Patent Application
20240252777
In conventional respiratory therapy systems, breathing gas is often humidified prior to delivery of the gas to the patient, in order to increase patient comfort and prevent drying out of the patient's airways, especially in the administration of high flow therapy (HFT) or high velocity therapy (HVT), such as high velocity nasal insufflation (HVNI). Accordingly, the humidity level of administered breathing gas, along with flowrate and temperature, is an important parameter in controlling these systems.
The systems, devices, and methods described herein relate to control of humidification of breathing gas provided by a respiratory therapy system. The methods described herein allow for control of breathing gas humidity independent of gas temperature and gas flowrate, thereby allowing a user or physician to independently set and control each of the temperature, flowrate, and humidity.
In one aspect, provided herein is a method for adjusting humidity of breathing gas supplied by a respiratory therapy system. The system comprises (i) a gas supply module configured to supply a flow of breathing gas; (ii) a liquid supply module configured to supply a flow of liquid; and (iii) a vapor transfer module configured to receive the flows of gas and liquid, humidify the gas, and output heated and humidified gas. The method comprises (a) supplying the flow of breathing gas from the gas supply module to the vapor transfer module; (b) supplying the flow of liquid from the liquid supply module to the vapor transfer module at a first liquid flowrate; (c) outputting the heated and humidified gas from the vapor transfer module at a first gas temperature, a first gas flowrate, and a first humidity; (d) adjusting the first liquid flowrate to a second liquid flowrate; and (e) outputting the heated and humidified gas from the vapor transfer module at about the first gas temperature, about the first gas flowrate, and a second humidity. A difference between the first humidity and second humidity is inversely proportional to the adjustment of the first liquid flowrate to the second liquid flowrate.
In a second aspect, provided herein is a respiratory therapy system configured to carry out the method of the first aspect.
The foregoing and other objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:
To provide an overall understanding of the systems, method, and devices described herein, certain illustrative embodiments will be described. Although the embodiments and features described herein are specifically described for use in connection with specific respiratory therapy systems, it will be understood that all the components and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to other types of respiratory therapy systems. The term “about” may be understood to mean within 20% or less of a value; for example, “about 40 L/min” can be understood as 32-48 L/min.
The systems, devices, and methods described herein relate to techniques for adjusting humidity of a breathing gas supplied to a patient from a respiratory therapy system. Some systems humidify breathing gas by flowing a liquid (e.g., water) past the gas in a vapor transfer device (e.g., a vapor transfer cartridge containing membrane(s), a convective flow humidifier). Such systems can be limited as to how many (and which) of the gas parameters (flowrate, temperature, and humidity) can be controlled independently of each other and with respect to parameters of liquid used for humidification, i.e., the liquid flowrate and liquid temperature. For example, a vapor transfer cartridge typically has a characteristic curve, which determines, for a given liquid temperature, liquid flowrate, and gas flowrate, what the absolute humidity of the output gas will be.
The variables (gas and liquid parameters) are further constrained when the same liquid that is used for humidification is also used for insulation of the breathing gas, because the liquid temperature of humidification is directly tied to the liquid temperature of insulation, which affects the gas temperature. At lower flowrates, the humidity will be higher and closer to the saturation level for the given gas temperature, which can lead to rain-out of the humidity into the gas flow path. At high flowrates, the humidity can be too low, which could be uncomfortable or harmful to the patient. Thus, the system is forced to compromise between low and high flowrates to accommodate the humidification constraints, or a different humidification technique must be used for different flowrate ranges, which narrows the range available to the physician when administering therapy with a given system and humidification technique. Accordingly, a method for independently controlling humidity would allow for a better range of therapy control on a given device.
In this example, the water temperature drops from 37.9° ° C. (at the delivery tube water inlet) to 37.8° C. (at the delivery tube water outlet). The water then enters the VTC and flows through the VTC from the water inlet to the water outlet, where the temperature has dropped to 37° C. The gas enters the VTC gas inlet at 38° C. and flows to the VTC gas outlet while heat and moisture are exchanged with the water flowing in the opposite direction. At the VTC gas outlet, the gas reaches 30.2 mg/L humidity. Along the delivery tube heat is exchanged with the water in the jacket, bringing the gas to a temperature of 37° C.
Provided herein is a method of adjusting the humidity of the gas by varying the liquid flow rate. Counterintuitively, lowering the water flowrate can be used to increase the humidity of the output gas for the same gas temperature and flowrate, when the temperature of the liquid exiting the humidifier is held constant. Lowering the liquid flowrate increases the liquid temperature gradient within the humidifier. If the liquid outlet temperature is held constant, then the liquid inlet temperature must be higher to account for the lower flowrate. The higher liquid inlet temperature increases the vapor pressure gradient between the liquid and the gas. Since the humidifier is in a counter-current arrangement, the higher temperature liquid is exchanging vapor with the gas that is about to exit the humidifier. The evaporation increases the water content of the gas, while evaporative cooling reduces how much the gas temperature rises. The result is that the gas output of the humidifier has a similar temperature when compared to a higher liquid flowrate, but has a greater humidity.
In some systems or therapies, the liquid flowrate may be inversely proportional to the gas flowrate. This will reduce humidity at lower gas flowrates to prevent rainout (condensation of water vapor in the delivery tube), and increase humidity at higher flowrates to improve humidification.
The foregoing is merely illustrative of the principles of the disclosure, and the apparatuses can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation. It is to be understood that the apparatuses disclosed herein, while shown for use in specific respiratory therapy systems, may be applied to apparatuses in other applications requiring humidification.
The methods described above can be implemented on a system including: (i) a gas supply module configured to supply a flow of breathing gas; (ii) a liquid supply module configured to supply a flow of liquid; and (iii) a vapor transfer module configured to receive the flows of gas and liquid, humidify the gas, and output heated and humidified gas.
The liquid supply module includes a heater configured to heat the liquid (e.g., water), a pump configured to circulate the liquid, and a reservoir configured to hold liquid and having an outlet port and a return port. The return port is in fluid communication with the vapor transfer module and configured to convey liquid from the vapor transfer module to the reservoir. In some implementations, the vapor transfer module includes a vapor transfer cartridge and a delivery tube. The vapor transfer cartridge has a gas inlet, a gas outlet, a liquid inlet, and a liquid outlet. The gas inlet receives the flow of breathing gas from the gas supply module, and the gas outlet outputs the heated and humidified breathing gas. The delivery tube has a gas lumen and a liquid lumen at least partially surrounding the gas lumen. The gas lumen is in fluid communication with the gas outlet of the vapor transfer cartridge so as to receive the heated and humidified gas from the gas outlet of the vapor transfer cartridge.
The delivery tube has a first end and a second end. The gas lumen receives the heated and humidified gas at the first end and conveys the heated and humidified gas to the second end. The liquid lumen has a first channel and a second channel. The first channel is configured to convey liquid from the first end to the second end, and the second channel is in fluid communication with the first channel at the second end and configured to convey the liquid from the second end to the first end. In some implementations, the second channel at the first end is in fluid communication with the liquid inlet of the vapor transfer cartridge, and the liquid inlet receives liquid from the second channel. In some implementations, the delivery tube further includes a first temperature sensor disposed at an inlet of the first channel and a second temperature sensor disposed at an outlet of the second channel. The first temperature sensor and second temperature sensor each measure a temperature, and a temperature difference between the measured temperatures can be less than 5%. In some implementations, a temperature difference between the measured temperatures is less than 20%, less than, 15%, less than 10%, or less than 5% of the first gas temperature. The temperature difference can be less than 1° C. In some implementations, the temperature difference is less than 5° C., 4° C., 3° C., 2° C., or 1° C.
In some implementations, the vapor transfer module and the liquid supply module define a liquid circulation loop, whereby liquid flows from the reservoir, to the heater, to the liquid lumen of the delivery tube, to the liquid inlet of the vapor transfer cartridge, through the vapor transfer cartridge, and to the reservoir via the return port. The liquid outlet of the vapor transfer cartridge is configured to convey liquid from the vapor transfer cartridge to the reservoir via the return port. In some implementations, the gas inlet and liquid outlet are disposed at a first end of the vapor transfer cartridge, and the gas outlet and liquid inlet are disposed at a second end of the vapor transfer cartridge, such that the liquid and gas flow through the vapor transfer cartridge in opposite directions. In some implementations, a liquid temperature at the liquid inlet is held constant before and after a temperature adjusting step as described above.
In some implementations, the system includes a nasal cannula coupled to the delivery tube and configured to convey the heated and humidified gas to the nares of a patient. In some implementations, the vapor transfer cartridge includes a plurality of hollow fibers. In some implementations, the vapor transfer cartridge includes a pleated membrane or a flat sheet membrane. In some implementations, the vapor transfer cartridge includes a heated wick. In some implementations, the gas supply module includes a blower configured to output the flow of breathing gas. In some implementations, the system includes a controller operatively coupled to the gas supply module and the liquid supply module and configured to adjust at least one of a gas temperature setpoint, a gas flowrate setpoint, a liquid flowrate setpoint, or a liquid temperature setpoint.
In some implementations, the second liquid flowrate is less than the first liquid flowrate, and the second humidity is greater than the first humidity. In some implementations, the second liquid flowrate is greater than the first liquid flowrate, and the second humidity is less than the first humidity. The first gas temperature can be 30 to 40° C. In some implementations, the first gas temperature is 25 to 45° C., or 30 to 40° C., or 32 to 38° C. The first gas flowrate can be 5 to 45 L/min. In some implementations, the first gas flowrate is 3 to 60 L/min, 4 to 50 L/Min, 5 to 45 L/min, 10 to 40 L/min, or 15 to 35 L/min. At least one of the first humidity or the second humidity can be 25-45 mg/L. In some implementations, at least one of the first humidity or the second humidity is 10-60 mg/L, 15-55 mg/L, 20-50 mg/mL, or 25-45 mg/L.
Base unit 202 may contain a blower configured to produce a flow of breathing gas. In the following, system 200 is described using a blower as an example; however, it is to be understood that base unit 202 (and the other base units described herein) may alternatively be connected to an external gas source such as a wall air outlet, an air tank, or an external blower. Furthermore, a VTC 216 is implemented in system 200; however, it is to be understood that alternatives may be implemented in system 200 (and the other systems described herein), such as a heated wire or hot pot humidifier. The alternatives may operate by disposing water over a heating plate in a chamber and flowing breathing gas into the chamber (either over the water or through the water) to be humidified. A heated wire can be disposed in a conduit to further heat the humidified breathing gas before delivering the breathing gas to a patient.
System 200 may further include a nasal cannula (not shown) coupled to patient connector 208. Alternatively, patient connector 208 may be a nasal cannula or other gas delivery device. In either case, system 200 may be operated with system parameters for high velocity respiratory therapy (e.g., the parameters in Tables 1 and 2). The nasal cannula or patient connector may be sized accordingly, and/or the blower may be operated at certain breathing gas flowrates. By using a blower, system 200 may absolve a need for an external source of pressurized air or breathing gas such as a pressurized tank or a wall air outlet.
In some implementations, there are certain cannula sizes that can be used on the high velocity respiratory therapy systems discussed herein due to certain system conditions or properties of the cannula. For example, there may be allowable cannula pressure drops for a given nasal prong inner diameter and flow setpoint. Table 2 shows exemplary ranges of cannula pressure drops for certain pressure drops and flow setpoints.
In some implementations, external reservoir 210 is a large container (>1 L, >2 L, >5 L, etc.) such as a bag or bottle, and the connecting tube 214 can be removably connected to auxiliary unit 204. Auxiliary unit 204 may be configured such that the liquid is fully enclosed in auxiliary unit 204 flowing from external reservoir 210. In this case, liquid is kept separate from base unit 202. This may prevent leaks and damage of components within base unit 202. In some implementations, gas path 212 is connected to the blower of base unit 202, but there is no other fluid communication between base unit 202 and auxiliary unit 204. Gas path 212 may be connected to base unit 202 by a valve, such as an occluder valve 452 of
While base unit 202 and auxiliary unit 204 are fluidically connected to at least allow breathing gas flow, it can be advantageous to otherwise minimize fluidic connections or contact between base unit 202 and auxiliary unit 204. For example, minimizing fluidic contact with base unit 202 may prevent damage to electronic components. As another example, previous systems have relied on conductive heating of liquid, which requires precise contact between two plates; thus, conductive heating is inefficient if precise contact cannot be established due to misalignment or deformation. Accordingly, couplings 222, 226, and 228 are configured to be contactless or non-contact couplings. Generally, this allows a sealed auxiliary unit without any openings and minimal requirements for tight tolerances. In some implementations, coupling 222 is a stator configured to magnetically couple to pump 224, which includes a rotor. Pump 224 may be shaped like a cup with a convex side protruding from auxiliary unit 204, and the stator may surround a cavity in recess 218, such that pump 224 sits within the cavity when auxiliary unit 204 is seated in recess 218. Pump 224 and coupling 222 may each be hermetically sealed, for example, to prevent fluid ingress into base unit 202. When auxiliary unit 204 is fully seated in base unit 202, the controller can operate the stator to magnetically generate rotation of the rotor of pump 224 to pump liquid through the auxiliary unit or through a jacket of delivery tube 206. As a result, the auxiliary unit 204 pumps liquid without an internalized power source or other electronic components to control the pump 224, and there is no need for liquid to flow through the base unit 202, which separately houses the controller and other components that may be susceptible to, e.g., water damage. Pump designs compatible with the present disclosure are described in U.S. patent application Ser. No. 15/783,566, the contents of which are hereby incorporated by reference in their entirety.
Similarly, coupling 226 may be a contactless or non-contact heating actuator, for example, heat actuator 326 of
Heated liquid may be used to heat, in turn, breathing gas. For example, delivery tube 206 may include a jacket configured to receive heated liquid and convey the heated liquid around an inner lumen that conveys the breathing gas. Heated liquid may travel along a full length of delivery tube 206 in a first direction towards patient connector 208, and then return in an opposite direction back to auxiliary unit 204. Heated liquid may also be conveyed into VTC 216 and vaporized into the breathing gas. For example, the liquid may be water used to humidify the breathing gas. Accordingly, the liquid may be heated to a target temperature, where the target temperature is a temperature at which the gas is to be delivered to the patient. The liquid may be circulated through auxiliary unit 204 and delivery tube 206 and back to the internal reservoir. In some implementations, the liquid travels a liquid path from the external reservoir to the internal reservoir (internal to auxiliary unit 204), then to a heating section (e.g., where the heating plate may be disposed), then through pump 224, then into the heating jacket of delivery tube 206, then into VTC 216, and then any remaining, un-vaporized liquid is returned to the internal reservoir. A similar configuration is described in further detail in relation to
Similar to coupling 226, coupling 228 may be a contactless or non-contact level sensor, for example, level sensor 328 of
Level sensor 228 may output one or more signals indicating the measured liquid level to the controller in base unit 202. The occluder valve or a pinch valve disposed along tube 214 can be used to isolate the volume of liquid in auxiliary unit 204. In implementations where liquid only leaves system 200 when vaporized into the breathing gas in VTC 216, the controller can determine the amount of liquid vaporized (i.e., the vaporization rate) or otherwise consumed (i.e., consumption rate) over time. In some implementations, this information is used to determine the flowrate of liquid needed from external reservoir 210 in order to keep the liquid level at a steady state, where the liquid flowrate from external reservoir 210 equals the vaporization rate, in order to, for example, prevent auxiliary unit 204 and VTC 216 from drying up or ensure the breathing gas is kept at a constant vapor concentration (e.g., humidity). In other implementations, the liquid level is not at a steady state, but the controller determines, based on the vaporization flowrate, an appropriate time interval at which to allow a fixed volume of the liquid to enter the internal reservoir from external reservoir 210 that is approximately equal to the amount of liquid vaporized during that time interval.
From the calculated vaporization rate, the controller may also compute the humidity of the breathing gas exiting VTC 216 in implementations where the liquid is water. Another device may be used to determine the flowrate (mass flowrate and/or volumetric flowrate) of breathing gas in system 200. Such a device may be disposed in base unit 202 to measure breathing gas entering or exiting the blower, or the device may be disposed in auxiliary unit 204 to measure breathing gas flowrate entering or exiting auxiliary unit 204 or VTC 216. The device may alternatively be disposed along or within delivery tube 206 or patient connector 208 for a patient-proximate measurement of the breathing gas flowrate. In any of these cases, the device outputs one or more signals indicating the breathing gas flowrate to the controller. Also knowing the consumption rate or vaporization rate, the controller can calculate the humidity of breathing gas based on the liquid consumption/vaporization rate and the breathing gas flowrate, because liquid in the closed auxiliary unit 204 may only exit system 200 as vapor in the breathing gas when liquid flow from external reservoir 210 is stopped.
Knowing the humidity can serve several purposes. For example, an inappropriately low or high humidity may indicate that auxiliary unit 204, VTC 216, or another component of system 200 has become defective and requires replacement, allowing the controller to halt operation of system 200 and notify the operator before the patient is harmed. As another example, the performance of system 200 may be monitored over time, using humidity as a monitored variable, in order to detect deterioration and extend the usable lifetime of system 200. In this case, there is no need to limit all devices to the performance of outliers during lifetime testing. In addition, knowing humidity, adjustment of a temperature within VTC 216 relative to a temperature within delivery tube 206 can allow for adjustment of the humidity if the humidity output is monitored for safety. In some implementations, system 200 stores (e.g., on a memory) a range of safe humidity levels for patient breathing gas, and the controller is configured to determine if the calculated humidity is within the safe range. If the calculated humidity falls outside of the safe range, the controller may adjust the power of pump 224 to adjust liquid flowrate and/or adjust the power of the blower to adjust breathing gas flowrate.
Latch 220 is configured to lock auxiliary unit 204 in recess 218 of base unit 202 when auxiliary unit 204 is correctly positioned/seated in recess 218 for proper operation of system 200 and interoperability between auxiliary unit 204 and base unit 202. A user may press against latch 220 to unlock auxiliary unit 204 and remove it from base unit 202. In order to ensure that auxiliary unit 204 is fully seated in recess 218 for proper operation, there may be one or more elements disposed in base unit 202 and auxiliary unit 204 configured to detect the presence, or the precise alignment of auxiliary unit 204 in recess 218. In some implementations, auxiliary unit 204 includes a RFID tag (e.g., RFID tag 350 of
Accordingly, the tag may also include information that can be read by the antenna or reader and transmitted to the controller or a memory of base unit 202. For example, the tag may include information describing the type of or feature in auxiliary unit 204, such as low flow, high flow, aerosolization, humidification, oxygenation, nitric oxide, helium, and/or closed loop oxygen control. The tag may also include information relating to the state of the specific auxiliary unit 204 and/or its various components. For example, the information may include use history (including the in-use date), a shelf-life or remaining lifetime, embedded licensing, and/or recommended operating parameters (limit flowrates or humidity). The controller may use any of the information described above to determine and execute appropriate adjustments to system 200 and any of its various components. For example, depending on the type or features of auxiliary unit 204, certain operations or features may be enabled or disabled by the controller in accordance with the in-use auxiliary unit 204.
RFID tags or other tags can provide additional information about an auxiliary unit such as the auxiliary unit type, when it was first used, the expiration date, etc. This can overcome the drawbacks of the above-mentioned systems. In some systems, the device needs to be aware of a change in auxiliary unit even if the capital unit is in standby. To detect an auxiliary unit change in these systems RFID may require the device to use too much power while in standby. As an example, an active valve can close the air path when the auxiliary unit is removed and close the water fill path when an auxiliary unit is installed. Such features may not function correctly if the auxiliary unit is added or removed when the device is off or in a standby mode. This can occur if the auxiliary unit is set up in advance to be ready for a patient. The device is off when the auxiliary unit is installed and water may flow uncontrolled into the device. It would be beneficial for the device to power on and close the valve.
In some implementations, auxiliary unit 204 incudes one or more magnets (e.g., alignment marker 348 of
System 200 may be configured to automatically switch to a stand-by or low-power mode under certain conditions. For example, system 200 may switch to stand-by mode when auxiliary unit 204 is not detected, when the blower is off and a user has not interacted with system 200 for a certain period of time, or when a user inputs a command to switch system 200 to the stand-by mode. When switching to stand-by or low-power mode, the controller may generate an alert to notify the user of the switch. System 200 may be configured to be powered by a standard wall outlet or a main battery. In either case, system 200 may include a reserve battery. The reserve battery may be a rechargeable battery, such as lithium-ion, lead-acid, nickel-cadmium, nickel-metal hydride, lithium-ion polymer, alkaline, or another equivalent. The reserve battery may be configured to provide power to system 200 when the wall outlet becomes unusable (e.g., during a power outage) or when the main battery requires replacement. In some implementations, system 200 can operate on solely the reserve battery for at least about 30 minutes, at least about 1 hour, at least about 2 hours, or at least about 5 hours. The stand-by or low-power mode may limit power usage of system 200 to a percentage of the maximum power usage of system 200 during normal operation (e.g., about 80%, about 70%, about 60%, about 50%, about 40%, about 30%, about 20%). In some implementations, the controller switches system 200 to the stand-by or low-power mode when the reserve battery is in use. When in stand-by or low-power mode, the controller may disable certain features, for example, to reduce power consumption. For example, the controller may disable heating elements or supplementary gas input, allowing operation of the blower and one or more alarms (e.g., auditory alarms, notifications on display 230).
System 200 may also include one or more temperature sensors, such as temperature sensors 342 and 344 of
Delivery tube 206 conducts the breathing gas to the patient. Jacketed delivery tubes are typically smaller in inside diameter than heated wire delivery tubes and have fewer related issues. For example, the weight of liquid needed to properly heat a larger tube can provide a poor user experience if the tube diameter is increased too much, because the user may have difficulty moving a tube substantially weighed down by the liquid. Smaller jacketed delivery tubes can work when the pressure of the pressure source is high enough. In system 200, breathing gas is pressurized and supplied from the blower in base unit 202, without external pressurization in some implementations, so limited pressure may be available. With a blower, the tube diameter needs to be increased to account for a lower pressure source. It may be advantageous to size a cross-sectional diameter of delivery tube 206 to be as large as possible, in order to accommodate the lower back pressure while maintaining functionality. Generally, an increased diameter increases the weight of the delivery tube due to the larger volume of liquid required to heat the gas. Increasing the diameter can also lead to water accumulation in the delivery tube. Unlike the larger heated wire tubes, which must be tilted to drain liquid to the patient, the smaller jacketed tube may deliver water to the patient by simply increasing the flow above a certain threshold where the water may be conducted along the delivery tube by the flow of breathing gas. Accordingly, an upper limit of the diameter may be set based on, when operating at a minimum breathing gas flowrate, the velocity of breathing gas is sufficient to convey any liquid that has built-up in delivery tube 206 as rain-out to patient connector 208 where it may be collected and removed. In some implementations, the breathing gas flowrate is 5 L/min, and the delivery tube inner diameter is less than or equal to about 0.26 in. Delivery tube 206 may be constructed of a flexible material as to allow a user or operator to manipulate delivery tube 206 without obstructing breathing gas flow.
The increased diameter can also make the delivery tube more prone to kinking. Accordingly, delivery tube 206 may be constructed to be kink resistant. In some implementations, delivery tube 206 includes a jacket. As discussed above, heated liquid may be used to heat, in turn, breathing gas. For example, delivery tube 206 may include a jacket configured to receive heated liquid and convey the heated liquid around an inner lumen that conveys the breathing gas. Heated liquid may travel along a full length of delivery tube 206 in a first direction towards patient connector 208, and then return in an opposite direction back to auxiliary unit 204. In some implementations, the jacket includes a plurality of ribs extending in a radial direction through the jacket from a first conduit defining a breathing gas lumen to a second conduit, wherein the jacket is defined as the annular space between the first conduit and the second conduit. The radial ribs define two or more channels of the jacket through which liquid may flow. The radial ribs allow bending of delivery tube 206 in any direction without kinking by preventing collapse of the inner breathing gas conduit when delivery tube 206 is bent. In some implementations, under flexure of delivery tube 206, one or more of the channels may collapse, but at least some of the channels and the breathing gas lumen remain open to allow for liquid and breathing gas flow, respectively. The jacket having radial ribs may mimic a thick-walled tube to prevent collapse of the breathing gas lumen. In some implementations, the breathing gas lumen wall has a thickness proportional to the breathing gas lumen inside diameter. In some implementations, the outer wall, defining the jacket, has a thickness proportional to the outer diameter of delivery tube 206 minus the inner diameter of the breathing gas lumen. In some implementations, each radial rib has a width proportional to the wall thickness of the breathing gas lumen.
Display 230 may be configured to show one or more parameters of system 200. For example, display 230 shows any of: breathing gas flowrate, liquid vaporization/consumption rate, humidity, liquid level, breathing gas velocity, heating plate temperature, and liquid temperature. In some implementations, display 230 acts as an interface for both alerting the user of system parameters and for accepting user inputs. User inputs may include target values for any of these parameters. The user inputs may be transmitted to the controller, which is configured to adjust the parameters, for example, by actuating one or more of the components of system 200.
As described above in relation to
The various components in base unit 302 may be configured to couple to corresponding components of auxiliary unit 304 in a non-contact manner. These components may be operatively coupled to a controller in base unit 302 for actuation and/or electronic communication. In some implementations, stator 322 is configured to magnetically couple to a rotor of pump 324. By magnetically coupling to the rotor, stator 322 may induce rotational motion in the rotor for non-contact control of pump 324. Heat actuator 326 may convey by non-contact means heat to or generate heat in heating plate 327 immersed in liquid. Heat actuator 326 may be operatively coupled to the controller to allow for indirect actuation of the rate at which heat is transferred to liquid surrounding heating plate 327. In some implementations, heat actuator 326 is a coil configured to generate a current in heating plate 327 via induction, the current generating heat due to a resistance in heating plate 327. The generated heat may transfer from immersed heating plate 327 to liquid on either side. In some implementations, level sensor 328 is a capacitive sensor configured to measure capacitance in internal reservoir 332. Internal reservoir 332 may have a constant cross-section 336, so the measured capacitance is indicative of a liquid level in internal reservoir 332. By utilizing capacitive sensing, the system may provide an early warning of low liquid levels and active control of the water level in the system. Measurements of flow rate and humidification may also be more accurate with the use of capacitive sensing to accurately measure remaining liquid water.
In some implementations, RFID reader 351 detects the presence of RFID tag 350 when auxiliary unit 304 is within recess 318. RFID reader 351 may read information stored on RFID tag 350. In some implementations, alignment marker 348 is disposed in latch 320, and alignment sensor 349 is configured to detect the presence of alignment marker 348 when latch 320 is in a locked position. Latch 320 in an unlocked position 321 is depicted in
Liquid may flow out of internal reservoir 332 to heating plate 327 and pump 324 due to hydrostatic pressure resulting from the height of internal reservoir 332 positioned above heating plate 327 and pump 324. In some implementations, pump 324 generates a suction pressure that draws liquid from internal reservoir 332, past heating plate 327, and into pump 324. Rotational motion of a rotor (not shown) in pump 324 may be used to convey the liquid along a flow path. The flow path may be partially enclosed in auxiliary unit 304. In some implementations, system 300 further includes a jacketed delivery tube (such as delivery tubes 206 and 406 of
In some implementations, pump 324 conveys the liquid in a cyclic manner, in which liquid outputted from pump outlet 346 is pumped first through the delivery tube jacket, then through the VTC, into internal reservoir 332 (e.g., through a recycled liquid reservoir inlet not shown), and finally past heating plate 327 before returning into pump 324. In this case, pump 324 generates enough pressure to convey the liquid through an entire cycle of this flow path for the liquid to return to pump 324. This ordered flow path may define a cycle or loop of fluid flow. This loop may be a closed loop, for example, if valve 340 is closed to prevent fluid flow through external tube 314. The loop may be sealed such that, when the loop is closed, liquid only leaves the loop as vapor in the VTC. In some implementations, the volume of liquid in the loop is at a steady state such that the rate of liquid leaving the loop as vapor in the VTC is equal to the rate of liquid entering the loop through tubes 314 and 315 from external reservoir 310. In other implementations, discrete volumes of the liquid are conveyed from external reservoir 310 through tubes 314 and 315 to the internal reservoir 332 at time intervals, such that the discrete volume for a given time interval is equal to the amount of liquid vaporized during that time interval.
Valve 340 may be used to isolate the volume of liquid in the loop, for example, by closing valve 340 to stop all liquid flow through tubes 314 and 315 from external reservoir 310. In some implementations, level sensor 328 outputs one or more signals to the controller in base unit 302 indicative of the liquid level in internal reservoir 332. Internal reservoir 332 may have constant cross-section 336, such that liquid level may be directly proportional to the volume of liquid in internal reservoir 332. When liquid flow is occluded by valve 340, liquid may only exit the loop by vaporization in the VTC. The controller can determine the vaporization rate (or consumption rate of liquid by the VTC) based on a change in liquid level in internal reservoir 332 over a period. If the controller also knows the breathing gas flowrate, for example, by receiving one or more signals indicating the flowrate, then the controller can be configured to determine the vapor content or humidity of the breathing gas using the breathing gas flowrate measurement(s) and the liquid level measurements. The absolute humidity can also be determined by the controller by also taking into account temperature measurements, for example, indicated by one or more signals transmitted to the controller by temperature sensors configured to measure the temperature of the breathing gas in the VTC, at the VTC exit, or in the delivery tube
While external valves such as valve 340 can be used to control liquid flow from an external reservoir, it can be advantageous have a valve built into an auxiliary unit to, for example, allow for optimized control of the liquid flow by a controller. Furthermore, as the use of breathing gas and liquid is intertwined, a built-in valve that provides simultaneous control over breathing gas and liquid flows may enable further optimization and ease of control.
In accordance with the implementations described above and in the following, an auxiliary unit for a respiratory therapy system is provided herein.
Delivery tube 406 is configured to receive a flow of breathing gas from auxiliary unit 404 and convey the breathing gas to a patient, through patient connector 408 at the distal end of delivery tube 406. In some implementations, a nasal cannula is connected to patient connector 408 to provide the breathing gas into at least one nare of the patient. The breathing gas may be humidified with the liquid by a VTC in auxiliary unit 404. Pump 424 may convey the liquid along a flow path, including through the VTC in which at least a portion the liquid may be vaporized into the breathing gas, which is simultaneously passed through the VTC. When auxiliary unit 404 is seated in the base unit, pump 424 may couple to a pump actuator in the base unit, and the pump actuator may be operatively coupled to a controller, which may control the power supplied to pump 424. For example, pump 424 may include a rotor, which is configured to magnetically couple to a stator in the base unit. Through the magnetic coupling, rotational motion of the rotor is generated and used to convey fluid along the flow path. In some implementations, the flow path includes a jacket of delivery tube 406.
Latch 420 allows auxiliary unit 404 to be locked and unlocked from its fully seated position in the base unit. Latch 420 may enable locking of auxiliary unit 404 by having a ridge that resides in a notch in the base unit. A user or operator may press against latch 420 to release latch 420 from the notch and unlock auxiliary unit 404 when removing it from the base unit. Latch 420 may have one or more components embedded in it. For example, a marker, such as alignment marker 348 of
Auxiliary unit outlet 472 functions as a port for connection of delivery tube 406 to auxiliary unit 404 for transmission of the breathing gas. Outlet 472 may have a shape such that delivery tube 406 can bend and rotate at outlet 472 without being kinked by the edges of outlet 472. The shape of outlet 472 may also prevent dislodging of delivery tube 406 from auxiliary unit 404. In some implementations, outlet 472 is cone shaped. In some implementations, outlet 472 is chamfered. In some implementations, outlet 472 is filleted. Outlet 472 may be configured to have no hard edges that may kink or damage delivery tube 406; for example, outlet 472 may be rounded.
Liquid entering auxiliary unit 404 through liquid tube connector 462 is directed to reservoir inlet 434 by an internal tube (not shown), such as internal tube 315 of
Liquid flows or is drawn into pump 424 from the heating section. The pump expels liquid out of pump outlet 446, which is in fluid communication with connector liquid outlet 470 of delivery connector 468. Delivery connector 468 may be an overmolded rubber piece having one or more lumens. Connector liquid inlet 470 conveys pumped, heated liquid from pump outlet 446 into a jacket of delivery tube 406. The jacket concentrically surrounds an inner gas conduit through which breathing gas is conveyed, such that the heated liquid flowing through the jacket insulates the breathing gas in the inner gas conduit. This feature may be advantageous as to maintain a sufficiently high breathing gas temperature in order to prevent rain-out of vapor in the breathing gas. Rain-out occurs when vapor in the breathing gas condenses into its liquid form during gas delivery. This condensation can cause obstruction of delivery tube 406, patient connector 408, or a nasal cannula connected to patient connector 408. The heated liquid travels in two directions in the jacket, and the jacket accordingly includes at least two lumens or channels, where each lumen or channel connects to either connector liquid outlet 470 or connector liquid inlet 471. For example, liquid is pumped through connector liquid outlet 470 into a first jacket channel, which conveys the liquid along delivery tube 406 in a first direction towards patient connector 408. At the distal end of delivery tube 406, where patient connector 408 is disposed, the liquid may change directions and enter a second channel which conveys the liquid along delivery tube 406 in a second direction which is substantially opposite of the first direction. The second channel conveys the liquid into connector liquid inlet 471 of delivery connector 468.
Connector liquid inlet 471 is in fluid communication with VTC liquid inlet 466 in order to convey the fluid from the jacket to VTC 416. Within VTC 416, liquid may be vaporized into the breathing gas conveyed into VTC 416 through first cap 464. For example, the liquid may be water, and VTC 416 may output from second cap 465 a flow of humidified breathing gas containing water vapor. For vaporization to occur, the temperature in VTC 416 may be at or near the gas therapy temperature. Heating plate 427 may heat the liquid to a sufficiently high temperature, e.g., about 100° F. VTC 416 may contain a plurality of fibers, which allow vapor to pass from the liquid flow into the breathing gas flow. Liquid that is not vaporized in VTC 416 may flow out of VTC liquid outlet 467, which returns the liquid to internal reservoir 432.
Breathing gas exiting second cap 465 of VTC 416 is directed through connector gas outlet 469 of delivery connector 468 into delivery tube 406. The breathing gas, which may be humidified or contain vapor, flows through the inner gas conduit of delivery tube 406 and is insulated or heated by liquid flowing through the jacket. At patient connector 408, the breathing gas may be directed directly to the patient or into one or more additional devices, such as a face mask or a nasal cannula.
Occluder valve 452 is configured to mate with the base unit when auxiliary unit 404 is fully seated. The base unit may include a controller, an actuator, and a gas path valve seal. The controller operates the actuator to adjust a position of the gas path valve seal in order to control breathing gas flow from the base unit into auxiliary unit 404. The gas path valve seal may be raised against the liquid path valve seal 457 in order to simultaneously control liquid flowrate through occluder valve 452, because liquid path valve seal 457 is a rigid piece joined to flexible portion which may be flexed to raise liquid path valve seal 457 to narrow a gap between liquid path valve seal 457 and valve liquid inlet 458. The actuator, gas path valve seal, and liquid path valve seal may have, but are not limited to, three positions, which are summarized in Table 3. The controller may operate the actuator to switch between each of these positions based on system inputs or received signals. Breathing gas may be directed by valve 452 into gas path 412, which conveys breathing gas into first cap 464 of VTC 416. Liquid may be directed by valve 452 into internal tube 415, which conveys liquid into internal reservoir 432.
Delivery tube 406 is connected to delivery connector 468 at auxiliary unit outlet 472 for receiving breathing gas and liquid flows. Delivery tube 406 includes an inner gas conduit 407 configured to receive breathing gas from second cap 465 of VTC 416 through connector gas outlet 469 of delivery connector 468. Delivery tube 406 includes a first jacket channel 474 configured to receive liquid from pump outlet 464 through connector liquid outlet 470 of delivery connector 468. Liquid flows through first jacket channel 474 and a second jacket channel 475, for example, to heat or insulate the breathing gas in inner gas conduit 407. In some implementations, first jacket channel 474 conveys liquid in a first direction away from auxiliary unit outlet 472 and towards patient connector 408. First and second jacket channels 474 and 475 each have distal ends disposed within patient connector 408, which may allow for fluid communication between first and second jacket channels 474 and 475. For example, the liquid flows in the first direction through first jacket channel 474, and, upon reaching patient connector 408, flows out of the distal end of first jacket channel 474 and into the distal end of second jacket channel 475. Liquid may then flow through second jacket channel 475 in a second direction which may be substantially opposite of the first direction. Second jacket channel 475 conveys the liquid back into delivery connector 468 through connector liquid inlet 471. In some implementations, first jacket channel 474 covers a first portion of inner gas conduit 407, the first portion having an approximately semi-circular cross-sectional shape. Second jacket channel 475 may cover a second portion on the opposite side of inner gas conduit 407, the second portion having an approximately semi-circular cross-sectional shape. Auxiliary outlet 472 in this implementation has a rounded (filleted) shape, which may prevent kinking of delivery tube 406, and occlusion of inner gas conduit 407, first jacket channel 474, and second jacket channel 475 when delivery tube 406 is bended or flexed.
First jacket channel 474 and second jacket channel 475 are divided into sub-channels 474a-d and 475a-d by a plurality of radial ribs. Each radial rib extends from an inner wall defining inner gas conduit 407 to an outer wall of delivery tube 406, wherein the annular space between the inner wall and outer wall defines the jacket. Each pair of radial ribs defines one sub-channel of the jacket through which liquid flows. The radial ribs allow bending of delivery tube 406 in any direction without kinking by preventing collapse of inner gas conduit 407 when delivery tube 406 is bent. In some implementations, under flexure of delivery tube 406, one or more of the sub-channels 474a-d and 475a-d may collapse or become occluded, but at least some of the sub-channels 474a-d and 475a-d and inner gas conduit 407 remain open to allow for liquid and breathing gas flow, respectively. The jacket having radial ribs may mimic a thick-walled tube to prevent collapse of inner gas conduit 407. In some implementations, the inner wall defining inner gas conduit 407 has a thickness proportional to an internal diameter of inner gas conduit 407. In some implementations, the outer wall, defining the jacket, has a thickness proportional to the overall diameter of delivery tube 406 minus the internal diameter of inner gas conduit 407. In some implementations, each radial rib has a width proportional to the inner wall thickness.
In
As described above, first jacket channel 474 is in fluid communication with connector liquid outlet 470 in order to receive liquid from pump outlet 446. Liquid is flowed or pumped through the sub-channels 474a-d and then through sub-channels 475a-d of second jacket channel 475. Inner gas conduit 407 is in fluid communication with connector gas outlet 469 to receive breathing gas from VTC second cap 465.
Tab 476 is disposed at the top of heating plate 427, near internal reservoir 432. In some implementations, tab 476 is disposed at the top of heating plate 427 such that, when liquid in internal reservoir 432 reaches a low enough level, tab 476 is exposed while the rest of heating plate 427 remains immersed in liquid. When auxiliary unit 404 is fully seated in the base unit, a temperature sensor (such as temperature sensor 342 of
It should be understood that the systems and devices shown in
Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented.
The systems and methods described may be implemented locally on a respiratory therapy system or a controller of a respiratory therapy system. The respiratory therapy system may include a data processing apparatus. The systems and methods described herein may be implemented remotely on a separate data processing apparatus. The separate data processing apparatus may be connected directly or indirectly to the respiratory therapy system through cloud applications. The respiratory therapy system may communicate with the separate data processing apparatus in real-time (or near real-time).
In general, embodiments of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter affecting a machine-readable propagated signal, or a combination of one or more of them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus.
A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.
The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).
Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices.
Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made part of this application.
Item 1. A method for adjusting humidity of breathing gas supplied by a respiratory therapy system, the system including:
Item 2. The method of item 1, wherein the liquid supply module includes:
Item 3. The method of any of items 1-2, wherein the vapor transfer module includes:
Item 4. The method of item 3, wherein the vapor transfer cartridge includes:
Item 5. The method of item 4, wherein the delivery tube includes:
Item 6. The method of item 5, wherein the delivery tube includes:
Item 7. The method of item 6, wherein the liquid lumen includes:
Item 8. The method of item 7, wherein the second channel at the first end is in fluid communication with the liquid inlet of the vapor transfer cartridge, and the liquid inlet receives liquid from the second channel.
Item 9. The method of item 7, wherein the delivery tube further includes a first temperature sensor disposed at an inlet of the first channel and a second temperature sensor disposed at an outlet of the second channel.
Item 10. The method of item 9, wherein the first temperature sensor and second temperature sensor each measure a temperature, and a temperature difference between the measured temperatures is less than 5% of the first gas temperature.
Item 11. The method of item 10, wherein the temperature difference is less than 1° C.
Item 12. The method of any of items 5-11, wherein the vapor transfer module and the liquid supply module define a liquid circulation loop, whereby liquid flows from the reservoir, to the heater, to the liquid lumen of the delivery tube, to the liquid inlet of the vapor transfer cartridge, through the vapor transfer cartridge, and to the reservoir via the return port.
Item 13. The method of any of items 4-12, wherein the liquid outlet of the vapor transfer cartridge is configured to convey liquid from the vapor transfer cartridge to the reservoir via the return port.
Item 14. The method of any of items 4-13, wherein the gas inlet and liquid outlet are disposed at a first end of the vapor transfer cartridge, and the gas outlet and liquid inlet are disposed at a second end of the vapor transfer cartridge, such that the liquid and gas flow through the vapor transfer cartridge in opposite directions.
Item 15. The method of any of items 4-14, wherein a liquid temperature at the liquid inlet is held constant before and after the adjusting step.
Item 16. The method of any of items 3-15, wherein the system further includes a nasal cannula coupled to the delivery tube and configured to convey the heated and humidified breathing gas to nares of a patient.
Item 17. The method of any of items 3-16, wherein the vapor transfer cartridge includes a plurality of hollow fibers.
Item 18. The method of any of items 3-16, wherein the vapor transfer cartridge includes a pleated membrane or a flat sheet membrane.
Item 19. The method of any of items 3-16, wherein the vapor transfer cartridge includes a heated wick.
Item 20. The method of any of items 1-19, wherein the gas supply module includes a blower configured to output the flow of breathing gas.
Item 21. The method of any of items 1-20, wherein the system further includes:
Item 22. The method of any of items 1-21, wherein the second liquid flowrate is less than the first liquid flowrate, and the second humidity is greater than the first humidity.
Item 23. The method of any of items 1-21, wherein the second liquid flowrate is greater than the first liquid flowrate, and the second humidity is less than the first humidity.
Item 24. The method of any of items 1-23, wherein the first gas temperature is 30 to 40° C.
Items 25. The method of any of items 1-24, wherein the first gas flowrate is 5 to 45 L/min.
Item 26. The method of any of items 1-25, wherein at least one of the first humidity or the second humidity is 25-45 mg/L.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/988,583, filed on Mar. 12, 2020, and entitled “SYSTEMS AND METHODS FOR HIGH-VELOCITY RESPIRATORY THERAPY”, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/031170 | 5/26/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63194595 | May 2021 | US |
