Abstract:
A method for controlling a ventilator includes the steps of providing an inhalation pressure limit, determining when a pressure in a connection to a patient circuit is greater than the inhalation pressure limit, and opening the valve when the pressure is greater than the inhalation pressure limit. An associated computer readable medium for controlling the method is also described.

Description:
BACKGROUND 
       [0001]    This application is a divisional application of co-pending U.S. patent application Ser. No. 13/994,847, filed Jun. 17, 2013, which in turn claims the benefit of pending international application no. PCT/IB2011/055574, filed Dec. 9, 2011, which claims the benefit of U.S. provisional application Ser. No. 61/425,515, filed Dec. 21, 2010. 
         [0002]    Ventilators are used in a variety of applications to provide non-invasive (e.g., via a mask) and invasive (e.g., via an endotracheal tube) ventilation of a patient. 
         [0003]    A Safety Valve, Positive Pressure Relief Valve (PPRV) and Negative Pressure Relief Valve (NPRV) are components in a ventilator and are often required by standards applicable to ventilators. Normally in known ventilators, the safety valve, PPRV and NPRV are three separate parts and each provides a specific function. Notably, the safety valve ensures that the pressure in the patient circuit does not exceed a certain level; the PPRV allows for inhalation at a predetermined (positive) pressure; and the NPRV allows air from the ambient to be delivered to the patient when the negative pressure in the patient circuit exceeds a predetermined (negative) pressure (e.g., during ventilation system failure). 
         [0004]    Known safety valves, PPRVs and NPRVs are normally purely mechanical in nature. As such, a threshold pressure is set (e.g., by a spring mechanism) and cannot be varied to accommodate different patient requirements during ventilation. For example, the safety valve can only be set to a specific value for relieving pressure above the highest pressure level in the ventilator, and the NPRV can be set to a specific negative pressure level for relieving pressure below a lowest pressure level in the ventilator. Additionally, over time in known actuators, the accuracy of the valve can be diminished. 
         [0005]    What is needed is an apparatus and method for use in a ventilator that overcomes at least the shortcomings of the known apparatuses described above. 
     
    
     SUMMARY 
       [0006]    In a representative embodiment, a valve for controlling a pressure in a ventilation system comprises: an electromagnet; a shaft connected to the electromagnet; and a diaphragm connected to the shaft. The electromagnet applies a force to the diaphragm based on an input. 
         [0007]    In another representative embodiment, a ventilation system comprises a ventilator connected to a patient circuit; a valve configured to control a pressure in the ventilation system, the valve comprising: an electromagnet; a shaft connected to the electromagnet; and a diaphragm connected to the shaft. The ventilation system comprises a controller connected to the valve and configured to provide an input to the valve. The electromagnet applies a force to the diaphragm based on the input. 
         [0008]    In accordance with another representative embodiment, a computer readable medium has a computer readable program code embodied therein. The computer readable program code is adapted to be executed to implement a method of controlling ventilation of a person. The method comprises: providing an inhalation pressure limit; determining when a pressure is greater than the inhalation pressure limit; and opening a valve when the pressure is greater than the inhalation pressure limit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The representative embodiments are best understood from the following detailed description when read with the accompanying drawing figures. The dimensions of features in the drawing figures may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements. 
           [0010]      FIG. 1A  is perspective view of a valve in accordance with a representative embodiment. 
           [0011]      FIG. 1B  is an exploded view of the valve depicted in  FIG. 1A . 
           [0012]      FIG. 2  is a simplified block diagram of a ventilation system in accordance with a representative embodiment. 
           [0013]      FIG. 3  is a flow diagram of a method of controlling a ventilation of a person in accordance with a representative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    In the following detailed description, for purposes of explanation and not limitation, representative embodiments disclosing specific details are set forth in order to provide a thorough understanding of embodiments according to the present teachings. However, it will be apparent to one having had the benefit of the present disclosure that other embodiments according to the present teachings that depart from the specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well-known devices and methods may be omitted so as not to obscure the description of the example embodiments. Such methods and devices are within the scope of the present teachings. 
         [0015]    Unless otherwise noted, when a first device is said to be connected to a second device, this encompasses cases where one or more intermediate devices may be employed to connect the two devices to each other. However, when a first device is said to be directly connected to a second device, this encompasses only cases where the two devices are connected to each other without any intermediate or intervening devices. 
         [0016]    In accordance with representative embodiments described below, a valve for use in a patient ventilation system is described. The valve functions as a safety valve, a PPRV and an NPRV and provides these functions as a single component. The valves of the representative embodiments are contemplated for use in non-invasive ventilation systems and in invasive ventilation systems. 
         [0017]      FIG. 1A  is perspective view of a valve  100  in accordance with a representative embodiment. The valve  100  is disposed over a connection  101  to a patient circuit (not shown in  FIG. 1A ), and provides pressure relief in ways described below in connection with representative embodiments. The valve  100  comprises a lower housing  102 , which is affixed to the connection  101 . An intermediate housing  103  is connected between the lower housing  102  and an upper housing  104 . As described more fully below, the upper housing  104  contains an electromagnet, which comprises a coil  105 . 
         [0018]      FIG. 1B  is an exploded view of the valve depicted in  FIG. 1A . The coil  105  is disposed around a magnet  106 . Together, the coil  105  and the magnet  106  comprise an electromagnet. A shaft  107  is attached to the coil  105  through magnet  106  and extends through the intermediate housing  103 . The shaft  107  is connected to a plunger  109  via a connector  108  as shown. The plunger  109  is seated in a diaphragm  110  and the diaphragm  110  is seated over an opening (not shown) in the connection  101 . As described more fully below, the coil  105  is driven in the positive and negative z-direction of the coordinate system shown in  FIG. 1B  by the application of current to the coil  105 . The movement of the coil  105  results in movement of the shaft  107  in same z-direction, which in turn raises (+ z-direction) or lowers (− z-direction) the plunger  109  and in turn raises (+ z-direction) or lowers (− z-direction) the diaphragm  110 . 
         [0019]    The diaphragm  110  is illustratively made of rubber, or a polymer material, or other suitable material. The diaphragm  110  comprises sidewalls  111  that allow the diaphragm  110  to be raised and lowered in response to forces applied to the plunger  109  by the electromagnet. In accordance with representative embodiments, the electromagnet provides a force through the plunger  109  to the diaphragm  110  that is commensurate with a desired pressure in the connection  101  and, therefore, the patient circuit. 
         [0020]    As described more fully below, the magnitude and direction (± z-direction) of the force provided by the diaphragm  110  is determined by the magnitude and direction of the current in the coil  105  determined by a controller (not shown in  FIG. 1B ). In certain embodiments, a threshold pressure is set in the controller. Based on feedback from a pressure transducer (not shown in  FIG. 1B ), the controller changes the direction of the current in the coil  105  to raise the plunger  109  and the diaphragm  110  via the shaft  107 . The raising of the diaphragm  110  allows air to be released from the connection  101  to the ambient through an opening (not shown) in the lower housing  102 , or allows air to be provided to the connection  101  from the ambient through the opening in the lower housing  102 . In other embodiments, the diaphragm  110  is selectively raised and lowered to maintain the pressure in the patient circuit at a predetermined level set in the controller. The controller receives pressure data from the pressure transducer and raises the diaphragm  110  if the pressure in the patient circuit rises above the predetermined level, and lowers the diaphragm  110  if the pressure in the patient circuit falls below the predetermined level. The selective raising and lowering of the diaphragm  110  is in response to changes in the direction of current in the coil  105  based on signals from the controller. 
         [0021]    Beneficially, when operating as a safety valve, based on the forces applied to the diaphragm  110 , the valve  100  can be set to relieve positive pressure or negative pressure based on a positive pressure threshold or a negative pressure threshold, respectively, set in the controller. When operating as a pressure regulator, the valve  100  can maintain the pressure in the patient circuit at a predetermined level through the selective raising and lowering of the diaphragm  110  to provide pressure relief. The ability to set the positive and negative pressure thresholds and to regulate the pressure in the patient circuit allows for a single component, valve  100 , to provide the functions of a safety valve, a PPRV, and a NPRV. Moreover, the ability to set the positive and negative pressure thresholds and to regulate the pressure in the patient circuit allows the valve  100  to be implemented in a variety of applications (e.g. neonatal ventilation, pediatric ventilation, and adult ventilation). 
         [0022]      FIG. 2  is a simplified schematic diagram of a ventilator  200  in accordance with a representative embodiment. The ventilator  200  may be configured to provide non-invasive ventilation or invasive ventilation. The ventilator  200  comprises an inhalation delivery system  201  and an exhalation system  202 , which are connected to a patient  203  via a patient circuit  204  comprising a patient interface (not shown). Certain aspects of the inhalation delivery system  201 , the exhalation system  202 , the patient circuit  204  and the patient interface of the ventilator  200  are known. For example, the inhalation delivery system  201 , the exhalation system  202 , the patient circuit  204  and the patient interface of the ventilator  200  of the ventilator  200  may be found, for example, in one of a variety of ventilators commercially available from Koninklijke Philips Electronics N. V., Eindhoven, The Netherlands. 
         [0023]    The ventilator  200  comprises the valve  100  illustratively provided between the inhalation delivery system  201  and the patient  203 . A pressure transducer  205  is connected to the patient circuit  204  between the patient  203  and the valve  100 . The pressure transducer  205  provides an electrical signal indicative of the pressure (pressure readings) in the patient circuit  204  between the patient  203  and the valve  100 . As described more fully below, these pressure readings are used to raise the diaphragm  110  (opening the valve  100 ), or to lower the diaphragm (closing the valve  100 ), or to maintain the diaphragm  110  in its current position. 
         [0024]    The ventilator  200  comprises a controller  206 , which receives the pressure readings from the pressure transducer  205 , and provides commands to a valve driver  207 . The valve driver  207  is illustratively a current amplifier/controller that provides a current in a particular direction and of a particular magnitude to the coil  105  of the valve  100  based on the commands from the controller  206 . As described above, the magnitude and direction of the current through the coil  105  dictates the magnitude and direction of the force applied to the plunger  109  and thus to the diaphragm  110 . As described more fully below, the movement of the diaphragm  110  and the force applied by the diaphragm  110  provide pressure relief or pressure regulation of the air in the patient circuit  204  between the patient  203  and the valve  100 . 
         [0025]    The controller  206  may be one of a variety of processing devices, such as a processor, microprocessor, or central processing unit (CPU), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or combinations thereof, using software, firmware, hard-wired logic circuits, or combinations thereof. In a representative embodiment, the controller  206  is a controller (e.g., microprocessor) of the ventilator  200 . In another embodiment, the controller  206  is a separate component from the ventilator  200 . In such an embodiment, the controller  206 , the pressure transducer  205  and the valve  100  comprise a stand-alone device that is connected to the patient circuit  204 . 
         [0026]    A memory (not shown) is included for storing executable software/firmware and/or executable code for the controller  206 . The executable software/firmware and/or executable code enables the determination of the pressure in the patient circuit  204  between the valve  100  and the patient  203  based on the data received from the pressure transducer. The executable software/firmware and/or executable code enable the determination by the controller  206  of the required magnitude and direction of the current to be supplied by valve driver  207  to the coil  105  of the valve  100 . The memory may be any number, type and combination of nonvolatile read only memory (ROM) and volatile random access memory (RAM), and may store various types of information, such as computer programs and software algorithms executable by the processor or CPU. The memory may include any number, type and combination of tangible computer readable storage media, such as a disk drive, an electrically programmable read-only memory (EPROM), an electrically erasable and programmable read only memory (EEPROM), a CD, a DVD, a universal serial bus (USB) drive, and the like. 
         [0027]    As described above, the controller  206  provides commands to the valve driver  207  regarding the direction and magnitude of the current to be supplied to the coil based on pressure readings from the pressure transducer  205 . In response, the valve  100  is configured to provide pressure relief or pressure regulation based on the pressure readings received from the pressure transducer  205 . In one example, a threshold limit (positive or negative) is set for a pressure in the patient circuit  204 . The threshold limit is the maximum (positive or negative) pressure that can safely be provided to the patient  203 . Pressure values above the threshold limit could be dangerous to the patient. For example, if the pressure measured by the pressure transducer  205  exceeds the threshold limit, upon receiving these data from the pressure transducer  205 , the controller  206  provides a command to the valve driver  207  to reverse the direction of current flow in the coil  105  of the valve  100 . The reversal of current flow causes the diaphragm  110  to be raised (+ z-direction in the coordinate system shown in  FIG. 1B ). If the threshold limit is a positive pressure, raising the diaphragm releases air to the ambient through the opening in the lower housing  102 . In another embodiment, rather than reversing the direction of current flow, the current to the coil  105  from the valve driver  207  is terminated based on commands from the controller  206 . With no current in the coil  105 , no force is applied by the plunger  109  to the diaphragm  110 . This results in the raising of the diaphragm  110  and the release of air to the ambient through the opening in the lower housing  102 . As should be appreciated, in this example, the valve  100  functions as a safety valve. 
         [0028]    In another example, a desired pressure in the patient circuit  204  between the patient  203  and the valve  100  is set in the controller  206 . If the pressure reading received by the controller  206  from the pressure transducer  205  indicates that the pressure is greater than the desired pressure (but less than a positive threshold pressure), the controller  206  provides commands to the valve driver  207  to terminate current flow in the coil  105  or to reverse current flow in the coil  105  causing the diaphragm  110  to be raised (+ z-direction in the coordinate system shown in  FIG. 1B ) and air to be released to the ambient through the opening in the lower housing  102 . If the next measurement data from the pressure transducer  205  indicates that the pressure in the patient circuit  204  between the valve  100  and the patient  203  is at or below the desired pressure, the controller  206  provides commands to the valve driver  207  to provide current having a determined magnitude and direction to cause the diaphragm  110  to be lowered (− z-direction in the coordinate system shown in  FIG. 1B ) and to provide a suitable force at the opening (not shown) to maintain the seal between the diaphragm  110  and the opening in the connection  101 . As described below in connection with a representative embodiment, the process of taking pressure readings and raising and lowering the diaphragm  110  as needed to regulate the pressure in the patient circuit  204  between the valve  100  and the patient  203  is iterative. As should be appreciated, in this example, the valve  100  functions as a positive pressure relief valve (PPRV). 
         [0029]    In another example, a desired pressure in the patient circuit  204  between the patient  203  and the valve  100  is set in the controller  206 . If the data received by the controller  206  from the pressure transducer  205  indicate that the pressure is a negative pressure (but not equal to a negative threshold pressure), the controller  206  provides commands to terminate current flow in the coil  105  or to reverse current flow in the coil  105  causing the diaphragm  110  to be raised (+ z-direction in the coordinate system shown in  FIG. 1B ) and air to be provided to the patient circuit  204  from the ambient through the opening in the lower housing  102 . If the next measurement data from the pressure transducer  205  indicates that the pressure in the patient circuit  204  between the valve  100  and the patient  203  is no longer at the negative pressure, the controller  206  provides commands to resume current flow to cause the diaphragm  110  to be lowered (− z-direction in the coordinate system shown in  FIG. 1B ) and to provide a force at the opening (not shown) sufficient to maintain the seal between the diaphragm  110  and the opening in the connection  101 . As described below in connection with a representative embodiment, the process of taking pressure measurements and raising and lowering the diaphragm  110  as needed to regulate the pressure in the patient circuit  204  between the valve  100  and the patient  203  is iterative. As should be appreciated, in this example, the valve  100  functions as a negative pressure relief valve (NPRV). 
         [0030]    By way of illustration of the use of valve  100  as an NPRV, consider the case where a patient  203  takes a “deep breath” with a magnitude so great that a blower (not shown) or other air source (not shown) in the inhalation delivery system  201  of the ventilator  200  could not provide a surge of air flow to the patient to satiate the breath required by the patient. In this case, the patient  203  will create a negative pressure to the patient circuit  204  between the patient  203  and the valve  100 . This negative pressure is detected by the pressure transducer  205  and a pressure reading is provided to the controller  206 . Based on the pressure reading, the controller  206  provides a command to the valve driver  207  to provide a current of magnitude and direction sufficient to raise the diaphragm and valve  100  will open to ambient through the opening in the lower housing  102 . The pressure transducer  205  provides a subsequent pressure reading to the controller  206  and the pressure in the patient circuit  204  between the patient  203  and the valve  100  is maintained at the desired level through control of the diaphragm  110  of the valve  100 . 
         [0031]      FIG. 3  is a flow diagram of a method  300  of controlling a ventilation of a person in accordance with a representative embodiment. A computer readable medium having a computer readable program code embodied therein is stored in the memory accessible by the controller  206 . The computer readable program code is adapted to be executed to implement the method through the controller  206 . 
         [0032]    At  301  the method comprises setting an inhalation pressure limit at the controller  206 . In an embodiment where the valve  100  is functioning as a safety valve this inhalation pressure limit is either the positive pressure threshold for the patient circuit  204  between the valve  100  and the patient  203 , or the negative pressure threshold for the patient circuit  204  between the valve  100  and the patient  203 . As should be appreciated, both a positive pressure threshold and a negative pressure threshold can be set in the microprocessor. In embodiments where the valve  100  functions as a PPRV or as an NPRV, the inhalation pressure limit is the desired pressure in the patient circuit  204  between the patient  203  and the valve  100 . It is emphasized that the valve  100  can be used as any of a safety valve, a PPRV and an NPRV. As such, the inhalation pressure limit can have multiple settings: the positive pressure threshold, the negative pressure threshold, and the desired pressure in the patient circuit  204  between the patient  203  and the valve  100 . As should be appreciated, the positive and negative thresholds are significantly greater in magnitude than the desired pressure in the patient circuit  204  between the patient  203  and the valve  100 . 
         [0033]    Beneficially, the inhalation pressure limit may be adjusted for a particular application. For example, the inhalation pressure limit can be set at a value useful in neonatal ventilation. The inhalation pressure limit can be set at a value useful in pediatric ventilation that is a greater pressure limit (positive or negative) than the inhalation pressure limit useful in neonatal ventilation. Additionally, the inhalation pressure limit can be set at a value useful in adult ventilation that is a greater pressure limit (positive or negative) than the inhalation pressure limit useful in pediatric ventilation. Notably, these inhalation pressure limits are merely illustrative, and it is emphasized that a wide range of inhalation pressure limits can be provided at  301  to the controller  206 . 
         [0034]    At  302  the valve  100  is closed by lowering the diaphragm  110 . As described above, current from the valve driver  207  is provided to the coil  105  and has a magnitude and direction determined by the controller  206  based on the desired pressure in the patient circuit  204  between the patient  203  and the valve  100 . 
         [0035]    At  303  an inhalation pressure is read. In a representative embodiment, a measurement of the pressure in the patient circuit  204  between the valve  100  and the patient  203  is made by the pressure transducer  205 . This pressure reading is provided to the controller  206 . 
         [0036]    The controller  206  compares the pressure reading from the pressure transducer  205  to a positive inhalation pressure limit stored in the memory. If the positive inhalation pressure limit is less than or equal to the pressure reading by the pressure transducer  205 , the method  300  continues at  305 . At  305 , the controller  206  provides a command to raise the diaphragm  110  of the valve  100 . Raising the diaphragm  110  allows air to be released to the ambient through the opening in the lower housing  102 . 
         [0037]    At  306  another pressure measurement is made by the pressure transducer  205 . The method  300  continues at  302  and the valve  100  is closed by lowering the diaphragm  110 . As described above, the magnitude and direction of the current from the valve driver  207  is determined by the controller  206  based on the pressure readings at  306  to lower the diaphragm  110  and to ensure a suitable force is applied by the plunger  109  to the diaphragm  110  to maintain the diaphragm  110  in a closed position. When the inhalation limit is set to a desired positive pressure, the valve  100  functions as a PPRV. 
         [0038]    The method  300  continues at  304 . The controller  206  compares the pressure reading from the pressure transducer  205  to a positive inhalation pressure limit. If the positive inhalation pressure limit is greater than the pressure reading by the pressure transducer  205 , the method  300  continues at  307 . 
         [0039]    At  307 , the controller  206  compares the pressure reading from the pressure transducer  205  to a negative inhalation pressure limit stored in the memory. If the negative inhalation pressure limit is less than or equal to (in magnitude) the pressure reading by the pressure transducer  205 , the method  300  continues at  308 . 
         [0040]    At  308 , the controller  206  provides a command to raise the diaphragm  110  of the valve  100  to open the valve  100 . Raising the diaphragm  110  allows for air from the ambient to be inhaled by the patient  203 . As described above, the magnitude and direction of the current from the valve driver  207  is determined by the controller  206  based on the pressure readings at  307  to raise the diaphragm  110  with sufficient force to overcome the negative pressure in the patient circuit  204  between the patient  203  and the valve  100 . 
         [0041]    After the valve  100  is opened, the method  300  continues at  306  and another pressure measurement is made by the pressure transducer  205 . The method  300  then continues at  302  and the valve  100  is closed by lowering the diaphragm  110 . As described above, the magnitude and direction of the current from the valve driver  207  is determined by the controller  206  based on the pressure readings at  306  to lower the diaphragm  110  and to ensure a suitable force is applied by the plunger  109  to the diaphragm to maintain the diaphragm  110  in a closed position. When the inhalation limit is set to a desired positive pressure, the valve  100  functions as a PPRV. 
         [0042]    If at  307  the negative inhalation pressure limit is greater (in magnitude) than pressure reading by the pressure transducer  205 , the method  300  continues at  309  and the method  300  repeats beginning at  303  with the valve  100  closed. If the desired pressure is set between the positive inhalation pressure limit and the negative inhalation pressure limit, the repetition of the method  300  allows for the regulation of the pressure in the patient circuit  204  between the patient  203  and the valve  100 . 
         [0043]    In an embodiment, the positive inhalation pressure limit is set to the positive pressure threshold. If the pressure measured by the pressure transducer  205  is greater than the positive inhalation pressure limit, at  305  the diaphragm  110  is raised to release air to the ambient. In another embodiment, the negative pressure limit is set to the negative pressure threshold. If the pressure measured by the pressure transducer  205  is greater (in magnitude) than the negative inhalation pressure limit pressure limit, at  308  the diaphragm  110  is raised to receive air from the ambient. In embodiments where the positive inhalation pressure limit is set to the positive pressure threshold, or the negative inhalation pressure limit is set to the negative pressure threshold, the valve  100  functions as a safety valve. After functioning as a safety valve (at  305  or  308 ), the method  300  continues at  306  and repeats as described above. 
         [0044]    While representative embodiments are disclosed herein, one of ordinary skill in the art appreciates that many variations that are in accordance with the present teachings are possible and remain within the scope of the appended claims. The invention therefore is not to be restricted except within the scope of the appended claims.