Abstract:
A system comprises a respiratory delivery arrangement adapted to cover at least one respiratory orifice of a patient. The system also comprises a first conduit having a first end and a second end, the second end connected to the respiratory delivery arrangement. A positive pressure is provided to the respiratory orifice via the first conduit and a second conduit having a third end and a fourth end, the fourth end connected to the respiratory delivery arrangement. An exhaled gas is extracted from the respiratory orifice by one or both of a valve configured to redirect flow through the respiratory delivery arrangement and a venturi opening.

Description:
PRIORITY CLAIM 
       [0001]    The present application claims priority to U.S. Provisional Application Ser. No. 61/172,413 entitled “Circuits to Allow CPAP to Provide Zero Pressure” filed on Apr. 24, 2009, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND INFORMATION 
       [0002]    Noninvasive CPAP procedures have come into widespread use for the treatment of sleep apnea and during episodes of acute and chronic respiratory failure without using endotracheal intubation. All forms of such non-invasive positive pressure ventilation (PPV) procedures require that a mask be worn over a respiratory orifice of a patient to provide an interface with a source of positive pressure. A leak port is provided on the mask to vent exhaled CO2 from the system. Current CPAP technology relies on a predetermined low pressure of greater than approximately 3-5 cm H 2 O to vent exhaled gas out of the leak port during exhalation. However, when a positive pressure supplied by a pressurized air source falls below this value, venting through the leak port ceases, thus causing a buildup of exhaled CO 2  within the mask. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention is directed to systems and method for providing ventilation to a respiratory delivery system when a positive pressure being supplied by a respiratory device falls below a threshold value. In one respect, the present invention is directed to a system comprising a respiratory delivery arrangement adapted to cover at least one respiratory orifice of a patient. The system comprises a leak port located adjacent o the respiratory delivery arrangement and first conduit having a first end and a second end, the second end connected to the respiratory delivery arrangement, a positive pressure being provided to the respiratory orifice via the first conduit and a second conduit having a third end and a fourth end, the third end being separated from the first end, the fourth end connected to the respiratory delivery arrangement. The system also comprises a valve located in the first conduit and having a first position and a second position, wherein when the valve is in the first position, (a) a positive pressure flows through the first and second conduits and (b) exhaled gas from the respiratory orifice exits the leak port, and wherein, when the valve is in the second position, (c) a positive pressure flows through only the second conduit and (d) exhaled gas from the respiratory orifice exits the leak port and through the valve. 
         [0004]    In another respect, the present invention is directed to a system comprising a respiratory delivery arrangement adapted to cover at least one respiratory orifice of a patient. The system comprises leak port located at or near the respiratory orifice. The system also comprises a first conduit having a first end, a second end, and a first valve, the first valve having a first position and second position, the second end connected to the respiratory delivery arrangement, a positive pressure being provided to the respiratory orifice via the first conduit. The system also comprises a second conduit located within the first conduit and having a third end, a fourth end and a venturi opening entraining gas from the third end to the ambient environment, the third end being separated from the first end, the fourth end connected to the respiratory delivery arrangement. When the first valve is in the first position, (a) a positive pressure flows through the first conduit and (b) a first portion of exhaled gas from the respiratory orifice exits the leak port and wherein, when the first valve is in the second position, (a) positive pressure flow through the first conduit is prevented, (b) an inhalation gas is drawn in from the opening via the first conduit, (c) a first portion of exhaled gas from the respiratory orifice exits the leak port and (d) a second portion of exhaled gas exits the venturi opening via the second conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a first exemplary embodiment of a system according to the present invention; and 
           [0006]      FIG. 2  shows a second exemplary embodiment of a system according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0007]    The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention is directed to a system and method for ventilating a CPAP system when a positive pressure being supplied by a CPAP blower falls below a predetermined threshold of approximately 3-5 cm H 2 O and, more specifically, when a positive pressure is at or close to zero. The exemplary embodiments of the present invention are directed to systems and methods that provide for an automatic adjustment of the CPAP device to the lowered positive pressure so that a venting of exhaled gases is permitted without any manual effort on the part of a wearer. It is noted that although embodiments of the present invention are described with respect to CPAP procedures, the present invention may be employed for the treatment of any respiratory conditions where a mask is used to administer an airway pressure including treatments for sleep apnea, hypopnea, snoring, somnolence, etc. without deviating from the spirit and scope of the present invention. As described herein, the term proximal refers to a direction approaching a CPAP device and the term distal refers to a direction approaching a respiratory mask worn over a respiratory orifice on a head of a patient. 
         [0008]    As will be described in greater detail hereinafter, the exemplary system of the present invention is configured to prevent a buildup of exhaled gases within a CPAP system, which can be potentially harmful to a wearer of the system. 
         [0009]      FIG. 1  shows a system  100  according to a first exemplary embodiment of the present invention. The system  100  comprises a CPAP blower  102  configured to provide pressurized air to a patient via a first conduit  110 . The CPAP blower  102  is connected to a computer  106  configured to control the flow of pressurized air through the system  100 , as those skilled in the art will understand. The first conduit  110  extends from a proximal end  112  connected to the CPAP blower  102  to a distal end  114  connected to a respiratory mask  104  covering a respiratory orifice (e.g., nasal cavity or oral cavity) of a patient (not shown). A leak port  122  is located on the respiratory mask  104  to provide a continuous exit of exhaled gas from the system  100  when a pressure therein is greater than approximately 3-5 cm H 2 O. It is noted that although the leak port  122  is shown on the mask  104  of the present invention, the leak port  122  may also be positioned elsewhere on the system  100  at a location that is substantially adjacent to the respiratory orifice of the patient. The first conduit  110  is formed of a substantially flexible and durable material known in the art and is dimensioned to permit a predetermined volume of air therethrough at a predetermined pressure, as those skilled in the art will understand. The system  100  also comprises a second conduit  116  open to the mask  104 . The second conduit  116  extends from a proximal end  118  open to a proximal portion of the first conduit and the CPAP blower  102  to a distal end open to the mask  104 . As will be described in greater detail below, the device  100  of the present invention is configured to bypass a need for a suctioning device to draw exhaled gas out of the system. It is noted however, that an optional suctioning device may be incorporated in the system  100  without deviating from the spirit and scope of the present invention. It is further noted that although the second conduit  116  is shown to extend through the first conduit  110 , the second conduit  116  may alternatively assume any position relative thereto as long as the distal end  120  opens into the mask  104  and provides a means for exhaled gas from the respiratory orifice to be removed independently of a pressure in the mask  104 . For example, in a first alternate embodiment, the second conduit  116  may be located externally of the first conduit  110  as long as the proximal and distal ends  118 ,  120  are fluidly connected to the CPAP blower  102  and mask  104 , respectively. 
         [0010]    The system  100  also comprises a valve  108  configured to selectively seal an opening  109  located adjacent thereto. The valve  108  is a two-way valve located substantially adjacent the proximal end  112  of the first conduit  110 . The valve  108  is connected to the computer  106  via one of a wired and a wireless connection. Thus, the computer  106  can automatically move the valve  108  from a first position to a second position when a predetermined condition is met, as will be described in greater detail hereinafter. In a first position, the valve  108  is configured to fluidly seal the opening  109  while leaving the first conduit  110  substantially unobstructed so that air can flow therethrough. In a second position, the valve  108  is moved so that the first conduit  110  is substantially sealed to airflow. Specifically, movement of the valve  108  to the second position fluidly seals a proximal portion  110 ′ of the first conduit  110  located proximally of the valve  108  with respect to a distal portion  110 ″ located distally thereof. In the second position, the opening  109  is fluidly connected to the distal portion  110 ″ so that the distal portions  110 ″ is open to the atmosphere, as will be described in greater detail hereinafter. 
         [0011]    In accordance with an exemplary method of the system  100 , the proximal end  112  of the first conduit  110  is connected to the CPAP blower  102  and the distal end  114  to the respiratory mask  104 . When the valve  108  is in the first position (i.e., when a positive air pressure exceeding a predetermined limit is being supplied), the first and second conduits  110 ,  116  remain unobstructed and positive air is guided through each of the first and second conduits  110 ,  116  in the directions A and B, respectively. Exhaled gas from the patient is then guided out of the system  100  via the leak port  122  located on the mask  104 . In an exemplary embodiment, the valve  108  remains in the first operative position as long as the positive air supply has a pressure greater than 5 cm. H 2 O, wherein the pressure is selected based on the breathing parameters of the patient, as those skilled in the art will understand. It is noted that the system  100  may further comprise a sensor  115  located in any of the components thereof to monitor pressure and/or flow, as those skilled in the art will understand. 
         [0012]    When the pressure of the positive air supply falls below 5 cm. H 2 O, the valve  108  moves to the second position. Movement of the valve  108  to the second operative position ensures that exhaled CO 2  is properly ventilated from the system  100 . Specifically, in the second position, the first conduit  110  is sealed to airflow such that positive airflow is only permitted in the direction B through the second conduit  116 . The second conduit  116  is sized and shaped so that air flow therethrough has a pressure of approximately 25 l/min. Exhaled CO 2  from the respiratory orifice of the patient then travels in the direction C to exit the leak port  122 . Furthermore, the exemplary embodiment of the present invention also guides the exhaled CO 2  in the direction D through the first conduit  110  and out of the opening  109 . Thus, whereas present CPAP devices would prevent a leakage of CO 2  at low pressure, the exemplary embodiment of  FIG. 1  facilitates venting of CO 2  from the system  100  when the air pressure in the system  100  falls below a predetermined parameter. The valve  108  remains in the second position until a CPAP air pressure once again exceeds 5 cm. H 2 O (e.g., when the patient returns to a sleeping state, etc.). 
         [0013]    In another embodiment of the present invention, the valve  108  of the system  100  may shift between the first and second positions upon receipt of a signal from the sensor  115  provided in the system  100 . Specifically, as those skilled in the art will understand, the sensor may be provided within one of the mask  104  or in the distal portion  110 ″ of the first conduit  110  located distally of the valve  108 , the sensor  115  being configured to measure the patient&#39;s breathing patterns and make a determination of whether the patient is in a sleep state or an awake state. As those skilled in the art will understand, the sensor  115  may be positioned anywhere within the system  100  so that the sensor  115  is provided with data corresponding to a patient&#39;s breathing patterns regardless of a position of the valve  108 . The sensor  115  may be connected to a database containing data corresponding to breathing patterns indicative of each of the two states. The database may be compiled with data from the patient or from a plurality of test subjects, as those skilled in the art will understand. The valve  108  may then be configured to remain in the first position when the patient is in the sleep state. As described in greater detail earlier, in the first position, the opening  109  may be sealed so that a positive air flows travels in the directions A, B and the leak port  122  permits exhaled gas to leave the system  100 . When the sensor  115  indicates that the patient has awakened, the valve  108  may move to the second position so that the opening  109  is open to the environment. Movement of the valve  108  from the first position to the second position then prevents air flow from the CPAP blower to travel through the first conduit  110  to the patient, as described in greater detail earlier. 
         [0014]      FIG. 2  depicts a system  200  according to an alternate embodiment of the present invention. The system  200  is formed substantially similarly as the system  100  of  FIG. 1  with the exception of an additional venturi opening  211  provided therein. Specifically, the system  200  comprises a first conduit  210  extending from a proximal end  212  connected to the CPAP blower  102  to a distal end  214  connected to a respiratory mask  204  covering a respiratory orifice (e.g., nasal cavity or oral cavity) of a patient (not shown). The mask  204  comprises a leak port  222  configured to facilitate the flow of exhaled CO 2  out of the system  200 . However, as will be described in greater detail below, the leak port  222  is optional only and may be omitted without deviating from the spirit and scope of the invention. The system  200  also comprises a second conduit  216  located within the first conduit  210 . The second conduit  216  extends from a proximal end  218  to a distal end  220  open to the mask  204 . The venturi opening  211  is formed as an opening on a wall of the first conduit  210  and, according to one embodiment of the present invention, is open to both the first and second conduits  210 ,  216 . The exemplary embodiment of the present invention is configured so that when there is a low pressure within the system  200 , the venturi opening  211  remains open to an ambient environment to permit entrained gas to exit therefrom. Specifically, since the proximal end  218  of the second conduit  216  is located adjacent the venturi opening  211 , a flow of entrained gas through the second conduit  216  is sufficient to cause the venturi opening  211  to permit flow therethrough, as those skilled in the art will understand. 
         [0015]    The valve  208  is a two-way valve formed substantially similarly as the valve  108 . Specifically, the valve  208  is connected to the computer  106  via one of a wired and a wireless connection. In a first position, the valve  208  is configured to fluidly seal an opening  209  while leaving the first conduit  210  substantially unobstructed. In a second position, the valve  208  separates the first conduit  210  into proximal and distal portions  210 ′,  210 ″ and opens the opening  209  to the atmosphere, as described in greater detail earlier. 
         [0016]    In accordance with an exemplary method for the system  200 , the proximal end  212  of the first conduit  210  is connected to the CPAP blower  102  and the distal end  214  to the respiratory mask  204 . When a positive air supply being supplied to the system  200  exceeds a predetermined threshold value, the valve  208  is in the first position. In this configuration, the positive air supply is directed through the first conduit  210  in the direction E. Exhaled gas from the respiratory orifice of the patient can exit the system  200  from the leak port  222  in the direction F. In one embodiment of the present invention, the venturi opening  211  may remain open when the positive air supply is being supplied. Thus, exhaled gas from the respiratory orifice may also flow proximally from the distal opening of the second conduit  216  and out of the venturi opening  211  in the direction G. It is therefore noted that, in an alternate embodiment of the invention, the leak port  222  may be omitted from the system  200  without affecting the principle of operation thereof. Specifically, the positive pressure within the system  200  may cause suction at the venturi opening  211 , thus forcing a movement of gas in the direction G through the second conduit  216  and out of the venturi opening  211 . However, it is submitted that this is not a required component of the present invention and that, in another exemplary embodiment, the venturi opening  211  may remain closed when positive air with a pressure above the predetermined threshold is being supplied to the system. Specifically, the system  200  may be provided with a blocking means (e.g., a valve, a plug, etc.) configured to prevent flow through the venturi opening  211  when the valve  208  is in the first position. The blocking means (not shown) may be removed from the venturi opening  211  when the valve  208  is moved to the second position, wherein a pressure of expiratory flow through the second conduit  216  may open the venturi opening  211  to permit flow thereoutof, as those skilled in the art will understand and as described in greater detail hereinafter. In an exemplary embodiment, the valve  208  remains in the first position as long as the positive air supply has a pressure greater than approximately 5 cm. H 2 O. 
         [0017]    When the positive air pressure falls below 5 cm. H 2 O, the valve  208  moves to the second position. In this position, positive pressure E from the CPAP blower is prevented from entering either the first or second conduits  210 ,  216 . Rather, the valve  208  opens the opening  209  so that atmospheric air is permitted to flow into the distal portion  210 ″ of the first conduit  210  in the direction H. The movement of exhaled gas through the system  200  follows the same pattern as described in the first valve position wherein a first portion of exhaled gas from the respiratory orifice exits the leak port  222  in the direction F and a second portion of the exhaled gas is guided through the second conduit  216  and out of the venturi opening  211  in the direction G. Specifically, the venturi opening  211  causes a suction to be applied adjacent thereto, the suction force drawings the exhaled gas proximally from the distal end  220  of the second conduit  216  and out of the venturi opening  211 . The valve  208  remains in the second operative configuration until a CPAP air pressure E once again exceeds 5 cm. H 2 O (e.g., when the patient returns to a sleeping state, etc.). This exemplary embodiment thus uses a valve  208  and a venturi opening  211  in combination to guide both the flow of positive and negative air through the system  200 . 
         [0018]    It is noted that various modifications may be made to the embodiments disclosed herein without deviating from the scope of the present invention. For example, although the present invention has been described with a venturi opening  211 , another gas withdrawal means may be provided on the system  200 . In one such exemplary embodiment, suction can be provided to the system  200  by a suction device or another suctioning means, as those skilled in the art will understand. 
         [0019]    While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.