameters: 1) arterial PO2 and PCO2, 2) difference in alveolar and arterial PO2, 3) venous admixture (known as a physiological shunt), and 4) physiological dead space. However, while these parameters are clinically useful, they offer quite limited information and are subject to misinterpretation when the underlying assumptions are not met. For the most part, the exact causes of hypoxemia are difficult to distinguish in any given patient using presently available tools. A multiple inert gas elimination technique (MIGET) was introduced in the early 1970s as a way to overcome many of the limitations imposed by the classical methods mentioned above. The uniqueness of MIGET is its use of inert gas data to quantitate the many pathological features of O2 and CO2 gas exchange in the acutely ill. Taking advantage of simpler gas exchange models applied to inert gases (compared to O2 and CO2), MIGET provides quantitative distributions of ventilation and blood flow with respect to V& / Q& ratio. It is the acquisition of these distributions that form the basis for the many calculations of O2 and CO2 gas exchange parameters that MIGET provides. Importantly, a special strength of MIGET is that it distinguishes regions of low V& A / Q& ratio from unventilated regions (shunt), and also regions of high V& A / Q& ratio from unperfused lung. MIGET also allows additional insights into gas exchange, which include 1) identification of the presence of diffusion limitation for O2, and 2) quantification of the role of extrapulmonary factors on arterial PO2 and PCO2 gas exchange limitation. However, MIGET has never evolved from a research tool to a clinical management tool due to: 1) measurement time delays; 2) operational complexity; and 3) substantial invasiveness. The goal of this proposed work is to develop and validate the instrumentation and methodology that provides the complex V& / Q& distribution and analysis of MIGET - but without the cited disadvantages. PUBLIC HEALTH RELEVANCE: For over 30 years, MIGET (Multiple Inert Gas Elimination Technique) has been a valuable research tool used to understand and characterize lung abnormalities. Physiological information from this technique could greatly improve therapy in the Intensive Care Unit (ICU), but the highly invasive methods make it impractical in any clinical setting. This proposed Non-Invasive MIGET System (NIMS) has the potential to provide MIGET information to improve patient management both in and outside of the ICU.