Simultaneous measurement of FRC and Dead Space under Artificial Ventilation.

功能残气量和死腔是优化人工通风最重要的参数之一。然而，这些参数的测量需要大规模的专用仪器，很难应用于人工呼吸机下的危重患者。目前，我们研制了无重复呼吸电路的这两个参数的同时测量系统。该系统主要基于氮气洗入法。该方法的常规测量方法难以实现呼吸流量和气体浓度的同步测量。为了避免这一困难，我们设计了计算机控制的通风系统来产生精确的流量。该系统只需要气体浓度数据就可以测量FRC和死腔的数值。为了进行计算机分析，研究了往复和连续两种通风模型。对10例肺功能正常成人的测量表明，连续流模型分析高估了FRC值，低估了死腔值。另一方面，FRC和死区的正确值是由往返模型得到的，一台微型计算机很难同时控制呼吸机、采集数据、计算FRC和死区。因此，我们将多处理器体系结构应用于该系统。

FRC (functional residual capacity) and dead space is one of the most important parameters for optimizing artificial ventilation. However, the measurement of these parameters requires specific apparatuses of large scale, and it is difficult to apply them to critically ill patients under artificial ventilation. Presently, we developed simultaneous measuring system of these two parameters with non-rebreathing circuit. This system is principally based on nitrogen wash-in method. Conventional measuring maneuver of this method has the difficulty in synchronized measurement of respiratory flow and gas concentration. To avoid this difficulty, we devised computer-controlled ventilating system to create precise flow rate. With this system, only the data of gas concentration is required for measuring values of FRC and dead space.For computer analysis, both to-and-fro and continuous ventilatory models were examined. Measurements of 10 adults of normal pulmonary function showed that the analysis with continuous flow model overstimated FRC value and underestimated dead space value. On the other hand, correct values of FRC and dead space were obtained from the to-and-fro model.It is difficult for only one microcomputer to proceed controlling ventilator, sampling data, and calculating FRC and dead space at a time. So we applied multiple processor architecture to this system.