Abstract:
A continuous positive airway pressure system features a housing forming an airway chamber, and an air pressure inlet and an air pressure outlet. The housing further defines internally a pair of tapered air jets, and a pair of tapered air receivers. The air receivers are located downstream of the air supply jets and disposed coaxially with respective ones of the air supply jets. Each receiver has a taper in an opposite direction to the direction of the taper of the air supply jets. A pair of nasal prongs is located downstream of the air receiving jets.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 11/966,805, filed on Dec. 28, 2007 and now issued as U.S. Pat. No. 8,210,182 on Jul. 3, 2012, which is incorporated herein, in its entirety, by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to pressure airway devices for supplying pressurized air used in the field of respiratory therapy, and more particularly to devices and methods that provide positive airway pressure to the nasal cannula of a person or particularly an infant. 
     BACKGROUND OF THE INVENTION 
     In the field of respiratory therapy it is known to provide a continuous positive airway pressure (CPAP) system and method for delivering continuous positive airway pressure, via the nasal cannula, to persons and particularly infants. This is particularly true in the case of prematurely born infants who frequently suffer with increased work of breathing due to immature lungs that have the propensity to collapse during exhalation and resist expansion during inhalation. 
     One particular method of treatment involves the use of nasal cannula that fits sealingly into the nares and are connected to a breathing system that generates a continuous flow of air with above atmospheric pressures, commonly referred to as continuous positive airway pressure (CPAP) therapy. The positive pressure is transmitted through the infant&#39;s airways and into the lungs thereby preventing collapse during exhalation and augmenting expansion during inhalation. 
     There are a wide variety of devices in use for CPAP. The CPAP devices often comprise what is referred to as a generator body, which is essentially a housing forming a chamber that receives air pressure from tubing. The generator body typically has an exhalation port for air to escape during the exhalation phase. Further, the generator body has a pair of nasal prongs which fit into the patient&#39;s nares to supply pressure into the nares. 
     It would be desirable to provide a CPAP device that has reduced size, improved performance, and/or other benefits with respect to the patient. Moreover, it is often desirable to be able to reduce the amount of pressure that needs to be supplied to a CPAP device, thereby simplifying the structure of the associated air pump, which may have benefits with respect to reduced size, energy consumption, sound, complexity and cost. Further, it is typically desirable to reduce the size and mass of the CPAP interface assembly which fits against the face. It may be desirable to have the head gear that attaches the CPAP device to be smaller, simpler and/or less cumbersome. It may also be advantageous to have such a device that facilitates handling of the patient by caretakers. 
     SUMMARY OF THE INVENTION 
     Some embodiments provide a CPAP device and method that has reduced size, improved performance, and/or other benefits with respect to the patient. 
     An aspect of the present invention in some embodiments involves a continuous positive airway pressure system, comprising a housing forming an airway chamber, and having an air pressure inlet and an air pressure outlet, and further defining internally a pair of tapered air jets; a pair of tapered air receivers each disposed coaxially with one of the air supply jets downstream of the air supply jets, and each having a taper in an opposite direction to the direction of taper of the air supply jets; and a pair of nasal prongs downstream of the air receivers. 
     Another aspect of the continuous positive airway pressure system in some embodiments comprises means for defining an airway chamber, and having an air pressure inlet and an air pressure outlet, and further defining internally a pair of tapered air jets; a pair of tapered air receiving means, each disposed coaxially with one of the air supply jets downstream of the air supply jets, and each having a taper in an opposite direction to the direction of taper of the air supply jets; and a pair of nasal interacting means downstream of the receiving means. 
     A further aspect of the present invention in some embodiments provides a continuous positive airway pressure method, providing air pressure to a housing forming an airway chamber, and further defining internally a pair of tapered air jets; directing air from the air jets to a pair of tapered air receivers, each disposed coaxially with one of the air supply jets downstream of the air supply jets, and each having a taper in an opposite direction to the direction of taper of the air supply jets; and directing air from the air receivers to a pair of nasal prongs downstream of the air receivers. 
     There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an infant patient also showing a CPAP device according to an embodiment of the present invention in use. 
         FIG. 2  is an exploded view of components of the CPAP device. 
         FIG. 3  is a perspective view of the device of  FIG. 2  in an assembled condition. 
         FIG. 4  is a cross sectional view taken through line  4 - 4  in  FIG. 3  of the CPAP device of  FIG. 3 . 
         FIG. 5  is a cross sectional view taken through line  5 - 5  of  FIG. 4 , showing a cross section of the CPAP device of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Some embodiments provide a CPAP device and method that has reduced size, improved performance, and/or other benefits with respect to the patient. Preferred embodiments of the invention will now be described with reference to the drawing Figures in which like reference numerals refer to like parts throughout. 
       FIG. 1  is a perspective view of a patient using a CPAP device according to an embodiment of the present invention. The device  10  includes a generator body  12  which receives positive airflow pressure from a supply tube  14 . The tube  14  is pressurized by an air pressurize device which is not illustrated. The generator body  12  also is connected to an outlet tube  15 . As will be seen in  FIGS. 2 through 4 , in a preferred embodiment the tubing for tubes  14  and  15  does not have a circular cross section, but rather has an oval or ellipsoid cross section. This oval cross section of the tubes  14  and  15  some times will provide a significant benefit. where used, in several respects. First, the oval tubing provides a greater volumetric area while still reducing the diameter of the tubing in one direction, and also allows for a more compact generator housing  16  as described in more detail below with respect to  FIGS. 2 through 4 . Second, the oval tubing has a tendency to lay flat if the patient turns his or her head and lies on the tubing. This relatively flat contact with the patient&#39;s head can be more comfortable and distribute the weight of the patient&#39;s head more evenly over the tubing as compared to circular tubing. However, some other aspects of the preferred embodiment that will be described below can still be obtained with the use of circular tubing. 
       FIG. 1  also illustrates, as will be seen in more detail in the subsequent Figures, that the generator body  12  includes a housing  16  (which has the inlet fitting  22  that connects to the tubing  14  and an outlet fitting  23  connected to the tubing  15 ) and also has an exhalation port  18  which permits outlet of the exhalation air. The housing  16  is attached to a receiver assembly  20  which includes prongs that fit into the patient&#39;s nares as will be described further below. 
     Turning next to  FIG. 2 , the housing  16  and its exhalation port  18  are illustrated. The housing  16  is essentially a rectangular box-shaped housing having the exhalation port  18 , and a pair of side structures on its side ends. The side structures each form sidewalls of the generator body and have the fittings  22  and  23  that receive the tubing  14  and  15 , which is preferably oval tubing, as described above. 
     One side of the rectangular box shape of the housing  16  is open, and is adapted to receive a receiver assembly  20  which will be described in more detail below. When the receiver  20  is mounted to close off the open end of the housing  18 , a receiver cap  24  is trapped inside. The receiver  20  includes a pair of nasal prongs  26  extending therefrom as well as a pair of headgear attachment flanges  28  projecting therefrom. The receiver nasal prongs  26  may be of any suitable size and shape as is suitable for interacting with the patient&#39;s nares. In addition, the headgear attachment flanges  28  may also be of any suitable size and shape to interact with a strap type headgear or an adhesive fastening arrangement, or any other type of patient attachment system. 
     Another advantage of the oval tubing  14  and  15  is that the housing  18  can have a relatively compact rectangular box shape, and the tubing  14  and  15  may be arranged with its major diameter at a diagonal angle, as can be seen by the orientation of the fittings  22  and  23 , thus allowing the tubing  14  and  15  to have a major diameter that is nearly as long as the diagonal length of the profile of the housing  18 . This contributes to the housing  18  having a desirably compact shape. 
     The assembly described above may be manufactured from any suitable materials. However, in one example, the housing  18  and its fittings  22  and  23 , as well as the receiver cap  24 , are manufactured from a plastic, such as a polycarbonate. The receiver  20 , including the headgear attachment flanges, and nasal prongs, may be molded from a biocompatible silicone. 
     Turning next to  FIGS. 4 and 5 , the air flow within the CPAP device is illustrated. Supply air enters the housing  16  via a fitting  22  from a pressurized source through the tubing  14 . The supply air enters a supply air channel  30  which feeds two supply air nozzle jets  32 . Supply air nozzle jets  32  each generally have a first cylindrical portion  34  and then transition to a slight outward taper region  35 . The tapered portion  35  is an outward flared conical taper with an included angle of approximately 4 degrees between the sidewalls. This outward taper has been found to provide a venturi effect which is beneficial to the airflow. 
     In addition to having a 4 degree included angle in the tapered portion  35 , the axial length of the portion  35  is approximately two times the starting diameter, i.e., the internal diameter of the cylindrical portion  34  of the jet  32 . This taper improves the efficiency of the nozzle and reduces the pressure required to drive the generator. 
     The jets  32  direct air towards the receiver cap assembly  24 , and more particularly to two funnel shaped receivers  38 . The nasal prongs  26  then receive air directly from the receivers  38 . The receivers  38  each have a conically tapered portion  39  with an inward flared cone having an included angle of 60 degrees between the sidewalls. A straight cylindrical portion  41  extends from the end of the conical portion  39 . 
     In one preferred embodiment, a distance D from a reference line A, which is the outlet end face  36  of the jet  32  relative to reference line B, which is the end face of the conical portion of the receivers  38 , has been found to be 1.8 times the internal diameter of the cylindrical portion  34  of the jets  32 . 
     The outlet fitting  23  leads to outlet tubing by which the patient pressure can be monitored at an outlet side of the device, i.e., pressure monitoring system that is not shown. 
       FIG. 5  is a cross section view showing at a different angle some of the various components referred to above using the same reference numerals. 
     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.