Patent Application
20060005834
None.
Not applicable.
1. Field of the Invention
Embodiments of the present invention are directed to methods and systems of providing breathing airway therapeutic gas flow to treat breathing disorders during sleep. More particularly, embodiments of the invention are directed to methods and systems where the control of therapeutic gas provided to a patient during an inhalation is based on airflow during a previous inhalation and a set point airflow, and is at least partially independently of pressure to achieve the flow.
2. Background of the Invention
Sleep-disordered breathing is common throughout the population and may encompass many conditions, such as snoring, hypopneas and apneas. Apnea may be a disorder where a person temporarily stops breathing during sleep. A hypopnea may be a period of time where a person's breathing becomes abnormally shallow, loosely defined to be a reduction in breathing volume by 50% or more for greater than ten seconds. In some cases, a hypopnea may precede an apnea event. Snoring is a disorder whose cause, in some cases, may be similar to the causes and effects of apnea and hypopnea.
Although snoring, hypopneas and apneas may have multiple causes, one trigger may be full or partial blockages of the patient's breathing airway. In particular, in some patients the pharynx, larynx, upper airway and/or other soft tissue in the respiratory tract may collapse due to forces of gravity, enlarged or swollen airway structures, narrowing and/or forces associated with lower pressure inside the body than outside the body. A collapse of the pharynx, larynx, upper airway and/or other soft tissue in the respiratory tract may thus cause a full or partial blockage, which may lead to snoring, hypopnea and/or apnea events.
Related art methods to counter collapse of the breathing airway may be the application of positive airway pressure, possibly by using a continuous positive airway pressure (CPAP) machine. This may be accomplished in the related art by placing a mask over at least the patient's nose, and providing within the mask a prescribed titration pressure communicated to the breathing airway. The pressure within the breathing airway may be greater than the pressure outside the body, thus holding open or splinting the airway.
In some related art CPAP machines, the doctor-prescribed titration pressure is supplied to the patient continuously regardless of the presence or absence of any breathing abnormality. Other CPAP machines may incorporate an auto-titration feature, which may initially apply a low pressure, and then may increase the pressure after detecting a full or partial collapse of the breathing airway. More particularly, related art devices may observe a patient's inhalation curve which, in the absence of a full or partial collapse, is bell-shaped. By algorithmically determining that the patient's inhalation curve has a flattened peak, the related art devices thus determine that a full or partial collapse of the patient's breathing airway has taken place and increase the applied positive airway pressure. If no flattening of the peak of the bell-shaped curve is detected, yet a second inhalation curve indicates a smaller volume inhaled by the patient, the related art devices either may not change to applied pressure, or reduce pressuring assuming that the patient is having difficulty breathing against the supplied positive airway pressure.
Moreover, related art CPAP devices with the auto-titration feature always tend toward a lower applied positive airway pressure. In other words, if a patient has exhibited no breathing abnormalities over a certain period of time, CPAP devices with the auto-titration feature begin lowering the applied positive airway pressure, e.g., 0.5 centimeters of water every two minutes. The lowering of the applied positive airway pressure continues until a breathing abnormality is detected, and then the positive airway pressure is again raised.
As can be appreciated from the above discussion, related art CPAP devices with the auto-titration feature may intentionally induce breathing abnormalities in a patient as part of the algorithmic mechanism to determine a positive airway pressure where breathing is free of abnormalities. However, patients use CPAP devices in an attempt to alleviate breathing abnormalities, and in this sense CPAP devices with the auto-titration feature fail in their intended purpose. CPAP devices without the auto-titration feature have no means to respond to changes in nasal airway resistance.
Thus, what is needed in the art is a method and related system of addressing sleep-disordered breathing that overcomes the deficiencies of the related art.
The problems noted above are solved in large part by a method and system of providing therapeutic gas to a patient to prevent breathing airway collapse during sleep. Some exemplary embodiments may be a method comprising providing a flow of therapeutic gas to a patient during a plurality of inhalations (the flow of therapeutic gas preventing collapse of the patient's breathing airway while the patient sleeps), detecting a flow rate of the therapeutic gas of at least one of the patient's nares during a first inhalation of the plurality of inhalations, and increasing the flow of therapeutic gas in a second inhalation of the plurality of inhalations based on an amount the flow rate of therapeutic gas in the first inhalation is less than a set point therapeutic gas flow (the increasing before the occurrence of a partial or full airway collapse).
Other exemplary embodiments may be a system comprising a blower, a flow sensor fluidly coupled to the blower (the flow sensor measuring therapeutic gas flow provided by the blower, wherein the blower and sensor are fluidly couple to at least one naris of a patient, and wherein the therapeutic gas flow prevents collapse of the patient's breathing airway while the patient sleeps), and a processor electrically coupled to the blower and flow sensor (the processor executing a program that controls the therapeutic gas flow from the blower provided to the patient). The processor, executing a program, reads therapeutic gas flow measured by the flow sensor during a first inhalation of the patient, and the program increases the speed of the blower in a second inhalation, the increase based on an amount the therapeutic gas flow in the first inhalation is less than a set point therapeutic gas flow (and the increasing before the occurrence of a partial or a full airway collapse).
Yet further exemplary embodiments may be a method comprising providing a flow of therapeutic gas to a patient during a plurality of inhalations (the flow of therapeutic gas preventing collapse of the patient's breathing airway while the patient sleeps), detecting a flow rate of therapeutic gas of at least one of the patient's nares during a first inhalation of the plurality of inhalations, and decreasing the flow of therapeutic gas in a second inhalation of the plurality of inhalations based on an amount the flow rate of therapeutic gas in the first inhalation is greater than a set point therapeutic gas flow.
Further exemplary embodiments may be a system comprising a blower, a flow sensor fluidly coupled to the blower (the flow sensor measuring therapeutic gas flow provided by the blower, the blower and flow sensor fluidly couple to at least one naris of the patient, and wherein the therapeutic gas flow prevents collapse of the patient's breathing airway), and a processor electrically coupled to the blower and the flow sensor (the processor executing a program that controls the therapeutic gas flow from the blower provided to the patient). The processor, executing a program, reads therapeutic gas flow measured by the flow sensor during a first inhalation of the patient and decreases the speed of the blower in a second inhalation (the decrease based on an amount of the therapeutic gas flow in the first inhalation is above a set point therapeutic gas flow).
Yet still other embodiments may be a method comprising operating a blower coupled to a motor providing a flow of air at pressures above atmospheric to at least one naris of a patient during a plurality of inhalations of a sleep state of a patient (the flow of air prevents partial or full breathing airway collapse), measuring an airflow through the at least one naris using an airflow detector (the measuring during a first inhalation of the plurality of inhalations), and increasing the blower speed in a second inhalation of the plurality of inhalations based on an amount the airflow in the first inhalation is less than a set point airflow (the increasing before the occurrence of a partial or full airway collapse).
Yet other exemplary embodiments may be a computer-readable medium containing a program that when executed performs a method comprising commanding a blower coupled to a motor to provide a flow of air at pressures above atmospheric to at least one naris of a patient during a plurality of inhalations of a sleep state of the patient (the flow of air prevents partial or fill breathing airway collapse), reading an airflow through the at least one naris using an airflow detector (the reading during a first inhalation of the plurality of inhalations), and commanding an increase in the blower speed in a second inhalation of the plurality of inhalations based on an amount the airflow in the first inhalation is less than a set point airflow (the commanding an increase before the occurrence of a partial or full airway collapse).
Yet further exemplary embodiments may be a method comprising operating a blower coupled to a motor to provide a flow of air at pressures above atmospheric to at least one naris of a patient during a plurality of inhalations (the flow of air prevents partial or full breathing airway collapse during sleep of the patient), measuring an airflow through the at least one naris using an airflow detector, the measuring during a first inhalation of the plurality of inhalations, and decreasing the blower speed in a second inhalation of the plurality of inhalations based on an amount the measured airflow in the second inhalation is above a set point airflow.
The disclosed devices and methods comprise a combination of features and advantages which enable them to overcome the deficiencies of the prior art devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings.
For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:
Certain terms are used throughout the following description and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function.
In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections.
Consider, for purposes of explanation of the relationship between pressure and air flow, the system illustrated in
Further consider that each tube 18, 22 has coupled thereto a pressure transducer 26, 28 respectively, each pressure transducers may be capable of reading a pressure within their respective tube 18, 22. Blowers 10, 12 may be operated in a pressure control mode. While the controlled pressure within each tube may be different, for purposes of explanation consider that the pressure within each tube 18, 22 are controlled to be the same. Further consider that the common chamber 20 is at a low pressure, such as vented to atmosphere. Thus, because of the pressure differentials between the tubes 18, 22 and the common chamber 20, there may be an airflow from-the tubes 18, 22 into the chamber 20 (as indicated by the arrows in
Now consider that the blowers 10, 12 are operated in a flow control mode, with each blower attempting to maintain a pre-determined air flow regardless of required pressure. In order to maintain the desired flow, blower 10 may need to develop a higher pressure to overcome the restriction of orifice 24 than the pressure that may be required of blower 12 for the same airflow. With these principles in mind, the specification now turns to the discoveries of the inventors and the methods and related systems flowing from those discoveries.
The inventors of the present specification have found that a person's nasal and upper airway resistance to air flow may have a significant effect on the proper application and viability of positive airway pressure techniques to treat sleep-disordered breathing. In particular, the inventors of the present specification have found that over the course of a sleep session, a person's nasal resistance may change significantly. For example, while sleeping a person may experience periodic swelling of the tissue within one or both of the nares, and this periodic swelling therefore creates periodic increases and decreases of resistance to airflow through the nose. Moreover, a portion of the population may experience full or partial blockages of one or both nares as a function of sleeping position, stage of sleep, and/or irritation of the airway (e.g., such as caused by allergens or excessive applied pressure). For example, a person lying on their back may have a small resistance to airflow through each naris, but one or both nares may become blocked almost instantaneously when that person sleeps on their side or on their stomach.
The changing nasal resistance experienced by some patients may render related art airway flow control devices and techniques unsuitable for their intended purpose. In particular, for CPAP devices that apply only a single pressure (the prescribed titration pressure) throughout the sleep session, increases an airway resistance to airflow may render the CPAP device ineffective. That is, the prescribed titration pressure may provide inadequate flow to ensure that the patient's breathing airway does not collapse given the higher nasal resistance. As for related art CPAP devices with auto-titration features, as mentioned in the Background section, these devices may increase the applied pressure only after a snoring, apnea or hypopnea event. A snoring, apnea and/or hypopnea event may result in an arousal from sleep of the patient. In the situation where the patient's airway resistance is decreasing, the related art auto-titration devices may apply excessive pressure, making it difficult for the patient to exhale and also causing an arousal from sleep of the patient.
Embodiments of the present invention are directed to methods and systems that proactively control therapeutic gas flow to the patient during inhalation (substantially independent of applied pressure) to minimize the occurrence of sleep-disordered breathing, such as snoring, hypopnea and/or apnea events in the patient.
The ROM 32 may store instructions executable by the processor 30. In particular, the ROM 32 may comprise a software program that implements the various embodiments of flow control for an airway flow control device. The RAM 34 may be the working memory for the processor 30, where data may be temporarily stored and from which instructions may be executed. Processor 30 may couple to other devices within the system by way of the A/D converter 38 and the D/A converter 36.
The airway flow control device in accordance with embodiments of the invention also comprises a fan or blower 40 fluidly coupled to a flow sensor 42 and pressure sensor 44. Blower 40 may be any suitable device, such as a vane-type blower, coupled to an electric motor 46. In alternative embodiments, a source of therapeutic gas, e.g., oxygen, may be used in addition to or in combination with the blower 40. Therapeutic gas pressure and flow created by the blower 40 may thus flow through a flow sensor 42 (of any suitable type) and to a patient's nostrils and/or mouth, possibly through tube 48 and mask 50. In accordance with embodiments of the invention, the airway flow control device 100 provides (substantially independent of applied pressure) a flow of therapeutic gas during inhalation to the patient to minimize sleep-disordered breathing such as snoring, hypopnea and/or apnea events.
As will be more thoroughly discussed below, the primary control parameter for delivery of therapeutic gas in any one inhalation is the flow of therapeutic gas to the patient during a previous inhalation. Control of the flow of therapeutic gas delivered by the airway flow control device may take many forms. In some embodiments, the flow may be controlled by selectively controlling blower 40 speed. For example a motor 46, controlled by a motor speed control circuit 52, may control blower 40. In some embodiments, the motor 46 may be a direct current (DC motor), and therefore motor speed control by the motor speed control circuit 52 may be accomplished by providing a varying voltage DC power to the motor 46. In alternative embodiments, the peak voltage provided to the motor 46 by the motor speed control circuit 52 may remain constant but may be modulated, such as by a pulse width modulation system. In yet other embodiments of the invention, the motor 46 may be an alternating current (AC) motor, and in these embodiments the motor speed control circuit 52 may provide power having varying frequency to the motor 46 to control motor and therefore blower speed. In yet still other embodiments of the invention, the motor 46 may be a stepper motor, and in these embodiments the motor speed control circuit 52 may control the speed the field rotates around the stator to control output shaft speed.
The airway flow control device 100 illustrates that the processor 30 may electrically couple to the motor speed control circuit 52 by way of an analog signal of the D/A converter 36. While communication between the processor 30 and the motor control speed circuit 52 in this manner may be preferred, any communication system that allows the processor to communicate a desired motor speed to the motor speed control circuit 52 would be operable, such as a predetermined plurality of motor speeds selected by delivery of a digital signal between the processor 30 and motor speed control circuit 52, and/or a serial or parallel packet-based communications system in which the processor 30 delivers messages containing the desired motor speed to the motor speed control circuit 52.
In alternative embodiments, the flow of therapeutic gas may be controlled by running the blower 40 at a relatively constant speed, and controlling the flow by control valve 55 at the direction of the processor 30. In yet other embodiments, a combination of controlling the blower 40 speed and the control valve 55 may be utilized.
Waveform 72 illustrates a first inhalation of the patient. In particular, the therapeutic gas flow as measure by the flow sensor 42 may initially be the amount that escapes through the vent port 54 (point 71). As the patient inhales the therapeutic gas flow may reach a peak 74, and then trail off again to an amount of flow escaping through the vent port 54 (point 76). As the patient exhales, pressure within mask 50 may increase, and thus therapeutic gas flow may drop as exhaled gases displace therapeutic gas exiting the vent port (as illustrated by portion 77). The peak flow rate of therapeutic gas measured during inhalation (taking into account the flow of approximately 40 liters per minute escaping through the vent port 54) may be on the order of 75 liters per minute; however, this only exemplary and indeed will change from patient to patient.
Still referring to
If a titration flow for the patient is not known, the next step in the process may be setting the therapeutic gas flow of the airway flow control device 100 to be an arbitrary starting point below which sleep-disordered breathing is likely to occur. In particular, some embodiments of the invention may make this initial flow setting to be 50 liters per minute (block 106). Other starting flows may be equivalently used. After the initial gas flow is set, the patient is allowed to sleep and a determination is made as to whether the patient snores or experiences a hypopnea and/or apnea event (block 108). If the patient experiences sleep-disordered breathing, the next step in the process may be to increase the therapeutic gas flow and perform the test again. In accordance with at least some embodiments of the invention, the increase may be 5 liters per minute (block 110) and again the patient is monitored for the presence of snoring, hypopnea and/or apnea events. The process continues (blocks 108 and 110) until such time as the patient sleeps without experiencing sleep-disordered breathing. The amount of time that the airway flow control device 100 monitors the patient for sleep-disordered breathing in this auto-titration flow phase may vary from a mere plurality of breaths to several hours. In accordance with at least some embodiments of the invention, the process determines that sleep-disordered breathing is not present at the current therapeutic gas flow set point if no snoring, hypopnea and/or apnea events occur within minutes of the patient falling to sleep.
Still referring to
Measuring therapeutic gas flow in accordance with embodiments of the invention may take many forms. In accordance with some embodiments of the invention, and to simplify the software program executed in the processor 30, the measured therapeutic gas flow is preferably the peak instantaneous flow rate measured during an inhalation. Referring again to
The next step in the exemplary method may be a determination of whether the measured therapeutic gas flow is higher than the titration flow set point (block 118). If the measured therapeutic gas flow is higher, the next step in the process may be decreasing motor 46 speed (block 120), thus decreasing the flow of therapeutic gas flow produced by the blower 40. In accordance with at least some embodiments of the invention however, the decrease in motor speed is a speed decrease to correct only a portion of the difference between the measured therapeutic gas flow and the titration flow set point. Some embodiments may attempt to correct approximately ten percent of the difference between the measured therapeutic gas flow and the titration flow set point (whether the correction is an increase of a decrease). Returning to block 118, if the measured therapeutic gas flow is not higher than the titration flow set point, the next step may be a determination of whether the measured therapeutic gas flow is lower than the titration flow set point (block 120). If so, in the exemplary process an increase in motor speed is effectuated to correct at least a portion of the difference between the measured therapeutic gas flow and the titration flow set point (block 124). If the measured therapeutic gas flow is neither higher than the titration flow set point nor lower than the titration flow set point, the motor speed is left unchanged (block 126), and the process returns to measuring the therapeutic gas flow during the next inhalation (block 116). After motor speed corrections are made (blocks 120 or 124), the process steps to measuring the therapeutic gas flow during the next inhalation (block 116).
Referring somewhat simultaneously to
Still referring somewhat simultaneously to
The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, while the airway flow control device 100 is shown in
