Abstract:
A gas flow diverter for increasing the turbulence of an incoming respiratory gas flow through a respiratory gas sensor is provided. The diverter is positioned at a patient or inlet end of a tube section of the sensor in order to divert the respiratory gas flow from the patient generally equally across the cross-sectional area of the tube section. The diverter can be formed integrally as a part of the sensor, or can be releasably attached to the sensor or to an adapter that is releasably connected to the inlet end of the sensor for use in situations in which the volume of the incoming respiratory gas flow from the patient is greatly reduced due to the size of the patient, i.e., when the patient is an infant.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional patent application U.S. application Ser. No. 10/863,697 and claims priority to U.S. Pat. No. 7,878,980 filed on Jun. 8, 2004 which claims priority to U.S. provisional application 60/478,706 filed on Jun. 13, 2003, the entirety of which are expressly incorporated herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to respiratory monitoring devices, and more specifically to a monitoring device with a gas flow diverter adapted specifically for use with infants. 
     BACKGROUND OF THE INVENTION 
     In order to measure the content of gas inhaled and exhaled by a patient utilizing a respirator, a monitoring device is often connected to the gas lines extending between the patient and the respirator in contact with the gases directed to and expired from the patient. To measure the volume and/or mass of the gas passing between the patient and the respirator, the monitoring device includes a sensor disposed within the path of the flowing gas in order to provide data on the gas flow that can be utilized to quantitatively determine the amount (volume and/or mass) of gas inhaled and/or exhaled by the patient. 
     For most sensors of this type, the gas flow is passed through a tube section of the sensor incorporating a type of restriction, and preferably a venturi, which creates a pressure drop between the inlet for the gas flow and the outlet for the gas flow from the tube section when the gas is flowing in either direction. This pressure difference is ascertained by a measuring device which senses the pressures at the gas flow inlet and gas flow outlet of the restriction in order to determine a corresponding flow rate for the gas flow which can then be used to determine the volumetric and/or mass flow rate of the gas. 
     However, based on the configuration of the restriction in the tube sections, in certain applications the measuring device is not capable of accurately determining the pressure differential within the tube section. More particularly, with regard to neonatal applications, due to the small volume of gas flowing into and out of the patient, with certain tube section designs the gas flow may pass completely through the center of the tube section without contacting the restriction. By not contacting the restriction, there is no consequent measurable pressure drop in the gas flow across the restriction. As a result, it is impossible for the measuring device to determine a volumetric and/or mass flow rate of the gas flowing through the tube section in order to effectively monitor the patient. 
     Therefore, it is desirable to develop a respirator sensor with a the tube section that is capable of directing the flow of gas through the tube section in a manner which ensures that the gas flow will contact the restriction present in the tube section, regardless of the size of the flow of gas. As a result, the tube section creates an effective pressure drop across the restriction within the section that can be measured by the measuring device to provide an accurate measurement of the volumetric or mass flow rate of the gas inhaled and exhaled by the patient. Further, it is desirable to form a device for this purpose that can be incorporated into original tube section constructions or can be used to retrofit existing tube sections in order to reduce the time and expense of forming tube sections with the device that is suitable for neonatal use. 
     SUMMARY OF THE INVENTION 
     According to a primary aspect of the present invention, a respirator sensor is provided that includes a generally hollow tubular section including a restriction, e.g., a venturi located within the center of the tube section. The tube section also includes a number of sampling sleeves or taps spaced along the restriction which withdraw a small amount of the gas flowing through the restriction at various points along the restriction in order to ascertain the magnitude of the pressure drop occurring across the restriction. The restriction disposed within the tube section does not extend completely across the interior of the tube section, such that gas is capable of flowing through the tube section around the restriction, thereby causing the measurable pressure drop. 
     In order to ensure that very small volume gas flows do not flow through the tube section without at least partially contacting the restriction to generate a measurable pressure drop, the tube section includes a baffle or gas flow diverter disposed within a gas flow inlet end of the sensor. The diverter is positioned on the tube section such that the entire gas flow contacts the diverter prior to entering the tube section. The shape of the diverter forces the gas flow to the outer portions of the passage through the tube section and subsequently allows a portion of the gas flow to flow into the center of the passage such that the gas flow is dispersed across the entire cross-sectional area of the tube section prior to encountering the restriction. Thus, the diverter serves to disperse the incoming flow of gas across the entire cross-sectional area of the interior of the tube section such that at least a portion of the incoming gas flow contacts the restriction to cause a measurable pressure drop in the gas flow as it flows across the restriction. 
     According to another aspect of the present invention, the gas flow diverter can be releasably attached to the tube section in the form of an adapter such that the tube section and sensor can be quickly and easily modified for use in either a conventional or a neonatal measurement and monitoring operation. 
     Numerous other aspects, features and advantages of the present invention will become apparent from the following detailed description taken together with the drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate the best mode currently contemplated of practicing the present invention. 
       In the drawings: 
         FIG. 1  is an isometric view of a respiratory sensor including a tube section connected between respiratory tubes and having a gas flow diverter constructed according to the present invention; 
         FIG. 2  is an isometric view of the tube section of  FIG. 1 ; 
         FIG. 3  a cross-sectional view along line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the tube section of  FIG. 2  with a neonatal tube adapter attached; 
         FIG. 5  is a side plan view of the gas flow diverter constructed according to the present invention; 
         FIG. 6  is an end plan view of the gas flow diverter of  FIG. 5 ; 
         FIG. 7  is a graph illustrating the error in gas flow measurements generated by various tube section designs at low gas flow volumes in comparison with the measurement errors created by the tube section and diverter of the present invention; 
         FIG. 8  is a cross-sectional view of a second embodiment of the present invention; and 
         FIG. 9  is an end plan view of the second embodiment of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, a respiratory sensor is indicated generally at  10  in  FIG. 1 . The sensor  10  is formed of a control housing  12  including a removable plug  13  from which extends a number of measuring lumens  14  formed integrally with one another in a bundle  15 . The lumens  14  are connected opposite the housing  12  to a tube section  16  having an inlet end  18  and an outlet end  20 . The tube section  16  can be formed of any suitable rigid, non-porous material, and is preferably formed from a hard plastic which allows the tube section  16  to be formed using any compatible molding process. The respective ends  18  and  20  of the tube section  16  are each connected to tubes  22  and  24  which are in turn connected to a patient and a ventilator (not shown) in order to direct gases from and into both the patient and the ventilator through the tube section  16 . The particular construction of the sensor  10  can vary from that shown in  FIG. 1 , with alternative constructions for the sensor  10  being disclosed in U.S. Pat. No. 5,929,831, commonly assigned with this application and incorporated herein by reference. 
     Referring now to  FIGS. 2-4 , the inlet end  18  has a collar  26  concentrically disposed around the inlet end  18  to form an inlet tube connection  28 . The outlet end  20  also has a collar  30  concentrically disposed around the outlet end  20  to form an outlet tube connection  32 . Between the collars  26  and  30 , the tube section  16  includes a number of reinforcing ribs  34  that extend between the collars  26  and  30  to increase the rigidity and durability of the tube section  16 . One of the ribs  34  further defines a number of taps or sampling sleeves  36 ,  38  and  40  to which the lumens  14  are each connected. Each of the sleeves  36 - 40  defines an aperture  42 - 46  therein that extends through the associated sleeve  36 - 40  and the aligned rib  34  into the interior of the tube section  16 . The connection of each of the lumens  14  to the sleeves  36 - 40  allows portions of the gas flowing through the tube section  16  to be directed along the lumens  14  to the control housing  12  for use in calculating and monitoring the flow rate of the gas flowing through the tube section  16 . 
     Between the inlet end  18  and outlet end  20 , the tube section  16  defines an interior passage  48  through which the respiratory gases flow. The passage  48  includes a restriction, which is preferably in the shape of a venturi  50  disposed, approximately equidistant, between the inlet end  18  and the outlet end  20 . The restriction  50  includes a main restricting member  52  that extends into the passage  48  in alignment with the rib  34  through which the apertures  42 - 46  extend, such that the apertures  42 - 46  also extend through the member  52  into fluid communication with the passage  48 . The restriction  50  also preferably includes a pair of fins  54  disposed generally opposite the main restricting member  52  and are spaced from one another. In a particularly preferred embodiment, the size of the main restricting member  52  is significantly larger than the size of the fins  54 , such that the main restricting member  52  extends into the passage  48  past the centerline of the passage  48 , in order to most effectively turbulate the flow of gas through the passage  48  to cause a pressure drop in the gas flow across the restriction  50 . In a preferred embodiment, the restricting member  52  and fins  54  have generally arcuate or curved outer surfaces located within the passage  48  such that the main member  52  and fins  54  operate to redirect the respiratory gas flow through the passage  48  into contact with each other, thereby creating a generally turbulent gas flow within the passage  48 . This causes the consequent pressure reduction across the restriction  50  which can be measured by sampling the gas flow at each end of the restricting member  52  through the apertures  42 - 46 . The pressure of the gas sampled at the apertures  42 - 46  and transmitted along the lumens  14  connected between sleeves  36 - 40  and the control housing  12  can then be utilized to determine the volume and/or mass flow rate of the gas flowing through the passage  48  and to monitor the breathing of the patient. 
     Due to variations in the configurations of the inlet end  18  and outlet end  20  of tube sections  16  made by different manufacturers, on certain occasions, e.g., when the sensor  10  is used in a neonatal application, the tube section  16  must be connected to an adapter  56  to properly attach and locate the tube  22  extending between the patient (not shown) and the tube section  16 . The adapter  56  includes a sleeve  58  engageable with the inlet connection  28  between the inlet end  18  and the collar  26 , and having a central opening  59  disposed in alignment with a nozzle  60  disposed opposite and extending outwardly from the sleeve  58 . The nozzle  60  is connected to the tube  22  extending from the patient and directs the respiratory gases into and out of the adapter  56  and the tube section  16 . The adapter  56  also includes gripping plate  61  integrally formed with and between the sleeve  58  and the nozzle  60  and through which the central opening  59  extends to facilitate the engagement of the adapter  56  with tube section  16 . 
     In order to ensure that the incoming gas stream passing through the adapter  56  into the tube section  16  contacts the restricting member  52  in a manner which produces a turbulent gas flow and a consequent pressure drop across the restriction  50  when the gas flow is small, e.g., when the patient is an infant, in one embodiment of the invention the inlet end  18  of the tube section  16  includes a baffle or gas flow diverter  62  positioned therein. The diverter  62  is positioned concentrically with respect to the inlet end  18 , passage  48 , and the adapter nozzle  60 , such that the incoming respiratory gas flow strikes the gas flow diverter  62  and is deflected around the diverter  62  substantially equally across the entire cross-sectional area of the passage  48 . 
     As best shown in  FIGS. 4-6 , in a preferred embodiment, the gas flow diverter  62  is formed with a body  64  having a flat or otherwise generally blunt end  66  positioned adjacent the inlet end  18 , and an inwardly tapering, frustoconical section  68  extending into the passage  48  from the flat end  66 . The tapering section  68  can extend away from the flat end  66  in a strictly conical fashion, or may be formed to have a slightly concave surface  70 , as best shown in  FIG. 5 , to assist in diverting the gas flow across the entire passage  48  within the tube section  16 . The diverter  62  can be formed of any suitable non-porous material, which can be rigid or semi-rigid in order to facilitate the insertion of the diverter  62  into the tube section  16 . However, in a preferred embodiment, the diverter  62  is formed of a metal, such as a stainless steel or aluminum, plastic or a rubber that is easily sterilizable for use with the tube section  16 . 
     The diverter  62  can be secured within the passage  46  at the inlet end  18  using any suitable means  71 ; such as an adhesive or a mechanical fastener, so long as the incoming gas flow is permitted to pass around the diverter  62  and into the passage  48 . In a preferred embodiment, the diverter  62  is secured within inlet end  18  by one or more locking members such as a number of deflectable fingers  72  formed on the inlet end  18  of the tube section  16  and engaged with the periphery of the flat end  66 . The fingers  72  are separated by slots  74  through which the respiratory gas stream striking the flat end  66  can flow into the passage  48 . The slots  74  disposed between the fingers  72  also enable each of the fingers  72  to be deflected slightly as the diverter  62  is inserted between the fingers  72 . Each finger  72  slides along the frustoconical section  68  of the body  64  until a locking tab or tabs  76  located on the outermost end of the fingers  72  engage corresponding notches  78  disposed on the flat end  66  of the diverter  62 . In a particularly preferred embodiment, the notches  78  are formed as a circumferential ridge disposed around the periphery  77  of flat end  66 . In this position, the diverter  62  is held by the fingers  72  concentrically with regard to the passage  48  defined by the tube section  16  during use of the sensor  10 . 
     Looking now at  FIGS. 5 and 6 , in a preferred embodiment, the flat end  66  is formed with a number of protrusions  80  thereon that extend outwardly from the flat end  66  in a direction opposite the frustoconical section  68 . The protrusions  80  define a number of ports  82  there between which are spaced from one another around the flat end  66  by the protrusions  80 . Any number of protrusions  80  and ports  82  can be formed on the flat end  66 , such that the number and positioning of the protrusions  80  and ports  82  on the flat end  66  can be defined as desired in order to direct the incoming gas flow striking the flat end  66  through the ports  82  and into the passage  48  at the desired locations. In a particularly preferred embodiment, four spaced protrusions  80  are formed on the flat end  66  to form four ports  82  between the protrusions  80  spaced equidistant from one another and at right angles to one another. These ports  82  are positioned in alignment with the slots  74  such that the portion of the gas flow passing through each port  82  subsequently enters the tube section  16  through the aligned slot  74 . 
     In operation, once the adapter  56  has been engaged with the inlet connection  28 , the incoming gas flow through the tube  22  passes into the nozzle  60  of the adapter  56  and strikes the flat end  66  of the diverter  62 . The incoming gas flow is directed by the protrusions  80  and ports  82  around the diverter  62  and through the slots  74  into the passage  48 . The portions of the gas flow passing through each slot  74  is allowed to expand along the concave surface  70  of the diverter  62  to fill the entire cross-sectional area of the passage  48 . Thus, at least a portion of the incoming gas flow is directed to impinge upon the main restricting number  52  while passing through the restriction  50  in order to generate a turbulent gas flow and a resulting pressure drop across the sampling sleeves  36 - 40 . 
     EXPERIMENTAL 
     To illustrate the effectiveness of the diverter  62  in creating measurable pressure drops within the tube section  16  of a sensor  10  with small incoming gas flows, a number of different experiments run utilizing tube sections  16  of various configurations both including and omitting the gas flow diverter  62 . In each of the experiments, a tube section  16  was connected to a 2.5 millimeter endotracheal tube through which a gas was pumped at flow rates varying from 5 ml/sec to 200 ml/sec. For each tube section  16  tested, the average inspired pressure and the maximum and minimum expired pressures were measured using the sampling sleeves  36 - 40 . The error percent for the maximum pressure and minimum pressure were calculated from the average, maximum and minimum pressure values, and subtracted from one another to determine the total expiratory error which is illustrated in each of Tables 1-7 and in the graph illustrated in  FIG. 7 . 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Competitive Tube 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Flow in liters/min. 
                 0.3 
                 0.6 
                 1.2 
                 1.8 
                 2.4 
                 3 
                 4.5 
                 6 
                 9 
                 12 
               
               
                 VOLUME: ml 
                 10 
                 20 
                 40 
                 60 
                 80 
                 100 
                 150 
                 200 
                 300 
                 400 
               
               
                 FLOW: ml/sec 
                 5 
                 10 
                 20 
                 30 
                 40 
                 50 
                 75 
                 100 
                 150 
                 200 
               
               
                 avg inspired pressure 
                 0.275 
                 0.877 
                 1.63 
                 2.473 
                 3.27 
                 4.02 
                 6.05 
                 8.25 
                 12.25 
                 16.15 
               
               
                 max expired pressure 
                 0.334 
                 0.897 
                 2.06 
                 3.88 
                 5.13 
                 4.92 
                 6.37 
                 8.49 
                 12.84 
                 17.02 
               
               
                 min expired pressure 
                 0.309 
                 0.786 
                 1.41 
                 2.17 
                 2.72 
                 3.91 
                 6.24 
                 8.412 
                 12.64 
                 15.96 
               
               
                 max expired % error 
                 21 
                 2 
                 26 
                 57 
                 57 
                 22 
                 5 
                 3 
                 5 
                 5 
               
               
                 min expired % error 
                 12 
                 −10 
                 −13 
                 −12 
                 −17 
                 −3 
                 3 
                 2 
                 3 
                 −1 
               
               
                 Total expired error 
                 9 
                 13 
                 40 
                 69 
                 74 
                 25 
                 2 
                 1 
                 2 
                 7 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 CPT - Old Tube Design 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Flow in liters/min. 
                 0.3 
                 0.6 
                 1.2 
                 1.8 
                 2.4 
                 3 
                 4.5 
                 6 
                 9 
                 12 
               
               
                 VOLUME: ml 
                 10 
                 20 
                 40 
                 60 
                 80 
                 100 
                 150 
                 200 
                 300 
                 400 
               
               
                 FLOW: ml/sec 
                 5 
                 10 
                 20 
                 30 
                 40 
                 50 
                 75 
                 100 
                 150 
                 200 
               
               
                 avg inspired pressure 
                 0.238 
                 n/r 
                 1.247 
                 n/r 
                 n/r 
                 1.967 
                 4.58 
                 6.16 
                 9.23 
                 12.08 
               
               
                 max expired pressure 
                 0.16 
                 n/r 
                 n/r 
                 n/r 
                 n/r 
                 n/r 
                 4.58 
                 6.19 
                 9.39 
                 11.96 
               
               
                 min expired pressure 
                 0.15 
                 n/r 
                 n/r 
                 n/r 
                 n/r 
                 n/r 
                 4.55 
                 6.14 
                 9.26 
                 12.13 
               
               
                 max expired % error 
                 −33 
                 n/r 
                 −100 
                 n/r 
                 n/r 
                 −100 
                 0 
                 0 
                 2 
                 −1 
               
               
                 min expired % error 
                 −37 
                 n/r 
                 −100 
                 n/r 
                 n/r 
                 −100 
                 −1 
                 0 
                 0 
                 0 
               
               
                 CPT old total expired 
                 4 
                 n/r 
                 0 
                 n/r 
                 n/r 
                 0 
                 1 
                 1 
                 1 
                 −1 
               
               
                 error 
               
               
                   
               
               
                 *n/r—no reading 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 CPT New Tube Design Without Baffle 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Flow in liters/min. 
                 0.3 
                 0.6 
                 1.2 
                 1.8 
                 2.4 
                 3 
                 4.5 
                 6 
                 9 
                 12 
               
               
                 VOLUME: ml 
                 10 
                 20 
                 40 
                 60 
                 80 
                 100 
                 150 
                 200 
                 300 
                 400 
               
               
                 FLOW: ml/sec 
                 5 
                 10 
                 20 
                 30 
                 40 
                 50 
                 75 
                 100 
                 150 
                 200 
               
               
                 avg inspired pressure 
                 0.429 
                 0.86 
                 1.73 
                 2.63 
                 3.62 
                 4.609 
                 7.018 
                 9.158 
                 12.94 
                 16.54 
               
               
                 max expired pressure 
                 0.3 
                 0.8 
                 n/r 
                 n/r 
                 n/r 
                 n/r 
                 6.78 
                 9.95 
                 12.88 
                 16.55 
               
               
                 min expired pressure 
                 0.25 
                 0.39 
                 n/r 
                 n/r 
                 n/r 
                 0.445 
                 6.5 
                 9.87 
                 12.59 
                 16.01 
               
               
                 max expired % error 
                 −30 
                 −7 
                 −100 
                 −100 
                 −100 
                 −100 
                 −3 
                 9 
                 0 
                 0 
               
               
                 min expired % error 
                 −42 
                 −55 
                 −100 
                 −100 
                 −100 
                 −90 
                 −7 
                 8 
                 −3 
                 −3 
               
               
                 CPT new no invention 
                 12 
                 48 
                 0 
                 0 
                 0 
                 −10 
                 4 
                 1 
                 2 
                 3 
               
               
                   
               
               
                 *n/r—no reading 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 CPT - Old Tube Design With Sieve 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Flow in liters/min. 
                 0.3 
                 0.6 
                 1.2 
                 1.8 
                 2.4 
                 3 
                 4.5 
                 6 
                 9 
                 12 
               
               
                 VOLUME: ml 
                 10 
                 20 
                 40 
                 60 
                 80 
                 100 
                 150 
                 200 
                 300 
                 400 
               
               
                 FLOW: ml/sec 
                 5 
                 10 
                 20 
                 30 
                 40 
                 50 
                 75 
                 100 
                 150 
                 200 
               
               
                 avg inspired pressure 
                 0.187 
                 0.593 
                 1.208 
                 1.78 
                 2.37 
                 2.92 
                 4.45 
                 5.98 
                 8.935 
                 11.73 
               
               
                 max expired pressure 
                 0.19 
                 0.58 
                 1.1 
                 1.55 
                 2.25 
                 2.9 
                 4.44 
                 5.99 
                 9.04 
                 11.92 
               
               
                 min expired pressure 
                 0.165 
                 0.535 
                 0.96 
                 1.16 
                 1.63 
                 2.23 
                 4.41 
                 5.95 
                 8.97 
                 11.85 
               
               
                 max expired % error 
                 2 
                 −2 
                 −9 
                 −13 
                 −5 
                 −1 
                 0 
                 0 
                 1 
                 2 
               
               
                 min expired % error 
                 −12 
                 −10 
                 −21 
                 −35 
                 −31 
                 −24 
                 −1 
                 −1 
                 0 
                 1 
               
               
                 CPT old with sieve 
                 13 
                 8 
                 12 
                 22 
                 26 
                 23 
                 1 
                 1 
                 1 
                 1 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                 CPT - New Tube Design With Sieve 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Flow in liters/min. 
                 0.3 
                 0.6 
                 1.2 
                 1.8 
                 2.4 
                 3 
                 4.5 
                 6 
                 9 
                 12 
               
               
                 VOLUME: ml 
                 10 
                 20 
                 40 
                 60 
                 80 
                 100 
                 150 
                 200 
                 300 
                 400 
               
               
                 FLOW: ml/sec 
                 5 
                 10 
                 20 
                 30 
                 40 
                 50 
                 75 
                 100 
                 150 
                 200 
               
               
                 avg inspired pressure 
                 0.210 
                 0.540 
                 1.200 
                 1.770 
                 2.380 
                 3.000 
                 4.580 
                 6.200 
                 9.270 
                 12.050 
               
               
                 max expired pressure 
                 0.165 
                 0.410 
                 1.090 
                 1.600 
                 2.020 
                 2.910 
                 4.510 
                 6.120 
                 9.350 
                 12.300 
               
               
                 min expired pressure 
                 0.145 
                 0.380 
                 0.860 
                 1.100 
                 1.380 
                 1.990 
                 4.430 
                 6.040 
                 9.040 
                 11.900 
               
               
                 max expired % error 
                 −21 
                 −24 
                 −9 
                 −10 
                 −15 
                 −3 
                 −2 
                 −1 
                 1 
                 2 
               
               
                 min expired % error 
                 −31 
                 −30 
                 −28 
                 −38 
                 −42 
                 −34 
                 −3 
                 −3 
                 −2 
                 −1 
               
               
                 CPT new with sieve 
                 10 
                 6 
                 19 
                 28 
                 27 
                 31 
                 2 
                 1 
                 3 
                 3 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 CPT - New Tube Design With Baffle With Four Slots 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Flow in liters/min. 
                 0.3 
                 0.6 
                 1.2 
                 1.8 
                 2.4 
                 3 
                 4.5 
                 6 
                 9 
                 12 
               
               
                 VOLUME: ml 
                 10 
                 20 
                 40 
                 60 
                 80 
                 100 
                 150 
                 200 
                 300 
                 400 
               
               
                 FLOW: ml/sec 
                 5 
                 10 
                 20 
                 30 
                 40 
                 50 
                 75 
                 100 
                 150 
                 200 
               
               
                 avg inspired pressure 
                 0.221 
                 0.6 
                 1.24 
                 1.89 
                 2.56 
                 3.13 
                 4.81 
                 6.53 
                 9.73 
                 12.56 
               
               
                 max expired pressure 
                 0.219 
                 0.61 
                 1.22 
                 1.88 
                 2.57 
                 3.19 
                 4.88 
                 6.58 
                 9.99 
                 13.05 
               
               
                 min expired pressure 
                 0.196 
                 0.62 
                 1.21 
                 1.81 
                 2.49 
                 3.11 
                 4.84 
                 6.52 
                 9.96 
                 12.99 
               
               
                 max expired % error 
                 −1 
                 2 
                 −2 
                 −1 
                 0 
                 3 
                 1 
                 1 
                 3 
                 4 
               
               
                 min expired % error 
                 −11 
                 3 
                 −2 
                 2 
                 −3 
                 −1 
                 1 
                 0 
                 2 
                 3 
               
               
                 CPT new with invention 
                 10 
                 −2 
                 1 
                 −2 
                 3 
                 4 
                 1 
                 1 
                 0 
                 0 
               
               
                   
               
             
          
         
       
     
     As seen in the results in each of Tables 1-6 and in the graph and  FIG. 7 , while the total expired error percent at very low volumetric flow rates was out of specification for each of the tube sections  16  utilized without the gas flow diverter  62 , the tube section  16  including the diverter  62  tested obtained accurate gas flow pressure readings for volumetric flow rates down to approximately 5 ml/sec. As a result, these results show that the diverter  62  is highly effective at causing a very small incoming gas flow to impinge upon the restrictions present in a tube section  16  of a sensor  10  in order to obtain accurate pressure differential measurements within the tube section  16  for monitoring the breathing of the patient. 
     Further, in separate testing done with diverters  62  having different port  82  configurations, the effect of blocking various ports  82  had a negligible effect on ability of the diverter  62  to effectively turbulate the gas stream. As represented in Table 7, data was collected on the valve of the inspired portion (positive plateau) and the highest and lowest values for the expired portion (negative plateau) of the breath or gas flow flowing through the tube section  16  with a diverter  62  having various ports  82  blocked. This data was then utilized to determine a percent difference between the maximum and minimum negative plateau values. As seen in the results illustrated in Table 7, all of the valves for the percent difference came out within the range for normal measurement errors. Thus, the blocking of any combination of ports  82  does not have any affect on the effectiveness of the diverter  62  to turbulate on expired gas flow. 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Ports 
                 Positive Plateau 
                 Negative Plateau 
                 Hi−lo 
                   
                 Port 
                 Port 
                 Port 
                 Port 
               
             
          
           
               
                 blocked 
                 10 
                 Highest 
                 Lowest 
                 diff. 
                 % diff 
                 #1 
                 #2 
                 #3 
                 #4 
               
               
                   
               
             
          
           
               
                 1 
                 2.49 
                 2.56 
                 2.53 
                 0.03 
                 1.2 
                 1.2 
                   
                   
                   
               
               
                 2 
                 2.48 
                 2.57 
                 2.45 
                 0.12 
                 4.8 
                   
                 4.8 
                   
                   
               
               
                 3 
                 2.5 
                 2.52 
                 2.46 
                 0.06 
                 2.4 
                   
                   
                 2.4 
                   
               
               
                 3, 1 
                 2.5 
                 2.56 
                 2.44 
                 0.12 
                 4.8 
                 4.8 
                   
                 4.8 
                   
               
               
                 3, 2 
                 2.5 
                 2.49 
                 2.46 
                 0.03 
                 1.2 
                   
                 1.2 
                 1.2 
                 2.8 
               
               
                 4, 2 
                 2.48 
                 2.52 
                 2.45 
                 0.07 
                 2.8 
                   
                 2.8 
                   
                 1.6 
               
               
                 4, 2, 1 
                 2.5 
                 2.53 
                 2.49 
                 0.04 
                 1.6 
                 1.6 
                 1.6 
                 4 
                   
               
               
                 1, 2, 3 
                 2.5 
                 2.57 
                 2.47 
                 0.1 
                 4 
                 4 
                 4 
                 2.4 
                 2.4 
               
               
                 4, 2, 3 
                 2.49 
                 2.46 
                 2.4 
                 0.06 
                 2.4 
                   
                 2.4 
                   
                   
               
               
                 none 
                 2.48 
                 2.52 
                 2.45 
                 0.07 
                 2.7 
               
               
                   
               
             
          
         
       
     
     While it is preferred to position the diverter  62  within the passage  48  formed by the tube section  16 , it is also contemplated that the diverter  62  can be located on other suitable sections of the sensor  10  to provide the identical function. For example, as best shown in  FIGS. 8 and 9 , in a second embodiment the adapter  56  is illustrated in which a number of ribs  84  are formed within a tapering section  86  of the sleeve  58  positioned adjacent nozzle  60 . The ribs  84  surround the central opening  59  within which can be secured to a diverter  62 ′ in a position concentric to the nozzle  60  and passage  48 . The diverter  62 ′ is formed virtually identically to the diverter  62  discussed previously. However, the diverter  62 ′ is formed to have an overall diameter at the flat end  66 ′ that is similar to the diameter of the nozzle  60  and not the diameter of the passage  48 . The diverter  62 ′ can be press-fit between the ribs  84  and/or secured there between by any suitable securing means, such as an adhesive or a mechanical fastener. Alternatively, the diverter  62 ′ and ribs  84  can be molded to the adapter  56  as a single unit. In this embodiment, an incoming gas flow through the tube  22  passes into the nozzle  60  and is directed from the nozzle  60  directly against the flat end  66 ′ of the diverter  62 ′. Upon striking the flat end  66 ′, the gas flow passes around the diverter  62 ′ and between the ribs  84  into the inlet end  18  of the tube section  16  in the manner described with regard to the diverter  62 . The incoming gas flow is thus turbulated by the diverter  62 ′ and is caused to flow in turbulent fashion into the tube section  16  and restriction  50  to provide accurate readings regarding the pressure drop across the restriction  50 . 
     Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.