Development of a monitor for tidal volume using ECG to eliminate

测量I导联和III导联的心电图，进行A/D转换，然后用笔记型个人计算机处理。检测QRS波群中的最大值和最小值，并利用Einthone‘s Delta将它们转换为正交导联系统中的值。然后计算最大值和最小值之间的差值。最后得到由导联-I差和导联垂直于导联-I的导联差组成的矢量角度，用三次样条函数对心跳间隔处的角度进行插补，得到一条连续的曲线。曲线上局部最大值和最小值之间的差值给出了潮气量相对值的估计值。这些数据处理是在实时基础上进行的。在心电图的同时，测量呼吸流量，并积分吸气流量以产生潮气量。潮气量的实测值与估计值之间的相关系数较大。该系数受预滤过、深呼吸、受试者的位置和异常心动图的影响。实验表明，该方法可以检测出阻塞性睡眠呼吸暂停。

Lead-I and -III electrocardiograms were measured, A/D converted, and then processed by a note-type personal computer. The maximum and minimum values in the QRS complex were detected, and using Einthoven's delta, they were converted into the values in an orthogonal lead system. Then the difference between the maximum and minimum values was calculated. Finally, the angle of a vector was obtained which consisted of the lead-I difference and the difference in the lead orthogonal to the lead-I.The angles obrained at the interval of heart beat were interpolated by a cubic spline function to yield a continuous curve. The difference between a local maxsimum and minimum in the curve gave the estimate for a relative value of tidal volume. These data processings were done on a real-time basis. Simultaneously with the electrocardiograms, respiratory flow was measured, and inspiratory flow was integrated to produce tidal volume. The crrelation coefficient between the measured and estimated tidal volume was large. The coefficient was influenced by prefiltering, deep breath, position of the subject, and abnormal dederto-cardiograms. Experiments suggested that obstructive sleep apnea could be detected by this method.