Abstract:
A ventilator includes a first pathway configured to supply a first gas; a second pathway configured to supply a second gas; a bypass element configured to provide a portion of the first gas and a portion of the second gas, the bypass element comprising a rib adjacent to a bypass conduit, wherein fluid flow is substantially laminar adjacent to the conduit. A bypass element is described.

Description:
BACKGROUND AND SUMMARY 
       [0001]    A ventilator delivers a flow of pressurized gas, such as air and/or a mixture of air and extra (supplemental) oxygen, to the airway of a patient in order to assist in or substitute for the patient&#39;s breathing. A ventilator operates cyclically, such that the gas is provided to the patient during an inspiratory phase (corresponding to inhalation) and received from the patient during a subsequent expiratory phase (corresponding to exhalation). In order to provide a mixture of air and extra oxygen, for example, the ventilator receives air through an air pathway and pure oxygen through a separate oxygen pathway, and thus controls respective levels of each gas to obtain the desired mixture, provided to the patient during the inspiratory phase. 
         [0002]    Generally, the patient interacts with a ventilator through conduits or “limbs,” which conduct gas flow. A single limb ventilator provides a single conduit for inspiratory and expiratory phases, meaning that the patient receives (pressurized) gas from the ventilator during inhalation and discharges gas to the ventilator during exhalation through the same conduit. Typically, the discharged gas is directed through the air pathway of the ventilator. When the inspiratory gas flow includes a mixture of air and oxygen, for example, the expiratory gas flow necessarily includes at least a portion of the extra oxygen, resulting in “oxygen contamination” in the air pathway. Therefore, during the subsequent cycle of the inspiratory gas flow, the gas from the air pathway includes a higher concentration of oxygen than pure air. When the gas from the air pathway is mixed with additional oxygen from the oxygen pathway, the mixed gas provided to the patient has a higher than desired concentration of oxygen. 
         [0003]    In order to ensure that the proper mixture of air and oxygen are provided, a sample of the mixture is taken. Because of limitations of known flow meters used in the determination of the mixture, the flow rate or flow volume of the sample is generally much smaller than that of the ventilator. Presenting the sample can be problematic, particularly in view of the limitations of the flow sensors and volume sensors. Moreover, sensing the oxygen and air in both inspiration and expiration can cause obstructions and compromised flow. 
         [0004]    In one aspect, a ventilator includes a first pathway configured to supply a first gas; a second pathway configured to supply a second gas; a bypass element configured to provide a portion of the first gas and a portion of the second gas, the bypass element comprising a rib adjacent to a bypass conduit, wherein fluid flow is substantially laminar adjacent to the conduit. 
         [0005]    In another aspect, a bypass element configured to direct a first gas and a second gas from a ventilator, the bypass element comprising: a rib adjacent to a bypass conduit, wherein fluid flow is substantially laminar adjacent to the conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a conceptual view of a portion of a ventilator, according to a representative embodiment. 
           [0007]      FIG. 2  is a perspective view of a ventilator including a bypass element, according to a representative embodiment. 
           [0008]      FIG. 3  is a cross-sectional view of a bypass element, according to a representative embodiment. 
           [0009]      FIG. 4  is a cross-sectional view of a portion of a bypass element, according to a representative embodiment. 
           [0010]      FIG. 5  is a graphical representation of a flow calibration curve in accordance with a representative embodiment.  FIG. 6  is a graphical representation of a flow calibration curve in accordance with a representative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment according to the present teachings. However, it will be apparent to one having ordinary skill in the art 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 to not obscure the description of the example embodiments. Such methods and devices are clearly within the scope of the present teachings. 
         [0012]      FIG. 1  is a conceptual view of a portion of a ventilator, according to a representative embodiment. The portion of the ventilator shown comprises air or oxygen flow  101  about a plurality of ribs within the conduits of the ventilator. As shown, the air (or oxygen) is diverted via a bypass conduit  103  to a flow-meter or volume-meter (not shown), and because the ventilator is a closed-system, the air (or oxygen) is returned by a bypass return  104 . Notably, and as will become clearer as the present description continues, bypass conduits and returns are provided for both the air and oxygen of the ventilator so that the flow rates or flow volumes may be measured. 
         [0013]    The ventilator measures air flow in the range of approximately −240 to approximately +240 SLPM (Standard Liters per Minute) and O2 flow in the range of approximately 0 SLPM to approximately 240 SLPM. In a representative embodiment, the flow measurement is part of the gas delivery assembly. The bypass element with ribs  102  overcomes issues of fill for injection molded parts. Beneficially, the geometry improves the fill and reduces the pressure required in an injection molding process. The area close to side-wall and flow diversion has been kept to a size to reduce turbulence as the flow in this area is close to a laminar flow Reynolds number. Stated somewhat differently, the Reynolds number is in the range of laminar flow. 
         [0014]    Usefully, the ribs  102  are substantially straight ribs and are angled to the direction of the flow of plastic from the injection gate. Notably, the angle ensures the ribs  102  do not cut across the path of the bypass holes (interface between the bypass element  100  and the bypass conduit  103  and the bypass return  104 ), which could cause flow noise. There is no step at the points where the flow diverts; this reduces the possibility of substantial recirculation, which could cause flow noise on the signal from the mass flow sensor. 
         [0015]    Notably, the ribs  102  provide a low pressure drop so that while the air or oxygen flow  101  is at a comparatively high pressure, the flow of air or oxygen in the bypass conduit  103  after the ribs  102  is comparatively low (e.g., less than 2.5 cm H 2 O). As discussed above, the bypass element  100  is used with the mass flow sensor (not shown) to measure the flow range of the delivered gases. The mass flow sensor has a measurement ranger on the order of approximately 0 LPM to approximately ±1 LPM. The bypass element  100  thus diverts portion of the main flow across the mass flow sensor. The bypass conduit  102  has been sized to so that when the main flow is ±240 SLPM the diverted flow does not exceed the plus or minus 1 liter per minute range of the mass flow sensor. The mass flow sensor is calibrated with the bypass as described below in connection with  FIGS. 5 and 6 . 
         [0016]      FIG. 2  is a perspective view (with certain parts in exploded view) of a ventilator  200  including a bypass element  100 , according to a representative embodiment. Many aspects of the ventilator are known, and as such many details thereof are not described to avoid obscuring the features of the bypass element  100  of the representative embodiments. 
         [0017]    The bypass element  100  is provided along the regions of air and oxygen flow of the ventilator, and comprises conduits for bypassing oxygen and air to a flow sensor  206  and returning the bypass oxygen and air from the flow sensor  206 . As shown, the flow sensor comprises an oxygen flow sensor and an air flow sensor. 
         [0018]    The bypass element  100  comprises an oxygen bypass conduit  202  and an air bypass conduit  203 . The bypass element further comprises an oxygen bypass return  204  and an air bypass return  205 . The bypass element  100  further comprises ribs (not shown in  FIG. 2 ) that maintain substantially laminar flow (i.e., Reynolds number comparatively low). Air and oxygen follow respective circuitous routes from the outlets of conduits  202 ,  203 , through respective sensors of the flow sensor  206  and back to the element  100 . The oxygen is provided to an inlet of an oxygen bypass return  204  and the air is provided to an inlet of an air bypass return  205 , and thus back into the ventilator  200 . 
         [0019]      FIG. 3  is a cross-sectional view of a portion of a ventilator, according to a representative embodiment.  FIG. 3  illustrates the ribs  102  of the bypass element  100  in accordance with a representative embodiment from a side where a flow sensor may be attached. 
         [0020]      FIG. 4  is a cross-sectional view of a portion of a ventilator, according to a representative embodiment.  FIG. 4  illustrates the ribs  102  of the bypass element  100  in accordance with a representative embodiment from an end view. Thus, airflow is into or out of the plane of the drawing plane. 
         [0021]      FIGS. 5 and 6  are calibration curves useful in scaling the flow of oxygen and air, respectively, at a flow meter. 
         [0022]    While preferred embodiments are disclosed herein, many variations are possible which remain within the concept and scope of the invention. Such variations would become clear to one of ordinary skill in the art after inspection of the specification, drawings and claims herein. The invention therefore is not to be restricted except within the spirit and scope of the appended claims.