Cabrera M E, Saidel G M, Cohen M H
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106.
Ann Biomed Eng. 1991;19(6):723-42. doi: 10.1007/BF02368078.
A noninvasive method to estimate cardiac output Q without special patient cooperation was developed by modifying a previous acetylene-helium (C2H2-He) rebreathing technique (ART). Estimation of Q using ART is based on a single-compartment model that is valid only under prescribed breathing; e.g., fast, deep breathing, and emptying of the rebreathing bag on each breath. To make the ART less dependent on subject cooperation, a more sophisticated mathematical model and estimation method are needed. For this purpose, we modeled the C2H2 and He concentration dynamics at the mouth over successive breaths using a multi-compartment model. This model takes into account the effects of breathing pattern, compartmental volumes, and gas solubility. From computer simulations and sensitivity analysis, we found that Q could be estimated from the available data with adequate precision. Our model and estimation method were tested on a group of six normal adult subjects, at rest and during submaximal exercise (75 watts). Estimates of Q from our new method (6.5 +/- 0.4 L/min at rest, 12.5 +/- 0.4 L/min at 75 watts) were in agreement with those obtained using a previous ART (7.0 +/- 0.3 L/min at rest, 12.6 +/- 0.5 L/min at 75 watts). We conclude that this approach promises to provide reliable estimates of Q in patients (e.g., children and elderly), at rest and during exercise, without the need of prescribed breathing patterns or changes in rebreathing bag volume.
通过改进先前的乙炔 - 氦气（C2H2 - He）重复呼吸技术（ART），开发出一种无需患者特殊配合即可估算心输出量Q的非侵入性方法。使用ART估算Q是基于一个单室模型，该模型仅在规定的呼吸条件下有效，例如快速、深呼吸以及每次呼吸时重复呼吸袋排空。为使ART减少对受试者配合的依赖，需要更复杂的数学模型和估算方法。为此，我们使用多室模型对连续呼吸过程中口腔处C2H2和He的浓度动态进行建模。该模型考虑了呼吸模式、室容积和气体溶解度的影响。通过计算机模拟和敏感性分析，我们发现可以从现有数据中以足够的精度估算Q。我们的模型和估算方法在一组六名正常成年受试者身上进行了测试，包括静息状态和次最大运动（75瓦）期间。我们新方法估算的心输出量（静息时为6.5±0.4升/分钟，75瓦时为12.5±0.4升/分钟）与先前使用ART获得的结果（静息时为7.0±0.3升/分钟，75瓦时为12.6±0.5升/分钟）一致。我们得出结论，这种方法有望在患者（如儿童和老年人）静息和运动期间提供可靠的心输出量估算，而无需规定的呼吸模式或重复呼吸袋容积的变化。
