Patent Application
20080127978
Pressure support devices are used as a therapeutic treatment to correct for sleep-related breathing disorders, such as obstructive sleep apnea, central sleep apnea, and Cheyne-Stokes respiration. By delivering pressure to an airway of a user to keep the airway open, pressure support devices prevent apnea events, which may include obstructions of the airway or reductions in airflow within the airway (i.e., complete or partial obstructions). Pressure support devices deliver a constant or variable pressure, either of which may be determined based on respiratory variables or other signals from the user.
For a constant pressure support device, for example a Continuous Positive Airway Pressure (“CPAP”) device, the pressure is often determined based on polysomnography (“PSG”) signals, such as electroencephalogram (“EEG”) signals, electrooculogram (“EOG”) signals, electromyogram (“EMG”) signals, electrokardiogram (“EKG”) signals, oxygen saturation, and/or nasal or oral air flow, which are monitored and assessed by a trained clinician who adjusts the pressure during one or more all-night sleep studies to ensure the prevention of obstructions. The PSG signals are used to determine sleep stage of the user. Pressure for a CPAP may also be set by a regression model that takes into account anthropometric characteristics, neck circumference, and the frequency of nocturnal breathing abnormalities.
Variable pressure support devices include Bi-Level Positive Airway Pressure (“BiPAP”) devices, which deliver different pressures for inhalation and exhalation to increase comfort and efficacy, and Automatic Positive Airway Pressure (“APAP”) devices which automatically adjust the pressure delivered based on a record of respiratory variables detected from the user. An APAP device can estimate the pressure to deliver without an all-night sleep study and can adjust the pressure relative to changes in respiratory variables detected during a single night and/or between nights. U.S. Pat. No. 6,425,861 describes another method for providing variable pressure in which an expert operator in a central location monitors PSG signals to manually adjust a CPAP device. This method requires both a PSG system incorporating wet electrodes, which are difficult to apply and uncomfortable to wear, and an expert operator to perform adjustments.
In a home setting, however, a system for monitoring sleep stage is difficult to implement. For example, the application of a PSG system is infeasible in a home setting. Wet electrode-based EEG systems are time-consuming and messy because they usually require applying a gel or paste to act as a conductive path and abrading the skin at the point of contact to remove the outer layer of dead skin to ensure signal quality. In addition, long-term application of wet electrodes is infeasible because of the long-term effects on the skin at the point of contact. As such, in home settings, pressure support devices incorporating a sleep stage system are currently infeasible. In addition, current pressure support devices, by not being able to monitor many relevant signals from the user, are incapable of providing feedback based on such signals to the user. Current pressure support devices may also provide inappropriate pressures at different time (e.g., too much pressure may prevent a user from falling asleep or awaken a sleeping user), owing to their inability to adjust to changes in a user's condition. Because of device discomfort and the lack of feedback, users often fail to comply with a treatment regimen.
As such, a need remains for comfortable, easy-to-use pressure support devices capable of adjusting the pressure delivered to effectively treat sleep apnea in a home setting. A need also remains for pressure support devices that can provide feedback to a user to encourage user compliance with a treatment regimen.
The systems and methods described herein relates to systems and methods for treating sleep apnea, which include a first dry electrode for detecting EEG signals of a user, positioned at or near a head of a user; a sleep stage processor for determining a sleep stage of the user based, at least in part, on the EEG signals detected by the first dry electrode, and a pressure delivery device for delivering a controllable stream of air to at least one of a nose and a mouth of the user, the stream of air having a pressure selected based, at least in part, on the sleep stage determined by the sleep stage processor. In some embodiments, a pressure processor determines the pressure of the controllable stream of air based, at least in part, on the sleep stage determined by the sleep stage processor. The sleep stage may be at least one of light sleep, deep sleep, awake, asleep, REM sleep, non-REM sleep, stage 1, stage 2, stage 3, and stage 4. In some embodiments, a headband is attached to and positions the first dry electrode on the user, where the headband is adapted to encircle a head of the user. The sleep stage processor may apply a neural network when processing the EEG signals to determine the sleep stage of the user.
The pressure delivery device may include a mask positioned at or near at least one of the nose and the mouth of the user, a tube connected to the mask for delivering air to the mask, and a pump connected to the tube for generating the controllable stream of air. The pressure delivery device may include at least one of a continuous positive airway pressure device, a bilevel positive airway pressure device, and an automatic positive airway pressure device. In some embodiments, the pressure delivery device delivers a stream of air having a lower pressure when the sleep stage indicates that the user is awake than when the sleep stage indicates that the user is asleep. In some embodiments, the pressure delivery device delivers a stream of air having a lower pressure when the sleep stage indicates that the user is in REM sleep than when the sleep stage indicates that the user is in non-REM sleep. In some embodiments, the pressure delivery device delivers a stream of air having a lower pressure when the sleep stage indicates that the user is in light sleep than when the sleep stage indicates that the user is in deep sleep.
In some embodiments, a wake-up device determines a wake-up time for the user based at least partially on the sleep stage of the user. The wake-up device may select the wake-up time according to a wake-up condition received from the user and to wake the user when the sleep stage of the user is transitioning between REM sleep and non-REM sleep.
A transmitter, in communication with the first dry electrode, may wirelessly transmit the EEG signals and a receiver may wirelessly receive the EEG signals from the transmitter and transmit the EEG signals to the sleep stage processor. In some embodiments, a second dry electrode, positioned at or near the head of the user, may detect the EEG signals of the user. An electrode processor may receive and process the EEG signals from the first and second dry electrodes. In particular, the electrode processor may generate a difference between an output of the first dry electrode and an output of the second dry electrode. In addition, a third dry electrode, positioned at or near the head of the user and in communication with the electrode processor, may detect the EEG signals of the user, where the third dry electrode serves as an electrical ground. A memory, in communication with at least one of the sleep stage processor and the pressure delivery device, may store at least one of a history of sleep stages of the user and a history of pressures at which the controlled stream of air is delivered to the user.
In some embodiments, a housing contains the sleep stage processor and a display, seated on the housing, depicts information based at least partially on the sleep stage. The display may depict at least one of an indicator denoting the sleep stage of the user and a respiratory event number representing an apnea-hypopnea index. The display may also or alternatively depict at least one of the EEG signals, a hypnogram corresponding to a history of sleep stages of the user, a sleep quality index representing sleep quality of the user over a period of time, and a total sleep number representing a total amount of sleep over a period of time.
In some embodiments, an actigraph may detect motion signals representing movement by the user, where at least one of the sleep stage of the user and the pressure of the controllable stream of air is determined based, at least in part, on the motion signals.
The first dry electrode may include a conductive fabric disposed in contact with skin of the user. A portion of the first dry electrode in contact with skin of the user may be flexible. The first dry electrode may detect at least one of a level of muscle tone of the user, an EOG signal, and a galvanic skin response, where the sleep stage processor determines the sleep stage based at least partially on at least one of the level of muscle tone, the EOG signal, and the galvanic skin response
The foregoing and other objects and advantages of the invention will be appreciated more fully from the following further description thereof, with reference to the accompanying drawings wherein:
The systems and methods described herein pertains to systems and methods for treating sleep apnea in which dry electrodes detect physiological signals to determine sleep stage and information related to sleep stage and pressure in a pressure support system may be selected or adjusted based on the sleep stage and/or sleep stage related information. These physiological signals could be EEG, EMG, EKG, EOG, electrodermal activity (“EDA”), oxygen saturation, movement, and/or any other signals detectable by electrodes. Dry electrodes, especially those which are lightweight and/or flexible, are more comfortable, even over longer periods of time, than wet electrodes. They are easier to use because they may easily be applied, for example, via a headband that can be slipped on the head and placed in contact with the forehead. The dry electrodes may therefore be used in a setting that does not require a medical professional to apply the electrodes. For example, a user can apply the dry electrodes in a home setting on a regular basis. The dry electrodes can be used in conjunction with a pressure delivery device.
The electrodes 118, 120, and 122 are disposed on an interior surface of the headband 104 such that the electrodes 118, 120, and 122 may contact the skin on the forehead of the human head 106, when the headband is worn by the user. Dry electrodes may alternatively or in addition be placed in contact with skin elsewhere on the user's body to detect physiological signals of the user.
The electrodes 118, 120, and 122 may be flexible. For example, the electrodes 118, 120, and 122 may be made of a conductive fabric, such as a silverized fabric. Other metals may also be used to render fabric conductive, such as copper, stainless steel, gold, or a blend of copper and silver. Other dry electrodes, such as capacitive electrodes, metal disk electrodes, conductive foam, conductive rubber, and micromachined spikes, may also be used. Exemplary metal disks used in electrodes may be made of stainless steel, copper, or other metals. Exemplary foam may be silverized or otherwise made conductive, and similar to conductive fabric has the advantage of being soft and pliable. Exemplary dry rubber electrodes comprise a flexible or inflexible rubber impregnated with a conductive material such as metal or carbon nanotubes. Micromachined spikes may be made of silicon, metal, or organic materials and have the advantage of being able to penetrate the layer of skin that impedes signal transmission. Exemplary dry electrodes that are capacitive as opposed to ohmic, exemplary conductive foam, and exemplary metal disk electrodes are described in “Dry and Capacitive Electrodes for Long-Term ECG-Monitoring” by Anna Karilainen, Stefan Hansen, and Jörg Müller, SAFE2005, 8th Annual Workshop on Semiconductor Advances for Future Electronics, 17-18 November 2005, Veldhoven, The Netherlands, p. 155-161. Exemplary capacitive electrodes that do not require contact with the user's skin are described in “Remote detection of human electroencephalograms using ultrahigh input impedance electric potential sensors,” by C. J. Harland, T. D. Clark, and R. J. Prance, Applied Physics Letters, Vol. 81, No. 17, Oct. 21, 2002, p. 3284-3286. Exemplary micromachined spikes are described in “Characterization of Micromachined Spiked Biopotential Electrodes” by Patrick Griss, Heli K. Tolvanen-Laakso, Pekka Meriläinen, and Göran Stemme, IEEE Transactions on Biomedical Engineering, Vol. 49, No. 6, June 2002, p. 597-604. The above references are hereby incorporated by reference herein.
The electrode processor 124 electrically connects to the electrodes 118, 120, and 122 such that electrode 120 serves as a ground. The electrode processor 124 may amplify and condition the difference between electrodes 118 and 122 to derive signals, such as EEG, EOG, EMG, EDA, and GSR signals. Alternatively, the electrode processor 124 may transmit said signals to the base 116 of the pressure delivery device 102 for processing. In some embodiments, the electrode processor 124 may include a wireless transmitter which wirelessly transmits signals for receipt by a wireless receiver disposed within the base 116. Alternatively, the electrode processor 124 may be in communication with the base 116 via a wire. For example, the wire may be integrated with the tube 114 and/or a support structure for holding the mask 112 and/or electrodes 118, 120, and 122 in place on the user. In some embodiments, the headband 104 may have two dry electrodes instead of three, such that the electrode processor 124 generates a difference between the two dry electrodes.
The headband 104 may be, for example, any of the illustrative headbands, or support structures for holding electrodes in place, described in the U.S. Application Ser. No. 11/586,196 filed Oct. 24, 2006, which is incorporated by reference herein in its entirety.
The base 116 includes a wireless antenna 126 to receive signals from the electrode processor 124 and components, such as receivers and processors implementing software, for processing the received signals.
The dry electrodes of step 302 may be like any of those described above with respect to
At step 306, a sleep stage of the user may be determined by a processor, such as the sleep stage processor 204 of
A pressure delivery device for delivering a pressurized stream of air to the user may be controlled at step 312. Exemplary pressure delivery devices may include a pump in connection with a mask that can be worn by the user, as described above with respect to
The summary information may be determined at step 410 by a processor that uses as inputs respiratory events, sleep stage, and/or other received signals to provide summary information 412, such as an indicator denoting the sleep stage of the user, a respiratory event number representing a number or frequency of apnea and/or hypopnea events (e.g., an apnea-hypopnea index), an EEG signal, a hypnogram corresponding to a history of sleep stages of the user, a sleep quality index representing sleep quality of the user over a period of time, a total sleep number representing a total amount of sleep over a period of time, a number of arousals, a sleep depth representing proportion of time spent in deeper sleep stages over a period of time, and a time spent in a particular sleep stage over a period of time. Displaying summary information may communicate results or progress of, and/or encourage compliance with, the therapeutic treatment being implemented by the pressure support system. The information may be displayed in a home or clinical setting to a user, doctor, or other trained professional, who may modify the therapeutic treatment based on the displayed information.
The wake-up condition received at step 414 may be a latest wake-up time received from the user. The sleep stage determined at step 406 may be used to determine a wake-up time, which is near, at, or before the latest wake-up time, at which a user may prefer to be awoken or may minimize sleep inertia after being awoken. For example, the wake-up time may be determined such as to wake the user when the sleep stage of the user is transitioning between REM sleep and non-REM sleep. The wake-up time may, alternatively or in addition, be determined such as to wake the user when the sleep stage is not deep sleep. Waking the user at step 418 may include sounding an alarm, which may be auditory, visual, tactile, electric, or any other form capable of waking a sleeping user.
The above described embodiments are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow. Furthermore, all of the flow diagrams and processes described above are illustrative. Steps may be added or removed to any of the flow charts, and steps may be performed in a different order.
This application claims the benefit of U.S. Provisional Application No. 60/872,920 filed Dec. 5, 2006, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60872920 | Dec 2006 | US |
