Patent Publication Number: US-2023149657-A1

Title: Ventilator

Description:
FIELD OF THE INVENTION 
     The present application relates to a ventilator for automated ventilation of a patient receiving healthcare. 
     BACKGROUND OF THE INVENTION 
     There is a need for more ventilators in order to treat patients suffering from COVID-19 due to the spread of the SARS-COV2 virus formerly known as the novel coronavirus 2019. A ventilator, and more particularly a mechanical ventilator, is a device that delivers controllable volumes of fluid, and particularly in gaseous form, such as a mixture of air and oxygen (O2), to a patient to replicate the inhalation and exhalation cycle of their lungs. These ventilators can be employed in a variety of ways. For example, certain patients can breathe normally on their own but would benefit from having an increased amount of oxygen in the air and the ventilator can provide a supply of air with a selectable content of oxygen. Alternatively, under some circumstances patients are intubated with a tube from the ventilator that pushes air (along with other fluids) into the lungs from the ventilator. This process is performed when the patient cannot maintain their airway, cannot breathe on their own without assistance, or both. This can be the result of the patient receiving anesthesia such that they will be unable to breathe on their own during surgery, or the patient may be too sick or injured to provide enough oxygen to the body without assistance. 
     A healthy adult lung consumes around 500 millilitres of air per breath cycle (the tidal volume) and have a breath rate of typically 10 to 12 breaths per minute for a total gas exchange of approximately 5 litres/minute. When a patient is unwell there may be fluid in their lungs (pneumonia) that reduces the capacity of the lungs and hence the tidal volume that might be applied. There are considerations such as fibrosis and other lung issues that may make the lung less elastic and hence again reduce the tidal volume requirement. Too much tidal volume for an unwell patient may give rise to high levels of lung inlet pressure. A healthy lung would respond to the induced volume with an intake pressure of around 15 centimeters of water (cmH2O) (1.5 KPa). However, healthcare professionals need to vary the induced volume according to the patient&#39;s needs, for example, perhaps boosting the pressure up to 50 cmH 2 O in order to get better ventilation and more oxygen transfer. Instrumental diagnostic feedback of a patients progress under ventilation can come from a ‘pulse optometry’ finger probe that delivers the blood (artery) oxygen level and hence indicates the success or otherwise of the ventilation. Carbon dioxide monitoring of the exhaled breath can also indicate the level of gas exchange going on in the lung, which is another measure of ventilation success. 
     Conventional ventilators employ the ‘bag-in-the-bottle’ approach where a breath volume is controlled by the amount of movement of a bellows system including a bellows. The mixture of air and oxygen is controlled by a complex electro-mechanical system of valves that feed the mixture into the bellows. Movement of the bellows by a mechanical mover is then employed to deliver a required volume of the mixture per breath to the patient. In more detail, a desired mixture ratio of air and oxygen is drawn into the bellows as the mechanical mover extends the bellows to increase an internal volume of the bellows. It is understood that in other applications, alternatively or in addition to either the air or the oxygen, or to both the air and the oxygen, other fluids can be included in the mixture, such as nitrous oxide (N 2 O) employed during operations for example. The volume within the bellows is then pushed to the patient by the mechanical mover contracting the bellows such that the internal volume of the bellows decreases. Conventional ventilators employ a volume-controlled-ventilation technique where a control system delivers predefined and set movements of the bellows to deliver a required volume of the mixture per breath to the patient. Ventilators have evolved over the years to provide pressure-controlled-ventilation (PCV) where the movement of a back of the bellows is servo controlled in a closed-loop manner such that an inhalation pressure to the patient is controlled. In this regard, a pressure of the internal volume of the bellows controls the movement of the bellows (extension and more particularly contraction thereof) that in turn controls the inhalation pressure to the patient. 
     Conventional ventilators of the bag-in-the-bottle type, that employ either volume-controlled or pressure-controlled ventilation, are complex and expensive to manufacture. These types of ventilators cannot precisely control relatively both the volume and pressure of the mixture delivered to the patient for a variety of reasons. 
     The bellows is a large, bulky device that is difficult to precisely control the internal volume in the extended and contracted states from part-to-part. Typically, valves with large contact area around a valve seat are employed to regulate fluid flow and it is difficult to precisely control the amount of fluid that flows through the valve as it is opening and closing. 
     The state of the art is lacking in techniques for improving a delivery of controllable volumes of fluid, and particularly a fluid mixture, to a patient to replicate the inhalation and exhalation cycle of their lungs. The present apparatus and methods provide a technique for improving the delivery of controllable volumes of fluid or a fluid mixture to a patient to replicate the inhalation and exhalation cycle of their lungs. 
     SUMMARY OF THE INVENTION 
     An improved ventilator for mechanical ventilation during a breathing cycle, which includes an inhalation cycle and an exhalation cycle. The ventilator is configurable to be in fluid communication with a supply of a first fluid. The ventilator includes an inhalation pathway and an exhalation pathway. A first fluid injector is in fluid communication with the supply of the first fluid for injecting the first fluid. The inhalation pathway receives the first fluid injected by the first fluid injector. A controller is operatively connected with the first fluid injector and programmed to selectively actuate the first fluid injector to inject the first fluid, which is received within the inhalation pathway such that an inhalation pressure in the inhalation pathway is within a predetermined range during the inhalation cycle. In an exemplary embodiment, the first fluid is air. 
     In an exemplary embodiment, preferably, the ventilator is configurable to be in fluid communication with a supply of a second fluid. The ventilator further includes a mixing chamber in fluid communication with the first fluid injector and with the inhalation pathway. The first fluid that is injected by the first fluid injector is communicated to the inhalation pathway through the mixing chamber. A second fluid injector is in fluid communication with the supply of the second fluid for injecting the second fluid. The second fluid that is injected by the second fluid injector is communicated to the inhalation pathway through the mixing chamber. The controller is further programmed to selectively actuate the first fluid injector and the second fluid injector to inject the first fluid and the second fluid respectively to form a mixture of the first fluid and the second fluid in the mixing chamber for inhalation by a patient during the inhalation cycle. A mixture ratio between the first fluid to the second fluid can vary between 0:100 and 100:0. A mixture pressure of the mixture of the first fluid and the second fluid is within the predetermined range during the inhalation cycle. Preferably the second fluid is oxygen. 
     In another exemplary embodiment, preferably, the ventilator further includes a third fluid injector in fluid communication with the supply of the first fluid for injecting the first fluid. The exhalation pathway receives the first fluid that is injected by the third fluid injector. There is a restriction orifice in the exhalation pathway. The controller is further programmed to selectively actuate the third fluid injector to inject the first fluid, which is is received in the exhalation pathway such that an exhalation pressure in the exhalation pathway is within a predetermined range during at least a portion of the exhalation cycle. 
     An improved ventilator includes a first fluid rail for storage of a predetermined volume of a first fluid and a second fluid rail for storage of a predetermined volume of a second fluid. A first fluid injector is fluidly connected with the first fluid rail and a second fluid injector is fluidly connected to the second fluid rail. A mixing chamber is fluidly connected with the first fluid injector and the second fluid injector and with an inhalation pathway. A third fluid injector is fluidly connected with the first fluid rail and with an exhalation pathway. There is a mouthpiece for a patient is fluidly connected with the exhalation pathway and an APL valve fluidly connected with the inhalation pathway and the mouthpiece. A breathing-rate-control valve is fluidly connected with the exhalation pathway and a drain conduit. A controller is operatively connected with the first fluid injector; the second fluid injector, the third fluid injector and the breathing-rate-control valve and programmed to actuate the breathing-rate-control valve to generate a breathing cycle including an inhalation cycle and an exhalation cycle; selectively actuate the first fluid injector and the second fluid injector to inject the first fluid and the second fluid respectively to form a mixture of the first fluid and the second fluid in the mixing chamber for inhalation by a patient during the inhalation cycle, whereby a mixture ratio between the first fluid to the second fluid can vary between 0:100 and 100:0; and actuate the third fluid injector to generate back pressure in the exhalation pathway during an exhalation cycle. Preferably the first fluid is air and the second fluid is oxygen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a ventilator according to an embodiment. 
         FIG.  2    is a top planar view of the ventilator of  FIG.  1   . 
         FIG.  3    is an elevational view of the ventilator of  FIG.  1   . 
         FIG.  4    is an elevational view of the ventilator of  FIG.  1    with a panel removed. 
         FIG.  5    is a detailed view of region A of the ventilator of  FIG.  4   . 
         FIG.  6    is a partial perspective view of the ventilator of  FIG.  1   . 
         FIG.  7    is a detail view of region B of the ventilator of  FIG.  6   . 
         FIG.  8    is a partial perspective view of the ventilator of  FIG.  1   . 
         FIG.  9    is a partial elevational view of the ventilator of  FIG.  5   . 
         FIG.  10    is a partial elevational view of the ventilator of  FIG.  6   . 
         FIG.  11    is a schematic view of the ventilator of  FIG.  1   . 
         FIG.  12    is a schematic view of a control system of the ventilator of  FIG.  1   . 
         FIG.  13    is a flow chart view of an algorithm for setting up the ventilator of 
         FIG.  1    to operate in the PCV mode of operation. 
         FIG.  14    is a schematic view of a ventilator according to another embodiment. 
         FIG.  15    is schematic view of a ventilator according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S) 
     Referring to the figures and first to  FIG.  1   , there is shown ventilator  10  according to an embodiment. Ventilator  10  includes platform  20 , body  30  and input/output device  40 . Platform  20  is rectangular in shape and includes base frame  50  upon which support plate  60  is arranged to support body  30  and input/output device  40 . Four swivel casters  70  are each connected near respective corners of platform  20  such that ventilator  10  is rollable and moveable. Swivel casters  70  preferably are the type that are anti-static such that an electric charge does not accumulate on ventilator  10  when it is moved. At least one of swivel casters  70 , and preferably at least two of them, includes a brake (not shown) that can be manually operated to secure ventilator  10  in a fixed position. Platform  20  may also be adapted to support at least two gas cylinders or bottles, and in the illustrated embodiment air cylinder  80  and oxygen cylinder  90  (best seen in  FIG.  8   ), that are mounted vertically near end  100  and secured to ventilator  10  by brackets  110 , which can be v-block type brackets with quick release straps  115 . Although cylinders  80  and  90  can be mounted in other configurations, applications are typically restricted to the vertical orientation due to safety regulations on the handling and storing of pressurized cylinders. Platform  20  has a larger footprint than body  30  and input/output device  40  to provide stability to ventilator  10 , which reduces the likelihood of the ventilator teetering when it&#39;s moved and allows end  120  to be pushed under a patient&#39;s bed or surgery table. 
     Body  30  includes upper frame  130  (best seen in  FIG.  4   ) upon which enclosure  140  is arranged. Enclosure  140  includes box  142  that includes a top, a bottom and three sides and removeable access plate  144  (best seen in  FIG.  3   ) that when combined with box  142  forms a fully enclosed body  30 . Preferably enclosure  140  is fabricated from stainless steel. In an exemplary embodiment, box  142  and access plate  144  can be laser cut from plate metal, and box  142  can be folded into the box form illustrated in  FIG.  1   . In alternative embodiments plate  60  of platform  20  can act as the bottom of enclosure  140  such that box  142  would then have four sides (the top and three sides). Enclosure  140  encloses various components of ventilator  10 , such as circuit components and electronics as will be described in more detail below. Rear handle  150  (best seen in  FIG.  6   ) and a pair of side handles  160  (best seen in  FIG.  3   ) provide a means for a healthcare worker to grasp and move ventilator  10  around. As used herein, terms like rear, front, top, bottom, upper and lower are employed to provide a frame of reference when discussing ventilator  10  and are not necessarily to be taken literally, since for example a rear of ventilator  10  in one context such as a patient&#39;s context can be considered a front of ventilator  10  in another context such as a healthcare worker&#39;s context. Rear handle  150  is suited for pushing the ventilator through a facility, such as a hospital, and side handles  150  can be employed to help position ventilator  10  next to a bed or surgery table. 
     Base frame  50  (seen in  FIG.  1   ) and upper frame  130  (seen in  FIG.  4   ) are preferably constructed from aluminum extrusion, which is a common form of aluminum that can be assembled quickly and inexpensively. Additionally, aluminum extrusion including closed-off t-slots is easy to clean and is a material known to be used in medical equipment. 
     Ventilator  10  also includes central post  170  (best seen in  FIG.  8   ) that is securely connected with platform  20 , and preferably with frame  50  of the platform, and extends vertically therefrom. Central post  170  provides a rigid support to secure body  30  and input/output device  40  and to attach and secure other equipment associated with ventilator  10 , such as brackets  110  employed for securing air and oxygen cylinders  80  and  90  respectively. 
     Referring again to  FIG.  3   , input/output device  40  includes touchscreen  180  (and preferably with an integrated operating system) and encoder wheel  190  positioned adjacent the touchscreen. Parameters associated with the use of ventilator  10  (such as tidal volume or inhale pressure as will be described in more detail below) are displayed on touchscreen  180  in one or more views. Each parameter can be adjusted by selecting the parameter by touching a respective portion of touchscreen  180  associated with that parameter and rotating encoder wheel  190  to cause a value of the parameter to change. Indicator lights  195  are positioned adjacent touchscreen  180  below encoder wheel  190  in the illustrated embodiment and provide visible status information related to ventilator  10 , such as alarms, warnings and operational readiness, and can be mono-coloured or multi-coloured light emitting diodes (LEDs) or other types of lights. As an example, status information can include air-supply pressure and temperature, oxygen-supply pressure and temperature, flow meter pressure level and temperature, battery power level, fluid injector diagnostics, mixture pressure and temperature, settable peak inlet pressure level, settable CO2 and blood O2 alarms, settable volume flow limits (for PCV control), settable PEEP limits, settable gas temp limits, and cough/distress detection via pressure abnormalities. 
     Referring to  FIGS.  5  and  12   , ventilator  10  also includes controller  200  that in the illustrated embodiment includes injector controller  205  and ventilator controller  210 . Controllers  205  and  210  are operatively connected with each other over communication link  215 , which can be one or more digital communication links and/or one or more analogue communication links. For example, communication link  215  can include a CAN communication bus. Injector controller  205  controls the actuation of fluid injectors that inject air from air cylinder  80  and oxygen from oxygen cylinder  90 , which will be described in more detail below, and is responsible for delivering commanded quantities of air and oxygen, and other fluids in other embodiments. Ventilator controller  210  is responsible managing breathing rate control and the delivery of fluids to the patient, and in this regard ventilator controller  210  commands the injector controller  205  to deliver the commanded quantities of air and oxygen, and the other fluids in the other embodiments. Ventilator controller  210  interfaces with input/output device  40  for displaying status information to a healthcare professional and for receiving commands from the healthcare professional for controlling ventilator  10 . Controller  200  communicates with and/or commands the various sensors and actuators employed in ventilator  10 , as will be described in more detail below, and together controller  200  and the various sensors and actuators is represented as control system  201  in  FIG.  12   . Controllers  205  and  210  can include both hardware and software components. The hardware components can include digital and/or analog electronic components. In the illustrated embodiment controllers  205  and  210  each include a processor and memories, including one or more permanent memories, such as FLASH, EEPROM and a hard disk, and a temporary memory, such as SRAM and DRAM, for storing and executing a program. As used herein, the terms algorithm, module and step refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. In exemplary embodiments the algorithms, modules and steps herein are part of electronic controllers  205  and  210 . In other embodiments controllers  205  and  210  can be replaced by a single controller that combines the functionality of controllers  205  and  210 . 
     Ventilator  10  can either be powered by 100 Vac-240 Vac standard mains-electricity supply or by battery  220  that operates at twelve volts dc (12 Vdc). Charging system  230  is included with ventilator  10  such that when the ventilator is plugged in the standard mains-electricity supply (for example, a wall outlet in a hospital) the charging system can charge battery  220 . Although only one battery  220  is illustrated, preferably ventilator  10  includes two batteries  220  such that one of the batteries can be changed without stopping the ventilator (referred to as hot swapping). Controller  200  includes a voltage regulator to ensure there is a constant 12 Vdc supply. Battery  220 , charging system  230  and other related power supply equipment are preferably located at a bottom of enclosure  140 , which helps to lower the center of gravity of ventilator  10 . 
     With reference to  FIGS.  5  and  11   , air filter assembly  240  is selectively fluidly connected with either air cylinder  80  or with external air supply  250  (seen in  FIG.  11   ) such as a hospital air ring main supply. Air filter assembly  240  connects through hose  260  to male connector  270 , which in the illustrated embodiment is a male Schrader valve connection. Female connectors  280  and  290 , in the form of female Schrader valve connections in the illustrated embodiment, are associated with air cylinder  80  and external air supply  250  respectively and are selectively connected with male connector  270 . The hospital air ring main supply is typically maintained at a desired air supply pressure, for example 4 bar. Regulator  300  regulates air pressure to the desired air supply pressure. For all connectors herein, in other embodiments, the sex between respective mating connectors can be reversed. 
     Oxygen filter assembly  310  is selectively fluidly connected with oxygen cylinder  90  or with external oxygen source  320  (seen in  FIG.  11   ) such as a hospital oxygen ring main supply. Oxygen filter assembly  310  connects through hose  330  to male connector  340 , which in the illustrated embodiment is a male Schrader valve connection. Female connectors  350  and  360 , in the form of female Schrader valve connections in the illustrated embodiment, are associated with oxygen cylinder  90  and external oxygen supply  320  respectively and are selectively connected with male connector  340 . The hospital oxygen ring main supply is typically maintained at a desired oxygen supply pressure, for example  4  bar. Regulator  370  regulates air pressure to the desired air supply pressure. Air and oxygen regulators  300  and  370  respectively are preferably medical standard pin index regulators that ensure that the correct type of fluid (in this case air and oxygen respectively) are connected to regulators  300  and  370 . 
     Air-filter assembly  240  includes filter  380 , pressure sensor  390  and temperature sensor  400 . Pressure sensor  390  measures air-supply pressure and temperature sensor  400  measures air-supply temperature downstream from regulator  300  and filter  380 . Oxygen-filter assembly  310  includes filter  410 , pressure sensor  420 , and temperature sensor  430 . Pressure sensor  420  measures oxygen-supply pressure and temperature sensor  430  measures oxygen-supply temperature downstream from regulator  370  and filter  410 . Although sensors  390  and  400  are included in air-filter assembly  240  and sensors  420  and  430  are included in oxygen-filter assembly  310 , in other embodiments these sensors do not need to be part of these assemblies and can be installed into ventilator  10  individually and separately. 
     Referring to  FIGS.  5 ,  9  and  11   , injector manifold assembly  440  includes air rail  450  fluidly connected with air-filter assembly  240  to receive filtered air, and oxygen rail  460  fluidly connected with oxygen-filter assembly  310  to receive filtered oxygen. Rails  450  and  460  allow storage of a predetermined volume of air and oxygen respectively, and can be an accumulator, a conduit, a pipe or other type of fluid container. Rails  450  and  460  can be connected to their respective filter assemblies  240  and  310  through rigid and/or flexible conduits. Air injectors  470  and  480  are connected with air rail  450  and with injector manifold  490 , and oxygen injectors  500  and  510  are connected with oxygen rail  460  and with injector manifold  490 . In the illustrated embodiment air injectors  470  and  480  are connected directly to air rail  450  and to ports  472  and  482  in injector manifold  490 , and oxygen injectors  500  and  510  are connected directly to oxygen rail  460  and to ports  502  and  512  in injector manifold  490 ; however, this is not a requirement and in other embodiments each injector  470 ,  480 ,  500  and  510  can be connected to their respective rail  450 ,  460  and/or respective ports  472 ,  482 ,  502  and  512  in injector manifold  490  through rigid and/or flexible conduits. Injector manifold  490  significantly reduces the amount of pipe work and fittings required, which simplifies the layout in enclosure  140  (seen in  FIG.  5   ) and reduces the assembly time of ventilator  10 . Injector manifold  490  has a plurality of through holes with a space for nuts  492  (seen in  FIG.  9   ) to be fitted to studs  452  in air rail  450  and studs  462  in oxygen rail  460  whereby tightening nuts  492  will pull air rail  450  and oxygen rail  460  onto respective injectors  470 ,  480 ,  500  and  510  and sandwich the injectors between the rails and the injector manifold. In an exemplary embodiment injector manifold  490  is made from a thermoplastic, such as Delrin, or other similarly suitable material for absorbing sound generated by injectors  470 ,  480 ,  500  and  510 . Injectors  470 ,  480 ,  500  and  510  are positioned opposite each other, and more particularly air injector  470  is positioned opposite oxygen injector  500  and air injector  480  is positioned opposite injector  510 , whereby controller  200  can actuate respective pairs of injectors at the same time in a manner to have a noise cancelling effect. 
     In an exemplary embodiment fluid injectors  470 ,  480 ,  500  and  510  are automotive-type-gaseous-fuel injectors that include an injection valve and a solenoid that is actuated to open the injection valve during an injection event to deliver precise quantities of fluid per injection, also known as commanded quantities. In other embodiments different types of fluid injectors can be employed, including fluid injectors that are hydraulically actuated. The quantity of fluid injected is controlled by the opening time and opened time of each of the injectors, which is collectively referred to herein as the opened time. The opened time of each fluid injector  470 ,  480 ,  500  and  510  is controlled by controller  200  that generates respective electrical signals that have respective pulse widths that actuate respective fuel injectors. The actuation of each of the injectors is compensated against changes in injection pressure in order to deliver a desired quantity of fluid. Injection pressure is defined herein as a difference between upstream fluid pressure and downstream fluid pressure with respect to a closed injection valve (it is understood that injection pressure changes during injection events due to changes in pressure upstream and downstream of the opened injection valve). Changes in pressure and temperature of a fluid upstream and of a fluid downstream of an injection valve can alter an injection pressure for the injection valve. In an exemplary embodiment, injectors 470, 480, 500 and 510 can deliver between 2 milliliters (ml) and 100 ml of fluid (that is, air or oxygen) per injection when the injection pressure is around 4 bar, and can be actuated between one (1) shot per second and forty (40) shots per second. A typical healthy human breath requires approximately 500 ml of air per breath cycle (also known as the ‘tidal volume’), and the breath rate is typically 10-12 breaths per minute, for a total gas exchange volume rate of approximately 5-6 litres/minute. 
     Air injector  470  is configured to introduce (that is, inject) air from air rail  450  into mixing chamber  520  within manifold  490 . Oxygen injector  500  and  510  are both configured to introduce (that is, inject) oxygen from oxygen rail  460  into mixing chamber  520 . Oxygen injector  510  may be employed as a backup injector for oxygen injector  500  and is not required in other embodiments. An air and oxygen mixture can be formed within mixing chamber  520  by selective activation of air injector  470  and oxygen injectors  500  and  510 . Since air contains 20.95% oxygen by volume already, the mixture formed in mixing chamber  520  can be considered an oxygen-enhanced air mixture, and the percentage of oxygen in the oxygen-enhanced air mixture can theoretically vary between 20.95% oxygen content by volume (no enhancement) up to 100% oxygen content by volume (no air). The gas injection approach is hugely dynamic in capability. For example, it has the capability to deliver 100% air in one breath and 100% oxygen in the next. Alternatively, a high concentration of oxygen can be delivered at the start of the breath and a low concentration later on in the breath to target oxygen delivery further down into the lungs. Still further, a desired oxygen concentration can be targeted for delivery to one or more different regions of the respiratory system by adjustably varying the oxygen concentration during selected timeframes during the inhalation cycle. 
     In other embodiments a dosing injector can be added to injector manifold assembly  440 , or alternatively, rather than injector  510  a dosing injector may be employed. A dosing injector is employed to inject a drug or other substance, which can be in a liquid state and/or a gaseous state, into mixing chamber  520  for delivery to the lungs by phasing injection such that it targets different areas of the lung according to time of injection during the breath. Mixing chamber  520  is fluidly connected to inhalation pathway  540  by conduit  530 . Mixing chamber  520  and/or conduit  530  (acting as a restriction orifice) can operate as a dampener, or low pass filter, to remove pressure pulsations caused by injection of the fuel injectors. A restriction orifice can be located at alternative locations along inhalation pathway  540  in order to remove pressure pulsations caused by injection of fluids. Injector manifold  490  include a port for fluid connection with conduit  530 . In other embodiments injector manifold  490  can includes a port fluidly connected to mixing chamber  520  and to a green hospital bag that allows a healthcare professional to manually fill a patient&#39;s lungs. 
     Air injector  480  is configured to introduce air into manifold  490  for delivery to exhalation pathway  560  by conduit  550 . Injector manifold  490  includes a port for fluid connection with conduit  550 . Air injector  480  is employed to generate positive end-expiratory pressure (PEEP). PEEP is a mode of therapy used in conjunction with mechanical ventilation. At the end of mechanical or spontaneous exhalation, PEEP maintains a patient&#39;s airway pressure above atmospheric pressure by exerting pressure that opposes passive emptying of the lung. This pressure is typically achieved by maintaining a positive pressure flow at the end of exhalation, also referred to as a back pressure. PEEP therapy can be effective when used in patients with a diffuse lung disease that results in an acute decrease in functional residual capacity (FRC), which is the volume of gas that remains in the lung at the end of a normal expiration. FRC is determined by primarily the elastic characteristics of the lung and chest wall. 
     Pressure sensor  570  and temperature sensor  580  measure mixture pressure and mixture temperature respectively of the mixture in mixing chamber  520 . Injector manifold  490  includes ports  472  and  482  (seen in  FIG.  9   ) for fluid connection with sensors  570  and  580  respectively. Air-supply pressure and mixture pressure can be employed to determine air-injection pressure. Oxygen-supply pressure and mixture pressure can be employed to determine oxygen-injection pressure. Mixture density can be determined by mixture pressure, mixture temperature and a mass mixture ratio between injected air and injected oxygen in mixture chamber  520 . The mass mixture ratio can be determined based on a mass of air injected into mixing chamber  520  relative to a mass of oxygen injected into the mixing chamber. Air-supply pressure and temperature can be employed to determine air-supply density, and oxygen-supply pressure and temperature can be employed to determine oxygen-supply density. The mass of air injected per injection event can be determined based on the air-supply density, the air-injection pressure and the on-time of air injector  470  or  480 . The mass of oxygen injected per injection event can be determined based on the oxygen-supply density, the oxygen -injection pressure and the on-time of oxygen injector  500  or  510 . 
     Piping manifold  600  is positioned at the top of enclosure  140  and preferably has two fluid connections with injector manifold  490  and four fluid connections to the patient. Mixture conduit  530  (seen in  FIGS.  5  and  11   ) for inhale extends between port  532  (seen in  FIG.  9   ) in injector manifold  490  and port  534  (seen in  FIG.  10   ) in piping manifold  600 . PEEP conduit (seen in  FIGS.  5  and  11   ) for exhale extends between port  552  (seen in  FIG.  9   ) in injector manifold  490  and port  554  (seen in  FIG.  10   ) in piping manifold  600 . The four fluid connections to the patient are by way of flexible hose connections  602 ,  604 ,  606 , and  608 , seen in  FIG.  11   . Hose  602  fluidly connects to inhalation pathway  540  at port  542  (seen in  FIG.  7   ). Hose  604  fluidly connects to exhalation pathway  560  at port  562  (seen in  FIG.  7   ). Hoses  606  and  608  are capillary tube connections between venturi flow meter  640  and ports  607  and  609  (seen in  FIG.  10   ) in piping manifold  600 . A majority of piping manifold  600  is within enclosure  140  except for a portion that protrudes out of a top of the enclosure (best seen in  FIGS.  5  and  7   ) where hoses  602 ,  604 ,  606  and  608  to the patient are connected. Piping manifold  600  is configured to be along inhalation pathway  540  between the patient and mixing chamber  520 , and along exhalation pathway  560  between the patient and drain conduit  610  connected, for example, to a hospital extraction system. Pressure relief valve  620  is connected to port  620  (seen in  FIG.  9   ) in piping manifold  600  and fluidly connected to inhalation pathway  540  and acts as a safety device to ensure inhalation pressure does not rise above a maximum inhalation pressure. In an exemplary embodiment the maximum inhalation pressure is set to 70 centimeters of water (cmH 2 O). An output of pressure relief valve  620  is fluidly connected to drain conduit  610  for extraction. Adjustable pressure limit (APL) valve  630  is connected with piping manifold  600  through flexible hose  602  and with venturi flowmeter  640 . APL valve  630  allows excess fresh mixture flow and exhaled gases from the patient to leave the system while preventing additional mixture from mixing chamber  520  from entering (that is, it prevents back flow during the exhalation cycle). Venturi flowmeter  640  is fluidly connected with patient mouthpiece  650 . Venturi flowmeter pressure sensors  660  and  670  are connected to ports  662  and  672  (seen in  FIG.  7   ) respectively in piping manifold  600  and are fluidly connected to hoses  606  and  608  respectively. Venturi flowmeter pressure sensors  660  and  670  can be employed in place of pressure sensor  570  that measures mixture pressure in mixing chamber  520 . Similarly, temperature sensor  580  that measures mixture temperature in mixing chamber  520  although does improve the operation of ventilator  10  it is not required in other embodiments. Exhalation pathway  560  passes through variable-flow restriction valve  680  in piping manifold  600 . Variable-flow restriction valve  680  is adjusted along with PEEP air injector  480  to control back pressure. In other embodiments variable-flow restriction valve  680  can be replaced with a fixed restriction orifice. Breathing rate of the patient is controlled by the opening and closing of breathing-rate-control valve  690 , which preferably is an electrically operated diaphragm valve, but can be other types of valves in other embodiments. Breathing-rate-control valve  690  is fluidly connected to port  692  (seen in  FIG.  10   ) and to exhalation pathway  560 . 
     Preferably, controller  200  can selectively perform self-diagnostic checks including pressure decay test for leaks, pressure and temperature sensor calibration, flow meter calibration and fluid injector calibration. With reference to  FIG.  13   , algorithm  700  in controller  200  for setting up ventilator  10  for the PCV mode of operation includes, for example, setting inhale pressure (Pinsp) in step  710  at a level between a range (e.g. 0-60 cmH 2 O), setting breathing rate (respiration rate RR) in step  720  at a level within a range (e.g. 0-30 p/min), setting I:E ratio (inhale to exhale time ratio) in step  730  at a level within a range (e.g. 5:1 to 1:5), setting PEEP (back pressure) in step  740  at a level within a range (e.g. 0-12 cmH 2 O), setting maximum inhalation pressure (PMax) in step  750  at a level within a range (e.g. 0-100 cmH 2 O), setting pressure rise rate in step  760  at a level within a range (e.g. 1-10 fastest to slowest). The steps in algorithm  700  can be performed in a different order than illustrated and described. In other embodiments ventilator  10  can be setup in the VCV mode of operation by a calculation methodology. 
     Referring now to  FIG.  14   , there is shown ventilator  12  according to another embodiment of the present disclosure. Elements in common with other embodiments illustrated herein are referenced by the same reference numbers, and if they operate and function in the same way, may not be described again in relation to other embodiments. In addition to air injectors  470 ,  480  and oxygen injector  500 , ventilator  12  includes a fourth fluid injector  515  configured to selectively introduce (that is, inject) a fluid from a separate fluid supply such as vessel  95  (arranged on ventilator  12 ) and/or external separate fluid supply  325 . Vessel  95  may be a cylinder of compressed gaseous fluid or another supply source capable of delivering fluid at a desired supply pressure to rail  465  and/or in some embodiments directly to fourth injector  515 . Fourth fluid injector  515  may be configured to introduce (separately and independently from that of injectors  470 ,  480  and  500 ) a quantity of fluid into mixing chamber  520  by controlling the opening time and opened time of injector  515  where the actuation of the injector is similarly compensated against changes in injection pressure in order to deliver a desired quantity of fluid. Optional filter assembly  315  connects through hose  335  to male connector  345 , which in the illustrated embodiment can be a male Schrader valve connection. Female connectors  355  and  365 , in the form of female Schrader valve connections in the illustrated embodiment, are associated with supply  95  and  325  respectively and are selectively connected with male connector  345 . Regulator  375  regulates fluid pressure to the desired fluid supply pressure, but it is understood that depending on the type of fluid to be introduced to mixing chamber  520 , regulator  375  may not be required. Similar to air and oxygen regulators  300  and  370 , regulator  375  is preferably medical standard pin index regulators that ensure that the correct type of fluid is connected to regulator  375 . Filter assembly  315  includes filter  415 , pressure sensor  425 , and temperature sensor  435 . Pressure sensor  425  measures fluid-supply pressure and temperature sensor  435  measures fluid supply temperature downstream from regulator  375  and filter  415 . 
     Although sensors  425  and  435  are included in fluid filter assembly  315 , in other embodiments these sensors do not need to be part of these assemblies and can be installed into ventilator  12  individually and separately. Pressure and temperature sensors  425  and  435  send their respective measurement signals to controller  200 , which is adapted to the current embodiment, and controller  200  controls the actuation of third fluid injector  515 . 
     Referring now to  FIG.  15   , there is shown ventilator  13  according to another embodiment where like reference numerals to the previous embodiment have like reference numerals and may not be discussed in detail if at all. In this embodiment solid lines between elements represents fluid connections, such as air and oxygen, and dashed lines between elements represents control system connections, such as electromagnetic signals. Filter  800  is a mouthpiece filter for filtering fluids to (mostly) and from the patient. Filter  810  is located at an end of an inhalation pipe before it merges with an exhalation pipe, and filter  820  is located at an end of the exhalation pipe. Chamber  830  accepts injections from PEEP air injector  480 , which is employed in cooperation with variable-flow restriction valve  680  (or a fixed restriction orifice in other embodiments) to generate a back pressure near the end of the exhalation cycle. Chamber  830  may be an accumulator, a conduit, a pipe or other type of fluid container. Safety valve  840  located along the exhalation pathway allows a patient to breathe through safety valve  840  in the event there is a failure somewhere along the inhalation pathway. Safety valve  840  can be opened by the patient or healthcare professional by manually depressing an actuator (not shown) on safety valve  840 . Networking controller  850  allows communications with other ventilators for multi-ventilator monitoring. All embodiments herein can include networking controller  850  and can communicate with a network and/or networked ventilators in other embodiments. 
     Ventilators  10 ,  12  and  13  by employing fluid injectors  470 ,  480 ,  500  and  510 / 515  is remarkably a very accurate and dynamic technique for delivering the correct mixture ratio and quantity of oxygen and air to a patient. Ventilator embodiments herein are pressure control ventilators. The injector control software employed in controller  205  is similar to gaseous-fuel injector control software already employed in low-pressure gaseous-fuel automotive applications, which has been proven effective in extremely demanding operating conditions, since both applications operate with comparable fluid pressures. This control software also compensates for lower air and oxygen supply pressures (for example, as air cylinder  80  and oxygen cylinder  90  start to run out). Several of the components are borrowed from the automotive industry (such as fluid injectors  470 ,  480 ,  500  and  510 / 515 , rails  450 ,  460  and  465 , filter assemblies  240 ,  310  and  315 , and controller  205 ) and are relatively low cost since they are mass produced for automotive applications and are off the shelf and available in large quantities. Ventilators disclosed herein are designed to operate from a 12 Vdc voltage. For hospital use, a mains to 12V converter is employed, but fundamentally the ventilator can operate from a 12V battery in the field, in the ambulance, in the hospital corridor, and in less developed countries. A standard car battery can provide several hours of operation, for example approximately eight (8) hours. Ventilators  10 ,  12  and  13  are transportable while continuing to offer full mechanical ventilation and monitoring as the patient is trolleyed to and from ambulance to an intensive care unit or hospital room. 
     In other embodiments ventilators  10 ,  12  and  13  can include a vacuum facility selectively fluidly connected to exhalation pathway  560 . The vacuum facility when fluidly connected to exhalation pathway  560  can extract fluids from the lungs. 
     The vacuum facility can be a connection to an external vacuum system in a hospital or can include a vacuum pump in the ventilator to pump fluid out of the lungs. 
     An improved ventilator for mechanical ventilation during a breathing cycle including an inhalation cycle and an exhalation cycle is disclosed herein, the ventilator is configurable to be in fluid communication with a supply of a first fluid and including an inhalation pathway and an exhalation pathway, the ventilator comprising a first fluid injector in fluid communication with the supply of the first fluid for injecting the first fluid, wherein the inhalation pathway receives the first fluid injected by the first fluid injector; and a controller operatively connected with the first fluid injector and programmed to 1) selectively actuate the first fluid injector to inject the first fluid wherein the first fluid is received in the inhalation pathway such that an inhalation pressure in the inhalation pathway is within a predetermined range during the inhalation cycle. The first fluid can be air. 
     The ventilator may also be configurable to be in fluid communication with a supply of a second fluid, the ventilator further comprising a mixing chamber in fluid communication with the first fluid injector and with the inhalation pathway, wherein the first fluid injected by the first fluid injector is communicated to the inhalation pathway through the mixing chamber; and a second fluid injector in fluid communication with the supply of the second fluid for injecting the second fluid, wherein the second fluid injected by the second fluid injector is communicated to the inhalation pathway through the mixing chamber; wherein the controller is further programmed to selectively actuate the first fluid injector and the second fluid injector to inject the first fluid and the second fluid respectively to form a mixture of the first fluid and the second fluid in the mixing chamber for inhalation by a patient during the inhalation cycle, wherein a mixture ratio between the first fluid to the second fluid can vary between 0:100 and 100:0; and wherein a mixture pressure of the mixture of the first fluid and the second fluid is within the predetermined range during the inhalation cycle. The second fluid can be oxygen. 
     The ventilator can further comprise a third fluid injector in fluid communication with the supply of the first fluid for injecting the first fluid, wherein the exhalation pathway receives the first fluid injected by the third fluid injector; and a restriction orifice in the exhalation pathway; wherein the controller is further programmed to selectively actuate the third fluid injector to inject the first fluid wherein the first fluid is received in the exhalation pathway such that an exhalation pressure in the exhalation pathway is within a predetermined range during at least a portion of the exhalation cycle. 
     The improved ventilator can optionally include a dosing injector fluidly connected to the mixing chamber. 
     The ventilator may also include a third fluid rail for storage of a predetermined volume of a fluid; the third fluid rail being fluidly connected to a fourth fluid injector for introducing fluid into the mixing chamber. The ventilator controller may be further programmed to selectively actuate any combination of the first fluid injector, the second fluid injector, and the fourth fluid injector to form a mixture of fluids injected respectively therefrom in the mixing chamber for inhalation by a patient during the inhalation cycle, wherein the mixture comprises any combination from 0 to 100 percent of each of the fluids injected respectively therefrom; and wherein a mixture pressure of the mixture of the first fluid, second fluid and fourth fluid is within the predetermined range during the inhalation cycle. The fourth fluid can be oxygen, nitrous oxide or other fluid. 
     While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.