Development of a monitor for tidal volume using ECG to eliminate

测量I导联和III导联心电图，A/D转换，然后由笔记本式个人计算机处理。检测QRS波群中的最大值和最小值，并使用Einthoven的δ，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，由I导联差值和与I导联正交的导联差值组成向量的夹角，用三次样条函数插值得到连续的曲线。曲线中局部最大值和最小值之间的差异给出了潮气量相对值的估计。这些数据处理是实时进行的。在心电图的同时，测量呼吸流量，并将吸气流量积分以产生潮气量。实测潮气量与估算潮气量的相关系数较大。该系数受预过滤、深呼吸、受试者位置和异常心电图的影响。实验表明，阻塞性睡眠呼吸暂停可以通过这种方法来检测。

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.