Systems and methods for respiratory-gated nerve stimulation
Systems and methods are provided for neurostimulation timed relative to respiratory activity. Neurostimulation may be delivered to the spinal cord, the vagus nerve, and/or branches of the vagus nerve to provide therapeutic outcomes by controlling or adjusting stimulation based on pulmonary activity. In particular, the systems and methods use a detecting device to detect respiratory activity over time. Specific points in the respiratory signal are identified where central autonomic nuclei may be more receptive to afferent input and a stimulator is instructed to provide neurostimulation to at least one auricular branch of a vagus nerve, or to a cervical branch of the vagus nerve, or to a spinal cord of the subject. In this regard, the neurostimulation is advantageously correlated to the detected respiratory activity providing improved therapeutic outcomes.
1. An apparatus comprising:
an electrode configured to be electrically coupled to an afferent nerve fiber of a vagus nerve of a subject;
a stimulation circuit connected to the electrode to deliver a stimulation signal to the electrode, thereby stimulating the afferent nerve fiber;
at least one processor configured to:
determine one or more pulmonary characteristics of the subject, the one or more pulmonary characteristics including a concentration of carbon dioxide; and
deliver the stimulation signal to the stimulation circuit to effectuate electrical stimulation of the subject based on the concentration of carbon dioxide.
2. The apparatus of claim 1 wherein the one or more pulmonary characteristics include at least one of inspiration and expiration and wherein delivering the stimulation signal includes timing a delivery of stimulations to the subject at a beginning of expiration and extending through a portion of expiration.
3. The apparatus of claim 2 wherein the processor is configured to terminate delivery of stimulations to the subject prior to inspiration.
4. The apparatus of claim 1 wherein the processor is configured to utilize an adaptive window to determine a timing of the pulmonary characteristic.
5. The apparatus of claim 1 further comprising a detector configured to monitor pulmonary activity of the subject and communicate a pulmonary activity waveform to the processor.
6. The apparatus of claim 5 wherein the detector includes at least one of a pulse sensor configured to measure blood pressure, a nasal cannula configured to measure respiratory flow or the concentration of carbon dioxide, or a respiration belt configured to measure expansion and contraction of a thorax of the subject during respiration.
7. The apparatus of claim 1 wherein the electrical stimulation is configured to achieve a therapeutic function to treat at least one of hypertension, inflammatory disorders, or gastrointestinal disorders.
8. The apparatus of claim 1 wherein the electrical stimulation includes at least one of:
a constant-current pulse;
a burst of bi-phasic square wave pulses;
a frequency between 1-100 Hz;
current intensity between 0.25 mA to 20 mA; and
a pulse width between 100-1000 microseconds.