Patent Application
20220401672
Breathing a reduced concentration of oxygen can be a powerful biological factor in treating various sicknesses and injuries, and also in sports training. For some purposes it can be administered continuously for hours or even days. For example, professional endurance athletes will train at higher altitudes or expose themselves to low O2 conditions using a hypoxicator generator to force their body to adapt to lower oxygen concentrations. As yet another example, a method referred to as acute intermittent hypoxia (AIH) has been utilized as part of a broader therapy for spinal cord injuries and other neurological problems.
In rodent models of spinal cord injuries, AIH triggers mechanisms of neural plasticity that enhance respiratory and non-respiratory function. AIH elicits long-term facilitation of phrenic motor neuron activity via a signaling cascade that up-regulates brain-derived neurotropic factor (BDNF) and subsequently initiates downstream cellular events that purportedly strengthen synapses between pre-motor and motor neurons. In experiments, rodents have been exposed to daily AIH for 7 consecutive days via a Plexiglas chamber flushed with 10, 5 min episodes of 10.5% O2; 5 min intervals of 21% O2, as described by Lovett-Barr, M. R., Satriotomo, I., Muir, G. D., Wilkerson, J. E., Hoffman, M. S., Vinit, S., Mitchell, G. S., 2012. Repetitive intermittent hypoxia induces respiratory and somatic motor recovery after chronic cervical spinal injury. J Neurosci 32, 3591-3600.
Clinical trials have modified existing air delivery technologies, such as traditional gas-delivery masks coupled to a dedicated canister of low-O2 gas to administer AIH interventions, where the person could take the mask off to receive normal O2 levels. Others have used commercially available pressure swing adsorption scrubber (PSA)-dependent generators, such as hypoxicator generators that are marketed to athletes for endurance training.
Thus, there is a continuing need for systems and methods that facilitate the delivery of controlled intermittent low O2 conditions for clinical or medically-therapeutic settings, where it is paramount to meet the specific control, calibration, and functionality needed to assist the patient or subject with achieving an effective therapeutic outcome.
The present disclosure provides systems and methods for a hypoxia therapy, including acute intermittent hypoxia therapy, or conditioning that overcomes the aforementioned drawbacks.
In one aspect, the present disclosure provides an apparatus for providing intermittent normoxia and hypoxia intervals to a subject. The apparatus includes a breathing component, a normoxia fluid source, a hypoxia fluid source, a manifold, at least one valve, and a control system. The breathing component can be configured to engage the subject to deliver at least one fluid to the subject for breathing. The normoxia fluid source can be coupled to the breathing component. The hypoxia fluid source can be coupled to the breathing component. The manifold can be fluidly coupled to the breathing component and arranged between the normoxia fluid source and the breathing component and the hypoxia fluid source and the breathing component to deliver fluid from the normoxia fluid source to the breathing component and deliver fluid from the hypoxia fluid source to the breathing component. The at least one valve can be configured to disrupt a flow of fluid from at least one of the normoxia fluid source and the hypoxia fluid source. The control system can be configured to cause the at least one valve to switch between delivery of fluid from the normoxia fluid source and the hypoxia fluid source while maintaining a positive fluid pressure at the breathing component over a full range of breathing by the subject.
In another aspect, the present disclosure provides a hypoxia delivery system. The system includes a breathing component, a subject monitoring system, a normoxia source, a hypoxia source, a first hose line, a second hose line, a valve system, and a controller. The breathing component can be configured to engage a face of a subject. The subject monitoring system can include a sensor configured to track a physiological parameter of the subject. The first hose line can be in fluid communication with the breathing component and the normoxia source. The second hose line can be in fluid communication with the breathing component and the hypoxia source. The valve system can be configured to control fluid flow from the normoxia source through the first hose line to the breathing component or from the hypoxia source through the second hose line to the breathing component. The controller can be in communication with the subject monitoring system and configured to control operation of the valve system using feedback from the subject monitoring system.
In another aspect, the present disclosure provides a method for providing intermittent normoxia and hypoxia intervals to a subject. The method includes securing a breathing component to the face of the subject, the breathing component including a hose manifold and at least one fluid sensor. The method also includes providing a normoxia fluid source, connecting the normoxia fluid source to the hose manifold, providing a hypoxia fluid source that is configured to provide a predetermined concentration of oxygen, and connecting the hypoxia fluid source to the hose manifold. The method also includes sensing at least one property of inspiratory and expiratory fluid from the subject with the at least one fluid sensor, and controlling normoxia and hypoxia control valves that are in fluid communication with the respective normoxia and hypoxia fluid sources to provide at least one period of normoxia fluid supply to the subject and at least one period of hypoxia fluid supply to the subject.
Acute Intermittent Hypoxia (AIH) (for example, 90 seconds hypoxia intervals of 10% FiO2 alternating with 60 seconds normoxia interval of approximately 20.8% FiO2) has generally been shown to enhance motor recovery in persons with intramedullary spinal cord lymphoma (iSCL). Optimizing the IH dose to elicit beneficial neural plasticity without triggering pathology is a topic of considerable research. There is growing empirical evidence that brief, repeated exposures to hypoxia (in particular, acute intermittent hypoxia) safely induces functional recovery in persons with chronic, incomplete spinal cord injury in both non-respiratory and respiratory motor systems. Furthermore, when coupled with traditional rehabilitation training, low-dose AIH can further enhance recovery of motor functions in persons with iSCL. For example, AIH can be combined with weight-supported treadmill walking.
Understanding how hypoxia dose parameters interact with various physiological systems to achieve beneficial neuroplasticity without attendant pathology is an important topic of current research. Despite the lack of IH paradigm standardization across laboratories, AIH studies in humans have converged on a safe and effective dosing involving exposure to relatively ‘mild’ severities (such as approximately 9% to 10% FiO2, for example) for approximately 90 seconds alternating with 60 seconds of normoxia for fifteen full cycles totally approximately 37.5 minutes. Such dosing has been documented to effectively promote functional recovery without such negative symptoms as cognitive impairments, episodes of autonomic dysreflexia or hypertension.
On the other hand, more severe (such as less than 9% FiO2, for example) and chronic hypoxic exposures (such as over 100 cycles, for example) can potentially elicit negative effects. Optimizing IH as an adjuvant for neurorehabilitation therefore requires determining the greatest therapeutic effect that avoids triggering pathology. In general, research efforts addressing such balance require precise delivery methods for a wide range of controlled and repeatable AIH protocols delivered with a high safety of margin.
Some methods of AIH rely on manually timed connection and disconnection of a hypoxic-air supply, which may produce inconsistent dosing intervals and delivered fraction of inspired oxygen (FiO2) values. In general, human error can lead to timing deviations, imprecision, and logging errors. Additionally, some scrubbers manufactured for athletic training may not deliver constant FiO2: flow variations from subject respiration and/or plumbing restrictions, as well as internal variable scrubber processes can cause FiO2 variation up to several percentage points of O2 concentration.
In some methods, individual respiratory flow variations of an AIH method may overcome the positive pressure supplied by commercially available hypoxia sources, resulting in possible discomfort and raised FiO2. Generally, translating AIH to the clinic requires the development of an automated delivery device that supports delivery consistency across multi-site clinical trials.
One method to improve motor function after SCI is through mild episodes of breathing low oxygen (i.e., acute intermittent hypoxia). As described briefly above, in rodent SCI models, AIH triggers mechanisms of neural plasticity that enhance respiratory and non-respiratory function. AIH elicits long-term facilitation of phrenic motor neuron activity via a signaling cascade that up-regulates brain-derived neurotropic factor (BDNF) and subsequently initiates downstream cellular events that purportedly strengthen synapses between pre-motor and motor neurons. One study exposed SCI rodents to daily (7 consecutive days) AIH via Plexiglas chamber flushed with 10, five minute episodes of 10.5% O2; 5 min intervals of 21% O2. They reported that these rodents substantially improved breathing capacity, as well as locomotor skills. More recently, results from clinical studies showed AIH-induced improvements in motor behaviors in persons with motor-incomplete SCI. In three separate studies, persons with iSCI showed increased ankle strength after a single day of AIH treatment that persisted for hours. Some studies have also uncovered substantial benefits of multi-session (up to 14 days) AIH on walking speed and endurance, as well as hand function.
Early clinical trials modified existing air delivery technologies to administer AIH interventions in persons with SCI. These AIH protocols consisted of 15, 60-90 second episodes of 10.0% O2 along with 60 second intervals of ambient room air (20.9% O2). These seminal studies involved or pressurized gas cylinders with programmable mechanical valve controls. Pressurized gas cylinder systems are well calibrated for laboratory application, but they are less feasible for clinic and home use due, in part, to stringent storage requirements and high maintenance costs, and the need for a specialist to administer and replenish gas from pressurized cylinders. The PSA-dependent delivery systems appear more practical since they have a smaller “footprint”, low maintenance costs, and minimal storage requirements; however, their inefficiencies in administering AIH requires further attention.
As briefly discussed above, breathing a reduced concentration of oxygen can be a powerful biological factor in treating various sicknesses and injuries, and also in sports training. For some purposes it can be administered continuously for hours or even days, in a procedure called Simulated Altitude Training. For other purposes (including sports training) an intermittent protocol (Intermittent Hypoxia Training, IH or IHT) is valuable: around 5 minutes of reduced oxygen (hypoxia, perhaps FiO2˜10%) followed by approximately 5 minutes of normal oxygen (normoxia, FiO2>20%), the sequence repeated multiple times. A protocol that can be valuable for recovery of spinal cord injury is Acute Intermittent Hypoxia (AIH). In this case the hypoxic and normoxic intervals are short (on the order of order 1 minute, for example), and an important aspect is the suddenness of concentration change (namely within a few seconds, preferably within 1 second). One example use of the technology is directed toward AIH, but may be also or instead useful for administering IH/IHT.
Some conventional methods of delivering Acute Intermittent Hypoxia can use pressurized gas cylinders and computer-controlled valves. High-pressure cylinders of precisely characterized gases are generally expensive for long term use, and inconvenient to replace. In addition the delivered flow rate is far too low to guarantee comfort when a subject feels a need to breathe deeply. Examples of the present disclosure include an AIH delivery system that avoids the gas-cylinder problems.
In some conventional methods, either a pressure swing adsorption scrubber, or membrane separation scrubber (sometimes called a hypoxicator) can be used to produce hypoxic gas conveniently and inexpensively. The produced gas can be manually connected to or disconnected from a user mask. The manual timing of this approach can be inconsistent, and breathing can be restricted in the disconnected state because there is no blower to help the subject inhale through the one-way mask inlet valve and associated tubing. Additionally, a normoxic valve positioned directly adjacent to the mask can be heavy and uncomfortable for the user. Furthermore, the scrubber output shows inconsistent oxygen concentration in its output, partly a ripple due to scrubber internal workings and partly a slow drift of oxygen concentration when the hose is disconnected, which will then take time to reverse during normoxia. Examples of the present disclosure can include features that facilitate accurate timing, comfortable breathing of normoxia, and more-consistent delivered FiO2 during hypoxia.
Some conventional methods of IHT can use a scrubber, along with computer-controlled switching valves that cannot deliver a rapid change in air concentration to the subject because the intervening tubes and chambers must be cleared first. In other methods, a rebreathing chamber can be used to deplete oxygen, but this too leads to long concentration-switching times. Examples of the present disclosure can improve on the rapidity of concentration change provided by these and similar methods.
Some conventional hypoxia delivery systems include a single Hypoxico 123 scrubber (an athletic “high altitude” training product) that can be either set to minimum FiO2 (assumed to be about 10%), or is adjusted to deliver an electrochemical sensor FiO2 reading of 10%. A CPAP-style output hose can be manually connected to, or disconnected from (thus allowing room-air inspiration), a subject's dual-valve CPAP face mask. A timer readout can be employed to generate the desired dosing intervals of 90 s hypoxia, 60 s normoxia. The experimenter can manually log fingertip SpO2, HR, and BP, as displayed by a GE Dash 4000 patient monitor, for example; and apply safety logic to terminate hypoxia administration or lengthen normoxia administration, if SpO2 falls below certain limits. While the hose is connected to the scrubber, hypoxic air is delivered with positive mask pressure; but when it is disconnected, normoxic breathing requires slight inspiratory effort due to pressure drop from the mask inlet valve. In addition, the actual FiO2 delivered to the subject, and the precise delivery times, are not accurately measured. In both manual and automated hypoxia delivery, each Hypoxico 123 scrubber can be equipped with the F-tube flow diverter for delivering lowest FiO2. The scrubber FiO2 setting is not computer controlled: rather, a valve is manually adjusted, and after a few minutes the delivered FiO2 settles to a value correlated with the output flow. The scrubbers exhibit limitations as to delivery flow rate and concentration consistency at FiO2=10%. The scrubber output passes through a HEPA filter, then is buffered by two 3L rubber reservoir bags to permit occasional or temporary hypoxia inspiration rates above scrubber output. Plumbing can be the standard CPAP wire-reinforced 19mm ID hose, with 22mm OD tapered rubber terminations, and various connectors, adapters, and tee fittings. Air can be delivered to a subject wearing a StarMed dual-valve CPAP mask, generally in conditions of continuous positive pressure except when a subject's deep breaths outpace the gas delivery.
As will be described, the present disclosure provides a generally cost-effective and easy-to-use apparatus for accurately and comfortably providing a human subject with scheduled bouts of hypoxia, interspersed with bouts of normoxia. The apparatus may be a relatively simple system that can be used in clinic or home settings. In some non-limiting examples, the scheduled bouts of hypoxia may be ten to twenty bouts with 90 seconds of air with oxygen reduced to the 10% level and the bouts of normoxia may be 60 seconds of atmospheric air with at least 20% oxygen. The changes in oxygen concentration presented to the subject occur rapidly. In some non-limiting examples, the changes in oxygen can occur in less than approximately 1 second to less than approximately 10 seconds.
In some examples, a hypoxic gas can be supplied by a pressure swing adsorption scrubber and possibly augmented by a mix chamber, with output concentration stabilized by shielding it from flow variations both when switching from normoxia and when a subject breathes deeply. The apparatus can supply constant positive pressure to a breathing component, such as a mask, for example by using a hypoxia reservoir during hypoxia intervals and by using a blower during normoxia intervals. The requisite sudden changes in concentration may be assured by using rapid-acting solenoid gas valves and dual hoses to the mask. In one example, a computer can be used to log valve actions, delivered gas concentration, and subject blood oxygen concentration. In general, the control system can automatically log all physiological data and sensor data to a drive which, in some instances, can eliminate the need for an administrator to constantly monitor a physical recording. A computer can also control the valves at scheduled times, and implement safety rules (e.g., altering normoxia duration as needed).
In some hypoxia delivery systems according to aspects of the present disclosure, the delivery system can support programmable interval timing to control instantaneous (or near instantaneous) gas switching via solenoid valves, smoother O2 concentration delivery at positive pressure, and biosignal monitoring and logging for switching feedback. In some examples, the feedback is closed loop feedback. The system can include slow electrochemical and fast fiber optic FiO2 sensors to measure delivered oxygen. In general, the system can provide relatively consistent interval lengths, reduce or eliminate observed systematic hypoxic duration errors that exceed 2 seconds, and deliver more consistent steady state FiO2. Additionally, the system may be qualitatively more comfortable for the subject with increased positive pressure of one or more of the hypoxia or normoxia supply.
Further illustrated in
By way of example, the solid arrows of
The mask 106 includes a manifold configured as two hoses 128 that, for example, can be configured as CPAP hoses that are distinct. In other examples, the manifold can be configured as a series of valves. In use, the hoses 128 remain filled with gas of the appropriate concentration, and their flow is simply stopped or started via the valves 104. With the pre-filled (i.e., constant filled) hoses 128, there is virtually no delay between a valve command and delivery of the desired concentration at the mask 106. Additionally, the mix chamber 116 is used to smooth pulsatile variations in FiO2 delivered from the scrubber 112. In general, the dual scrubbers 112 and the four reservoir bags 114 guarantee comfort and minimize disturbance to FiO2 when the subject 124 takes occasional deep breaths. In some non-limiting examples, the mask 106 or other breathing components may be selectively detachable from the hypoxia delivery system 100, disposable, and replaceable.
The scrubbers 112, the reservoir bags 114, and the mix chamber 116 are part of a general hypoxia source 130. In some non-limiting examples, the hypoxia source 130 includes the two scrubbers 112 that are configured as Hypoxico 123 scrubbers with F-tube flow restrictors. Each scrubber 112 can be manually adjusted to deliver FiO2 and approximately 10% (or sham=20.9%) after warmup. Additionally, in some non-limiting examples, the hypoxic source 130 includes the reservoir bags 114 that are configured as four 3-liter reservoir bags which allow the subject 124 to breathe deeply and comfortably. Further, in some non-limiting examples, the hypoxic source 130 includes the mixing chamber 116 that is configured as a 6-liter gas mixing chamber that is added between the scrubbers 112 and the valves 104. The mixing chamber 116 can minimize 0.5 Hz output ripple in the scrubber 112 FiO2. The mixing chamber 116 can be formed from a generally cylindrical container having a screw port on each end. In some examples, the screw ports can include threaded caps with adapter nozzles that fit standard CPAP tubing. Fan-mixed room air is presented to the scrubber 112 inlets to reduce the chance that concentrated O2 from the scrubber 112 may affect delivered FiO2.
The blower 118 is part of a general normoxia source 140. The normoxia source 140 is configured to push room air through the plumbing (e.g., hoses 128) to the mask 106 with the normoxia source 140 delivery pressure regulated by a variable transformer. In some non-limiting examples, the voltage of the transformer can be set to approximately 20V AC to reduce cooling and drying sensations of high airflow. Continuous positive mask pressure is maintained during both hypoxia and normoxia for easy breathing including during deep breaths.
Still referring to
In one non-limiting example, signals from the fingertip sensor 108, the blood pressure monitor 110, and the heart rate monitor are captured by a conventional Masimo Root Platform (Maximo, Irvine Calif. USA) patient monitor. Just before the mask 106 is a FiO2 sensor 132 which can be configured as a Maxtec OM25-RME electrochemical sensor (Maxtec, Salt Lake City, Utah 84119) with serial output. The device exhibits 12-second settling time and uses only single-point calibration. In some instances, it may be useful to calibrate the sensor to match atmospheric FiO2 at 20.9% (or slightly less due to humidity). In some cases, a FiO2 sensor may not be accurate near the 10% therapeutic value. In some examples, the FiO2 sensor can be a Presens single channel fiber optic oxygen transmitter (Oxy1-ST, Regensberg, Germany) along with the corresponding glass fiber oxygen sensor (PM-PsT7) and temperature probe (Pt100).
The computer 102 can include an automated system that has three functions that can be controlled by a program, such as a custom C# program, for example. The first function is logging time-stamped valve-switching events and polling the MaxTec (for breathing component FiO2) and Masimo (for SpO2, HR, and BP) for 1 Hz logging. The second is sending commands to the Arduino-based valve relays. For example, valve 104A opens and valve 104B closes for 90 seconds (hypoxia). The third significant function of the computer is applying a safety-related valve-control rules: For example, if fingertip SpO2 drops below 70% during hypoxia, a 60 second normoxia interval is immediately begun. If SpO2 has not risen to 80% at the end of a normoxia interval, an additional 60 second normoxia interval is initiated. In other examples, the SpO2 thresholds may be different and the time intervals may be different.
The blower 118 of
In general, the automated switching of the hypoxia delivery system 100 achieves both quick switching between gas intervals as well as consistency between the lengths of the intervals.
In some examples of hypoxia delivery systems, one or two oxygen scrubbers (hypoxicators) are each able to deliver at least 500 mL/s when output FiO2 is set to 10%. As shown in
In general, in a hypoxia delivery system, such as the system 100, reservoir bags (two each of the 3L size) can be T-connected to each scrubber output line to serve as reservoirs. These elastomeric balloons react with very slight pressure until 90% full, then rapidly climb in pressure to match scrubber output. When a deep-breathing subject inhales faster than the scrubber output, the difference comes from the reservoir bags. Since those bags are quickly lowered to near-zero pressure, at that point breathing becomes moderately harder for the subject. But only if the bags are fully depleted does the subject apply suction to the scrubber output—this dramatically increases scrubber output FiO2. With four bags total it can be difficult for such suction to be applied by most subjects.
Another example reservoir (such as the reservoir 170 of
In some examples the output of a scrubber or scrubbers can be fed through a mixing chamber. Some examples of mixing chambers can include a 6L mixing chamber that is cylindrical, 5.5 inch diameter and 16.5 inches long, with an inlet at one end and an outlet at the other. With a combined scrubber outflow of approximately 1L/s, the 0.5 Hz ripple of FiO2 (magnitude 1% or more) is attenuated by a factor of almost 10.
Thus three example approaches toward substantially constant FiO2 output from the scrubber have been provided: (A) avoiding altering the outflow resistance during the switch to normoxia delivery, through control of hypoxia vent resistance; (B) avoiding exposing the scrubbers to reduced pressure by subject deep breathing, by providing sufficient reservoir volume (preferably at nearly constant volume around 0.1 psi); (C) attenuating ripple of the FiO2 value with a mix chamber. Although these steps lead to nearly constant FiO2 during a session, they do not account for possible output differences due to air humidity or scrubber wear. One example fourth step is to measure the output FiO2 with reasonable accuracy. Therefore, to gain a meaningful measurement of administered FiO2 during hypoxia the sensor can be occasionally calibrated with 10% calibration gas.
To achieve the rapid switching of subject FiO2 which is desired for AIH, solenoid gas valves may be used. Such valves have 1 inch orifices and switch almost instantaneously. One way to use these valves is to have four. The scrubber output can be split within the manifold by a tee into two hoses, with valves on each side of the tee. One of the hoses connects to the subject mask, and one passes through some further plumbing to a vent. The valves are switched substantially simultaneously so one is closed when the other is open. Thus, these two valves allow scrubber flow to be rapidly switched from subject to vent, or the reverse. The venting plumbing resistance may be, for example, similar to the resistance of subject hose and mask, so that scrubber flow is not disturbed by the switch. When scrubber flow is disturbed by a vent line whose resistance is lower than the mask line, then output FiO2 begins a slow change to a higher value, only to begin returning when venting ends. Since the concentration settling time is minutes, it is evident that such disturbance should be minimized for most use environments.
Similarly, the blower normoxia output, as discussed above, goes to a tee with a valve on each side. One side of the tee goes to a vent, and the other goes through a hose to the subject mask. Once again, these two valves may be switched substantially simultaneously to be held always in the opposite state. In other words, the blower output is directed either to the subject or to vent. This switching may be substantially simultaneous with scrubber switching, so at all times one of the two sources (scrubber, blower) is directed to the subject, while the other is directed to vent. The blower vent valve is not as important as the scrubber vent valve, and could be eliminated (see, for example
One example feature of the described plumbing system is that the normoxia hose to the mask and the hypoxia hose to the mask may be two separate hoses within a manifold. These two hoses join right next to the mask. If they joined far from the mask, any change of gas would have to displace the internal volume of the hose before it reaches the mask. By using double hoses that join adjacent the mask, each is filled with the FiO2 value it will be delivering, so initiating flow in either will deliver the required gas to the mask within a very small time.
The rebreathing concept for hypoxia (see, for example
By using valves to isolate the rebreathing system during normoxia, the contents of the hoses are not altered. Then using multiple dedicated hoses to the mask, the subject experiences very rapid changes in FiO2. During hypoxia, air is inhaled from the upper chamber and exhaled into the lower chamber (as controlled by one-way valves on mask inlet and outlet). The change of volume is accommodated by a single 3L reservoir bag. During normoxia, a blower feeds a dedicated inlet hose, and an outlet hose is allowed to vent.
The control, logging and safety for the intermittent hypoxia system (see, for example
The computer logs the valve commands and the FiO2 readings. It also receives and logs SpO2 (fingertip oximeter) oxygen and pulse readings, and possibly other physiological measures. The computer may monitor SpO2 at any desired time interval and automatically (and/or with some degree of user input) make decisions to either terminate hypoxia or lengthen normoxia.
In general, oxygen concentration and flow rate are inversely related. Increasing the flow resistance increases the oxygen extraction effectiveness. For a single Hypoxico 123, for example, the oxygen concentration is plotted against flow rate in
Flow rates are significantly affected by flow restrictions imposed by the respiratory behavior of the participant. Deep inhalations imposed by the participant are extreme enough to deplete the 2-liter gas reservoir bags and therefore pull extra flow through the Hypoxico 123.
In some non-limiting examples, steady state hypoxia delivery provided by the Hypoxico 123 is not a constant 10% but fluctuates between values of 9.5% and 10.8%. This output is oscillatory as illustrated in
Illustrated in
The systems and methods described herein generally describe an automated hypoxia delivery system that can reliably deliver a precise AIH dosing based on conventional protocols. In addition to automating specified hypoxia delivery intervals, the new system can address imperfections in the manual system including, the elimination of steady state FiO2 concentration ripple, and ensuring a sufficient positive pressure supply without compromising O2 concentration dosage.
The rapidly-responding 1-Hz sampling Presens FiO2 sensor (though other sensors may be used) showed that manual switching times of FiO2 supplied to the mask were inconsistent. For a target 90 second hypoxia interval, the best fit to concentration jump times can be a mean of 91.2 second plus or minus 1.8 seconds. For a target delivery of 60 seconds normoxia, a mean can be 57 seconds plus or minus 1.8 seconds. Lengthening of the average hypoxia intervals may be partially attributed to the lack of positive pressure in the manual system during normoxia: lacking positive pressure, subject inhalation after the normoxia interval begins will result in continued hypoxia readings at a mask sensor. Further, rapidly-settling 1-Hz sampling can show that FiO2 of air supplied to the mask could be reliably switched in less than one second, via solenoid valves.
As discussed above, scrubber-delivered FiO2 is inversely related to volume flow rate, which is primarily governed by a flow-restricting valve on Hypoxico 123 generators. To an occasional deep breather, one of the most noticeable defects of a single scrubber is the limited flow rate. Two scrubbers, according to aspects of the present disclosure, can provide approximately 400 and 700 mL/s when FiO2 is at 10%. However, it should be appreciated that flow rate values may vary based on ambient temperature.
In general, sedentary adults exhibit minute ventilation of 85 to 348 mL/s (i.e., an average inspired flow rate). However, the required flow capacity may be dictated by occasional extremes, rather than averages. In some examples, the peak inspiratory flow rate expected during a typical inhalation can be up to 4 times the inspiratory average (e.g., between approximately 340 to 1390 mL/s). Examples described herein include a system having two scrubbers combined that can deliver a total flow rate (with slight positive pressure at a mask) at approximately 1100 mL/s. In some examples according to the present disclosure, additional scrubbers can be used to accommodate deeper breathers that produce a flow greater than 1390 mL/s.
In some examples where heightened breathing flow rates are expected, and two scrubbers are employed, reservoir bags may be used to avoid applying negative pressure to the scrubber output. In some examples, each reservoir bag can hold roughly 3-liters of gas when inflated, but do not deliver gas with a sustained pressure. As a result, a subject's breathing may only slightly increase in difficulty if inhaling at a faster rate than the scrubbers can deliver. Increasing the stored gas volume to multiple reservoir bags can alleviate difficulty breathing (e.g., a feeling of choking due to the increased flow resistance during deep inspiration). Even if the FiO2 is somewhat increased by a subject's emptying, the change is likely negligible, and the subject does not feel choked of inspiratory gas. In general, when a subject breathes gently/shallowly, then FiO2 can essentially remain constant, as desired for a reproducible hypoxia exposure.
In some implementations, devices or systems disclosed herein can be utilized using methods embodying aspects of the disclosure. Correspondingly, description herein of particular features, capabilities, or intended purposes of a device or system is generally intended to inherently include disclosure of a method of using such features for the intended purposes, a method of implementing such capabilities.
In this regard, for example
Each of the thresholds that may be evaluated at any of decisions 312, 314, and 318 may be user programmed into the system and can be updated based on specific needs of a patient. For example, a hypoxic threshold can be between approximately 70% and 80% FiO2 depending on the needs of the patient. In particular, a hypoxic interval may terminate if a patient's fraction of inspired oxygen falls below 70%.
Now that particular devices, systems, and methods according to the present disclosure have been described above, a non-limiting example of an automated pressure-swing absorption system to administer low oxygen therapy for persons with a spinal cord injury will be described below.
Three able-bodied individuals (2 males and 1 female) participated in an investigation. Study participants signed informed consent and could withdraw at any time. They did not have history of neurological, pulmonary, cardiovascular, and/or severe musculoskeletal impairments. Participants completed at least one of the three experimental sessions. Data collection occurred on separate experimental sessions.
Air delivery system: As illustrated in
Air flow regulation: A microcontroller can be used to control air delivery intervals during ‘automated’ AIH protocols. During ‘manual’ AIH protocols, switching between air sources can often results in random errors in temporal sequencing of AIH. Automated valve-switching where each selected solenoid valve directs air flow using 110 VAC and 10.5 watts power consumption via a microcontroller can reduce or eliminate sequencing. The microcontroller can time a solid-state relay to distribute power to either pair of four total solenoid valves. Solenoid valves can direct air flow within the breathing circuit. Constant flows from the PSA output (hypoxia or sham) and a fan that supplies room air at positive pressure (blower) can be constantly provided. In the case of low O2 (or sham) delivery, one valve can deliver PSA output air to the mask and the other valve can recirculate blower air to the spacious room. In the case of room air delivery, one valve can deliver blower air to the mask and the other valve redirected unused low O2 air to the spacious indoor environment.
Room air blower: An 18.9 liter, high-flow air blower can provide continuous positive pressure air to the breathing circuit. Using a 20-ampere variable transformer set to about 20VAC blower operating speed can be regulated to produce a flow rate of 1.25 liters s−1 to the mask. The room air blower provides continuous positive pressure of air to ease inspiration through the face mask.
Mask: A non-rebreather mask can be an interface between subject and air delivery system. The mask can include a one-way inlet valve that opens during inspiration of room air or delivery of positive pressure air from the generator. During expiration, the inlet valve can close, and a second one-way outlet valve can open to allow exhaled air to escape to surrounding environment. Air leakage at the mask can reduce inspired FiO2. Inflatable padding along a face mask perimeter can reduce air leakage, and a neoprene sleeve with hook and loop strappings can secure the mask to the subject's head.
Oxygen analyzers: Two in-line O2 analyzers can be used to monitor and record O2 concentration within a breathing circuit. A MAX-250E galvanic, partial pressure sensor can be affixed to the breathing circuit tee connector proximal to the non-rebreather mask. The sensor can provide estimates of oxygen with a measurement range of 0 to 100%, a response time of 15 s, and full-scale linearity±1.0%. Using a MaxO2® analyzer. Single-point calibration of this sensor can be performed at room air and ˜23° C. prior to each use.
In some instances, serial data transmitted from the analyzer (1 Hz) corresponded to changes in absolute O2 concentration±0.2% error, with about 12-second settling time. To measure O2 levels during rapid transitions in air sources, a high-precision fiber optic microsensor can be used. The PM-Pst7 provided estimates of O2 concentration with a measurement range of 0 to 100%, a temporal resolution of t90=ls, a resolution of±0.01% at 1.0% O2 and±0.05% at 20.9% O2, and an accuracy of±0.05% at 20.9% O2 when properly calibrated. The high-precision O2 analyzer transmitted these digital data to a PC at 1 Hz.
Pneumotach flow sensor: A factory-calibrated linear pneumotachometer was used with an amplifier to measure air flow rate. The sensor has a linear range of±800-liters s−1 and accuracy of±2.0% at room air. Flow rate can be calibrated rate using integration of the analog flow signal to a fixed 3-liter volume (calibration syringe). Flow rate signals can be acquired using a PC-based acquisition system at 1000 Hz. The sensor data estimated the magnitude and frequency of variations in air flow within the breathing circuit.
Temperature sensor: Temperatures of ambient room air and of the breathing circuit can be recorded before and during AIH and SHAM delivery protocols. A NTC thermistor was affixed adjacent to the O2 analyzer during recordings. The sensor provided a measurement range of −50 to 99° C., a resolution of 0.1° C., and accuracy of±2.0° C. A sensor can estimate the magnitude of variations in air temperature at the face mask during AIH and SHAM treatment protocols.
Cardiopulmonary Monitor: To ensure safety, a stand-alone cardiopulmonary monitoring system recorded participant blood O2 saturation (SpO2), and heart rate (HR) every second, and blood pressure (BP) every five minutes. During ‘automated’ AIH delivery, a custom PC-based control software was used to acquire these parameters at 1 Hz via universal serial bus (USB).
Manual delivery: The ‘manual’ AIH protocol requires a trained administrator to physically control the supply of air to a participant's non-rebreather facemask. “Manual” can be referred to as the use of a protocol administrator to ensure the air delivery system hose is either physically connected to or disconnected from the facemask at alternating time intervals (
Automated delivery: The ‘automated’ delivery system provides alternating air delivery without the need for a trained administrator (
To automate air delivery, a stand-alone AIH delivery application can be used that uses the C# programming language. As opposed to ‘manual’ switching between low O2 and room air sources, this software application provided a user interface to command switching protocols to the airflow controller. The control software required USB-interface between the microcontroller and a laptop PC running, for example, the Windows 10® operating system. The application provided protocol adjustments, as well as acquired dose timing and physiological data to ensure safety and efficacy. The application can enable users to 1) configure physiological recordings from a patient monitor, 2) adjust duration, and frequency of low O2 intervals, 3) establish safety limits that truncate or terminate low O2 exposure, and 4) save/load person-specific protocol settings. Collectively, these features provide safe, consistent, and flexible AIH delivery options that are not available in current ‘manual’ systems.
Safely and consistently administering AIH treatment protocols is of highest priority. Regardless of delivery system, participant comfort and attention was monitored, as well as, their SpO2, HR, and BP before, during, and after AIH delivery. For ‘manual’ AIH delivery protocols, a 75% SpO2 safety limit was implemented that prompted trained personnel to remove low O2 hosing from a participant's facemask until SpO2 levels returned to baseline levels. This required ‘manual’ switching between air sources based on visually inspected SpO2 readings. The ‘automated’ delivery system used real-time data acquisition and recording of SpO2, HR, and BP to eliminate the possibility of human switching and recording errors. In cases where SpO2 measurements fell below 75%, the ‘automated’ delivery system provided one or more 60 s intervals of room air until SpO2 measurements returned to >90%. In cases where systolic blood pressure exceeded 150 mmHg, the delivery system provided room air.
The sequence of ‘manual’ AIH treatment protocols is susceptible to human error, but the extent of this error remains unclear. In brief, the ideal dose timing of AIH consists of 15, 90 s breathing episodes of oxygen-deprived air alternating with 60 s intervals of room air. To deliver this sequence of concentration intervals to the participant, trained personnel physically attached and detached air-supply tubing to the participant's face mask. In example 1, the cumulative and absolute timing errors were measured while a trained administrator (S1) delivered a single sequence of AIH treatment (
Adequate flow to the face mask is important for maintaining safe and comfortable breathing during AIH treatment protocols. The PSA systems rely on pumps (e.g., vacuum) to distribute air mixtures through the breathing circuit. However, air flow from the PSA systems are oscillatory due to alternating pump phases and other mechanisms. The pulsatile air flow propagates from the generator to the face mask and varies according to generator flow settings. In Example 2, the amplitude and frequency of fluctuations in air flow is evaluated proximal to the face mask via the ‘manual’ delivery system (one PSA with reservoir bags) that delivered 10.0% and 20.9% FiO2. Air flow measurements were repeated using the ‘automated’ system (two PSA with reservoir bags).
An AIH delivery system must provide consistent levels of O2 to the face mask to accommodate variations in breathing (i.e., deep inhales, yawns) during AIH therapy. Breathing in low O2 often triggers episodes of deep breathing to increase tissue oxygenation, but also may exceed the available air supplied by the ‘manual’ single PSA system. Consistency in the O2 supply examined within and between the AIH delivery systems during quiet breathing of a study participant (S2). Similar to Example 1, each system delivered a sequence of AIH. An O2 sensor was attached proximal to the face mask and measured O2 concentrations during the AIH sequence. S2 was then instructed to take a series of deep breaths during a single 60 s bout of low O2. A similar protocol involved the use of an ‘automated’ AIH system.
AIH dosing: Precise timing and amplitude of air delivery ensure safe and reliable AIH treatments. Physical switching during ‘manual’ AIH delivery is subject to dosing accuracy and timing errors. The accuracy of the delivery systems (manual, automated) was estimated to the ‘ideal’ AIH protocol defined above. Specifically, the normalized root mean square error (NRMSE) of the goodness-of-fit (GOF, eq. 1) was computed between delivery systems and the ‘ideal’ delivery protocol.
where {tilde over (y)} is the ‘ideal’ output, y is the output from either the ‘manual’ or ‘automated’ delivery system, and
TE
abs=Σi=130|yi−{tilde over (y)}| (2)
Flow rate: While continuous air flow to the face mask ensures user comfort and stability of AIH treatment, there is potential for fluctuations in air flow within the breathing circuit that may compromise consistency of air delivery. Thus, the extent to which frequency, amplitude, and range of flow rate change was quantified during steady-state room air and low O2 air delivery. The peak amplitudes and ranges in measured flow rate were compared between the AIH systems (manual', ‘automated’) and FiO2 (low O2 at 10.0%, ambient O2 at 20.9%).
Oxygen concentrations: Consistent and reliable FiO2 to the face mask is necessary to maintain safe and accurate AIH treatments. Fluctuations in air flow from the PSA systems contribute to fluctuations in O2 concentrations during AIH protocols, but the magnitude of these fluctuations remains unclear. The relationship between air flow to the face mask and oxygen-deprived air generated from the breathing circuit of the ‘manual’ and ‘automated’ delivery systems was quantified. A major design feature of the ‘automated’ system is the addition of a mixing chamber air from the HYP-123 generator. To examine the extent to which the mixing chamber reduced fluctuations in constant-resistance FiO2, the mean absolute standard deviation (MAD) in fluctuations between the ‘automated’ delivery system (with and without the mixing chamber) and FiO2 (low O2 at 10.0%, ambient O2 at 20.9%) was compared.
During episodes of low O2 delivery, positive pressure from the PSA device ensures the AIH delivery system expels oxygen-rich air to the environment and delivers oxygen-depleted air to the breathing circuit. However, spontaneous deep breaths (e.g., yawn or sighs) and other patient specific ventilation patterns may disrupt this air separation due, in part, to pressure and/or the depletion of the available air supply by the single generator. Limited air flow from the ‘manual’ (single PSA) system during deep breathing contributes to increases in the inspiratory work of breathing and to negative pressure changes within the breathing circuit. The extent to which this vacuum may reduce generation of oxygen-depleted air needed to be characterized. Peak O2 concentration generated from a single versus a double PSA system were compared while a participant (S2) performed five consecutive deep breaths at 10.0% FiO2.
However, spontaneous deep breathes (e.g., yawn) may disrupt this air separation due, in part, to reduction in air volume within the breathing circuit. Limited air flow from the ‘manual’ (single PSA) system during deep breathing contributes to increases in the inspiratory work of breathing and to negative pressure changes within the breathing circuit. The extent to which this vacuum may reduce generation of oxygen-depleted air is not clear. Peak FiO2 generated from a single versus a double PSA system was compared while a participant (S2) performed five consecutive deep breaths at 10.0% FiO2.
Air temperature: Stable air temperature during AIH treatment is important for ensuring breathing comfort, as well as, for preserving SHAM blinding. However, the extent to which changes in O2 during AIH protocols may result in differences in air temperature when administering room air and low O2 is not known. Air temperature within the breathing circuit was measured during two sequences (30 episodes) of AIH and SHAM and quantified air temperature changes and compared these changes between the two air delivery methods.
All statistical analyses were preformed using SPSS® 26 (IBM SPSS Inc, USA) and reported data as mean±1 standard error (SE). Statistical significance corresponded to a p-value <0.05. The Levene Test was used to determine homogeneity of variances between the independent factors. If variances differed (p >0.05), non-parametric tests were used. The TEabs to a null expectation of 0 (no error) was used using a one-sample t-test. The effects of transitioning between room air and low O2 on TEabs was compared using a two-sample t-test. To compare the effects of AIH delivery systems on amplitude and range of the peak flow rate estimates, a linear mixed-model with fixed effects and Bonferroni corrections can be used for the multiple contrasts. A two-way analysis of variance (ANOVA) model provided comparison between the main effects of AIH delivery system (‘manual’, ‘automated’) and FiO2 (10.0%, 20.9%) and their interactions on fluctuation in O2 and temperature within the breathing circuit.
In this study, the performance of two AIH delivery systems was examined. The results include between-system comparisons for dose timing, air flow, FiO2, and air temperature constancy.
AIH dose timing: The ‘manual’ delivery system is less accurate in administering an AIH protocol at prescribed timing intervals than the ‘automated’ delivery system. Goodness-of-fit between ‘ideal’ and ‘manual’ AIH delivery equated to 34.8% as compared to 98.1% between ‘ideal’ and ‘automated’ AIH delivery (
Fluctuations in flow rate: Flow rates differed between the ‘manual’ and ‘automated’ AIH delivery systems (
Variations in FiO2: Consistency in FiO2 is important for ensuring safe and effective AIH treatment. The reduced accuracy of AIH delivery in the ‘manual’ system is due, in part, to inherent fluctuations in FiO2 (
Changes in breathing volume imposed by the participants' ventilation cause breath-by-breath fluctuations in FiO2 during AIH treatment. During quiet breathing, average flow rates are less than 0.2 liters s−1. However, deep breathing may exceed the available air supplied by the single PSA system since the required flow capacity is dictated by occasional extremes, rather than averages. Deep breaths in succession, with peak flow rates exceeding 1 liter s−1, depleted the ‘manual’ system's reservoir bags and reduced the PSA outlet resistance leading to less effective O2 removal. As a result, oxygen concentrations increased 65.7% during deep breathing of low O2 air. However, the ‘automated’ system's mixing chamber reduced the swing in FiO2 by 28.5% during extreme deep breathing.
Temperature during AIH delivery: Significant changes in temperature within the breathing circuit were observed during AIH and SHAM protocols. The temperature fluctuated approximately±2.2° C. The ‘manual’ delivery system produced marginally higher temperatures (26.6±0.1° C.) as compared to the ‘automated’ system (26.1±0.1° C.; p <0.001). The ‘manual’ system generated a small, but significant difference (p =0.001) in temperature between AIH (26.8±0.1° C.) and SHAM (26.4±0.1° C.). However, no significant temperature differences were found between AIH (26.2±0.1° C.) and SHAM (26.0±0.1° C.) using the ‘automated’ delivery system (p =0.6). The greatest fluctuations in air temperature occurred within 45 min of system start-up. The ‘automated’ air temperatures were compared after a 45 min warm-up. The average air temperature was significantly lower (p<0.001) before warm-up at 26.6±0.1° C. versus 27.0±0.1° C. after a 45 min warm-up.
Mild exposure to breathing low O2 (i.e., AIH) is a novel treatment to enhance motor function after SCI. While the ‘manual’ AIH delivery system enabled several exciting proof-of-principle experiments in humans, this technology faces design challenges that limit possible translation to clinical and home use. Here, significant inconsistencies exist in dose timing, volume flow rates, FiO2, and to a lesser extent temperature stability of the ‘manual’ AIH delivery system.
The ‘automated’ AIH delivery system improved dose timing accuracy. The new system outperformed the ‘manual’ system by more than 63%. This is not surprising since the automated system used programmable relay switch circuits to control the state of solenoid valves on the order of milliseconds. The transition time is a major contrast to the ‘manual’ system with an administrator who switched between air sources 100x slower. Manual switching resulted in accumulation of timing errors that equated to an extra dose of low O2 over the course of a daily exposure protocol. Fatigue may have resulted in larger errors in manual switching with time, but the results from S1 showed no positive correlation between the absolute timing error size and episode number. Timing errors are likely to vary drastically between and within administrators and treatment days. However, the ‘automated’ delivery system eliminates this variability and affords greater temporal consistency as compared to ‘manual’ AIH delivery protocols.
There are several other air delivery systems to consider, but present with deficiencies that limit their translation potential. Several commercial companies offer stand-alone PSA systems (e.g., HYP123; Hypoxico, Inc.) that transform enclosed rooms into high-altitude training experiences. While these systems are capable of achieving low O2 levels at or near 10%, these enclosures require several minutes for transition between ambient room air and low O2. They also do not ensure a room with uniform concentration of the prescribed air mixture. Alternatively, high-pressure gas cylinders may be a reasonable consideration since they have the capacity to deliver high precision air mixtures. Gas companies (e.g., Praxair Technology Inc., USA) provide customized gases, as well as various accessories such as check valves, fittings, regulators, alarms, and gauges. However, these cylinders require administrative operating expenses, gas handling equipment, and storage areas free from liquids, combustibles, and corrosive materials. Clinical facilities routinely accommodate these requirements, but at a premium.
Maintaining a net positive pressure of air flow to the facemask accommodates a broader range of end-users with varying breathing frequencies and tidal volumes. Average resting minute ventilation of healthy adults is between 0.09 to 0.35 liters While a single PSA meets these ventilatory demands, the required flow rate capacity needs to accommodate breath-by-breath variations in flow rates that exceed this average. A previous report showed that peak inspiratory flow rate can be nearly 4 times the average resting rate. Moreover, participants often yawn during AIH; while the physiological triggers that may induce yawns is debatable, a yawn induces rapid inspiration ˜400% greater than resting tidal volume. In either case, a second PSA with reservoir bags meets these transient increases volume and flow rate demands, as well as, ensures positive pressure at the mask for comfortable breathing.
While two PSA systems are sufficient to meet a broad range of flow rate demands, they may not be necessary. One alternative strategy to multiple PSAs is to increase the reservoir volume. Elastic reservoir bags reduce negative pressure (i.e., suction) caused when the end user's respiratory flow variations overcome the positive pressure supplied by the PSA. If the reservoir volume is emptied by several large, rapid breaths, then mask inflow is limited to the PSA flow rate. Any further inhalation is impeded, and PSA output pressure may drop by as much as 25.4 cm H2O, for a moderate increase in flow rate, along with a rise in O2 concentration. As was observed in one example participant (S2), deep inspiration raised the mean ventilation well above 1.0 liters s′ with peak flow rates 3 times the average, causing breathing difficulty as the inspiration rate was faster than the generators supplied. The resulting FiO2 climbs gently while two reservoir bags are being emptied. When the bags are depleted, O2 briefly jumps to about 17% at each deep breath. The ‘automated’ system doubles the reservoir volume to 12 liters, alleviates the breathing challenge due to higher flow resistance during deep inspiration and mitigates disturbance to O2 concentration. Notably, even when inflated, the reservoir bags do not deliver air with a sustained pressure. If charged to approximately 7.6 cm of water pressure, bag pressure drops to 1.3 cm after delivering 0.02-0.03 liters, requiring the subject to pull the gas through the hose system with noticeable breathing difficulty.
The ‘automated’ system also reduced unwanted fluctuations in steady-state FiO2 that were inherent to the ‘manual’ delivery system (
In this example, a stand-alone graphical user-interface to prescribe, monitor, and log dosing parameters and physiological data was implemented during AIH treatments. The user-interface enabled the administrator to preset the level of threshold detection for SPO2, HR, and BP parameters for end-user safety. Thus, the AIH protocol does not require an administrator to disconnect low O2 sources in response to cycle-to-cycle variations in the end-user's de-saturation and re-saturation rates in addition to keeping track of timing intervals. Further, override commands are implemented for the administrator to immediately stop low oxygen delivery at any point in the cycle if deemed necessary. Automated monitoring and logging of the end-user's vitals eliminates the possibility of adverse events resulting from prolonged exposures to low O2 even when the administrator fails to override the automated switching.
An ‘automated’ AIH delivery system that confers several advantages over the previous ‘manual’ AIH system is described. The automated system 1) incorporated digital control to automate precise interval timing for temporal consistency 2) eliminated large fluctuations in delivered O2 concentration to increase accuracy, 3) added physiological monitoring via closed loop feedback to increase safety, 4) added of continuous positive pressure to accommodate end user respiratory variations and breathing comfort, and 4) implemented a stand-alone graphical user interface for prescribing personalized treatment protocols, as well as, logging physiological responses. Together, these new features provide a consistent, safe, and flexible AIH delivery system for the development of new AIH treatment protocols.
In
Within this specification aspects have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that aspects of the present disclosure may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.
Thus, while the invention has been described in connection with particular aspects and non-limiting examples, the invention is not necessarily so limited, and that numerous other examples, uses, modifications and departures from the examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein.
Various features and advantages of the invention are set forth in the following claims.
The present application is based on and claims priority to U.S. Provisional Patent Application No. 62/925,306, filed on Oct. 24, 2019, which is incorporated herein by reference in its entirety.
This invention was made with government support under HD 081274 awarded by the National Institutes of Health and under W81XWH-15-2-0045 awarded by the Department of Defense. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/057357 | 10/26/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62925306 | Oct 2019 | US |
