Abstract:
A method and related systems to selective control operational modes of positive airway pressure systems. At least some of the illustrative embodiments are a method comprising inserting a memory card into a card reader of a positive airway pressure device, and selectively operating the positive airway pressure device in at least one of a first pressure control mode where pressure applied is substantially continuous across a patient&#39;s respiratory cycle, or a second pressure control mode where the pressure applied is reduced during exhalation of the patient (the operating based on information stored on the memory card).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of provisional application Ser. No. 60/688,264, filed Jun. 7, 2005, titled “methods and related systems to selective control operational modes of positive airway pressure systems,” which application is incorporated by reference herein as if reproduced in full below. 
     
    
     BACKGROUND  
       [0002]     Sleep disordered breathing is common throughout the population, and some sleep disorder breathing may be attributable to disorders of the respiratory tract. For example, sleep apnea is a situation where a person temporarily stops breathing during sleep. A hypopnea is a period of time where a person&#39;s breathing becomes abnormally slow or shallow. In some cases, a hypopnea may precede an apnea event.  
         [0003]     Although hypopneas and apneas may have multiple causes, one trigger for these type events may be full or partial blockages in the respiratory tract. In particular, in some patients the larynx may collapse due to forces of gravity and/or due to forces associated with lower pressure in the upper airway than outside the body. A collapse of the pharynx, larynx, upper airway or other soft tissue in the respiratory tract may thus cause the full or partial blockage, which may lead to a hypopnea or apnea event.  
         [0004]     One method to counter collapse of the larynx is the application of positive airway pressure to the nostrils, possibly by using a CPAP machine. Using a positive airway pressure device, such as CPAP, the pressure within the pharynx, larynx, or upper airway may be greater than the pressure outside the body, thus pneumatically splinting open the airway. However, patients respond differently to different pressure control philosophies, thus limiting the marketability of a positive airway pressure device implementing a single pressure control philosophy.  
       SUMMARY  
       [0005]     The problems noted above are solved in large part by a method and related systems to selective control operational modes of positive airway pressure systems. At least some of the illustrative embodiments are a method comprising inserting a memory card into a card reader of a positive airway pressure device, and selectively operating the positive airway pressure device in at least one of a first pressure control mode where pressure applied is substantially continuous across a patient&#39;s respiratory cycle, or a second pressure control mode where the pressure applied is reduced during exhalation of the patient (the operating based on information stored on the memory card).  
         [0006]     Other illustrative embodiments are systems comprising a first blower configured to fluidly couple to a first naris of a patient, a processor coupled to the first blower and configured to control the speed of the first blower, and a card reader electrically coupled to the processor, wherein the card reader is configured to read information from a memory device insertable into the card reader The processor, based on the information, operates the first blower in at least one of a first pressure control mode where pressure applied to the first naris of the patient is substantially continuous across a patient&#39;s respiratory cycle, or a second pressure control mode where the pressure applied is reduced during exhalation of the patient.  
         [0007]     Other illustrative embodiments are a computer readable medium storing a program that, when executed by a processor, performs a method comprising reading (by a positive airway pressure device) information from a removable memory device, and implementing at least one of a first pressure control mode where pressure applied to the second naris of the patient by the positive airway pressure device is substantially continuous across a patient&#39;s respiratory cycle, or a second pressure control mode where the pressure applied by the positive airway pressure device is reduced during exhalation of the patient.  
         [0008]     The disclosed devices and methods comprise a combination of features and advantages which enable it to overcome the deficiencies of the prior art devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     For a detailed description of the various embodiments of the invention, reference will now be made to the accompanying drawings in which:  
         [0010]      FIG. 1  shows a system for providing positive airway pressure to a patient in accordance with at least some embodiments of the invention;  
         [0011]      FIG. 2  shows a control system which maybe used to control a positive airway pressure device in accordance with at least some embodiments of the invention; and  
         [0012]      FIG. 3  shows two sets of waveforms to illustrate at least some pressure control modes implemented in accordance with embodiments of the invention. 
     
    
     NOTATION AND NOMENCLATURE  
       [0013]     Certain terms are used throughout the following description and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function.  
         [0014]     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections.  
         [0015]     Further, use of the terms “pressure,” “applying a pressure,” and the like shall be in reference herein, and in the claims, to gauge pressure rather than absolute pressure. Thus, applying a negative pressure shall mean applying a pressure less than atmospheric pressure.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]      FIG. 1  illustrates a device  30  for providing positive airway pressure to a patient in accordance with some embodiments of the invention. A device  30  constructed in accordance with embodiments of the invention has the capability of individually controlling pressure and/or therapeutic gas flow to each nostril or naris of the patient. Thus, a first flow path comprises a blower  32  fluidly coupled to a flow sensor  34  and pressure transducer  36 . Blower  32  may be any suitable device, such as a vane-type blower coupled to an electric motor. In alternative embodiments, a source of therapeutic gas, e.g. oxygen, may be used in addition to or in combination with the blower  32 . Therapeutic gas pressure and flow created by the blower  32  may thus flow through the flow sensor  34  (of any suitable type) and to a first naris of a patient possibly through tube  38 . A positive airway pressure device  30  in accordance with embodiments of the invention also comprises a second blower  40  coupled to a second flow sensor  42  and second pressure transducer  44 . The blower  40  may be of similar design and construction to that of blower  32 . In alternative embodiments, the blower  40  may be used in combination with or replaced by a source of compressed therapeutic gas, e.g. oxygen. Therapeutic gas pressure and flow created by blower  40  may thus flow through the flow sensor  42  (of any suitable type) and to a second naris of the patient, possibly through tube  46 .  
         [0017]     In accordance with some embodiments of the invention, the positive airway pressure device  30  controls pressure and/or flow to each naris of a patient individually. In some embodiments, therapeutic gas flow to the patient may be divided among the nares so as not to force any one naris to carry all the therapeutic gas flow. In order to ensure that each naris is carrying at least part of the therapeutic gas flow, the flow path for each naris may need individual pressure and/or flow control. Control of the pressure, and therefore the therapeutic gas flow, may take many forms. In some embodiments, the pressure may be controlled by selectively controlling blower speed, e.g. by controlling the speed of the motor coupled to the blower. In alternative embodiments, the blowers  32 ,  40  may be operated at a constant speed and the pressure provided to the patient may be controlled by pressure control valves  48 ,  50  for the blowers  32 ,  40  respectively. In yet other embodiments, a combination of controlling the blower speed in a pressure control valve may be utilized.  
         [0018]      FIG. 2  illustrates a control system  60  which may be used to control the positive airway pressure device as illustrated in  FIG. 2 . In particular, motors  62 ,  64  couple one each to blower  32 ,  40  (not shown in  FIG. 2 ) respectively. The speed of the output shaft of each motor  62 ,  64  (and therefore the blower speed) is controlled by a motor speed control unit  66 ,  68  respectively. In at least some embodiments, the motors  62 ,  64  may be DC motors, whose speed is controlled by varying the applied DC voltages. In alternative embodiments, voltage to each of the motors  62 ,  64  may remain constant, but may be modulated, such as by pulse width modulation control. In yet other embodiments of the invention, the motors  62 ,  64  may be AC motors, and in these embodiments the motor speed control circuits  66 ,  68  may provide control voltages having varying voltages and frequencies to the motors so as to control motor speed.  
         [0019]     The control system  60  also comprises a microcontroller  70  coupled to the motor speed control circuits  66 ,  68 . The microcontroller  70  may be any suitable microcontroller or microprocessor having its own read only memory  71  storing programs executable by the microcontroller  70 , or possibly external read only memory. The microcontroller  70 , executed programs, provides an indication to each of the motor speed control circuits  66 ,  68  of a desired motor speed. Although microprocessor control is preferred, the positive airway pressure device may be equivalently implemented with individual processor, memory, and input/output modules, or by way of an analog control system. Setting motor speed for a flow circuit to a naris may be based, in some embodiments, on pressures read by the microcontroller  70  from the pressure transducers  36  and  44 . In other embodiments, setting motor speed for a flow circuit to a naris may be based on gas flows measured by the flow sensors  34  and  42 .  
         [0020]     In accordance with embodiments of the invention, the microcontroller  70  is provided with a doctor prescribed titration pressure. In some embodiments, the doctor prescribed titration pressure is provided by way of a dial-type input or other form of user interface. In other embodiments, the doctor prescribed titration pressure is provided by way of a secure digital interface memory card  74 , such as a SDSDB or SDSDJ card produced by SanDisk of Sunnyvale Calif. When using memory such as a secure digital interface memory card  74  as the mechanism to provide the doctor prescribed titration pressure to the control system  60 , a card reader  72  may be used, such as a card reader part number 547940978 manufactured by Molex Incorporated. As will be discussed more fully below, the card reader  72  and memory card  74  may also be used to provide operational information to the control system.  
         [0021]     Based on the prescribed titration pressure, the microcontroller ramps the speed control signal passed to each of the motor speed control circuits  66  and  68  to achieve the prescribed titration pressure, at least during the inhalation of the patient. If a naris is severely congested or otherwise blocked, however, therapeutic gas flow may move only through an open naris at the prescribed titration pressure. Moreover, throughout the night, the restriction or resistance to airflow experienced within each naris may change (e.g. as a function of congestion experienced within each naris, as a function of an amount of swelling of the soft tissue within each naris, or as a function of nasal cycle (which may be caused by brain triggered muscle contractions)). Thus, even at the prescribed titration pressure applied to each naris the patient may receive inadequate therapeutic gas. Co-pending and commonly owned application Ser. No. 11/156,432, titled “Method and related system to control applied pressure in CPAP systems,” filed Jun. 20, 2005 and incorporated by reference herein as if reproduced in full below, describes methods and systems to control applied pressure to address nasal cycle effects in delivery of therapeutic gas.  
         [0022]     In accordance with embodiments of the invention, the positive airway pressure device  30  selectively applies differing pressure control strategies.  FIG. 3  illustrates at least two modes of operation in relation to a patient respiration. The applied pressure graph of  FIG. 3  shares a time axis with the measured airflow graph to illustrate the relationship. In particular, the applied pressure graph of  FIG. 3  illustrates application of a continuous pressure (by line  300 ) in relation to the inhalation portion  302  of a patient respiration and the exhalation portion  304  of the patient respiration. In this mode of operation, the device  30  ( FIG. 1 ) operates as a continuous positive airway pressure device.  
         [0023]      FIG. 3  also illustrates a second mode of operation (by dash-dot line  306 ). In this second mode of operation, the pressure applied by the device  30  is a function of the whether the patient&#39;s respiration is in the inhalation portion or exhalation portion. In particular, while the patient&#39;s respiration is in the inhalation portion  302 , the device  30  applies a first pressure (illustrated by region  308 ). When the patient&#39;s respiration is in the exhalation portion  304 , the device  30  applies a second, lower pressure (illustrated by region  310 ). Thus, the pressure applied is reduced during exhalation, possibly to reduce the amount of effort required by the patient to exhale, or if applied on a single naris to ensure approximately the same narial airflow during exhalation. Application of differing pressures in this manner may be referred to as bi-level pressure application. In some embodiments, the pressure applied during exhalation may be negative (less than atmospheric), and thus assist the patient in exhalation.  
         [0024]     Although  FIG. 3  shows the pressure applied in the bi-level mode to be higher than in the continuous mode, this need not necessarily be the case. Further, the mode of operation may be the same as between the nares, or differing modes of operation may be used with respect to each naris. In other embodiments, selectively using differing modes of operation may be used in a device  30  that applies pressure to both nares simultaneously (single plenum coupled to the nares).  
         [0025]     Referring again to  FIG. 2 , in accordance with some embodiments of the invention, which of the illustrative pressure control modes to utilize (or in what combination) may be communicated to the control system  60  of device  30  ( FIG. 1 ) by way of memory card  74  and card reader  72 . In particular, the microcontroller  70  may read information off the memory card  74 , and the information defines the operational mode. Thus, in some embodiments data in the form of the patient&#39;s prescription set point and pressure control mode may be read from the memory card  74  by way of the card reader  72 . Based on that data, the microcontroller may thus implement the control mode. In alternative embodiments, the memory card  74  holds a program that is executed by the microcontroller  70 , and executing the program may thus implement the desired pressure control modes. Thus, device  30  may be selectively operated in a continuous positive airway pressure and/or a bi-level mode, thus negating the need for the patient to purchase a second device if the pressure control strategy for the patient should change.  
         [0026]     In accordance with at least some embodiments, the memory card  74  is inserted into the card reader  72  through an aperture in a cover of the positive airway pressure device. In particular,  FIG. 4  illustrates a portion of an outer cover  80  of a positive airway pressure device  30 . The outer cover  80  has therein an aperture  82 . In accordance with some embodiments of the invention, the memory card  74  is inserted into the card reader  72  (not visible in  FIG. 4 ) through the aperture  82 . Thus, in these embodiments the positive airway pressure device  30  may receive the patient&#39;s titration pressure and/or information regarding the mode the positive airway pressure device should operate. As mentioned above, the information on the memory card  74  may be data that triggers an operational mode whose software already resides within the positive airway pressure device, or in alternative embodiments the software instructions to implement a particular operation mode may be stored on memory card itself Thus, the positive airway pressure device may be provided information that changes operational modes without having to disassemble the positive airway pressure device, such as to replace programmable read only memories storing programs executed by the microcontroller  70 .  
         [0027]     The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.