Surgery – Truss – Pad
Patent
1990-08-06
1992-07-28
Kamm, William E.
Surgery
Truss
Pad
A61N 1365
Patent
active
051333490
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a method for adapting the stimulation frequency of a heart pacemaker to the burden of a patient, whereby a characteristics regulator controls the stimulation frequency dependent on a burden-dependent regulating variable and whereby, by changing the stimulation frequency during defined time intervals, an identification is made to see whether a measured value dependent on the cardiac minute output thereby changes, and whereby an optimization controller influences a characteristic that represents the relationship between the regulating variable and the stimulation frequency which correspondingly influences this change in measured value.
2. Description of the Prior Art
A method of this species is disclosed by EP-A-2 0 165 566. The stimulation frequency of a heart pacemaker is thereby regulated dependent on the central venous blood oxygen saturation in the heart. The central venous blood oxygen saturation is calculated according to the principle of reflection oximetry that, for example, is disclosed in detail in DE-A-31 52 963.
An optimum adaptation to the individual hemodynamic situation of the patient that changes over time is not possible with a permanently prescribed, invariable characteristic such as the relationship between blood oxygen saturation and stimulation frequency. In the EP-A2-0 165 566, an optimizing control that acts continuously in addition to the characteristics control is thereby provided. The optimizing control continuously monitors the tendency of the value of the blood oxygen saturation and, by automatic elevation or lowering of the frequency, determines whether an improvement (measured value increase) of the value of the blood oxygen saturation ensues or not. It is not only one defined characteristic but an entire family of characteristics that is now allocated to every value of blood oxygen saturation.
This arrangement, however, has the disadvantage that it makes a decision after every change in frequency whether a positive or negative reaction of the blood oxygen saturation ensued and, thus, there is the risk of incorrect decision as a consequence of disturbing changes of the oxygen saturation that are dependent on burden above all.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to design a method of the species initially cited such that the optimum adaptation of the regulation of the stimulation frequency to the hemodynamic situation of the patient becomes more independent o disturbing influences and is thus further improved.
This object is inventively achieved in that the change of the stimulation frequency is periodically repeated during optimization intervals prescribed by the heart pacemaker and an acquisition of the measured value dependent on cardiac minute output respectively ensues phase-synchronized with the change in stimulation frequency. Disturbing influences can be largely eliminated due to the multiple repetition of changes in the stimulation frequency.
DESCRIPTION OF THE DRAWINGS
FIG. 1 generally shows a heart pacemaker and lead in relation to a human heart.
FIG. 2 is a graph showing the relationship between stimulation frequency and cardiac minute output.
FIG. 3 is a schematic block diagram of the control path used in the method of the present invention.
FIG. 4 is a schematic block diagram of a control circuit for practicing the method of the present invention.
FIG. 5 is a graph showing a family of characteristic curves for oxygen saturation versus stimulation frequency in accordance with the principles of the present invention.
FIG. 6 shows a stimulation phase diagram for illustrating the principles of the method in accordance with the principles of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an arrangement of a heart pacemaker known from DE-A-31 52 963. The heart pacemaker HS contains a power supply part Ba, an electronic switch Sch having a measuring amplifier MV, and the two-pole electrical coupling IK. The two-p
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Kamm William E.
Siemens Aktiengesellschaft
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