Patent Publication Number: US-2022226588-A1

Title: Medical ventilator having in-series piston pumps

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 63/139,025, bearing the present title, filed on Jan. 19, 2021, which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This application generally relates to medical ventilators. 
     BACKGROUND 
     Existing ventilators are expensive and have long lead times to manufacture. Furthermore, many technical limitations with respect to performance, durability, ease of manufacturing, safety and efficiency exist in current ventilator designs. It is necessary or desirable to overcome these and other deficiencies in the art, especially when the public health requires the scaling up of production of sufficient numbers of suitable ventilators to address pandemics as experienced in recent years. 
     SUMMARY 
     One or more embodiments are directed to a ventilator apparatus, comprising a drive motor acting as a prime mover, receiving energy from a power source and providing a rotational mechanical motor output; a drivetrain, coupled to said drive motor, that receives said rotational mechanical motor output and converts the same into an oscillating linear mechanical movement; an elongated drive shaft, coupled to said drivetrain and driven thereby, the drive shaft further coupled to and powering two fluid pumps including a first (expiratory) fluid pump and a second (inspiratory) fluid pump, said drive shaft disposed in-line with and between said two fluid pumps; wherein said drive shaft translates axially along an axis of the drive shaft according to said oscillating linear mechanical movement of the drivetrain, and wherein said drive shaft forces a linear movement of both of said fluid pumps along said axis; a first fluid pathway that receives an expiratory input volume of fluid into said first (expiratory) fluid pump during a first phase of operation of said apparatus and discharges an expiratory output volume of fluid out of said first (expiratory) fluid pump during a second phase of operation of said apparatus; and a second fluid pathway that receives a breathing gas volume into said second (inspiratory) fluid pump during said first phase of operation of the apparatus and discharges said breathing gas volume during said second phase of operation of the apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and advantages of the concepts disclosed herein, reference is made to the detailed description of preferred embodiments and the accompanying drawings. 
         FIG. 1  illustrates an exemplary view of a ventilator system in a first state according to one or more exemplary embodiments. 
         FIG. 2  illustrates an exemplary view of a ventilator system in a second state according to one or more exemplary embodiments. 
         FIG. 3  illustrates an exemplary end view of a ventilator system from one end thereof according to one or more embodiments. 
         FIG. 4  illustrates an exemplary top view of a ventilator system according to one or more embodiments. 
         FIG. 5  illustrates an exemplary top view of a ventilator system and certain gas pathways and accessories according to one or more embodiments. 
         FIG. 6  illustrates an exemplary perspective view of the system including its housing as may be used in one or more embodiments. 
         FIG. 7  describes exemplary settings and corresponding functions accessible using a user interface of the system. 
         FIG. 8  illustrates another exemplary perspective view of the system and the use of limit switches therein to control the mechanical linear driving motions. 
         FIG. 9  illustrates yet another exemplary perspective view of one or more embodiments including placement of some gas pressure switches in the gas lines thereof. 
         FIG. 10  illustrates an exemplary side view of a ventilator system according to one or more embodiments. 
         FIG. 11  illustrates another exemplary side view of a ventilator system according to one or more embodiments. 
         FIG. 12  illustrates an end view of a ventilator system and some of the pressure switches used therein according to one or more embodiments. 
         FIG. 13  illustrates another exemplary top view of a ventilator system and limit switches according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of a mechanical ventilator  10  in a first state according to an embodiment. The ventilator  10  includes an expiratory piston pump  100  and an inspiratory piston pump  200 . Each pump  100 ,  200  includes a moveable piston  120 ,  220  disposed in a cylinder  130 ,  230 , respectively. The cylinders  130 ,  230  can comprise an acrylic material (e.g., polymethyl methacrylate) or another material. The pistons  120 ,  220  are mechanically coupled in series with a connecting rod or shaft  140 . Since the pistons  120 ,  220  are mechanically coupled in series, the pistons  120 ,  220  operate in phase with each other, moving linearly along a main axis of connecting rod or shaft  140 . For example, when piston  120  is in an expanded state, piston  220  is also in an expanded state (and vice versa), as illustrated in  FIG. 1 . Likewise, when piston  120  is in a compressed state, piston  220  is also in a compressed state, as illustrated in  FIG. 2 . The pistons  120 ,  220  can comprise stainless steel, plastic, or another material. 
     The pistons  120 ,  220  are driven by a drive motor  150  acting as a prime mover which receives energy from an energy source such as an AC or a DC electric power supply (i.e., utility power outlet and/or battery or similar source). The motor  150  is in mechanical communication with a drive motor assembly  160  acting as a powertrain that takes the rotational motor movement and translates the rotational motion of the motor  150  into a linear motion, in some aspects, oscillating linearly (back and forth) along an axis or direction congruent with a major dimension of the connecting rod or shaft  140 .  FIG. 6  shows conceptually the direction of axis  600  through or parallel to the main or major axis of the connecting rod shaft, which will also coincide in this exemplary embodiment with the direction of movement of timing belt  170 . In an example, the drive motor assembly  160  is in mechanical communication with piston  120  via a timing belt  170 . When the motor  150  rotates in a first direction, the linear motion created by the drive motor assembly  160  causes a driving rod ( FIG. 8 ) to push piston  120 , and thus piston  220 , from the expanded state (or expanded position) to the compressed state (or compressed position). When the motor  150  rotates in a second direction (opposite to the first direction), the linear motion created by the drive motor assembly  160  causes the a driving rod to pull or retract piston  120 , and thus piston  220 , from the compressed state to the expanded state. The direction and speed of the motor  150  is controlled by a microprocessor-based controller  180  that is in electrical communication with the motor  150  and which in some examples may control a driving voltage, frequency and/or current supplied to the motor  150 . Limit switches  1 ,  2  ( FIG. 8 ) can be used to limit the linear motion of the drive motor assembly  160 , for example to limit the position of the driving rod (e.g., a sensor or object on driving rod) relative to the limit switches  1 ,  2 . Limit switch  1  can correspond to the start position of the driving rod (e.g., when the pistons  120 ,  220  are in the expanded state). Limit switch  2  can correspond to the stop position of the driving rod (e.g., when the pistons  120 ,  220  are in the compressed state). Additional details regarding the operation of the drive motor assembly  160  are illustrated in  FIG. 8 . We also note the exemplary embodiment of  FIG. 8  which shows the use of limit switches  801  to sense and limit the linear motion of the drivetrain, pistons, and optionally to cause reversal of said movement to switch directions so that the apparatus has the described cyclic movement. 
     Piston  220  moves in phase with piston  120 , as discussed above, since they are mechanically coupled in series. Therefore, pushing piston  120  from a (first) expanded state to a (second) compressed state causes piston  220  to be pushed from a complementary (first) expanded state to a complementary (second) compressed state. Likewise, pulling or retracting piston  120  from the compressed state to the expanded state causes piston  220  to be pulled/retracted from the compressed state to the expanded state. 
     A plurality of O-rings  181  is used to form fluid-tight seals in each pump  100 ,  200 . For example, O-rings  181  are disposed on each piston  120 ,  220  to form a fluid-tight seal around each piston  120 ,  220 . The seal may be resistant to unwanted gas flow by said seal as the seal is seated in a dimensionally-matching aperture and maintains a sufficient pressure on any gap between the seal and the aperture or between the seal and the inner shaft to prevent gas flow between opposing sides of said seal. In addition, one or more O-rings  181  is disposed between the connecting rod  140  and cylinder  130  to form a fluid-tight environment within and between the gas volumes in said cylinders. Additional O-rings  181  can be used to seal the fluid connections into and out of each cylinder  130 ,  230  as shown. 
     The ventilator system  10  also includes a common housing  240  that houses the components of the system and a user interface  250  disposed on or in the housing  240 . The housing  240  is shown open so that the inner components can be seen in the figure, but the housing can comprise a shell or a multi-part base portion onto which the components are secured and an upper portion or lid that fits over the components to close them off within the housing and to prevent damage or contamination to the components. In some embodiments, all of the housing, or alternatively just the upper lid of the housing may be constructed of a transparent material so the workings of the inner parts can be visible during operation. The base and upper parts of the housing may be glued with epoxy to one another, fused using plastic welding methods, or secured to one another with mechanical fasteners such as screws, optionally with a fluid-resistant gasket sealing leakage of fluids into or out of the housing  240 . 
     A user interface  250  is electrically coupled to the processor based controller  180  which may be constructed on a printed circuit board (PCB) or other electronic integrated circuit to receive one or more input signals from the user interface  250  to set one or more parameters, settings, and/or operating modes (collectively, settings) of the ventilator. A ribbon connector or printed circuit lines can connect the user interface panel  250  with the internal processor circuits and other electrical components on electrical controller  180 . Examples the settings that can be set with the user interface  250  include (1) ventilation operating mode (e.g., volume control with PEEP, pressure control with PEEP, pressure support, and/or another ventilation operating mode), (2) the patient&#39;s tidal volume, (3) the positive inhalation pressure set point (e.g., when operating in pressure-control mode), (4) the purified oxygen concentration and flow rate, (5) oxygen concentration in patient&#39;s inhalation gas, (6) expiratory flow rate, (7) respiratory rate, (8), I:E ratio, and/or (9) breath pause length. Examples of these and/or other settings are illustrated in  FIG. 7  which can be set or modified using the user interface panel and processor based controller. Additional or fewer settings can be provided in other embodiments. 
       FIG. 3  is a rear side view of the ventilator  10  according to an embodiment. Some components of the overall device described may be removed from certain views for ease of viewing, but the present examples are illustrative of the invention so as to explain to those of skill in the art how these non-limiting embodiments are configured and arranged. Of course, similar or equivalent configurations and arrangements can be equally contemplated, for example by positioning or sizing some of the components differently as suits an application of interest. As illustrated, cylinder  230  includes one-way, e.g., check valves  301 - 303 . Valve  301  can be used to allow ambient or compressed air into cylinder  230 . Valve  302  can be used to allow purified oxygen from an oxygen tank or hospital supply line into cylinder  230 . Valve  303  can be used to output an oxygen-enriched gas mixture (i.e., a mixture of ambient/compressed air from valve  301  and oxygen from valve  302 ) to the patient via an inhalation line  310 . One-way valves  301  and  302  only allow fluid to flow into cylinder  230 . One-way valve  303  only allows fluid to flow out of cylinder  230 . 
       FIG. 4  is a top view of the ventilator  10  to further illustrate the operation of each pump  100 ,  200  and associated gas flows. When piston  120  transitions from the compressed state to the expanded state, a negative pressure is formed in cylinder  130  to receive the exhaled gas via exhalation line  400 . Fluid communication between cylinder  130  and exhalation line or pathway  400  is controlled by a one-way valve  304  that only allows fluid to flow into the cylinder  130 . The exhaled gas passes through a replaceable filter  405  (e.g., a bacterial filter) that can filter out droplets, bio materials, contaminants and aerosol particles, such as from patients having a contagious illness (e.g., COVID-19 or another contagious illness). The replaceable filter  405  can be replaced after patient use to reduce the likelihood of cross-contamination. 
     When piston  220  transitions from the compressed state to the expanded state, a negative pressure is formed in cylinder  230  to receive air and purified oxygen from one-way or check valves  301  and  302 , respectively. Thus, cylinders  130 ,  230  respectively store exhaled gas and oxygen-enriched gas-to-be-inhaled in the next breath concurrently when the respective pistons  120 ,  220  transition from the compressed state to the expanded state. The valves  301 ,  302 , and  304  close when pistons  120 ,  220  reach the respective positions corresponding to the expanded state. 
     When expiratory piston  120  transitions from the expanded state to the compressed state, a positive pressure is formed in cylinder  130  to force the exhaled gas out of cylinder  130  (e.g., into the atmosphere) via output line  410 . Fluid communication between cylinder  130  and output line  410  is controlled by a one-way valve  305  that only allows fluid to flow out of the cylinder  130 . When piston  220  transitions from the expanded state to the compressed state, a positive pressure is formed in cylinder  230  to force the oxygen-enriched gas-to-be-inhaled into the inhalation line  310  for patient inhalation. Thus, cylinders  130 ,  230  respectively discharge exhaled gas and oxygen-enriched gas-to-be-inhaled in the next breath concurrently when the respective pistons  120 ,  220  transition from the expanded state to the compressed state. 
     The inhalation line  310  can be fluidly coupled to a humidifier to increase the water-vapor content of the oxygen-enriched gas-to-be-inhaled. In some embodiments, a humidifier can be integrated into the ventilator system  10 . 
     In volume-control mode, the processor-based controller  180  determines the position of the pistons  120 ,  220  to transition from the expanded state to the compressed state based on the patient&#39;s tidal volume, which is received by the controller  180  as a user input via user interface  250 . The controller  180  can have a user input or can be pre-programmed with the diameters of the cylinders  130 ,  230  which the controller  180  can use to determine the position of the pistons  120 ,  220  to form the set-point tidal volume in each cylinder  130 ,  230  (e.g., the displacement of each piston  120 ,  220  equals the set-point tidal volume). In one example, each cylinder  130 ,  230  has approximately a 4-inch diameter. Other diameters of cylinders  130 ,  230  can also be provided. The position of the pistons  120 ,  220  can be determined by the number of rotations of motor  150 , which can be stored in the memory of controller  180  as a look-up table, a formula, or other relationship. Fully compressing piston  220  therefore results in the delivery of the tidal volume set point to the patient (e.g., via inhalation line  310 ). 
     The frequency that the controller  180  transitions the pistons  120 ,  220  between the compressed state and the expanded state corresponds to the respiratory rate, which is an input setting in user interface  250 . Additional input settings that can be used by the controller  180  include the inspiratory-rate-to-expiratory-rate ratio (or I:E ratio) and any pause between inspiration (inhalation) and expiration (exhalation). The controller can determine the expiratory flow rate using the inputs of respiratory rate, I:E ratio, and optionally the breath pause length. The expiratory flow rate corresponds to the speed that the pistons  120 ,  220  transition (e.g., retract) from the expanded state to the compressed state, which the controller  180  can determine based on the diameter of the cylinders  130 ,  230 . The speed of the pistons  120 ,  220  can be controlled by adjusting the rotational speed of motor  150 , which can be stored in the memory of controller  180  as a look-up table, a formula, or other relationship. 
     To achieve the desired oxygen concentration in the patient&#39;s inhalation gas, the controller  180  can calculate the required purified oxygen flow rate based on the calculated piston  120 ,  220  retraction speed, the diameter of the cylinders  130 ,  230 , and the purified oxygen concentration. The required purified oxygen flow rate can be displayed on the user interface  250  with instructions for a nurse or other health care professional to set accordingly (e.g., by adjusting a valve in the hospital oxygen line). Alternatively, the valve  302  can be adjusted by the controller  180  (e.g., based on a pressure sensor in the purified oxygen intake line) to achieve the required purified oxygen flow rate. 
     Each one-way valve  301 - 305  can be a check valve, a solenoid valve, or another one-way valve. When the one-way valves  301 - 305  are check valves, the one-way valves  301 - 305  open and close automatically in response to the relative pressure differential across the respective valve. When the one-way valves  301 - 305  are solenoid valves, the one-way valves  301 - 305  open and close in response to electrical control signals sent from the controller  180 . Each one-way valve  301 - 305  has a normally-closed position and an open position. The default for each valve  301 - 305  is the normally closed-position, and each valve  301 - 305  opens only in response to a minimum pressure differential across the valve (e.g., in a check valve) or in response to a control signal (e.g., in a solenoid valve). 
     The ventilator  10  includes pressure sensors that are in electrical communication with the controller  180 . For example, a PEEP pressure sensor  420  is located in, or in fluid communication with, the exhalation line  400  to sense the pressure in the exhalation line  400 . The controller  180  controls the expansion of piston  120  so that a minimum positive end-expiratory pressure (PEEP) remains in the patient&#39;s lungs at the end of the exhalation cycle. The PEEP can be set via the user interface  250  (e.g., a graphical user interface or other interface) on the ventilator  10 . Examples of PEEP set points include the range of 3 cm H 2 O to 5 cm H 2 O, but higher or lower PEEP set points can be used. In operation, the controller  180  stops the rotation of motor  150  to stop pistons  120 ,  220  from further transitioning to the expanded state (e.g., to the left in  FIG. 4 ) when the feedback from the PEEP pressure sensor  420  indicates that the PEEP pressure in the exhalation line is at the set point PEEP (e.g., 4 cm H 2 O) and/or within a tolerance range thereof (e.g., plus or minus 10% of the PEEP set point). 
     A positive pressure sensor  430  and a negative pressure sensor  440  are located in, or in fluid communication with, the inhalation line  310  to sense the positive and negative pressure, respectively, in the inhalation line  310 . The controller  180  controls the compression of piston  220  so that positive inhalation pressure in the inhalation line  310 , measured by positive pressure sensor  430 , is less than or equal to a positive inhalation pressure set point. The positive inhalation pressure set point can be set via the user interface  250  (e.g., a graphical user interface or other interface) on the ventilator  10 . In operation, when the ventilator  10  operates in pressure-control mode, the controller  180  stops the rotation of motor  150  to stop pistons  120 ,  220  from further transitioning to the compressed state (e.g., to the right in  FIG. 4 ) when the feedback from the positive pressure sensor  430  indicates that the positive pressure in the inhalation line is at the positive inhalation pressure set point (e.g., 20 cm H 2 O) and/or within a tolerance range thereof (e.g., plus or minus 10% of the positive inhalation pressure set point). Reaching the positive inhalation pressure set point indicates to the controller  180  that the patient has received or inhaled a predetermined amount of oxygen-enriched gas mixture when the ventilator  10  operates in pressure-control mode. 
     When the ventilator  10  operates in volume-control mode, the controller  180  uses the positive pressure sensor  430  to generate an alarm when the positive inhalation pressure reaches or exceeds a maximum or peak positive inhalation pressure. The controller  180  does not use the positive inhalation pressure set point in volume-control mode. Otherwise, in volume-control mode, the piston  220  is fully compressed to deliver the entire volume of the oxygen-enriched gas mixture to the patient. 
     When the ventilator  10  operates in pressure-support mode (e.g., when the patient can initiate a breath, such as when the patient is weaning off ventilator-assisted respiration), the controller  180  uses the negative inhalation pressure sensed by negative pressure sensor  440  as a trigger to determine when the patient has initiated a breath. The trigger causes the controller  180  to begin the inspiration or inhalation cycle by starting the rotation of motor  150  to transition the pistons  120 ,  220  from the expanded state to the compressed state. The controller  180  does not use the negative inhalation pressure in pressure-control mode or volume-control mode. 
       FIG. 5  is another top view of ventilator  10  with example labels and descriptions of certain components thereof including some non-limiting arrangement of gas pathways for clarity. 
       FIG. 6  illustrates a ventilator system  10  and its placement in housing  240  according to an exemplary arrangement. It should be understood that the mechanical arrangement of the components shown in this and other exemplary embodiments is not limiting, and those skilled in the art can re-arrange or substitute various parts of the invention as described and illustrated without loss of generality. 
       FIG. 9  illustrates another view of system  10  according to an exemplary arrangement. Specifically, we note the use of pressor sensors such as PEEP pressure sensor  420 , positive pressure sensor (PCV)  430  and negative pressure sensor  440  which can function as a trigger. Each pressure sensor can sense a gas pressure in a line in which it is placed and provide a corresponding pressure value signal that can be an electrical signal indicating said pressure and can be sent as necessary over a wired or wireless communication line to a display or to processor  180  for triggering a function or for inclusion in a logic operation. 
       FIGS. 10 and 11  are side views of ventilator  10  taken from opposing ends of the system. We note the side view of timing belt  170  in a preferred embodiment. 
       FIG. 12  is a front side view of ventilator from the opposing side as the rear side view illustrated in  FIG. 3 . We can see the placement of pressure sensors  430  and  440  in an exemplary configuration. 
       FIG. 13  is a top view of ventilator  10 .  FIG. 13  is identical to  FIG. 1  except that  FIG. 13  illustrates the first and second limit switches  1301 ,  1302  which can limit the backward and forward positions, respectively, of the driving rod (e.g., using position bracket  1310 ). 
     As can be seen, a technical advantage of the disclosed ventilator is that it can be manufactured quickly and inexpensively without sacrificing functionality. In addition, the disclosed ventilator is re-usable even with patients that may have infectious diseases such as COVID-19 or other respiratory ailments. 
     This disclosure should not be considered limited to the particular embodiments described above. Various modifications, equivalent processes, as well as numerous structures to which the technology may be applicable, will be apparent to those skilled in the art to which the technology is directed upon review of this disclosure.