System and method to modulate phrenic nerve to prevent sleep apnea
An implantable medical device for treating breathing disorders such as central sleep apnea wherein stimulation is provided to the phrenic never through a transvenous lead system with the stimulation beginning after inspiration to extend the duration of a breath and to hold the diaphragm in a contracted condition.
1. A method of prolonging a breath in a patient having a diaphragm innervated by a phrenic nerve and a vein near the phrenic nerve, the method comprising:
measuring respiration of the patient to find an inspiration phase of a natural, unstimulated breath; and
stimulating the phrenic nerve for a stimulation period, via a stimulation electrode located in the vein, starting proximate a peak of the inspiration phase with a stimulation magnitude that is sufficient to still the diaphragm and interrupt exhalation resulting in:
no significant lung volume change over a portion of the stimulation period; and
a trapping of air in at least one lung for the portion of the stimulation period, wherein the trapping reduces a breathing rate over the portion of the stimulation period, after which unstimulated exhalation of the air in the at least one lung occurs.
2. The method of claim 1 further characterized by said stimulating beginning at a time after the peak of the inspiration phase.
3. The method of claim 1 further comprising: repeating the measuring and stimulating steps for breaths over a period of time thus reducing an amount of air exchanged over the period of time.
4. The method of claim 1 wherein locating the stimulation electrode in the vein comprises implanting the stimulation electrode in a pericardiophrenic vein.
5. The method of claim 1 wherein prolonging the breath maintains a carbon dioxide concentration in the patient's blood above a threshold to prevent the onset of sleep disordered breathing.
6. A method of prolonging a breath in a patient having a diaphragm innervated by a phrenic nerve, a vein near the phrenic nerve and a lung associated with the phrenic nerve, the method comprising:
measuring respiration of the patient to find an inspiration phase of a natural, unstimulated breath; and
stimulating the phrenic nerve for a stimulation period exceeding an expiration phase duration of the natural, unstimulated breath, via a stimulation electrode located in the vein, starting proximate a peak of the inspiration phase, said stimulating interrupting exhalation, wherein there is no significant lung volume change in the lung and air is retained in the lung for a portion of the stimulation period, thereby reducing a breathing rate over the portion of the stimulation period, after which unstimulated exhalation of the retained air occurs, and wherein a capacity of the patient's body to regulate respiration is maintained.
7. The method of claim 6 further characterized by said stimulating beginning at a time after the peak of the inspiration phase.
8. The method of claim 6 further characterized by said stimulation period being sufficient to prevent apnea.
9. The method of claim 6 further comprising: repeating the measuring and stimulating steps for breaths over a period of time thus reducing an amount of air exchanged over the period of time.
10. The method of claim 6 wherein prolonging the breath maintains a carbon dioxide concentration in the patient's blood above a threshold to prevent the onset of sleep disordered breathing.
11. A method of reducing a breathing rate in a patient having a diaphragm innervated by a phrenic nerve and a vein near the phrenic nerve, the method comprising:
measuring respiration of the patient to find an inspiration phase of a natural, unstimulated breath; and
stimulating the phrenic nerve for a stimulation period, via a stimulation electrode in the vein, starting proximate a peak of the inspiration phase, with a stimulation magnitude that is sufficient to cause contraction of at least part of the diaphragm, resulting in trapped air in at least one lung and interrupting exhalation of the trapped air for a portion of the stimulation period, after which unstimulated exhalation of the trapped air occurs, said stimulation period being sufficient to reduce the breathing rate of the patient and reduce an amount of air exchanged by the at least one lung over the stimulation period while maintaining a capacity of the patient's body to regulate respiration.
12. The method of claim 11 , further comprising a step of measuring an observed breathing rate without stimulation and then delivering stimulation pulses at a fixed stimulation rate that is less than the observed breathing rate.
13. The method of claim 11 , further comprising a step of sensing motion or position of the patient and adjusting the stimulation magnitude based on the motion or the position of the patient.
14. The method of claim 11 wherein reducing the breathing rate maintains a carbon dioxide concentration in the patient's blood above a threshold to prevent the onset of sleep disordered breathing.