Mặc dù không phải đang sử dụng trong một máy điều hòa nhịp tim thị trường phát hành, đây là một bộ cảm biến thú vị và hiệu quả. Nó sử dụng một nhịp dẫn chuyên ngành với một diode phát sáng (LED) và một bộ tách sóng quang | 56 Handbook of Cardiac Pacing MIXED VENOUS OXYGEN SATURATION 6 Though not in current use in a market-released pacemaker this is an interesting and effective sensor. It utilizes a specialized pacing lead with a light emitting diode LED and a photodetector Fig. . The LED delivers brief pulses of light in the right ventricular blood pool that are reflected back to the photodetector. The detector determines the color and thus the degree of oxygenation of the venous blood. As the oxygenation drops the paced rate increases Fig . This is a very physiologic system however reliability problems with the specialized lead have kept it from mainstream use. There are many other sensors that are not in general use at this time. These have been listed in Table . The most important new concept in sensor-driven pacing is the use of more than one sensor to determine the need for a rate change. These pacemakers combine two sensors . activity with minute ventilation Fig. . A specialized lead for measuring the oxygen saturation in the right ventricle. A photoemitter light emitting diode is combined with a photodetector on the lead body. Note that a special quadrapolar lead is used with a 4 pole connector. Fig. . As oxygen saturation in the venous system decreases with exertion the pacing rate will be increased to match the workload. Sensor-Driven Pacing 57 QT with minute ventilation temperature with activity or QT and activity to regulate the heart rate. The advantage of using a combination of sensors relates to combining the strengths of each sensor to overcome their individual shortcomings. Using the rapidly responding activity sensor with the slower but more physiologic minute ventilation sensor results in a fast and accurate system. Each sensor may also be used to check the accuracy of the other. Should one sensor indicate a need for rate increase to the maximal rate yet the other indicate that the patient is at rest the device may use the data of the more .
