Abstract:
A high flow ventilation system delivers oxygen-enriched air to a patient at flow rates greater than 10 L/min using only conventional wall flow meters as found in most hospitals. The ventilation system combines the output of a plurality of wall flow meters into a specially configured gas mixing apparatus. The gas mixing apparatus provides oxygen-enriched air with an F i O 2  (fraction of inspired oxygen) of approximately 21-100% with a total oxygen flow rate of 10-20 L/min or higher as required for high flow ventilation therapy. The oxygen-enriched air is delivered to the patient through a bite block device that allows insertion of an endoscope while simultaneously delivering high flow ventilation therapy to the patient through a large annular air flow passage around the endoscope.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Application 62/117,852, filed on Feb. 18, 2015. This and all patents and patent applications referred to herein are incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to ventilation systems for delivering breathing gases to a patient. More particularly, it relates to a high flow ventilation system for delivering oxygen-enriched air to a patient during endoscopy procedures, such as bronchoscopy or gastrointestinal endoscopy. 
       BACKGROUND OF THE INVENTION 
       [0003]    Medical procedures are often performed using some form of sedation, ranging from mild anxiolysis to general anesthesia. While under the effects of sedation, a patient&#39;s respiratory drive may diminish, which can lead to lower levels of circulating oxygen. This diminished respiratory drive resulting in lower circulating oxygen is often managed by providing patients with supplemental oxygen during the procedure, often through a facemask or through a nasal cannula. Oxygen flow is controlled using a wall-mounted flow meter connected to a central pressurized oxygen supply system in the hospital, which allows the medical team to titrate oxygen flow going to the patient. Conventional flow meters found in most hospitals measure oxygen flow from 0-10, or sometimes 0-15, liters per minute (L/min), providing a measured flow of supplemental oxygen to patients during medical procedures. While this flow rate of oxygen may be adequate to support patients in some cases, it may not be adequate to support patients in instances where medical procedures are more complicated or prolonged, placing patients at risk for potential complications such as cardiovascular or respiratory compromise. 
         [0004]    Higher oxygen flow rates than those provided by the conventional wall-mounted flow meter will generally require a higher pressure oxygen source and a specialized high flow oxygen mixing and delivery system. These requirements can add significantly to the cost of ventilation therapy. Furthermore, while most hospital rooms are equipped with more than one standard wall oxygen flow meter, most are not equipped with high pressure oxygen sources. 
         [0005]    Endoscopy procedures, such as bronchoscopy or gastrointestinal endoscopy, may further compromise the ability of the patient to maintain adequate oxygenation because the endoscope partially occludes the airway during the procedure. Thus supplemental oxygen is of particular importance in these procedures. 
         [0006]    In instances where oxygen flow is insufficient to support patients, more invasive means of respiratory support may be required, such as endotracheal intubation and mechanical ventilation. These more invasive ventilation methods incur additional cost and add incrementally to the complexity and risk of the medical procedure. Furthermore, the presence of an endotracheal tube will interfere with the ability to perform endoscopy on the patient. 
         [0007]    Accordingly, a device which facilitates increased oxygen delivery to patients without requiring endotracheal intubation would be desirable for patients undergoing medical procedures, particularly those involving bronchoscopy or gastrointestinal endoscopy. It is preferable that this be accomplished with the use of conventional wall flow meters and without costly apparatus. 
         [0008]    The high flow ventilation system described herein may also be used for patients in acute respiratory distress as a temporizing measure while arrangements for invasive (endotracheal intubation) or non-invasive ventilation (continuous positive airway pressure) are made. 
       SUMMARY OF THE INVENTION 
       [0009]    In keeping with the foregoing discussion, the present invention provides a high flow ventilation system for delivering oxygen-enriched air to a patient that provides oxygen flow rates greater than 10 L/min using only conventional wall flow meters as found in most hospitals. This is accomplished by combining the output of a plurality of wall flow meters into a specially configured gas mixing apparatus. The gas mixing apparatus provides oxygen-enriched air with an F i O 2  (fraction of inspired oxygen) of approximately 21-100% with a total oxygen flow rate of 10-20 L/min or higher as required for high flow ventilation therapy. 
         [0010]    In one preferred embodiment, the oxygen-enriched air from the gas mixing apparatus is delivered to the patient through a specially configured bite block device that allows insertion of an endoscope while simultaneously delivering high flow ventilation therapy to the patient. A bite block is an apparatus designed to be placed between the upper and lower jaw to keep the patient&#39;s mouth open during medical procedures, such as bronchoscopy or gastrointestinal endoscopy. The configuration of the bite block device creates a large annular air flow passage around the endoscope, which facilitates the delivery of oxygen-enriched air to the lungs. Conventional bite blocks designed for endoscopy do not provide an air passage for ventilating the patient, requiring that supplemental oxygen be delivered to the patient through a nasal cannula or other means. 
         [0011]    Alternatively, the gas mixing apparatus of the invention can also deliver high-flow, oxygen-enriched air to a patient using a laryngeal mask airway, an endotracheal tube, an endoscopy mask or a standard ventilation mask. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic drawing of a gas mixing apparatus in accordance with the invention. 
           [0013]      FIGS. 2A-2E  are schematic drawings of the components of a bite block device in accordance with the invention. 
           [0014]      FIG. 3  is a schematic drawing of the bite block device assembled. 
           [0015]      FIG. 4  is a schematic drawing of the gas mixing apparatus and the bite block device assembled together. 
           [0016]      FIGS. 5A-5D  are drawings of a preferred embodiment of the gas mixing apparatus.  FIG. 5A  is a front view,  FIG. 5B  is a side view,  FIG. 5C  is a first end view and  FIG. 5D  is a second end view of the gas mixing apparatus  100 . 
           [0017]      FIGS. 6A-6F  are drawings of the components of a preferred embodiment of the bite block device. 
           [0018]      FIG. 7A  is a perspective view showing a version of a T-piece adapter with a bite block insert integrated directly into it. 
           [0019]      FIG. 7B  is a phantom view showing the interior structure of the T-piece adapter of  FIG. 7A . 
           [0020]      FIG. 7C  is a cutaway view showing a cross section of the T-piece adapter of  FIG. 7A . 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0021]      FIG. 1  is a schematic drawing of a gas mixing apparatus  100  in accordance with the invention. The gas mixing apparatus  100  utilizes a plurality of jet mixing devices  102 ,  104  for mixing pure oxygen with ambient air at the desired ratio. Each jet mixing device has a tubing barb  106 ,  108  that allows it to be connected via tubing to a standard wall oxygen flow meter. A jet mixing device, also commonly known as a Venturi device, is a gas mixing device that directs a flow of pressurized oxygen through a small diameter jet orifice positioned in a gas mixing chamber within a tubular housing with one or more air entrainment ports in the wall of the tubular housing. When the oxygen exits the jet orifice, ambient air is entrained through the ports into the housing and mixes with the oxygen in the gas mixing chamber. The size of the air entrainment ports regulates the ratio of oxygen to ambient air. Jet mixing devices or Venturi devices that can be used in the gas mixing apparatus are commercially available having fixed ratios from 24% to 60% oxygen or with an adjustable ratio from 24% to 60% oxygen. Commercially available jet mixing devices or Venturi devices are generally limited in the flow rate of oxygen that they are capable of delivering. The output from a plurality of jet mixing devices is therefore combined to provide oxygen flow rates greater than 10 L/min. 
         [0022]    A range of oxygen flow rate from 10 to 20 L/min is adequate for most applications. Thus, in the example shown in  FIG. 1 , the gas mixing apparatus  100  has a first jet mixing device  102  and a second jet mixing device  104  that are connected to a Y-connector  110 , which acts as a manifold to combine the output from the two jet mixing devices. If higher oxygen flow rates are desired, three or more jet mixing devices can be combined with an appropriately shaped manifold. A large diameter flexible tube is used to connect the outflow port  112  of the Y-connector  110  to the bite block device to direct the oxygen-enriched air from the gas mixing apparatus to the patient. 
         [0023]      FIGS. 2A-2E  are schematic drawings of the components of a bite block device  120  in accordance with the invention and  FIG. 3  is a schematic drawing of the bite block device  120  assembled. The bite block device  120  includes a bite block component  121 , a T-piece adapter  130  and a bite block insert  135 .  FIG. 2A  shows a top view and  FIG. 2B  shows a side profile view of the bite block component  121 . The bite block component  121  has a tubular body  122  with a flange  126  on one end of the tubular body. As seen in the top view of  FIG. 2A , there is a central passage  124  through the tubular body  122  of the bite block component  121 . The central passage  124  and the tubular body  122  can have an approximately rectangular cross section as shown, or alternatively they may each have a round, oval, oblong or other desired cross-sectional shape.  FIG. 2D  shows a top view and  FIG. 2E  shows a side profile view of the bite block insert  135  that facilitates connection of the T-piece adapter  130 , shown in  FIG. 2C , to the bite block component  121 . In the example shown, the bite block insert  135  has a rectangular external shape that is adapted to insert into the central passage  124  of the bite block component  121  and a circular internal passage  137  that is shaped for connection to a connection port  138  of the T-piece adapter  130 , which is shown in  FIG. 2C . Alternatively, the T-piece adapter  130  can be configured to connect directly to the bite block component  121  or these two components can be integrated together. 
         [0024]    At the top of the T-piece adapter  130  is an endoscope port  132  that is sized and shaped for insertion of an endoscope. The endoscope port  132  has a flexible diaphragm  131  with a central opening  133  or other sliding seal to seal around the body of the endoscope when it is inserted, while allowing longitudinal movement of the endoscope. On the right hand side of the T-piece adapter  130  is an inlet port  134  that is adapted for connection to the outflow  112  of the gas mixing apparatus  100  via a piece of flexible tubing. On the left hand side of the T-piece adapter  130  is an outlet port  136  that is adapted for connection to an air reservoir, for example an expandable/collapsible breathing bag. 
         [0025]      FIG. 4  is a schematic drawing of the high flow ventilation system with the gas mixing apparatus  100  and the bite block device  120  with the T-piece adapter  130  assembled together. In use, each jet mixing device of the gas mixing apparatus  100  is connected to a standard wall oxygen flow meter via a piece of flexible tubing. The outflow of the gas mixing apparatus  100  is connected in turn to the bite block device  120  via a piece of large diameter flexible tubing  140  that attaches to the inlet port of the T-piece adapter  130 . The flow rate of oxygen is adjusted to the desired level and the bite block component  121  of the bite block device  120  is inserted into the patient&#39;s mouth and held in place by a strap. An endoscope can then be inserted into the endoscope port  132  and through the bite block device  120  into the patient. High flow, oxygen-enriched air will be delivered through the annular space between the endoscope and the central passage of the bite block device and into the patient&#39;s lungs. 
         [0026]    The high flow ventilation system of  FIG. 4  may also be configured to include an air reservoir, an air heater and a humidifier. Sensors, monitoring devices and anesthesia delivery equipment may also be used with the ventilation system. 
         [0027]    The apparatus of the present invention can be made in many different configurations that meet the functional requirements for a high flow ventilation system described above. By way of example,  FIGS. 5A-5D  illustrate a preferred embodiment of the gas mixing apparatus.  FIG. 5A  is a front view,  FIG. 5B  is a side view,  FIG. 5C  is a first end view and  FIG. 5D  is a second end view of the gas mixing apparatus  100 .  FIGS. 6A-6F  are drawings of the components of a preferred embodiment of the bite block device  120 . 
         [0028]    The gas mixing apparatus  100  of  FIGS. 5A-5D  has a first jet mixing device  102  and a second jet mixing device  104  that are connected together by a Y-connector  110  having a single outflow port  112 . Each jet mixing device has a tubing barb  106 ,  108  for connecting to a standard wall oxygen flow meter with a piece of flexible tubing. As described above, each jet mixing device has a small diameter jet orifice  103  in fluid connection with the tubing barb  106 ,  108  and positioned within a gas mixing chamber  114  enclosed by the tubular housing  109 . One or more air entrainment ports  105  in the wall of the tubular housing  109  allow ambient air to be entrained into the housing and mixed with the oxygen. The size of the air entrainment ports  105  can be adjusted with a sliding, rotating or removable shutter  107  to regulate the ratio of oxygen to ambient air from 21% up to 100% oxygen. Each jet mixing device  102 ,  104  may have its own shutter  107  to adjust the size of its air entrainment ports  105  or a single shutter mechanism may be configured to adjust both jet mixing devices at once. 
         [0029]    The bite block device  120  of  FIGS. 6A-6F  includes a bite block component  121  and a T-piece adapter  130 .  FIG. 6A  shows a side profile view of the bite block component  121 , which has a tubular body  122  with a central passage  124  and a flange  126  on one end. The flange  126  is curved to conform to the curvature of a patient&#39;s mouth and has a plurality of hook-shaped lugs  128  for fastening a strap to attach the bite block device  120  to the patient. Preferably, the bite block component  121  is molded of a flexible polymer or elastomer for the patient&#39;s comfort.  FIG. 6B  shows a front view and  FIG. 6C  shows a bottom view of a T-piece adapter  130 . The T-piece adapter  130  has an endoscope port  132 , an inlet port  134 , an outlet port  136 , and a connection port  138  that is configured to connect to the bite block component  121 . The endoscope port  132  is furnished with a flexible diaphragm  131  with a central opening  133  to seal around the body of the endoscope when it is inserted, while allowing longitudinal movement of the endoscope.  FIG. 6D  is a top view,  FIG. 6E  is a bottom view and  FIG. 6F  is a side profile view of the bite block component  121  assembled together with the T-piece adapter  130 . 
         [0030]      FIGS. 7A-7C  show a version of the T-piece adapter  130  with the bite block insert  135  integrated directly into it.  FIG. 7A  is a perspective view of the T-piece adapter  130 ;  FIG. 7B  is a phantom view showing the interior structure of the T-piece adapter  130 ; and  FIG. 7C  is a cutaway view showing a cross section of the T-piece adapter  130 . 
         [0031]    The various components of the high flow ventilation system may be made by a variety of manufacturing processes, including machining, injection molding, rotational molding, casting, additive manufacturing, 3-D printing, etc, using medical grade polymers and elastomers or other suitable materials. 
         [0032]    The gas mixing apparatus  100  and the bite block device  120  of the high flow ventilation system may be provided to hospitals and medical providers as separate components or they may be provided together in a kit or procedure tray, along with connection tubing and other necessary components. Preferably, the kit or procedure tray will be provided sterile and ready to use. 
         [0033]    In alternative embodiments, the gas mixing apparatus  100  of the invention can also be used with a laryngeal mask airway, an endotracheal tube, an endoscopy mask or a standard ventilation mask. These components can also be provided in a kit or procedure tray for convenience of use.