Analyzing a stimulation period characteristic for psychiatric disorder therapy delivery

This application claims the benefit of U.S. Provisional Application No. 61/046,225 to Giftakis et al., entitled, “ANALYZING WASHOUT PERIOD AND STIMULATION PERIOD CHARACTERISTIC FOR PSYCHIATRIC DISORDER THERAPY DELIVERY” and filed on Apr. 18, 2008, the entire content of which is incorporated herein by reference.

The disclosure relates to medical devices, and, more particularly, to configuration of therapy parameters.

Implantable medical devices, such as electrical stimulators or therapeutic agent delivery devices, may be used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, peripheral nerve stimulation, functional electrical stimulation or delivery of pharmaceutical agent, insulin, pain relieving agent or anti-inflammatory agent to a target tissue site within a patient. A medical device may be used to deliver therapy to a patient to treat a variety of symptoms or patient conditions such as chronic pain, tremor, Parkinson\'s disease, other types of movement disorders, seizure disorders (e.g., epilepsy), urinary or fecal incontinence, sexual dysfunction, obesity, mood disorders, gastroparesis or diabetes. In some therapy systems, an implantable electrical stimulator delivers electrical therapy to a target tissue site within a patient with the aid of one or more electrodes, which may be deployed by medical leads. In addition to or instead of electrical stimulation therapy, a medical device may deliver a therapeutic agent to a target tissue site within a patient with the aid of one or more fluid delivery elements, such as a catheter or a therapeutic agent eluting patch.

During a programming session, which may occur during implant of the medical device, during a trial session, or during a follow-up session after the medical device is implanted in the patient, a clinician may generate one or more therapy programs that provide efficacious therapy to the patient, where each therapy program may define values for a set of therapy parameters. A medical device may deliver therapy to a patient according to one or more stored therapy programs. In the case of electrical stimulation, the therapy parameters may define characteristics of the electrical stimulation waveform to be delivered. Where electrical stimulation is delivered in the form of electrical pulses, for example, the parameters may include an electrode combination, an amplitude, which may be a current or voltage amplitude, a pulse width, and a pulse rate for the pulses. In the case of a therapeutic agent delivery device, the therapy parameters may include a dose (e.g., a bolus or a group of boluses) size, a frequency of bolus delivery, a concentration of a therapeutic agent in the bolus, a type of therapeutic agent to be delivered to the patient (if the medical device is configured to deliver more than one type of agent), a lock-out interval, and so forth.

In general, the disclosure is directed to devices, systems, and methods for automatically determining at least one characteristic of a washout period following delivery of therapy to a patient. A washout period includes the period of time following delivery of therapy to a patient during which at least one carryover effect from the therapy dissipates. In the case of electrical stimulation therapy, the carryover effect generally refers to a physiological effect generated in response to the delivery of an electrical stimulation signal, where the effect persists after termination of the stimulation signal. Accordingly, at the end of the washout period, one or more physiological effects from the delivery of electrical stimulation therapy to the patient are substantially absent. Carryover effects from delivery of therapy may be automatically determined based on one or more physiological parameters of the patient, which may be monitored during the delivery of therapy and after the cessation of therapy delivery (e.g., the “post-stimulation” period). The physiological parameters may include, for example, at least one of a bioelectrical brain signal (e.g., electroencephalogram or electrocorticogram), a heart rate, respiratory rate, electrodermal activity, facial electromyogram or thermal activity of the patient\'s body.

In some embodiments, at least one characteristic of a washout period is automatically determined for a plurality of therapy programs based on at least one physiological parameter of the patient. A therapy program defines respective values for a set of therapy parameters. In the case of electrical stimulation therapy, the therapy parameters may include voltage or current amplitude and frequency of the electrical signals, and, in the case of electrical pulses, the pulse width, pulse rate, and duty cycle of the pulses. A signal indicative of the physiological parameter (i.e., a physiological signal) may be monitored before, during, and after the delivery of therapy according to a particular therapy program. In response to the delivery of therapy, the physiological signal may change. Thus, the change in the signal during the post-stimulation period may be monitored to determine a characteristic of the washout period, such as a duration of the washout period, an amplitude of the physiological signal waveform during the washout period, a trend in the physiological signal waveform during the washout period, a power level of the physiological signal measured in a particular frequency band of the physiological signal waveform, ratios of power levels between different frequency bands, and the like.

The washout period may be useful for timing trials of different therapy programs. For example, during a trial session in which therapy is delivered to the patient according to a plurality of therapy programs to determine an efficacious therapy program or range of acceptable therapy parameter values, it may be desirable to deliver test stimulation according to subsequent therapy programs after the stimulation and at least some carryover effects of the prior delivered therapy program have substantially dissipated. The stimulation effects occur while therapy is delivered. Accordingly, at least one physiological signal of the patient may be monitored to automatically determine when the stimulation and carryover effects of the prior delivered therapy have substantially dissipated, i.e., when the washout period of the prior delivered therapy has substantially ended.

In some embodiments, washout periods characteristics, alone or in addition to other metrics, may be useful for evaluating and ordering (e.g., ranking) therapy programs. Other metrics for ordering therapy programs may include the type, severity or duration of side effects, an efficacy rating, and a power rating, e.g., the power required for the medical device to generate and deliver the therapy according to the therapy program.

The characteristics of at least one physiological signal of the patient during the washout period may be useful for assessing the efficacy of a therapy program, and, in some cases, adjusting at least one parameter value of the therapy program.

The characteristics of the one or more physiological signals during the washout period may also be useful for determining a patient mood state during the washout period. The patient mood state may be a symptom of a psychiatric disorder with which the patient is afflicted. For example, a particular waveform trend or waveform amplitude of the physiological signal may be associated with a particular patient mood state, such as an anxious state, a depressive state, and the like. Thus, the monitored signal during the washout period may be compared to a trend template or amplitude threshold value to determine the patient mood state. The probability of the mood state occurring during therapy delivery based on the therapy program may be determined based on the determined patient mood state associated with a therapy program.

A therapy system for managing a psychiatric disorder of the patient may be controlled based on a patient mood state that is determined based on a characteristic of a physiological signal. Therapy may be delivered to a patient according to a therapy program, and a physiological parameter of the patient may be monitored during or after therapy delivery in order to determine a patient mood state. In some embodiments, the therapy delivery is stopped prior to determining the patient mood state and the therapy delivery is restarted upon detecting a negative mood state. In other embodiments, therapy delivery is delivered until a positive mood state is detected, at which point the therapy delivery may be stopped.

In one embodiment, the disclosure is directed to a method comprising delivering therapy to a patient according to a therapy program during a first period, wherein the therapy program defines a value for at least one therapy parameter for managing a psychiatric condition (e.g., a psychiatric disorder) of the patient, monitoring a physiological signal of the patient during a second period following the first period, and automatically determining a characteristic of a washout period based on the monitored physiological signal, wherein the washout period occurs during the second period, and wherein at least one carryover effect from the therapy substantially dissipates during the washout period. The therapy may be electrical stimulation therapy or delivery of one or more therapeutic agents.

In another embodiment, the disclosure is directed to a method comprising delivering therapy to a patient according to a therapy program during a first period, monitoring a physiological signal of the patient during a second period following the first period, receiving information indicative of a patient mood state, wherein the patient mood state occurs during the second period, associating the patient mood state with at least one characteristic of the physiological signal during the second period.

In another embodiment, the disclosure is directed to a system comprising a sensor that generates a signal as a function of at least one physiological parameter of a patient, a medical device that delivers therapy to a patient according to a therapy program to manage a psychiatric condition during a first period, wherein the therapy program defines a value for at least one therapy parameter, and a processor that monitors the signal during a second period following the first period, and automatically determines a characteristic of a washout period for the therapy program based on the signal, wherein the washout period occurs during the second period, and wherein at least one carryover effect from the therapy substantially dissipates during the washout period.

In another embodiment, the disclosure is directed to a system comprising means for delivering therapy to a patient according to a therapy program during a first period, wherein the therapy program defines a value for at least one therapy parameter for managing a psychiatric condition of the patient, means for monitoring a physiological signal of the patient during a second period following the first period, and means for automatically determining a characteristic of a washout period based on the monitored physiological signal, wherein the washout period occurs during the second period, and wherein at least one carryover effect from the therapy substantially dissipates during the washout period.

In another embodiment, the disclosure is directed to a method comprising receiving a signal indicative of a physiological parameter of a patient during a first period during which therapy according to a first therapy program is delivered to the patient, detecting a carryover effect from the delivery of the therapy according to the first therapy program based on the signal, where the carryover effect occurs during a washout period following the first period, and automatically initiating delivery of therapy to the patient according to a second therapy program at a time based on the washout period.

In another embodiment, the disclosure is directed to a method comprising establishing a baseline state of a physiological signal of a patient, delivering electrical stimulation therapy to a patient according to a first therapy program during a stimulation period, monitoring the physiological signal of the patient during a post-stimulation period following the stimulation period, automatically determining when the physiological signal returns to first state that is based on the baseline state, and automatically delivering electrical stimulation therapy to the patient according to a second therapy program after the physiological signal returns to the baseline state.

In another embodiment, the disclosure is directed to a system comprising a sensor that generates a signal as a function of a physiological parameter of a patient, a medical device that delivers therapy to the patient according to a first therapy program during a first period, and a processor that receives the signal from the sensor during a second period following the first period, detects a carryover effect from delivery of the therapy according to the first therapy program based on the signal, where the carryover effect occurs during a washout period during the second period, and automatically controls the medical device to deliver therapy to the patient according to a second therapy program at a time based on the washout period.