CONTROL SCHEMES FOR MECHANICAL COUGH

This disclosure relates to control schemes for a system including mechanical cough functionality, and corresponding methods. Among other benefits, this disclosure reduces if not eliminates retrograde displacement of secretions within a patient's airway during a mechanical cough mode.

TECHNICAL FIELD

This disclosure relates to control schemes for a system including mechanical cough functionality, and corresponding methods.

BACKGROUND

Respiratory ventilation may be characterized as including both an inspiratory phase and an exhalation phase. During the inspiratory phase, inspiratory gases are drawn into the lungs, and during the exhalation phase, exhalation gases are expelled from the lungs.

Mechanical ventilators are used to assist with breathing. Conventional ventilators typically push inspiratory gases including oxygen into the patient's lungs. Many patients who use a ventilator also need other types of assistance related to treating and maintaining their airways and lungs. For example, some patients may use a nebulizer to deliver drugs to their lungs and/or airways. Further, some patients may need help clearing secretions from their lungs and/or airways.

Some patients may also need cough assistance. To use some known cough assistance devices, which may be referred to as mechanical insufflation-exsufflation (MIE) devices, a patient must be disconnected from mechanical ventilation, and connected to a separate device. After a cough assistance, or MIE, maneuver is performed, the patient must be disconnected from the MIE device, and reconnected to the mechanical ventilation. Often, suctioning of the patient airway is also performed after the patient has been disconnected from the MIE device and reconnected to the mechanical ventilation to remove secretions not adequately cleared from the patient airway during the MIE maneuver.

SUMMARY

In some aspects, the techniques described herein relate to a system, including: a respiratory device configured to deliver fluid to a patient, wherein the respiratory device is operable in a mechanical cough mode; and a controller configured to issue one or more commands to the respiratory device such that, during an insufflation phase of the mechanical cough mode, (i) a flow rate of the fluid conducted to the patient by the respiratory device is substantially constant throughout the insufflation phase, or (ii) a flow rate of the fluid conducted to the patient by the respiratory device gradually increases throughout the insufflation phase.

In some aspects, the techniques described herein relate to a system, wherein, during the insufflation phase of the mechanical cough mode, a flow rate of the fluid conducted to the patient by the respiratory device is substantially constant throughout the insufflation phase.

In some aspects, the techniques described herein relate to a system, wherein, during the insufflation phase of the mechanical cough mode, a flow rate of the fluid conducted to the patient by the respiratory device gradually increases throughout the insufflation phase.

In some aspects, the techniques described herein relate to a system, wherein the controller is configured to issue one or more commands to the respiratory device such that, during the insufflation phase of the mechanical cough mode, the pressure of the fluid conducted to the patient by the respiratory device substantially follows a line having a constant positive slope.

In some aspects, the techniques described herein relate to a system, wherein the controller is configured to issue one or more commands to the respiratory device such that, during the insufflation phase of the mechanical cough mode, the pressure of the fluid conducted to the patient by the respiratory device oscillates relative to the line.

In some aspects, the techniques described herein relate to a system, wherein the controller is configured to issue one or more commands to the respiratory device such that, during the insufflation phase of the mechanical cough mode, the flow rate of the fluid conducted to the patient by the respiratory device substantially follows a line having a constant positive slope.

In some aspects, the techniques described herein relate to a system, wherein the controller is configured to issue one or more commands to the respiratory device such that, during the insufflation phase of the mechanical cough mode, the flow rate of the fluid conducted to the patient by the respiratory device oscillates relative to the line.

In some aspects, the techniques described herein relate to a system, further including: a connection; and a patient interface connected to the connection, wherein the respiratory device is configured to conduct flow to the patient through the patient interface via the connection.

In some aspects, the techniques described herein relate to a system, further including: a pressure sensor; and a flow rate sensor, wherein the controller is configured to interpret signals from the pressure sensor as a pressure of the fluid conducted to the patient by the respiratory device and to interpret signals from the flow rate sensor as a flow rate of the fluid conducted to the patient by the respiratory device.

In some aspects, the techniques described herein relate to a system, wherein the respiratory device is operable in a ventilation mode.

In some aspects, the techniques described herein relate to a system, wherein: the respiratory device is a ventilator, and the controller is configured to issue one or more commands to the ventilator such that the mechanical cough mode is activated periodically.

In some aspects, the techniques described herein relate to a system, wherein the respiratory device is a ventilator or a mechanical insufflation-exsufflation device.

In some aspects, the techniques described herein relate to a method, including: conducting fluid to a patient using a respiratory device operating in a mechanical cough mode such that, during an insufflation phase of the mechanical cough mode, (i) a flow rate of the fluid conducted to the patient by the respiratory device is substantially constant throughout the insufflation phase, or (ii) a flow rate of the fluid conducted to the patient by the respiratory device gradually increases throughout the insufflation phase.

In some aspects, the techniques described herein relate to a method, wherein the pressure of the fluid conducted to the patient by the respiratory device substantially follows a line having a constant positive slope.

In some aspects, the techniques described herein relate to a method, wherein the pressure of the fluid conducted to the patient by the respiratory device oscillates relative to the line.

In some aspects, the techniques described herein relate to a method, wherein

the flow rate of the fluid conducted to the patient by the respiratory device substantially follows a line having a constant positive slope.

In some aspects, the techniques described herein relate to a method, wherein the flow rate of the fluid conducted to the patient by the respiratory device oscillates relative to the line.

In some aspects, the techniques described herein relate to a method, wherein the respiratory device is configured to conduct fluid to the patient through a patient interface via a connection.

In some aspects, the techniques described herein relate to a method, wherein a controller issues one or more commands to the respiratory device in response to signals from a pressure sensor or a flow rate sensor.

In some aspects, the techniques described herein relate to a method, wherein the respiratory device is operable in a ventilation mode.

DETAILED DESCRIPTION

This disclosure relates to control schemes for a system including mechanical cough functionality, and corresponding methods. Among other benefits, this disclosure reduces if not eliminates retrograde displacement of secretions within a patient's airway during mechanical insufflation-exsufflation (MIE), which is referred to herein as mechanical cough, and is sometimes referred to as mechanically assisted cough.

FIG.1is a block diagram schematically illustrating an exemplary system10that includes a respiratory device100with integrated mechanical cough functionality for use by a patient102, which in an example of this disclosure is a human patient. InFIG.1, the respiratory device is incorporated into a larger device which also functions as a ventilator. While a ventilator is shown, this disclosure extends to other respiratory devices that are not incorporated into ventilators, including dedicated mechanical insufflation-exsufflation (MIE) devices. Further, while a particular ventilator is described below and shown inFIG.1, this disclosure extends to other ventilator configurations.

The respiratory device100may be configured to provide both traditional volume controlled ventilation and pressure controlled ventilation. The respiratory device100has an optional multi-lumen tube connection103, a main ventilator connection104, and a patient oxygen outlet105. The patient102has a patient interface, or connection,106(e.g., a tracheal tube, a nasal mask, a mouthpiece, and the like) that is connectable to the main ventilator connection104and/or the patient oxygen outlet105by a patient circuit110.

As will be described below, the patient circuit110may be implemented as an active patient circuit or a passive patient circuit. Optionally, when the patient circuit110is implemented as an active patient circuit, the patient circuit110may include one or more ports111configured to be connected to the optional multi-lumen tube connection103. The port(s)111allow one or more pressure signals109to flow between the optional multi-lumen tube connection103and the patient circuit110. A pressure signal may be characterized as gas(es) obtained from a fluid (and/or gas) source for which a pressure is to be measured. The gas(es) obtained are at the same pressure as the fluid (and/or gas) source.

The main respiratory device100connection104is configured to provide gases112that include room air114optionally mixed with oxygen. While identified as being “room air,” the room air114may include air obtained from any source external to the respiratory device100. The gases112may be used as inspiratory gases (during the inspiratory phase of a breath) or insufflation gases used during the insufflation phase of a cough. The main respiratory device100connection104is configured to receive gases113, which may include exsufflation gases exhaled by the patient102during an exsufflation phase of a cough.

The air114is received by the respiratory device100via a patient air intake116. The oxygen that is optionally mixed with the air114may be generated internally by the respiratory device100and/or received from an optional low pressure oxygen source118(e.g., an oxygen concentrator), and/or an optional high pressure oxygen source120. When the oxygen is generated internally, the respiratory device100may output exhaust gases (e.g., nitrogen-rich gas122) via an outlet vent124. Optionally, the respiratory device100may include a low pressure oxygen inlet126configured to be coupled to the optional low pressure oxygen source118and receive optional low pressure oxygen128therefrom. The respiratory device100may include an optional high pressure oxygen inlet130configured to be coupled to the optional high pressure oxygen source120and receive optional high pressure oxygen132therefrom.

The patient oxygen outlet105is configured to provide doses or pulses of oxygen140to the patient connection106(via the patient circuit110) that are synchronized with the patient's breathing. Unlike the gases112provided by the main respiratory device100connection104, the pulses of oxygen140do not include the air114.

The gases112and/or the pulses of oxygen140delivered to the patient circuit110are conducted thereby as inspiratory or insufflation gases108to the patient connection106, which at least in part conducts those gases into the patient's lung(s)142. Whenever the patient exhales during the exhalation phase of a breath or exsufflation phase of a cough, exhaled gases107enter the patient circuit110via the patient connection106. Thus, the patient circuit110may contain one or more of the following gases: the gases112provided by the respiratory device100, the pulses of oxygen140, and the exhaled gases107. For ease of illustration, the gases inside the patient circuit110will be referred to hereafter as “patient gases.”

Optionally, the respiratory device100includes a suction connection150configured to be coupled to an optional suction assembly152. The respiratory device100may provide suction154to the optional suction assembly152via the optional suction connection150. The suction assembly152may be configured to be connected to the patient connection106, a suction positionable inside the patient connection106, and/or a drain.

Referring toFIG.1, optionally, the respiratory device100includes a nebulizer connection160configured to be coupled to an optional nebulizer assembly162. The respiratory device100may provide gases164(e.g., the air114) to the optional nebulizer assembly162via the optional nebulizer connection160. The optional nebulizer assembly162may be configured to be connected to the patient circuit110.

Optionally, the respiratory device100may include an outlet port166through which exhaust167may exit from the respiratory device100.

The respiratory device100may be configured to be portable and powered by an internal battery (not shown) and/or an external power source (not shown) such as a conventional wall outlet.

The respiratory device100further includes a pressure sensor170and a flow rate sensor172. The locations of the pressure and flow rate sensors170,172are exemplary and non-limiting. Further, while both a pressure and flow rate sensor170,172are shown, the respiratory device100does not require both a pressure and a flow rate sensor170,172, and in one embodiment includes one or the other of the pressure or the flow rate sensor170,172.

The pressure and flow rate sensors170,172are configured to generate signals that are interpreted by a controller180as a pressure and a flow rate, respectively, of a fluid conducted to the patient102. While only one of each of the pressure and flow rate sensors170,172are shown inFIG.1, the respiratory device100could include additional pressure and/or flow rate sensors. The controller180is configured to follow one or more of a plurality of control schemes and to issue one or more commands to the respiratory device100, and in particular to one or more components of the respiratory device100such as a motor of a compressor and/or one or more valves, to adjust the pressure and/or flow rate of the fluid conducted to the patient102.

The controller180includes a memory connected to one or more processors. The memory is configured to store various tables, algorithms, and instructions, which are executable by the processor(s). The processor(s) may be implemented by one or more microprocessors, microcontroller, application-specific integrated circuits (“ASIC”), digital signal processors (“DSP”), combinations or sub-combinations thereof, or the like. The processor(s) may be integrated into an electrical circuit, such as a conventional circuit board, that supplies power to the processor(s). The processor(s) may include internal memory and/or the memory may be coupled thereto. The present disclosure is not limited by the specific hardware component(s) used to implement the processor(s) and/or the memory.

The memory is a computer readable medium that includes instructions or computer executable components that are executed by the processor(s). The memory may be implemented using transitory and/or non-transitory memory components. The memory may be coupled to the processor(s) by an internal bus.

The memory may include random access memory (“RAM”) and read-only memory (“ROM”). The memory contains instructions and data that control the operation of the processor(s). The memory may also include a basic input/output system (“BIOS”), which contains the basic routines that help transfer information between elements within the respiratory device100.

Optionally, the memory may include internal and/or external memory devices such as hard disk drives, floppy disk drives, and optical storage devices (e.g., CD-ROM, R/W CD-ROM, DVD, and the like). The respiratory device100may also include one or more I/O interfaces (not shown) such as a serial interface (e.g., RS-232, RS-432, and the like), an IEEE-488 interface, a universal serial bus (“USB”) interface, a parallel interface, and the like, for the communication with removable memory devices such as flash memory drives, external floppy disk drives, and the like. In an example, the controller180is arranged entirely within the respiratory device100.

The processor(s) is configured to execute software implementing the processes and control schemes discussed herein, including interpreting information from one or both the sensors170,172and issuing one or more corresponding commands to execute the control schemes discussed herein. Such software may be implemented by the instructions stored in memory.

While a particular embodiment of a respiratory device100has been shown inFIG.1, it should be understood that this disclosure extends to variations of the respiratory device100, including devices that include lesser or greater functionality relative to the respiratory device100, and including devices that include fewer or more mechanical components relative to those that are shown inFIG.1.

A known control scheme will now be described with reference toFIGS.2A and2B.FIGS.2A and2Bare representative of a device, such as a ventilator or MIE device, conducting fluid to a patient when operating in a mechanical cough mode. In this disclosure, the term “fluid,” when used herein to refer to fluid being conducted relative to the patient by a device, encompasses gas, such as air or patient gases, and any particles or other substances, such as water, medications, or secretions, that may be entrained or suspended in that gas.

FIG.2Ais a graph of a pressure of the fluid conducted to the patient by the device relative to time, andFIG.2Bis a graph of a flow rate of the fluid conducted to the patient by the device relative to time during the same cycle.

The prior art device conducts fluid to a patient following a pressure control line200by targeting a set pressure. The flow rate of the fluid conducted to the patient follows line202. Beginning with the insufflation phase, which occurs during the time labeled insufflation time in theFIGS.2A and2B, the prior art device conducts fluid to a patient beginning at time T1such that the pressure initially exhibits a relatively steep positive slope. The slope of the control line200gradually lessens, while remaining positive, until a set insufflation pressure is reached at an intermediate time Ti. The set insufflation pressure is set by a physician in one example. The pressure is held at the set insufflation pressure between time Tiand T2, which is when the insufflation phase ends. The result of the steep initial pressure is a relatively high flow rate conducted to the patient between times T1and Tiwhen compared to the flow rates conducted to the patient between times Tiand T2. The prior art device then completes the cycle by performing an exsufflation phase, pause phase (which is optional), and then, if necessary, repeating the cycle until the secretion has advanced within the airway to a point where it can be removed, either via suction or natural expulsion.

The present disclosure controls the respiratory device100in a mechanical cough mode in which the fluid conducted to the patient102does not exhibit the relatively steep, abrupt pressure and flow rates at the beginning of the insufflation phase, as in the prior art device ofFIGS.2A and2B. Rather, in the present disclosure, the controller180is configured to issue one or more commands to the respiratory device100such that, during an insufflation phase of the mechanical cough mode, a pressure of a fluid conducted to the patient102by the respiratory device100gradually increases throughout the insufflation phase. Example control schemes will now be described.

In a first example control scheme, as shown inFIGS.3A and3B, the controller180is configured to issue one or more commands to the respiratory device100such that, during the insufflation phase of the mechanical cough mode, the pressure of the fluid conducted to the patient102by the respiratory device100substantially follows a control line300having a constant positive slope. This approach has the effect of maintaining the flow of the fluid conducted to the patient at essentially the lowest level required to achieve the set pressure by the end of insufflation, and thereby minimizing or eliminating the movement of secretions toward the patient's lungs during the insufflation phase.

In this disclosure, the term “control line” is used to refer to a line representing an active control target of the respiratory device100, as opposed to, for example, line302inFIG.3B, which is a line representing changes in another flow characteristic as a result of the respiratory device100actively following the control line300. A control line may be embodied as an algorithm and/or lookup table on software of the controller180. In some embodiments, the control line is a pressure, and in other embodiments the control line is a flow rate. The controller180is configured to interpret signals from one or both of the sensors170,172and issue various commands to components of the respiratory device100to substantially follow the control line corresponding to a particular control scheme. The term “substantially follow,” when used relative to the controller180controlling the respiratory device100to substantially follow a control line, is used to refer to the controller180actively attempting to follow the control line within acceptable deviations and tolerances in this art.

With continued reference to the embodiment ofFIGS.3A and3B, in which the control line300relates to a pressure, at time T1the pressure is zero and at time T2the pressure equals the set insufflation pressure. Again, the set insufflation pressure may be set by a physician. Because the control line300has a constant positive slope, the pressure conducted to the patient102gradually increases at a constant rate throughout the entirety of the insufflation phase. As such, with reference toFIG.3B, the flow rate, represented by line302, is substantially constant between times T1and T2and exhibits a slope of zero. It should be noted that the slope of line302is based on a lung compliance of a particular patient, and may not always exhibit a zero slope. Further, in an example, the amplitude of line302is less than the flow rate in the prior art device ofFIG.2B. InFIGS.3A and3B, the patient102does not experience a variable flow rate, including a flow rate that is initially relatively large as shown inFIG.2B, which reduces if not eliminates the likelihood of retrograde displacement of secretions during the insufflation phase. Retrograde displacement is movement of the secretion within an airway of the patient102in the direction toward the lungs142of the patient102, and away from the respiratory device100. Forward displacement, on the other hand, is movement toward the respiratory device100. Unless otherwise described, the exsufflation and pause phases (note, again, a pause phase is optional) of this disclosure are controlled substantially similar to how they are controlled inFIGS.2A and2B. Cycles are repeated, if necessary, and secretions are either expelled naturally or removed using suction.

FIGS.4A and4Billustrate another example control scheme. In this example, the controller180is configured to issue one or more commands to the respiratory device100such that, during the insufflation phase of the mechanical cough mode, the flow rate of the fluid conducted to the patient102by the respiratory device100substantially follows a control line402having a constant positive slope. Specifically, unlike in the example ofFIGS.3A and3B, the respiratory device100is controlled to provide a particular flow rate as opposed to a particular pressure. The control line402is such that, at time T1, the flow rate is zero and at time T2the flow rate has increased to a point where the pressure, indicated at line400, equals the set insufflation pressure. Alternatively, the flow rate may increase until the flow rate equals another physician-set value, such as a peak insufflation flow (PIF), which may be within a range between about 10-120 liters per minute (LPM). Because the flow rate gradually increases at a constant rate throughout the entirety of the insufflation phase, the pressure follows a line400that gradually increases in steepness, and in particular exhibits a positive slope that gradually increases, between times T1and T2.

Control line300and line302are shown inFIGS.4A and4Bfor reference. While control line402does exceed the flow rate provided in the control scheme ofFIGS.3A and3Bfollowing an intermediate time T1, the patient102never experiences a sharp increase in pressure or flow rate because of the gradually increasing control line402. Further, the pressure does not exceed a set insufflation pressure, in this example. Thus, the control scheme ofFIGS.4A and4Balso reduces if not eliminates retrograde displacement of secretions.

InFIG.4B, the control line402begins at a flow rate of zero at time T1. In another example, the control line402could begin at a flow rate greater than zero at time T1. In that example, the control line402could remain substantially flat, exhibiting a slope of substantially zero, between times T1and T2. Alternatively, the control line402could remain substantially flat while increasing slightly between times Tiand T2.

With reference toFIGS.5A and5B, another control scheme is disclosed. In this control scheme, during the insufflation phase of the mechanical cough mode, the pressure of the fluid conducted to the patient102by the respiratory device100substantially follows control line500, which oscillates about a line504having a constant positive slope. In other words, the control line500is similar to a sine wave oscillating about an axis, which here is line504. In this example, line504is equivalent to control line300, and exhibits a pressure of zero at time T1and exhibits the set insufflation pressure at time T2. The control line500oscillates by an amplitude506relative to the line504. Beginning at time T1, the control line500oscillates above the line504. In this example, the control line500completes three oscillations relative to line504between times T1and T2. This disclosure extends to control lines500that complete at least one oscillation between times T1and T2. The resultant flow rate, represented by line502, conducted to the patient102also oscillates relative to line508by an amplitude510. The line508is equivalent to line302in one example. Oscillating pressure and/or flow rate in this manner may help free secretions within the airway of the patient102, while also reducing if not eliminating the likelihood of retrograde secretion displacement.

With reference toFIGS.6A and6B, still another control scheme is disclosed. In this control scheme, during the insufflation phase of the mechanical cough mode, the flow rate of the fluid conducted to the patient102by the respiratory device100substantially follows control line602, which oscillates relative to a line604having a constant positive slope. The control line602is similar to a sine wave oscillating about an axis, which here is line604. The line604is equivalent to line402in one example. The control line602oscillates by an amplitude606relative to the line604. Beginning at time T1, the control line602oscillates in a direction above the line604, and in this example completes three oscillations between times T1and T2. The resultant pressure, represented by line600, of the fluid conducted to the patient102also oscillates relative to line608by an amplitude610. The line608exhibits a constant positive slope, in this example. In another example, the line608is equivalent to line400. Again, the oscillations may help free secretions within the airway of the patient102. InFIGS.5A,5B,6A, and6B, the oscillations are only present during the insufflation phase, however they could also be present during the exsufflation phase or the pause phase.

InFIGS.5A and6B, the control lines500and602are considered to gradually increase throughout the insufflation phase in this disclosure, despite the oscillations, because the control lines500,602substantially follow, and oscillate about, lines that gradually increase throughout the insufflation phase and because the control lines500,602exhibit minimum values at time T1and maximum values at time T2.

In one aspect of this disclosure, the respiratory device100is able to periodically, at pre-programmed intervals, function in a mechanical cough mode. In this aspect, the controller180can issue one or more commands to the respiratory device100such that the respiratory device100delivers fluid according to one of the control schemes ofFIGS.3A-6Bat pre-programmed intervals, such as every hour or every four hours, between normal operation of the respiratory device100in a ventilation mode. When operating in this mode, the respiratory device100may be said to be operating in an “intermittent cough” mode.

It should be understood that terms such as “about,” “substantially,” and “generally” are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret those terms.