Respiratory rectification
A means for treating breathing disorders by stimulating respiratory muscles or nerves to entrain respiratory systems while leaving respiratory drive intact. Embodiments of the invention employ frequency analysis to determine if appropriate stimulation energy is being applied.
1. A method of treating breathing disorders comprising the steps of:
a. stimulating a phrenic nerve or at a frequency below an intrinsic breathing rate at an intensity sufficient to entrain respiration while leaving intrinsic drive to breathe intact, wherein intrinsic drive to breathe is manifested as periodic activation of airway muscles.
2. The method of claim 1 , wherein the stimulation of the phrenic nerve or hemidiaphragm is at the frequency that results in 2:1 entrainment.
3. The method of claim 1 , wherein leaving the intrinsic drive to breath intact causes spontaneous breathing of an unstimulated lung.
4. The method of claim 1 , wherein leaving the intrinsic drive to breath intact causes breaths interlaced among entrained breaths.
5. The method of claim 1 , further including the steps of:
a. sensing a signal representative of a patient's respiration;
b. determining a frequency distribution from the sensed respiration signal;
c. comparing the frequency distribution of the sensed respiration signal to a target frequency distribution; and
d. adjusting the intensity of the stimulation based on the comparison.
6. The method of claim 5 , further including the steps of:
a. measuring the power of an array of sensed respiration signals that fall within a frequency zone related to the stimulation frequency;
b. measuring the total power of sensed respiration signals over a broader frequency zone; and
c. comparing the measured power of signals within the frequency zone related to the stimulation frequency to the measured power of signals of the broader frequency zone.
7. The method of claim 6 , wherein the broader frequency zone is between 0 and 0.6 Hertz.
8. The method of claim 6 , wherein the broader frequency zone is between 0.1 and 0.5 Hertz.
9. A method of treating breathing disorders comprising the steps of:
a. stimulating a phrenic nerve or diaphragm of a patient at a fixed frequency different from an intrinsic respiration frequency of the patient;
b. sensing a signal representative of the patient's respiration;
c. determining a frequency distribution of the sensed respiration signal;
d. comparing the frequency distribution of the sensed respiration signal to a target frequency distribution;
e. adjusting the intensity of the stimulation based on the comparison of frequency distributions until the stimulation is at an intensity sufficient to entrain respiration while leaving intrinsic drive to breathe intact.
10. The method of claim 9 , wherein the stimulation intensity is adjusted by changing the current of the stimulation.
11. The method of claim 10 , wherein the stimulation current is increased or decreased in the range between 1 and 10 mA in suitable steps.
12. The method of claim 9 , wherein the stimulation signal comprises a series of pluses and the intensity is adjusted by changing the duration of the individual pulses.
13. The method of claim 12 , wherein the stimulation pulse duration is increased or decreased in the range of 100 to 500 μs in suitable steps.