Abstract:
A low flow heated/humidified respiratory gas delivery system, especially useful for low flow rates as preferred in the treatment of neonate and other such patients, wherein the respiratory gas is heated and humidified as desired for delivery to the patient and the temperature is monitored at the point of delivery to the patient.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 11/846,765 filed Aug. 29, 2007 entitled NOSE CANNULA HEATED/HUMIDIFIED GAS DELIVERY SYSTEM. 
     
    
     FIELD OF THE INVENTION AND BACKGROUND 
       [0002]    This invention relates in general to respiratory care and therapy, and, in particular, to the controlled delivery of heated and/or humidified respiratory gases to a user being so cared for or treated. More particularly, this invention relates to controlling the temperature of the gas or gases used for such care or treatment at the point of the delivery of such gas or gases to the user. 
         [0003]    In the administration of heated and/or humidified gas or gases to a user or patient, especially those considered as requiring neonatal care, such as premature infants and some pediatric patients, it is desirable to closely control and monitor the temperature at which the gas or gases are delivered. Such gases may be oxygen, heliox, nitrogen, or combinations thereof, as well as other gases known to those healthcare providers or clinicians providing such services. For convenience of illustration the term “gas” will be used hereinafter, but it is to be understood that such term includes a single gas as well as a combination of gases used in respiratory care and therapy by a user or patient. Also, for purposes of convenience, the term user or patient will be referred to hereinafter as “patient”. 
         [0004]    Respiratory gas delivered to, for example, neonate patients is preferably delivered at a low flow rate, between about 1 and about 15 liters per minute. When heated gas flows through a delivery conduit at such low flow rates, the temperature of the gas will decrease in transit to the patient delivery point, resulting in a lower temperature gas being applied to the patient and condensate being formed in the gas delivery conduit. The lower temperature gas can cause irritation of the nares and other discomforts to the patient, as well as reducing the core temperature of the patient. In addition, the accumulation of condensate can result in the gas propelling a bolus of condensate into the patient&#39;s respiratory system causing coughing or choking. Accordingly, it is highly desirable that the temperature of the respiratory gas being delivered to the patient be controlled at the very point where the gas is being delivered to the patient, to insure that the desired gas temperature is being applied to the patient with the desired humidification level. Such controlled delivery will increase the patient&#39;s comfort level, and reduce the amount of condensate heretofore occurring in available heated-gas delivery systems. 
       SUMMARY 
       [0005]    The above and other needs are met by a low flow heated/humidified respiratory gas delivery system, especially useful for low flow rates as preferred in the treatment of neonate and other such patients, wherein the respiratory gas is heated and humidified as desired for delivery to the patient and the temperature is monitored at the point of delivery to the patient. In this manner, the gas temperature can be controlled so that the temperature of the gas being applied to the patient is accurately maintained, and the formation of condensate in the delivery conduit is minimized to reduce accumulation. Patients are believed to be much more tolerable of such a treatment, and less likely to be disengaged therefrom. Fewer adverse reactions, such as abrasions, are believed to be incurred, and the patient can still be fed or can eat without necessitating the removal or disconnecting of the gas delivery system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the drawing figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
           [0007]      FIG. 1  is an illustration of the delivery system wherein a delivery tube or conduit is coupled with a suitable heater to deliver heated/humidified gas to a patient through a nose cannula; 
           [0008]      FIG. 2  is an enlarged partial sectional view of a portion of the delivery tube or conduit through which heated/humidified gas is delivered to the nose cannula to illustrate the manner in which the respiratory gas is heated; 
           [0009]      FIG. 3  is an exploded illustration of a portion of the delivery tube or conduit through which heated/humidified gas is delivered to the nose cannula for application to the patient; 
           [0010]      FIG. 4  is an exploded illustration of another portion of the delivery tube or conduit through which the temperature of the heated/humidified gas is monitored at the point of delivery to the patient; 
           [0011]      FIG. 5  is an enlarged illustration of a portion of the delivery tube or conduit illustrated in  FIGS. 3 and 4  in an embodiment in which the nose cannula is formed with a partition which separates the input of respiratory gas to the patient from the sensing of the gas temperature for controlling the operation of the heater to better illustrate the monitoring of the temperature of the gas as it is being applied to the patient, and the path of the air flow; 
           [0012]      FIG. 6  is an enlarged illustration of a portion of the delivery tube or conduit illustrated in  FIGS. 3 and 4  in an embodiment in which the nose cannula is formed without a partition which separates the input of respiratory gas to the patient from the sensing of the gas temperature for controlling the operation of the heater to better illustrate the monitoring of the temperature of the gas as it is being applied to the patient, and the path of the air flow; and 
           [0013]      FIG. 7  is an enlarged illustration of a portion of the delivery tube or conduit illustrated in  FIGS. 3 and 4  in an embodiment in which the nose cannula is formed with a partition which directs the input of respiratory gas in a flow path in direct fluid communication with the gas temperature sensor immediately prior to the gas being applied to the patient for controlling the operation of the heater to better illustrate the monitoring of the gas temperature and the path of the respiratory gas flow. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring now to  FIG. 1 , there is illustrated a respiratory gas delivery system  100  wherein a source of suitable respiratory gas (not shown) is coupled to a connector  8  and passes through a conduit  9  for connection to a humidification chamber which may be, for example, a reusable or a single-patient-use humidification or nebulizing chamber  10  through an inlet coupling  11 . As is known to those skilled in the art, the respiratory gas may nebulize a liquid, or a liquid with medicant, contained in the chamber  10 , or the respiratory gas may be bubbled through the liquid if desired, and the heated gas passed from the chamber  10  with, or without, a vapor mist as prescribed by a healthcare provider or clinician. The temperature of the respiratory gas passing from the chamber  10  is heated by means of a heater  15 , such as the heater disclosed in U.S. Pat. No. 6,988,497 assigned to Smiths Medical ASD, Inc. of Rockland, Mass. 
         [0015]    The heated gas is passed out from the chamber  10  through an outlet connector  12  and passes through a standard flexible delivery tube or conduit  20 , for delivery to a patient through a nose cannula  50 . As illustrated in  FIG. 2 , the delivery tube or conduit  20  may be of the type disclosed in Anthony V. Beran, et al, U.S. Pat. No. 6,167,883, “MEDICAL AIR-HOSE INTERNAL FLOW HEATER” assigned to the assignee of the present invention and the disclosure of which is incorporated herein by reference. As illustrated therein, a flexible ribbon  34  spans the width of a first portion  20   a  of the flexible tube  20 , and carries therein a heating element  42 , preferably an electrically conductive wire or plurality of wires connected to a power supply in order to heat the flow of gas traveling within this portion of the delivery tube  20   a . While there is illustrated a heater wire  42  carried within the tube  20  by a flexible ribbon  34 , the wire  42  may be positioned within the tube  20  without being supported by a flexible ribbon such as, for example, by being coiled along the interior of the tube  20 . 
         [0016]    As better illustrated in  FIG. 4 , the distal portion  42   a  of the heating element  42  terminates at the entrance into the nose cannula  50 , at the point at which the heated gas is applied or administered essentially directly to the patient. In this manner, the respiratory gas is heated all the way through the first portion  20   a  of the flexible tube  20  so that the slow rate of flow of the respiratory gas will not cool the gas below the desired temperature, but is applied directly to the patient at the clinician prescribed temperature level. Maintaining the respiratory gas heated to the prescribed temperature level at the point of delivery to the patient, will thereby minimize the occurrence of condensate formation. 
         [0017]    The temperature of the respiratory gas being delivered to the nose cannula  50  through the flexible tube  20 , is controlled by a sensor  60 , preferably a thermister, which is carried within a second portion  20   b  of the flexible tube  20  extending from an input  13  from the heater  15  to a position within the nose cannula  50  directly adjacent to the point at which the respiratory gas is applied or administered,  56 , essentially directly to the patient, as best illustrated in  FIGS. 5-7 . The positioning of the sensor in this position, in the nose cannula, will give direct feedback to the clinician of the temperature of the respiratory gas entering the patient&#39;s nose. The output from the sensor  60  may, if desired, be coupled to a digital display  65  to provide the clinician with an accurate visual display of the temperature of the respiratory gas as actually being administered to the patient. 
         [0018]    Because the air flow is constantly flowing from the outlet  12  of the chamber  10  to the patient&#39;s nose cannula  50 , only inspiratory air is delivered to the patient through the first portion  20   a  of the flexible tube  20 . Accordingly, re-breathing of exhaled air by the patient is substantially minimized or eliminated entirely. 
         [0019]    As best illustrated in the embodiment of  FIG. 5 , the nose cannula  50  may be formed with a partition  55  which separates the input of the respiratory gas to the patient from the sensing of the gas temperature for controlling the operation of the heater  15 . The positioning of the sensor  60  in this manner, in the nose cannula  50  in thermal contact with the respiratory gas at the point of administration of the gas to the patient,  56 , results in substantially reducing or eliminating the effect that ambient room temperature and humidity might have on control of the gas temperature and moisture content. It is to be understood, however, that the nose cannula  50  may be constructed without the partition  55  separating the input of the respiratory gas to the patient from the sensing of the gas temperature. In such an embodiment the sensor  60 , however, is still to be positioned in substantially direct thermal contact with the respiratory gas at the point of administration,  56 , of the gas to the patient. 
         [0020]    As best shown in the embodiment of  FIG. 6 , the nose cannula  50  is constructed without the partition  55 , and the sensor  60  is still positioned directly adjacent to the point of administration,  56 , of the gas to the patient. 
         [0021]    The foregoing description of a preferred embodiment for this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment described has been chosen and described in an effort to provide the best illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited for the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled. 
         [0022]    Also, this application was prepared without reference to any particular dictionary. Accordingly, the definition of the terms used herein conforms to the meaning intended by the inventors acting as their own lexicographer in accordance with the teaching of the application, rather than any dictionary meaning which is contrary to or different from the inventors&#39; meaning regardless of the authoritativeness of such dictionary. 
         [0023]    Referring now to the embodiment of  FIG. 7 , the nose cannula  50  is constructed with a partition  55   a  that directs the flow of the respiratory gas in a first flow path of movement directly into contact with the sensor  60  through which the temperature of the respiratory gas is controlled. The respiratory gas thereafter passes in a second flow path essentially directly to the cannula outlets  56  for application to the patient. In this manner the effect that ambient room temperature and humidity might have on control on the respiratory gas temperature and moisture control is diminished while obtaining the benefits of the sensor  60  being positioned in substantially direct thermal contact with the respiratory gas at the point of administration  56  of the gas to the patient.