Abstract:
A system for delivering warm, humidified oxygen to patients at very low flow rates, the system including a conduit having an inlet connected to a source of humidified oxygen at a first flow rate and an outlet end for delivering humidified oxygen to a patient at a second flow rate that is less than the first flow rate. A first flowpath extends through a sidewall of the conduit for continuously bleeding oxygen from the conduit and a second flowpath extends through the sidewall of the conduit downstream from the first flowpath for continuously bleeding oxygen from the conduit at a rate of from about 0 liters/minute or above. A substantially solid member is movably positionable adjacent the second flowpath for selectively blocking and unblocking portions of the second flowpath for defining a variably dimensionable flow path in order to control over the amount of oxygen flowing through the second flowpath.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of co-pending application Ser. No. 09/543,656, filed Apr. 5, 2000, and entitled NEO-NATAL OXYGEN DELIVERY SYSTEM, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to devices for supplying fluids to patients and more particularly to devices for supplying warm, humidified oxygen gas to patients. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Oxygen is commonly delivered in the practice of medicine to patients as a gas. The oxygen flows from a source to a delivery device such as a nasal cannula, for delivery to the patient&#39;s respiratory tract. 
     The administration of oxygen to patients, including neonatal, pediatric and elderly patients, requires the selection of an oxygen delivery system that suits the patient&#39;s size, needs and therapeutic result. Typically, the oxygen gas delivered directly from a hospital oxygen delivery system is dry and cold. Delivering dry and cold oxygen to an infant, for example, can undesirably lower body temperature and promote dehydration. Accordingly, it is often preferred to warm and humidify the oxygen so that the patient inhales a warm gas-liquid mixture. 
     It has proved difficult to supply warm oxygen having sufficient humidity at flow rates of less than about 2 liters/minute. Standard equipment available for both warming and humidifying oxygen is suitable for use with adults and is adjustable to deliver a volumetric fluid flow of from about 2 to about 15 liters per minute. These devices, however, generally require a minimum flowrate of at least about 2 liters per minute in order to operate. Pediatric patients, particularly neonatal patients, require a flow rate of less than about 2 liters per minute, sometimes only slightly above zero liters per minute (e.g. about ⅛ liter per minute). 
     Accordingly, there is a need in the art for a device which enables warm, humidified oxygen to be supplied to pediatric/infant patients at flow rates of from about 2 liters per minute and below. 
     It is therefore an object of the invention to provide a system for controlling the flow rate of fluid, such as warm, humidified oxygen, from a fluid source. 
     An additional object of the invention is to provide a system of the character described that is compatible with existing equipment, such as oxygen humidifiers. 
     A further object of the invention is to provide a system of the character described that is suitable for use with pediatric patients. 
     It is another object of the invention to provide a system of the character described that is selectively adjustable to enable an oxygen flow rate of from about 0 to about 2 liters per minute. 
     A further object of the invention is to provide a system of the character described that is uncomplicated in configuration and convenient to use. 
     A still further object of the invention is to provide a system of the character described that is economical and suitable for use with conventional oxygen delivery systems. 
     With regard to the foregoing, the present invention is directed to a system for use with standard humidification equipment having a flow rate of at least about 3 liters/minute for delivering fluids such as oxygen, preferably warm, humidified oxygen to patients at a flow rate of from about 0 to about 2 liters/minute. As used herein, the term “warm/humidified oxygen” refers to oxygen gas having a temperature of from about 30° C. to about 37° C. (about 86° F. to about 98.6° F.) and a relative humidity of from about 80 to about 100%. 
     The system includes a conduit having an inlet connected to a source of humidified oxygen at a flow rate of at least about 3 liters/minute and an outlet end for delivering humidified oxygen to a neo-natal patient at a flow rate of from about 0 to about 2 liters/minute. A first aperture extends through the sidewall of the conduit for bleeding oxygen from the conduit so that the flow in the conduit is reduced to about 2 liters/minute. A second aperture is provided downstream from the first aperture and extends through the sidewall for bleeding oxygen from the conduit at a rate of from about 0 to about 2 liters/minute. A substantially solid member is movably positionable adjacent the second aperture for defining a variably dimensionable flow path to enable control over the amount of oxygen bled through the second aperture. 
     In another embodiment, the invention is directed to a system for controlling the flow rate of fluid from a fluid source, such as humidified oxygen, for delivery to a patient. 
     In a preferred embodiment, the system includes a conduit having an interior and an exterior separated by a substantially continuous sidewall, an inlet end in flow communication with an outlet end for flow of fluid from the fluid source through the conduit from the inlet end toward the outlet end, the inlet end being in flow communication with the source of fluid at a first flow rate and the outlet end being in flow communication with a fluid delivery device for delivering fluid to the patient at a second flow rate that is lower than the first flow rate. 
     A first aperture extends through the sidewall for passage of fluid from the interior to atmospheric regions adjacent the exterior of the conduit and for reducing the flow rate of fluid within the conduit to a third flow rate that is less than the first flow rate and greater than or equal to the second flow rate. A second aperture is provided downstream from the first aperture extends through the sidewall. A substantially solid member is movably positionable adjacent the second aperture for defining a variably dimensionable flow path for passage of fluid from the interior to atmosphere regions adjacent the exterior of the conduit. Variation of the dimension of the variably dimensionable flow path selectively enables escape of fluid from the interior of the conduit to provide the second flow rate of fluid. 
     In another embodiment, the invention relates to a system for delivering humidified oxygen to a patient. The system preferably includes a conduit having an inlet connected to a source of humidified oxygen at a first flow rate and an outlet end for delivering humidified oxygen to a patient at a second flow rate that is less than the first flow rate. A first flowpath extends through a sidewall of the conduit for continuously bleeding oxygen from the conduit. A second flowpath is located downstream from the first flowpath and extends through the sidewall of the conduit for continuously bleeding oxygen from the conduit at a rate of from about 0 liters/minute or above. A substantially solid member is movably positionable adjacent the second flowpath for selectively blocking and unblocking portions of the second flowpath for defining a variably dimensionable flow path in order to control over the amount of oxygen flowing through the second flowpath. 
     In yet another aspect, the invention relates to a method for delivering treatment fluids, such as humidified oxygen, to pediatric patients from a source of fluid of the type used for adults and having a flow rate above about 3 liters per minute. The method includes the steps of providing the oxygen source, placing it in flow communication with a delivery system in accordance with the invention and manipulating the delivery system to achieve a desired flow rate to the patient of from about 0 to about 2 liters per minute. 
     The invention advantageously enables warm, humidified oxygen to be delivered at low flow rates heretofore unobtainable by conventional hospital equipment. The invention thus enables the use of standard oxygen and other delivery and humidification systems in the treatment of pediatric and other patients having treatment flow rate requirements below those available from standard treatment equipment. The system also advantageously adapts to fit pediatric output components, such as pediatric cannulas having smaller tubing size, while connecting to adult or standard input components having larger tubing sizes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features and advantages of the present invention will become further known from the following detailed description considered in conjunction with the accompanying drawings in which: 
     FIG. 1 is an exploded perspective view of a preferred embodiment of a flow control device in accordance with the invention. 
     FIG. 2 is a perspective view of the device of FIG. 1 in an assembled state. 
     FIG. 3 is a plan view of an oxygen delivery system utilizing the device of FIG.  1 . 
     FIG. 4 is a side plan view of a flow member component of the device of FIG.  1 . 
     FIG. 5 is an enlarged view of a portion of the component of FIG.  4 . 
     FIG. 6 is a side plan view of an alternate embodiment of the component of FIG.  4 . 
     FIG. 7 is a perspective view of a flow control component of the system of FIG.  1 . 
     FIG. 8 is an end view of the system of FIG. 1 showing the relationship between a flow component and a control component. 
     FIG. 9 is an inlet end view of the component of FIG.  7 . 
     FIG. 10 is an enlarged side plan view of a portion of the system of FIG. 1 showing a control member fully blocking an aperture. 
     FIG. 11 is an enlarged side plan view of a portion of the system of FIG. 1 showing a control member partially blocking an aperture. 
     FIG. 12 is an enlarged side plan view of a portion of the system of FIG. 1 showing an aperture in an unblocked state. 
     FIG.  13 . is a perspective inlet end view of a flow control device in accordance with another embodiment of the invention. 
     FIG. 14 is a perspective outlet end view of the device of FIG.  13 . 
     FIG. 15 is a side plan view of a flow member component of the device of FIG.  14 . 
     FIG. 16 is a top plan view of the component of FIG.  15 . 
     FIG. 17 is an inlet end view of a cap member component of the system of FIG.  13 . 
     FIG. 18 is a side view of the component of FIG.  17 . 
     FIG. 19 is a cross-sectional view of FIG. 18 taken along line  19 — 19 . 
     FIG. 20 is a side plan view of a flow control device in accordance with another embodiment of the invention. 
     FIG. 21 is a perspective view of a flow control component of the device of FIG.  20 . 
     FIG. 22 is a partial cross-sectional view taken along line  22 — 22  of FIG.  20 . 
     FIG. 23 is a front perspective view of a flow control system in accordance with yet another embodiment of the invention. 
     FIG. 24 is an exploded perspective view of the device of FIG.  23 . 
     FIG. 25 is a front end view of a component of the device of FIG.  23 . 
     FIG. 26 is a left side view of the component of FIG.  25 . 
     FIG. 27 is a right side view of the component of FIG.  25 . 
     FIG. 28 is a rear plan view of another component of the device of FIG.  23 . 
     FIG. 29 is a rear perspective view of the component of FIG.  28 . 
     FIGS. 30 a ,  30   b  and  30   c  are detailed cross-sectional side views of the system of FIG. 23 showing the relationship between the flow component and the control component. 
     FIG. 31 is a rear perspective view of a flow control system in accordance with still another embodiment of the invention. 
     FIG. 32 is a side plan view of another component of the flow control system of FIG.  31 . 
     FIG. 33 is a front end view of the component of FIG.  34 . 
     FIG. 34 is a close-up view of a portion of the component of FIG.  34 . 
     FIGS. 35 a  and  35   b  are front and rear perspective views, respectively, of a component of the flow control system of FIG.  31 . 
     FIG. 36 is a cross-sectional side view of the component of FIGS. 35 a  and  35   b.    
     FIGS. 37 a ,  37   b  and  37   c  are cross-sectional side views of the system of FIG. 31 showing the relationship between the flow component and the control component. 
    
    
     DETAILED DESCRIPTION 
     With initial reference to FIGS. 1-3, there is shown a system  10  for controlling the flow rate of fluid, such as a gas-liquid mixture, in flow communication with a source of fluid, such as a source of warm, humidified oxygen  12 . The system  10  is available to deliver the flow of warm, humidified oxygen to a pediatric or infant patient as by a pediatric or infant sized nasal cannula  14 . Each component of the system  10  is preferably made of a plastic material, such as polyethylene and manufactured using extrusion, blow molding or thermo-forming techniques. 
     As noted previously, the term “warm/humidified oxygen” refers to oxygen gas having a temperature of from about 30° C. to about 37° C. (about 86° F. to about 98.6° F.) and a relative humidity of from about 80 to about 100%. A preferred source of warm/humidified oxygen is provided by flowing hospital grade oxygen through a heated humidifier available under the trade name ConchaTherm IV from Hudson RCI of Temecula, Calif. The instruction manual for the ConchaTherm IV states that it requires a flow rate of 2 liters per minute or greater to prevent overheating of its electronic circuitry. 
     To avoid problems associated with circuit overheating and the like, it is desirable to operate the humidifier at a setting above its lowest possible setting. Accordingly, it is preferred that when the ConchaTherm IV humidifier is used as a source of warm, humidified oxygen, that it be operated at a flowrate of from about 3 to about 15 liters per minute, most preferably from about 6 to about 10 liters per minute. The system of the present invention enables these flowrates to be reduced to flowrates suitable for pediatric or infant patients, i.e. from about slightly above 0 liters per minute, such as about ⅛ liter per minute, to about 2 liters per minute. 
     The system  10  includes flow member  16  having an open inlet end  18  placeable in flow communication with the source of humidified oxygen  12  as by tubing  20  opposite an outlet end  22  in flow communication with a fitting  24  and placeable in flow communication with the cannula  14  as by tubing  26 . A control member  28  cooperates with the flow member  16  for adjustably controlling the flow of humidified oxygen out of the fitting  24 . The fitting  24  is sized to cooperate with pediatric sized delivery apparatus, i.e., pediatric tubing, cannulas and the like, while the inlet end  18  is sized to cooperate with the tubing  20  for flow communication of the oxygen from standard source apparatus, such as the ConchaTherm IV humidifier. In this regard, the end  18  may include flange  29  for snugly engaging the tubing  20 . 
     With additional reference now to FIGS. 4-6, the flow member  16  is preferably provided by a conduit  30 , an open first end of which provides the inlet end  18 . The opposite end of the conduit  30  is closed, as by end wall  32 . The fitting  24  extends through the end wall  32  to provide a path for flow of the oxygen. The conduit  30  is preferably cylindrical and includes cylindrical sidewall  36 . The cylindrical sidewall  36  is substantially solid with the exception of an aperture  38  and an aperture  40  which are spaced apart from one another and extend through the sidewall  36 . The aperture  38  is preferably upstream of the aperture  40  or located between the aperture  40  and the inlet end  18  and is preferably a circular aperture. The aperture  40  is preferably a triangular shaped aperture, as best seen in FIG.  5 . 
     In another embodiment shown in FIG. 6, the aperture  38  is provided by a plurality of apertures  38 ′ and the aperture  40  is provided by a plurality of apertures  40 ′. Each aperture  38 ′ is preferably in alignment with each other aperture  38 ′ and each aperture  40 ′ is preferably aligned with each other aperture  40 ′ around the periphery of the sidewall  36 . 
     With additional reference to FIGS. 7-9, the control member  28  includes a cylindrical member  42  having an open end  44  opposite a closed end  46 . The closed end  46  is preferably provided as by a circular end wall  48  enclosing the end of the cylindrical member  42 . The end wall  48  includes an aperture  50  centrally located and sized to receive the fitting  24  in a snap-fit relationship to maintain the control member  28  and the flow member  16  closely adjacent one another. The diameter of the cylindrical member  42  is greater than that of the cylindrical member  30  to enable the cylindrical member  42  to receive the cylindrical member  30 , preferably sized to provide an annular area  52  there between (FIGS. 3 and 8) having a width sufficient to enable the flow of warm, humidified oxygen from the cylindrical member  30  through the apertures  38  and  40 . 
     As shown in FIGS. 8 and 9, the control member  28  preferably includes projections  54  and  56  which extend from interior sidewall  58  of the cylindrical member  42  and rotatably engage opposite sides of the exterior of the cylindrical member  30 . The projection  56  is opposite the projection  54  so that a portion of the cylindrical member  30  is captured there between. The rotation of the cylinders  30  and  43  is preferably limited as by stops  60  and  62  located on the exterior of the cylindrical member  30  for engaging the outside edges of the projection  54  or the projection  56 , as may be preferred. The stops  60  and  62  are preferably located such that contact with the stop  60  defines the position of the projection  54  when it fully blocks or sealingly covers the aperture  40  against flow there through and contact with the stop  62  defines the position of the projection  54  when it fully clears or opens the aperture  40  for flow there through. 
     As best seen in FIGS. 10-12, the cylindrical member  42  and the cylindrical member  30  are rotatable relative to one another so that the projection  54  may be positioned to be clear of the aperture  40 , partially block the aperture  40  or completely block the aperture  40 . In this regard, the apertures  38  and  40  (and the apertures  38 ′ and  40 ′) function to enable the inlet flow of humidified oxygen, represented by the arrow  66  (FIG. 3) to be altered to provide a desired outlet flow of humidified oxygen, represented by the arrow  68 , to the patient. 
     For example, standard equipment available for warming and humidifying oxygen is generally not suitable for use with pediatric patients, particularly neonatal patients, who require treatment rates of less than about 2 liters per minute, sometime only slightly above zero liters per minute. The system  10  is suitable for use with standard humidification equipment, such as the ConchaTherm IV described above, and is adjustable to control humidified oxygen available at a flow of from about 3 to about 15 liters per minute in order to provide delivery of humidified oxygen at a flow rate of from about 0 liters per minute to about 2 liters per minute. It will be understood, however, that the invention may be configured to yield various desired flow rates from a given flow source. 
     For example, as described herein the aperture  38  is sized to reduce the flow rate in the cylindrical member  30  from an input flow rate from the humidifier of about 8 liters per minute to a maximum flow rate in the cannula  14  of about 2 liters per minute or less. In this case, the aperture  38  provides a passage sized to leak a flow rate of about 6 liters per minute there through and into the annular area  52  and out of the open end  44  to the surrounding atmosphere, as represented by the arrows  70 . In this regard, it will further be appreciated that the cylindrical member  42  also serves to expand, deflect and muffle the flow represented by the arrows  70  to minimize noise and directional air flow which might disturb the patient. 
     The aperture  40  and the projection  54  cooperate to enable the flow rate  68  to be maintained at about 2 liters per minute, adjusted to about 0 liters per minute or reduced to a desired flow rate within this range. When the aperture  40  is fully blocked by the projection  54  as shown in FIG. 10, the flow rate  68  will be about 2 liters per minute, as flow will not be conducted from the conduit  30  through the aperture  40 . When the aperture  40  is partially blocked by the projection  54 , as shown in FIG. 11 with a portion  72  of the cylindrical member  42  cut away, a flow indicated by arrows  74  travels from the conduit  30  there through in the manner of the flow  70 , reducing the flow indicated by arrow  68  delivered to the patient to a rate of less than about 2 liters per minute and greater than about 0 liters per minute. The degree of blockage of aperture  40  can be adjusted to provide any desired flow rate within this range. When the projection  54  is fully clear of the aperture  40 , as shown in FIG. 12, the flow  74  will be about 2 liters per minute such that the flow  68  will be about 0 liters per minute. 
     A pressure gauge or meter may be connected in line with the tubing  68  and/or the system may be calibrated prior to use to facilitate delivery of desired oxygen flow rates to the patient. For example, to calibrate the system, a flow meter may be connected in place of the cannula  14  and the dimension of the aperture  40  adjusted as previously described. The rotational position of the flow control member may be recorded against the flow rate  68  measured by a flow meter. In this regard, indicia such as symbols designating open and closed and gradations there between (e.g., ¼, ½, ¾, etc.) may be provided around the circumference of the control member and a corresponding mark or indicia provided on the flow member  16  to indicate the relative dimension of the aperture in terms of blockage by the projection  54  or other indicia corresponding to the flow rate. 
     For the purpose of an example, the system  10  is preferably dimensioned as set forth in Table 1 for use in delivering a flow rate of from about 0 to about 2 liters per minute when used with an oxygen humidifier capable of providing warm, humidified oxygen at an output of about 6 liters per minute. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Dimension 
                 Distance (inches/cm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 A (FIG. 5) 
                 0.001 
               
               
                   
                 B (FIG. 5) 
                 0.015 
               
               
                   
                 C (FIG. 5) 
                 0.033 
               
               
                   
                 D (FIG. 5) 
                 0.055 
               
               
                   
                 E (FIG. 5) 
                 105° (0.878 inch dia.) 
               
               
                   
                 F (FIG. 4) 
                 0.870 inch dia. 
               
               
                   
                 G (FIG. 4) 
                 1.50 
               
               
                   
                 H (FIG. 8) 
                 2.00 
               
               
                   
                 I (FIG. 9) 
                 0.878 inch dia 
               
               
                   
                 J (FIG. 9) 
                 0.166 
               
               
                   
                 K (FIG. 9) 
                 2.00 
               
               
                   
                 L (FIG. 3) 
                 1.06 
               
               
                   
                 M (FIG. 4) 
                 0.80 
               
               
                   
                 Aperture 3 8 
                 0.040 dia. 
               
               
                   
                   
               
             
          
         
       
     
     Turning now to FIGS. 13-19, there is shown another embodiment of a system  100  for controlling the flow rate of fluid, such as a gas-liquid mixture, from a source of fluid, such as a source of warm, humidified oxygen for delivery to a patient as by a nasal cannula. 
     The system  100  includes flow member  102  having an inlet end  104  placeable in flow communication with the source of warm, humidified oxygen and an opposite outlet end  106  in flow communication with a fitting  108  and placeable in flow communication with a cannula. A control member  110  cooperates with the flow member  102  for adjustably controlling the flow of humidified oxygen out of the fitting  108 . 
     The flow member  102  is preferably provided by a conduit  112 , an open end of which provides the inlet end  104 . The opposite end of the conduit  112  is closed, as by end wall  114 . The fitting  108  extends through the end wall  114  to provide a flow path for the warm, humidified oxygen. Cylindrical sidewall  118  of the conduit  112  is substantially solid with the exception of at least one aperture  120  and at least one aperture  122  which are spaced apart from one another and extend through the sidewall  118 . The aperture  120  is preferably upstream of the aperture  122  and is preferably a circular aperture. The aperture  122  is preferably a circular aperture. An additional fitting  124  optionally extends from the fitting  108  for connection with a flow meter for measuring the flow rate of humidified oxygen being delivered to the patient. The exterior of the end wall  114  is preferably flanged to provide a snap-fit relationship with the control member  110  which permits relative rotation of the control member  110  and the flow member  102 . 
     With reference to FIGS. 17-19, the control member  110  includes a cap member  126  including an aperture  128  centrally located and sized to receive the fitting  108  or the exterior of the end wall  114 . The end wall thickness of the cap member  126  (FIG. 19) is sized to provide a snap-fit relationship with the flanged exterior of the end wall  114  of the flow member  102  to maintain the control member  110  and the flow member  102  adjacent one another. The circumference of the cap member  126  is preferably textured, such as knurls  131 , to facilitate grasping thereof. 
     The cap member  110  includes projections  132  and  134  which extend from the interior circumference of the cap member  110  and rotatably engage opposite sides of the exterior of the conduit  102 . The projection  132  is opposite the projection  134  so that a portion of the conduit is captured there between. The rotation of the cap member relative to the conduit is preferably limited by as by stops  136  and  138  located on the exterior of the conduit  102  for engaging the outside edges of the projection  132 . The stops  136  and  138  are preferably located such that contact with the stop  132  defines the position of the projection  132  when it fully blocks the aperture  122  and contact with the stop  138  defines the position of the projection  132  when it fully clears the aperture  122 . 
     A shroud  140  (FIGS. 13 and 14) is preferably provided to surround the conduit  102  to provide an annular area  142  there between sufficient to enable the flow of humidified oxygen from the flow member  102  through the apertures  120  and  122 . The shroud  140  is preferably of two-piece construction and including a pair of half cylinders  144  and  146  which press fit together. A plurality of elongate baffle members  148  preferably extend between the interior of the shroud  140  and the exterior of the conduit  112  in the annular area  142  there between and are located so as to contact one or more of the apertures  120 , as may be desired. The baffle members  148  are preferably co-formed with the half cylinders  144  and  146 . The baffle members  148  function to selectively cover one or more of the apertures  120  and to disrupt and diffuse flow exiting the undercovered apertures  120  and  122 . The shroud member  140  abuts the cap member  110  but is preferably not connected thereto. 
     The cap member  110  and the flow member  102  may be rotated relative to one another to selectively position the projection  132  relative to the aperture  122  in the manner previously described for projection  54  and aperture  40  of system  10  of FIGS. 1-12. 
     Turning now to FIGS. 20-22, there is shown another embodiment of a system  200  for controlling the flow rate of fluid, such as a gas-liquid mixture, from a source of fluid, such as a source of humidified oxygen for delivery to a patient as by a nasal cannula. 
     The system  200  includes a flow member  202  having an inlet end  204  placeable in flow communication with the source of humidified oxygen opposite an outlet end  206  in flow communication with a fitting  208  and placeable in flow communication with a cannula for delivery of the humidified oxygen to a patient. A control member  210  cooperates with the flow member  202  for adjustably controlling the flow of humidified oxygen out of the fitting  208 . 
     The flow member  202  is preferably provided by a conduit  212 , one open end of which provides the inlet end  204 . The opposite end of the conduit  212  is closed, as by end wall  214 . The fitting  208  extends through the end wall  214  to provide a flow path for the oxygen. The cylindrical sidewall of the conduit  212  is substantially solid with the exception of at least one aperture  218  and at least one aperture  220  which are spaced apart from one another and extend through the sidewall of the conduit  212 . The aperture  218  is preferably upstream of the aperture  220  between aperture  220  and inlet end  204  and is preferably a circular aperture. The aperture  220  is preferably a triangular shaped aperture. 
     The control member  210  is preferably provided by a semi-circular member  222  having a width that is preferably at least as great as the largest width dimension of the aperture  220  and having a radius corresponding to the inner radius of the conduit  212  so that an outwardly facing surface  224  of the control member  210  will bear against interior sidewall  226  of the conduit  212 . 
     As shown in FIG. 22, a pair of generally L-shaped channels  228  are preferably co-formed with the conduit  212  and extend circumferentially around the interior sidewall  226  of the conduit  212  for slidably receiving the semi-circular member  222 . A stop  230  preferably extends from the surface  224  of the member  222  to engage the length extremes or edges of the aperture  220  and limit travel of the member  222 . As will be appreciated, the member  222  may be slidably positioned to vary the flow rate of humidified oxygen through the aperture  220 . That is, the stop  230  may be positioned at position A to substantially close the aperture  220  and provide a flow through the fitting  208  to the patient of about 2 liters per minute, at position B to substantially open the aperture  220  and provide a flow through the fitting  208  of about 0 liters per minute and at points there between, such as points C or D, to provide flow rates within the range of about 0 to about 2 liters per minute as may be desired. A gasket material, such as rubber strips  232  may be positioned between the member  222  and the sidewall  226  between the channels  228  to minimize leakage when the member  222  is positioned to seal the aperture  220  or a portion thereof. 
     FIGS. 23-29 show another embodiment of a system  300  for controlling the flow rate of humidified oxygen to patients including pediatric or infant patients. The system  300  includes a flow member  302  and a control member  304 . 
     The flow member  302  is preferably provided by a conduit  306  having an open inlet end  308  placeable in flow communication with a source of warm, humidified oxygen. The opposite end of the of the conduit  306  is closed as by end wall  310 . A fitting  312  connectable to a cannula and associated tubing extends through the end wall  310  to provide a flow path for the warm, humidified oxygen. To facilitate rotation of the conduit  306  relative to the control member  304  in the assembled system  300 , a pair of wings  314  and  316  project from the fitting  312  adjacent the end wall  310  for grasping by a user. 
     Cylindrical sidewall  318  of the conduit  306  is substantially solid with the exception of apertures  320  and  322  which are spaced apart from one another and extend through the sidewall  318 . The aperture  320  is upstream of the aperture  322  and is preferably a single circular aperture. The aperture  322  preferably includes a lateral slit portion  324  parallel to the length of the conduit  306  and a v-shaped slit  326  extending generally perpendicular to the slit portion  324  along the circumference of the conduit  306 . 
     The control member  304  is configured to selectively engaging portions of the aperture  322  for controlling the area of the aperture  322  available to bleed off oxygen traveling through the conduit  306 . In this connection, a projection  328  is preferably defined on the surface of the conduit  306  for selectively engaging notches  330  located on an interior surface of the control member  304  for facilitating incremental relative movement of the control member  304  and the conduit  306 . To enable a snap-fit relationship between the conduit  306  and the control member  304 , the end wall  310  of the conduit  306  preferably includes a flange  332  for engaging fingers  334  located adjacent an aperture  336  defined through end wall  338  of the control member  304  for passage of the end wall  310 , the wings  314  and  316  and the fitting  312 . Indicia  340  and  342  are preferably provided on the exterior of the end wall  338  for aligning with the wing  314  when the aperture is fully opened and fully closed, respectively. Likewise, the exterior surface of sidewall  343  of the control member  304  preferably includes knurls  344  for facilitating grasping by the user during adjustment of the system  300 . 
     With reference to FIGS. 28 and 29, the control member includes interior cylindrical sidewalls  350  and  352  spaced apart by an open area or slot  354 . As will be appreciated with reference to FIGS. 30 a ,  30   b  and  30   c , the control member  304  and the conduit  306  may be moved relative to one another for selectively engaging portions of the aperture  322  for controlling the area of the aperture  322  available to bleed off oxygen traveling through the conduit  306 . 
     Fingers  356 ,  357  and  358  project between the exterior of the sidewall  350 , the interior of the end wall  338  and the interior of the conduit  306  for strength. Likewise, fingers  359 ,  360  and  361  project between the exterior of the sidewall  352 , the interior of the sidewall  338  and the interior of the conduit  306 . The fingers  357  and  358  are preferably of a lesser width than that of the slot  354  to enable escaping oxygen to expand relatively quickly and thereby reduce its velocity to reduce noise associated with the oxygen that is being bled off through the aperture  322 . 
     For the purpose of an example, the conduit  306  may be dimensioned similar to that of the conduit or cylindrical member  30 . For use with a source of warm, humid oxygen having an output of about 8 liters/minute, the aperture  320  preferably has a diameter of about 0.04 inches, so that it may leak or bleed a flow rate of about 6 liters per minute there through. The lateral slit  324  preferably has a length of about 0.33 inches and a length of about 0.52 inches. The v-shaped slit  326  preferably extends about 105° around the circumference of the conduit  306  and tapers in width from about 0.55 inches adjacent the slit  324  to about 0.01 inches at its tip. The slot  354  of the cover member  304  preferably tapers outwardly over the thickness of the sidewall  350  (about 0.55 inches, for example), with slot  354  preferably having an initial width of about 0.3 inches and a terminal width of about 0.5 inches. 
     FIGS. 31-36 show another embodiment of a system  400  for controlling the flow rate of humidified oxygen to patients including pediatric or infant patients. The system  400  includes a flow member  402  and a control member  404 . 
     The flow member  402  is preferably provided by a conduit  406  having an open inlet end  408  placeable in flow communication with a source of warm, humidified oxygen. The opposite end of the of the conduit  406  is closed as by end wall  410 . A fitting  412  connectable to a cannula and associated tubing extends through the end wall  410  to provide a flow path for the warm, humidified oxygen. To facilitate rotation of the conduit  406  relative to the control member  404  in the assembled system  400 , a pair of wings  414  and  416  project from the fitting  412  adjacent the end wall  410  for grasping by a user. 
     Cylindrical sidewall  418  of the conduit  406  is substantially solid with the exception of apertures  420  and  422  which are spaced apart from one another and extend through the sidewall  418 . The aperture  420  is upstream of the aperture  422  and is preferably a single circular aperture. The aperture  422  is preferably a lateral slit  424  having a length axis parallel to the length of the conduit  406 . 
     The control member  404  is configured to selectively engaging portions of the aperture  422  for controlling the area of the aperture  422  available to bleed off oxygen traveling through the conduit  406 . In this connection, a spiraled interior sidewall  426  is provided on the control member  404 . A projection  428  is preferably defined on the surface of the conduit  406  for selectively engaging either a notch  430  defined along an uppermost edge of the sidewall  426  or a side edge  431  of the sidewall  426 . As will be appreciated, the notch  430  and the edge  431  define the limits of travel of the projection  428 . 
     To enable a snap-fit relationship between the conduit  406  and the control member  404 , the end wall  410  of the conduit  406  preferably includes a flange  432  for engaging fingers  434  located adjacent an aperture  436  defined through end wall  438  of the control member  404  for passage of the end wall  410 , the wings  414  and  416  and the fitting  412 . Indicia  440  is preferably provided on the exterior of the end wall  438  for aligning with the wing  414  or  416  to indicate the degree to which the aperture or slit  422  is opened or closed or the approximate flowrate of gas being delivered to the patient. Likewise, the exterior surface of sidewall  443  of the control member  404  preferably includes knurls  444  for facilitating grasping by the user during adjustment of the system  400 . 
     An open area or slot  450  is located between side edge  431  and an opposite side edge  452  of the spiraled sidewall  426 . As will be appreciated with reference to FIGS. 37 a ,  37   b  and  37   c , the control member  304  and the conduit  306  may be moved relative to one another for selectively engaging portions of the aperture  322  for controlling the area of the aperture  322  available to bleed off oxygen traveling through the conduit  306 . For example, the aperture  422  is totally blocked in FIG. 37 a ; partially blocked in FIG. 37 b  and totally unblocked in FIG. 37 c.    
     Reinforcing members  456  and  458  are provided to reinforce the sidewalls  443  and  426 , respectively. The members  456  and  458  are preferably flat, having a triangular outline. One leg of each member is against to the interior of the sidewall it is reinforcing and the other leg is against the interior of end wall  438 . 
     For the purpose of an example, the conduit  406  may be dimensioned similar to that of the conduit  306 . For use with a source of warm, humid oxygen having an output of about 8 liters/minute, the aperture  420  preferably has a diameter of about 0.04 inches, so that it may leak or bleed a flow rate of about 6 liters per minute there through. The lateral slit  424  preferably has a length of about 0.30 inches and a width of about 0.011 inches. 
     The spiraled sidewall  426  preferably increases in height in a cubic function to help linearize the air flow through the slit  424  as a function of the relative position of the flow member  402  and the control member  404 . The height difference between the lowest and highest portions of the sidewall is preferably about 0.3 inches so that the end ranges of relative rotation of the flow member and the control member represent the slit  424  being fully blocked or fully open. The spiraled sidewall  426  preferably has a diameter of about 0.4 inches (the member  404  having an outer diameter of about 2 inches). 
     As will be appreciated, the invention enables warm, humidified oxygen to be delivered to patients in a manner which has not previously been possible. For example, limitations in the design of conventional equipment for providing warm, humid oxygen requires that they be operated at flow rates that are generally greater than the desired flow rate that the oxygen be delivered to the patients such as pediatric and infant patients and many elderly patients. Furthermore, to avoid problems with overheating and the like, such equipment should, practically speaking, be operated at flow rates significantly greater than its minimum possible operating flow rate. 
     The invention interfaces between conventional humidification equipment and its normal operating parameters to enable warm, humidified oxygen to be delivered at the very low flow rates often required for various patients. Thus, the humidification equipment can be operated at conditions which avoid overheating and other problems, yet the patient is able to receive very low flow rates of the warm, humid oxygen. Accordingly, the invention satisfies a long felt need in the art in a convenient and efficient manner. 
     The foregoing description of certain embodiments of the present invention has been provided for purposes of illustration only, and it is understood that numerous modifications or alterations may be made in and to the illustrated embodiments without departing from the spirit and scope of the invention as defined in the following claims.