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Device and method for manipulating minute ventilation

Device and method for manipulating minute ventilation description/claims

This application is related to U.S. patent application Ser. No. 10/686,891, “BREATHING DISORDER DETECTION AND THERAPY DELIVERY DEVICE AND METHOD”, by Tehrani et al., filed Oct. 15, 2003, and incorporated herein by reference.

The present invention relates to devices, systems, and methods useful for providing ventilation through stimulation of the diaphragm.

The human body's ability to maintain homeostasis is due in part due to respiratory functions controlled by the brain and associated feedback systems. In maintaining homeostasis, respiratory functions typically alter both blood oxygen saturation and carbon dioxide partial pressures.

Certain pathological conditions such as circulation delay in heart failure patients may lead to instability in the respiratory feedback systems. Circulatory delay is believed to cause phase shift or time delay in the inherent blood gas sensing feedback loop. One manifestation of this is resulting breathing disorders including periodic breathing, Cheyne-Stokes, and apnea (predominantly central sleep apnea (CSA)). Cheyne-Stokes respiration is believed to occur in part because of this circulatory delay and perceived drop in SaO2 levels. Central apnea, and, in some cases obstructive apnea, is believed to occur in part due to a drop in partial pressure of CO2 following a Cheyne-Stokes hyperventilation pattern. Other conditions such as congestive heart failure (CHF) may be able to derive a benefit by an increase in the partial pressure of O2 above that which is normally maintained.

Mechanical ventilators have been used to take over breathing to ensure adequate oxygen levels in patients who cannot sufficiently breath on their own or who stop breathing at night during apnea events. Mechanical ventilators control the inflow and egress of respiratory gasses by controlling combinations of flow, pressure and/or volume. The ventilator delivers an inspiration via positive pressure delivered into the trachea and lungs and can control exhalation by manipulating pressure and flow.

Diaphragm stimulation has been used to create respiration in patients who cannot breath on their own and has been suggested to stimulate breathing when apnea occurs. Diaphragmatic stimulation has generally been used to control inspiration via contraction of the diaphragm muscle which creates negative intra-thoracic pressure resulting in inspiration. Exhalation has generally been a passive process driven by lung and thoracic compliance.

The ventilators and proposed diaphragm stimulation have not addressed the causes of breathing disorders, but rather have been limited to supplementing breathing when breathing is insufficient or not present.

The present invention provides an implantable device for delivering electrical stimulation waveforms to the diaphragm through one or more electrodes. In particular, one aspect of the invention provides stimulation waveforms that are directed to manipulation of patient blood gases, e.g., SaO2 and PCO2. In order to achieve manipulation of blood gas concentration, in one embodiment minute ventilation is increased or decreased with respect to a baseline minute ventilation. This may be done by manipulation of one or more parameters affecting minute ventilation. Some of the parameters may include, for example, tidal volume, respiration rate, flow morphology, flow rate, inspiration duration, slope of the inspiration curve, and diaphragm-created or intrathoracic pressure gradients. The implantable device may be programmed by a programmer that is coupled to a flow sensor that measures the natural respiration and stimulation respiration of a subject. Normal breathing of a patient is observed to establish a baseline reference minute ventilation, and the device is programmed to produce stimulation waveforms that may provide either a decrease or an increase in the patients minute ventilation.

In one embodiment of the invention the reference minute ventilation of a patient is obtained by observing normal breathing of a patient in an awake state, and increased and decreased minute ventilation are obtained by interacting with the patient.

In another embodiment the reference minute ventilation of a patient is obtained by observing the patient in the sleeping state, and increased and decreased minute ventilation are obtained by applying a predetermined multiplier.

In yet another embodiment the minute ventilation is decreased from the reference level by decreasing one or more of the following parameters: respiratory rate, inspiration duration, and tidal volume.

In still another embodiment the minute ventilation is increased from the reference level by increasing one or more of the following parameters: respiratory rate, inspiration duration, and tidal volume.

In a further embodiment an electrical stimulation waveform is provided for creating an enhanced negative intrapleural pressure during exhalation.

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