Patent Application
20190255269
The presently disclosed subject matter relates to devices and methods for assisting breathing in a subject. Specifically, the presently disclosed subject matter relates to an assisted breathing device comprising a fluidic diverter, which converts a pressurized airflow into trains of vortices that prevent upper airway obstruction in a subject without the need for a tight-fitting mask, and methods of using the same.
An estimated 18-30 million Americans have obstructive sleep apnea (OSA), a chronic sleep-related breathing disorder that involves a decrease or complete halt in airflow despite an ongoing effort to breath. In OSA, muscles relax during sleep, causing soft tissues surrounding the pharynx to collapse and obstruct the upper airway. Airway obstruction leads to reduction or complete pauses in breathing during sleep. The brain responds to the resulting hypoxia and hypercapnia by alerting the body, causing a brief arousal from sleep that restores normal breathing. This disruptive cycle can occur hundreds of times each night.
Adverse outcomes independently associated with OSA include daytime sleepiness and fatigue, drowsy driving with increased risk of motor vehicle accidents, cardiovascular morbidities (e.g. hypertension, stroke, heart attack), metabolic syndrome and type 2 diabetes, nonalcoholic fatty liver disease, perioperative complications, and premature death. OSA is thought to account for 15-20% of the 40-50,000 deaths and almost 4,000,000 emergency department visits annually.
OSA is most likely to occur during the inspiration phase of respiration during sleep. Inspiration is associated with generation of negative intrathoracic pressure. Air enters into the airway because the pressure in the lungs is less than the atmospheric pressure outside the nares. For a patient with OSA, the collapse of the airway's soft tissue is likely to occur because negative pressure exists within the upper airway during inspiration.
Continuous Positive Air Pressure, or CPAP, is an effective and widely recognized therapy for obstructive sleep apnea, but is often under prescribed by physicians and under-utilized by patients. With CPAP therapy, the airflow is actively being “pushed” into the patient's airway. The pneumatic splint of CPAP maintains an open upper airway, thus preventing collapse of the soft tissues and airway obstruction. In the context of CPAP therapy, the term “positive airway pressure” means that the pressure from the airflow applied to the lumen of the airway is greater than the pressure applied to the airway from the surrounding soft tissue.
Currently marketed CPAP devices require a tightly sealed interface between the mask and patient's face to deliver pressurized air to the patient's upper airway, thereby creating positive pressure. In its basic form, the mask is placed over the patient's mouth and nose (i.e., a full face mask). If the mask is not sealed correctly, the air will then follow the path of least resistance, escaping out into the atmosphere where the pressure is lower. The patient will experience this as air bleeding out from the system, but more importantly, the positive pressure that is the basic of operation for CPAP therapy cannot be maintained. Consequently, the soft tissues surrounding the pharynx are more likely to collapse and obstruct the upper airway.
An alternative to a full face mask is a nasal apparatus that only works if the patient does not open his or her mouth at night. If the patient opens his or her mouth, the fully pressurized respiratory tract will lose pressurization as the air will follow the path of least resistance and rush out of the mouth. For patients that open their mouths, an additional apparatus to keep the mouth closed must be employed. Chin straps and bite guards are two approaches to help mouth breathers keep their mouths closed during sleep.
CPAP is efficacious when used nightly as prescribed, but is not well tolerated by patients. Studies show that somewhere between 46% and 83% of patients are not compliant with CPAP therapy and remove the CPAP device early in the night or skip use altogether. Compliance is poor due to the discomfort and inconvenience associated with CPAP. Issues that result in patient non-compliance include mask discomfort, nasal dryness, congestion, difficulty adapting to the unrelenting positive air pressure across the mouth and nose, abdominal bloating due to air entering the digestive tract, and facial skin irritation due to the requirement of a tight seal between the mask and face.
Accordingly, a need exists for alternative treatments for obstructive sleep apnea.
The present inventors have now developed a device and method for providing positive airway pressure to a subject in need thereof, without the need for a seal between the device and the face of a subject, by using a fluidic diverter to generate pulsatile vortex airflow for delivery to the nasal passageway of the subject.
In one embodiment, a method for assisting breathing in a subject in need thereof is provided, the method comprising: passing a pressurized airflow through a fluidic diverter, wherein the fluidic diverter converts the pressurized airflow into pulses of pressurized air that are diverted alternately to provide a first and a second train of pulses of pressurized air; and directing the first and second trains of pulses of pressurized air into a nasal passageway of a subject to assist breathing.
In another embodiment, a device for assisting breathing is provided, the device comprising: a compressor for providing a pressurized airflow; a fluidic diverter fluidly coupled to the compressor, the fluidic diverter comprising: an actuator comprising an inlet for receiving the pressurized airflow, a first outlet, and a second outlet; a flow path disposed on the actuator and fluidly coupled to the inlet and each of the first and second outlets; and a cover disposed on the actuator to enclose the flow path; wherein: the fluidic diverter converts the pressurized airflow into pulses of pressurized air diverted alternately into each of the first and second outlets; wherein the pulses of pressurized air exit the first and second outlets and enter a nasal passageway of a subject to assist breathing.
These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.
The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
The details of one or more embodiments of the presently-disclosed subject matter are set forth in this document. Modifications to embodiments described in this document, and other embodiments, will be evident to those of ordinary skill in the art after a study of the information provided in this document.
While the following terms are believed to be well understood by one of ordinary skill in the art, certain definitions are set forth to facilitate explanation of the presently-disclosed subject matter. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the presently-disclosed subject matter belongs.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently-disclosed subject matter.
As used herein, the term “about,” when referring to a value or to an amount of mass, weight, time, volume, concentration or percentage is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed method.
It should be understood that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.
The devices and methods disclosed herein leverage the properties of pulsatile vortex airflow to overcome limitations of current CPAP devices and provide a well-tolerated therapy for OSA. Unlike the continuous airflow of CPAP methods, characterized by the continuous motion of air particles along specific path lines, vortex airflow is pulsating and formed of trains of toroid vortices. As rotating regions along an axis line, these vortices give the vortex airflow its unique properties. Vortices of pressurized air travel relatively far, compared to continuous airflow, without losing structure. The disclosed devices and methods deliver vortex airflow to the upper respiratory tract of a patient, eliminating the need for a tight-fitting interface (e.g., mask). Unlike continuous airflow, when vortex airflow is directed toward the nasal passageway of a patient, the majority of the vortex airflow will enter or push into the airway due to the celerity and penetration properties of the vortices. Once entered, the vortex airflow acts in the same manner as the continuous airflow of CPAP technology by applying the required pressure on the lumen to splint the airway.
The devices and methods disclosed herein employ a fluidic diverter flow control mechanism to convert continuous pressurized airflow into vortex airflow. Advantageously, fluidic diverters require a source of pressurized air, have no moving parts, add little weight to a device, and require no external power to operate (other than power required to operate the source of pressurized air). Further, fluidic diverters can be scaled to vary size, periodic frequency, and flow rate.
Generally, embodiments of the present disclosure produce trains of vortices, which operate to apply positive pressure to an airway independent of the surrounding conditions (i.e., whether a mask is sealed to the face or not). The laws of physics demonstrate that a pressurized airstream (gas) flows from an area of high pressure to an area of lower pressure. In the case of CPAP, the airstream takes the path of least resistance, such as out the side of an ill-fitting mask or out of a patient's mouth. However, embodiments of the present disclosure produce vortex airflow comprising trains of vortices with mass flow that is sufficient to produce enough pressure to keep the airways of the respiratory tract from collapsing. In addition, the trains of pulses (i.e., vortices) of pressurized air produced by the devices and methods described herein are able to penetrate the nasal passageway and provide positive airway pressure despite not being a closed system because of the match between the impedance of the trains of pulses of pressurized air and the impedance of the airway tract. Matching the impedance of the vortex airflow with the impedance of the airway tract is not a necessity for the devices and methods disclosed herein; however, doing so maximizes the vortex airflow entering into the nasal passages, thereby providing the most efficient therapy. The vortex airflow need only be directed toward the nares of the subject to give a desired effect of preventing respiratory occlusion. A nasal cannula positioned proximate to the nares of the subject will deliver the trains of vortices that selectively enter the respiratory tract without a loss of pressurized airflow from the mouth.
Various embodiments of devices comprising fluidic diverters and methods for assisting breathing using trains of pulses of pressurized air are described in detail below.
As used herein, the terms “pulsatile airflow,” “pulsatile vortex airflow,” “vortex airflow,” and “pulses of pressurized air” are used interchangeably to refer to a pulsed airflow, wherein each pulse comprises a toroid vortex of pressurized air. A series of such pulses forms a train of pulses or vortices of pressurized air.
Fluidic diverters are well known in the art of aerodynamics for use in controlling fluid flow; however, the application of fluidic diverters to avert obstruction of the upper airway and assist breathing, particularly in the treatment of obstructive sleep apnea, represents a significant advancement over current CPAP technologies. The skilled artisan will appreciate that various configurations and designs of fluidic diverters may be employed in the devices and methods described herein.
Referring now to
The flowpath 130 may comprise a variety of configurations suitable for generating a pulsatile airflow. In the exemplary fluidic diverter 100 of
Referring to
Referring to
In one embodiment, the nasal cannula 180 is comprised of a chamber 184 fluidly coupled to a first prong 182a and a second prong 182b, wherein each of said prongs 182a and 182b is configured to be positioned proximate to a nostril of a subject. The chamber 184 is fluidly coupled to each of the first and second tubes 190. In a specific embodiment, the nasal cannula 180 is configured to keep the two trains of vortices separated as they enter the nostrils of a subject. In one embodiment, the nasal cannula 180 comprises a septum (not shown) for dividing the chamber 184 into a first compartment for receiving pulsatile airflow from the first tube 190 and a second compartment for receiving pulsatile airflow from the second tube 190. In such an embodiment, the first compartment of the cannula 180 is fluidly coupled to the first prong 182a and the second compartment is fluidly coupled to the second prong 182b. The nasal cannula 180 having a septum maintains two distinct trains of vortices, each entering a separate nostril of the user.
As stated above, the fluidic diverter 100 creates two streams of vortex airflow, i.e., two trains of pulses of pressurized air. Conventional jets of air or other fluid, such as those used by existing ventilators and CPAP devices, produce a laminar flow of air that transitions into turbulent flow of air, which disperses very quickly as a free jet. However, the vortex airflow generated by embodiments of the present disclosure are defined by trains of vortices 170 that remain coherent in shape (i.e., the trains of vortices have a lower rate of dispersion) and produce high rates of the flow. The fluidic diverter 100 generates trains of vortices 170 as the airflow is diverted between the two outlets 120 of the fluidic diverter. Each vortex 170 then advects downstream under its own induced velocity. Based on the operating frequency of the fluidic diverter 100, this process can be repeated tens/hundreds/thousands of times per second. Patients may not be able to discern that the airflow is actually composed from a train of vortices 170, and may experience the trains of vortices 170 as if they were a continuous jet.
The enhanced celerity of the trains of vortices 170 is associated with the ability of the flow to sustain high momentum (i.e., penetration of the flow) for longer distances. The vortices 170 that exit the outlets 120 or the nasal cannula 180 will enter the nostril and respiratory tract without significant reflection and/or loss to the environment. The pressurized airflow source 150 and the fluidic diverter 100 generate pressure (i.e., “power”) that is sufficient to keep the passageways of the respiratory tract from collapsing and causing occlusion.
In addition to higher penetration of flow, another advantage of the embodiments described herein is the ability to direct air pressures specifically to the occluded area of the respiratory tract. Use of trains of vortices 170 enables airstreams to be produced that will selectively flow to areas of greater resistance based on the principle of impedance matching. The coherent structure of the flow, together with the ability to match the impedance of the trains of vortices 170 with the impedance of the airway (e.g., nasal passageways/respiratory tract), eliminates the need for a closed system that requires a mask. The impedance of the trains of pulses of pressurized air 170 may be matched to the impedance of the patient's airway (i.e., nasal passageways/respiratory tract).
According to the concept of impedance matching, the maximum energy transfer (i.e., with minimum reflections) occurs when the impedance of the source (input) matches the impedance of the load (output). Impedance is a general term used to describe resistance. While often associated with electric circuits, the concept of impedance is also applicable to the behavior of flow in fluid mechanics. The impedance of the flow in a system (i.e., tube, channel, nasal cavities, etc.) is determined from the ratio of pressure to the flow rate. Like an electrical circuit, flow impedance is a function of frequency. Thus, impedance can be modified for pulsatile airflow. In the context of electrical circuits, impedance matching is a method used for maximizing power (energy) transfer of an electrical wave between a load and a source. Analogized to fluid flow, impedance matching is a method used for maximizing the transfer of waves from one medium to the next with minimum loss to reflections. The impedance value of a nasal airway is patient-specific, and determined by the ratio of lung pressure and flow rate (i.e., velocity of the flow moving in the airway). When the impedance values are matched between a nasal airway and a vortex airflow, maximum flow is transferred from outside the nares into the nasal passageway, with minimal loss to reflections.
As described above, the trains of vortices 170 are formed by passing a pressurized airflow 160 through the fluidic diverter. A frequency of the trains of vortices can be varied by adjusting factors such as the geometry of the actuator 105, the flowpath 130, and the input pressure of the airflow 160 from the airflow source 150. The impedance of the pressurized airflow 160 is directly related to the frequency of pulses and, thus, the fluidic diverter 100 described herein may produce trains of vortices 170 with varying impedance. In certain embodiments, the frequency of pulses of pressurized air ranges from about 1 Hz to about 50 kHz.
Advantageously, a magnitude of a vortex of pressurized air is adjusted in the devices and methods disclosed herein by adjusting a magnitude of the airflow entering the fluidic diverter 100.
Generally, different obstructive sleep apnea patients require different levels of air pressure to open their airways of the respiratory tract. This variation in the required air pressure necessary to open subjects' airways may be caused by variation in the locations and severity of subjects' airway blockage and/or degree of occlusion.
Referring to
In one embodiment, a method for assisting breathing in a subject in need thereof is provided, the method comprising passing a pressurized airflow through a fluidic diverter, wherein the fluidic diverter converts the pressurized airflow into pulses of pressurized air that are diverted alternately to provide a first train and a second train of pulses of pressurized air; and directing the first and second trains of pulses of pressurized air into a nasal passageway of a subject to assist breathing. In certain embodiments, the first and second trains of pulses of pressurized air enter the nasal passageway and avert respiratory tract occlusion, thereby treating obstructive sleep apnea. In a specific embodiment, each of the pulses of pressurized air comprises a toroid vortex of pressurized air.
In a specific embodiment, the method further comprises generating the pressurized airflow by a compressor. In another embodiment, a magnitude of the vortex of pressurized air is adjusted by adjusting a magnitude of the airflow entering the fluidic diverter.
In one embodiment, the first train of pulses of pressurized air exits the fluidic diverter via a first outlet, and the second train of pulses of pressurized air exits the fluidic diverter via a second outlet.
In an embodiment, the first and second trains of pulses of pressurized air are directed into the nasal passageway of the subject by positioning the first outlet proximate to a first nostril of a subject and the second outlet proximate to a second nostril of the subject, without the use of a nasal cannula.
Alternatively, in another embodiment, the first and second trains of pulses of pressurized air are directed into the nasal passageway of the subject through a nasal cannula fluidly coupled to each of the first and second outlets of the fluidic diverter, wherein the nasal cannula is configured to be positioned proximate to the nostrils of the subject. In such an embodiment, a seal is not present or necessary between the nasal cannula and the nostrils of the subject in order to prevent airway occlusion.
In one embodiment, the nasal cannula is fluidly coupled to the first outlet via a first tube and is fluidly coupled to the second outlet via a second tube, wherein each of said first and second tubes delivers a train of pulses of pressurized air to the nasal passageway of the subject via the nasal cannula.
In a specific embodiment, the methods described herein further comprise matching a frequency of the pulses of pressurized air to an impedance of the nasal passageway. In a very specific embodiment, the frequency of the pulses of pressurized air ranges from about 1 Hz to about 50 kHz.
In another embodiment, a device for assisting breathing is provided, comprising: a compressor for providing a pressurized airflow; a fluidic diverter fluidly coupled to the compressor, the fluidic diverter comprising: an actuator comprising an inlet for receiving the pressurized airflow, a first outlet, and a second outlet; a flow path disposed on the actuator and fluidly coupled to the inlet and each of the first and second outlets; and a cover disposed on the actuator to enclose the flow path; wherein: the fluidic diverter converts the pressurized airflow into pulses of pressurized air diverted alternately into each of the first and second outlets; wherein the pulses of pressurized air exit the first and second outlets and enter a nasal passageway of a subject to assist breathing. In certain embodiments, each of said pulses of pressurized air comprises a toroid vortex of pressurized air. Advantageously, the devices disclosed herein do not require a seal between the first and second outlets and the nostrils and/or nasal passageway of the subject.
In certain embodiments, the device further comprises a first tube having a first end and a second end, the first end coupled to the first outlet and the second end coupled to a nasal cannula; and a second tube having a first end and a second end, the first end coupled to the second outlet and the second end coupled to the nasal cannula, wherein the nasal cannula is configured to be positioned proximate to nostrils of a subject. Advantageously, the devices disclosed herein do not require a seal between the nasal cannula and the nostrils and/or nasal passageway of the subject.
In a more specific embodiment, the nasal cannula comprises a chamber fluidly coupled to a first prong and a second prong, wherein each of said prongs is configured to be positioned proximate to a nostril of a subject. Optionally, the nasal cannula comprises a septum for dividing the chamber into a first compartment for receiving pulses of pressurized air from the first tube and a second compartment for receiving pulses of pressurized air from the second tube, wherein the first compartment is fluidly coupled to the first prong and wherein the second compartment is fluidly coupled to the second prong.
In one embodiment, a frequency of the pulses of pressurized air is such that an impedance of the pulses of pressurized air is matched to an impedance of the nasal passageway.
In another embodiment, the device assists breathing in a subject suffering from obstructive sleep apnea by providing positive airway pressure to avert respiratory tract occlusion.
All documents cited are incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to one skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/366,697, filed Jul. 26, 2016, the contents of which are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/043257 | 7/21/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62366697 | Jul 2016 | US |
