Abstract:
An airflow sensor (thermal sensor assembly) that is designed to adhesively attach to different styles of a cannula and that can detect the movement of respiratory air through the nasal and/or oral cavities. When secured to the cannula, the airflow sensor has its nasal and oral sensing elements in positions that will maximize signal accuracy, minimize airflow signal artifacts, and minimize occurrences of signal loss due to direct patient skin contact. The airflow sensor does not disturb the flow of air from the patient or add any discomfort to the patient. The airflow sensor can be attached to most nasal or nasal/oral cannulae used in sleep disorder diagnostics.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority of U.S. Provisional Patent Application No. 61/449,358 filed Mar. 4, 2011, which is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to sleep disorder diagnostics. More particularly, the present disclosure relates to cannulae and airflow sensors used in sleep disorder diagnostics. 
       BACKGROUND 
       [0003]    Sleep apnea is characterized by a cessation or reduction of breathing that lasts at least 10 seconds and that is repeated at least 5 times an hour while the patient is sleeping. Obstructive sleep apnea (OSA) refers to apnea syndromes due primarily to collapse of the upper airway during sleep. It is estimated that 2 to 4% of middle aged people have OSA. OSA has two specific classifications of events: apnea and hypopnea. An apnea event is defined as an absence of airflow and a hypopnea event as a reduction in airflow associated with a blood oxygen reduction (desaturation) of 3 to 4%. 
         [0004]    The American Academy of Sleep Medicine&#39;s Manual for the Scoring of Sleep and Associated Events©2007 (AASM) requires the use of an oral/nasal thermal sensor for the detection of apnea and a nasal air pressure transducer hypopnea. Both of these devices require the use of different technologies to measure the same physical phenomena, which is the movement of air in and out of the patient. 
         [0005]    In the case of apnea, to measure nasal air pressure, it is standard to use a nasal cannula coupled to a pressure transducer. In the case of hypopnea, to measure air temperature, it is standard to mechanically attach the thermal sensor to the cannula. The coupling of the pressure transducer and the thermal sensor to the cannula can interfere with the patient&#39;s flow of air (i.e., can interfere with the patient&#39;s breathing), cause the thermal sensor to be deflected away from the flow of air (i.e., cause the thermal sensor to be misaligned with the flow of air), and have the thermal sensors actually come in contact with the patient&#39;s skin. All of these effects will cause errors in the thermal sensor signal, which can lead to incorrect diagnostics. 
         [0006]    Example of known air flow sensors can be found in U.S. Pat. Nos. 5,558,099; 5,832,592; and 5,161,541 to Bowman et al. However, the air flow sensor assemblies in these references are adhered directly adhered to the patient&#39;s upper lip and do not allow the use of a nasal cannula, as required by the AASM for scoring hypopneas, without mutual interference between the cannula and the air flow sensor assemblies. The same issue exists in the disclosures of U.S. Pat. Nos. 5,311,875, 6,491,642 and 7,608,047 to Stasz and in the disclosure of U.S. Pat. Nos. 6,254,545 and 6,485,432 to Stasz et al. None of these prior references allow the use of the required cannula without either affecting the flow of air in or the patient&#39;s comfort. 
         [0007]    With respect to diagnosing hypopnea, state of the art measurement requires the separate attachment of the thermal sensor to the cannula and of the cannula to the patient. This is a tedious and laborious task as the individual patient setup must secure the thermal sensor to the cannula, place both the cannula and the thermal sensor on the patient and then, secure the cannula and the thermal sensor on the patient (for example, by using adhesive tape). Securing the thermal sensor to the cannula must be made precisely and in relation to the patient: that is, the thermal sensor should be in the path of the airflow, the thermal sensor should not be touching any objects that can influence the sensors ability to sense the temperature of the airflow, the cannula should be centered on the nares of the patient, and the cannula should not be occluded by the thermal sensor. All this must be done just before the cannula and the thermal sensors are secured (taped down) to the patient. 
         [0008]    Further, the sleep industry also uses combination nasal/oral cannulae as described in U.S. Pat. No. 7,337,780 to Curti et al, an in U.S. Design Pat. No. D559,383 to Nalagatla et al. These combination nasal/oral cannulae allow the measuring of both nasal and oral airflows. Such nasal/oral cannulae have nasal prongs to measure the nasal air pressure as well as some form of ducting that protrudes into or over the oral cavity. The combined use of oral thermal sensor and these nasal/oral cannulae would cause the oral thermal sensors to be ineffective in that they would occlude the ducting opening or would require the oral ducting on the cannula to be shifted in order for the oral thermal sensor to be properly positioned, which would cause the oral ducting to properly capture the oral airflow component. 
         [0009]    Furthermore, sleep laboratories are looking towards medical devices that are single patient use for the diagnosis of OSA on patient&#39;s with highly infectious conditions. However, there are presently no acceptable single use thermal sensors for measuring apnea that can function properly in combination with a nasal or nasal/oral cannula. U.S. design Pat. Nos. D590,058 and D607,993 to Cowen show airflow sensors shaped to work with cannulae using existing concepts for reusable sensors. These designs will not allow the manufacturing of a cost effective device for single patient use. 
         [0010]    Bowman, referenced above, and others disclose using an adhesive to hold the thermal sensor in place while on the patient. However, this requires the use of non aggressive medical adhesive. These thermal sensors cannot be placed on the cannula as this type of adhesive will not last the duration of a sleep study. 
         [0011]    Several of the prior art references disclose the addition of an adhesive being applied that will attach the thermal sensor directly to the patient. However, the shape and the properties of the flexible substrate that is usually comprised in the thermal sensor do not allow for the thermal sensor to be easily attached to the patient. 
         [0012]    Some prior art approaches allow for the placement of the thermal sensing element on top of a substrate. Such approaches require the thermal wave to pass through the substrate before reaching the sensor. This can lead to incorrect reading of the air temperature. 
         [0013]    Therefore, improvements in thermal sensors for cannulae are desirable. 
       SUMMARY 
       [0014]    In a first aspect, the present disclosure provides a thermal sensor assembly to measure a temperature of air expelled by an individual, the thermal sensor assembly to be secured to a cannula having nasal prongs, the thermal sensor assembly secured to the cannula and the cannula secured to the individual defining an installed position. The thermal sensor assembly comprises: a substrate having a sensor portion, the substrate further having a sensor side and a backside, the backside being opposite the sensor side, the sensor portion defining an alignment aperture, the alignment aperture to receive at least one of the nasal prongs to align the thermal sensor assembly to the cannula; at least one nasal thermal sensor formed on the sensor side of the substrate and at the sensor portion of the substrate, the at least one nasal thermal sensor being adjacent to the alignment aperture, the at least one thermal sensor to sense, in the installed position, a temperature of air expelled through a nasal opening of the individual; and an adhesive layer formed on the backside of the substrate and at the sensor portion of the substrate, the adhesive layer to adhere the sensor portion of the substrate to the cannula. 
         [0015]    In another aspect, the present disclosure provides a thermal sensor assembly to measure a temperature of air expelled by an individual, the thermal sensor assembly to be secured to a cannula having nasal prongs, the thermal sensor assembly secured to the cannula and the cannula secured to the individual defining an installed position. The thermal sensor assembly comprises: a substrate having a sensor portion, the substrate further having a sensor side and a backside, the backside being opposite the sensor side, the sensor portion defining an alignment feature, the alignment feature to receive at least one of the nasal prongs to align the thermal sensor assembly to the cannula; at least one nasal thermal sensor formed on the sensor side of the substrate and at the sensor portion of the substrate, the at least one nasal thermal sensor being adjacent to the alignment feature, the at least one thermal sensor to sense, in the installed position, a temperature of air expelled through a nasal opening of the individual; and an adhesive layer formed on the backside of the substrate and at the sensor portion of the substrate, the adhesive layer to adhere the sensor portion of the substrate to the cannula. 
         [0016]    Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures. 
           [0018]      FIG. 1  shows an embodiment of a thermal sensor assembly of the present disclosure secured to a cannula. 
           [0019]      FIG. 2  shows a top view of the thermal sensor assembly of  FIG. 1 . 
           [0020]      FIG. 3  shows a bottom view of the thermal sensor assembly of  FIG. 1 . 
           [0021]      FIG. 4  shows a side view of the thermal sensor assembly of  FIG. 1 . 
           [0022]      FIG. 5  shows a front view of the thermal sensor assembly of  FIG. 1  being secured to a nasal portion of a cannula. 
           [0023]      FIG. 6  shows a rear view of the thermal sensor assembly of  FIG. 1  being secured to the nasal portion of a cannula. 
           [0024]      FIG. 7  shows a front view of the thermal sensor assembly of  FIG. 1  secured by a tab to a cannula. 
           [0025]      FIG. 8  shows a rear view of the thermal sensor assembly of  FIG. 1  secured to by a tab to a cannula. 
           [0026]      FIG. 9  shows another front view of the thermal sensor assembly of  FIG. 1  secured by a tab to a cannula. 
           [0027]      FIG. 10  shows another rear view of the thermal sensor assembly of  FIG. 1  secured to by a tab to a cannula. 
           [0028]      FIG. 11  shows a front view of the thermal sensor assembly of  FIG. 1  being secured to a nasal portion of an oronasal cannula. 
           [0029]      FIG. 12  shows a rear view of the thermal sensor assembly of  FIG. 1  being secured to a nasal portion of an oronasal cannula. 
           [0030]      FIG. 13  shows a front view of the thermal sensor assembly of  FIG. 1  secured by a tab to an oronasal cannula. 
           [0031]      FIG. 14  shows a rear view of the thermal sensor assembly of  FIG. 1  secured by a tab to an oronasal cannula. 
           [0032]      FIG. 15  shows a front view of the thermal sensor assembly of  FIG. 1  being secured by tabs to an oral section of an oronasal cannula. 
           [0033]      FIG. 16  shows a rear view of the thermal sensor assembly of  FIG. 1  being secured by tabs to an oral section of an oronasal cannula. 
           [0034]      FIG. 17  shows a bottom view of another embodiment of a thermal sensor assembly in accordance with the present disclosure. 
           [0035]      FIG. 18  shows a bottom view of another embodiment of a thermal sensor assembly in accordance with the present disclosure. 
           [0036]      FIG. 19  shows a bottom view of another embodiment of a thermal sensor assembly in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    Generally, the present disclosure provides a thermal sensor assembly that can be securely fixed to a cannula, in the correct position on the cannula, before the cannula is secured to the patient. The technician handling the cannula and the thermal sensor assembly only needs to be concerned about placing the cannula properly on the patient. The present disclosure allows for an easier and more accurate placement of the thermal sensor assembly and the cannula with respect to each other and with respect to the patient. Once the thermal sensor assembly is secured to the cannula, the technician simply has to tape the cannula in place, on the patient, and does need to be concerned about separately placing thermal sensors on the patient. The present disclosure allows for the placement of the thermal sensor directly in the path of the airflow. That is, there are no obstacles or materials between the thermal sensor and the flow of air. The present disclosure further allows the accurate placement of thermal sensors (thermal sensor assembly) on most nasal and oral/nasal cannulae presently on the market. 
         [0038]      FIG. 1  shows an embodiment of a thermal sensor assembly  300  of the present disclosure. The thermal sensor assembly  300  is secured to a nasal cannula  10 , which is secured to a patient  302 . The thermal sensor assembly  300  has a sensor portion  308  that can be adhesively secured to the cannula  10  at the nasal portion  304 . Similarly an oronasal cannula with an oral section  110  as shown at  FIGS. 11 and 12  could have the oral section  20  of the sensor attached. The sensor portion  308  has nasal thermal sensors  16  and  18  positioned to receive air flowing out the nasal openings  306  of the patient  302 . The cannula  10  has nasal prongs  307  inserted into the nasal openings  306  (nares). The nasal prongs  307  propagate air flowing out of the nasal openings  306  towards, for example, an air pressure monitor. The shape and size of nasal prongs  307  are such that only a portion of the air flowing out of the nasal openings  306  enters the nasal prongs  307 . Another portion of the air flowing out of the nasal openings  306  impinges on the nasal thermal sensors  16  and  18 . Additionally, the thermal sensor assembly  300  has a tail portion  8  and an intermediate portion  6  that physically connects the sensor portion  308  to the tail portion  8 . As will be described in greater detailed below, the thermal sensor assembly  300  of  FIG. 1  also has a tab  14  that can be used to further secure the thermal sensor assembly to the cannula  10 . 
         [0039]    The thermal sensor assembly  300  can comprise a thin, flexible non-electrically-conductive substrate (an electrically insulating substrate) such as, for example, mylar, polyester, and any other suitable type material that can be made thin and flexible. 
         [0040]      FIG. 2  shows a top view of the thermal sensor assembly  300  with such a substrate  310 . The substrate  310  has electrically conductive traces  312  defined thereon. The electrically conductive traces  312  terminate at electrodes  28 , which are defined at the tail portion  8  and which can be connected to any suitable measurement apparatus through any suitable connector arrangement. The electrical conductive traces  312  also electrically interconnect the nasal thermal sensors  16  and  18 , as well as an oral thermal sensor  22 , which can be secured to the oral section  120  of the cannula  10 . The nasal and oral thermal sensors of the embodiment of  FIG. 12  are electrically connected in series; however, any other type of electrical connection between the nasal and oral thermal sensors is also within the scope of the present disclosure. The electrically conductive traces  312  can include, for example, a conductive ink or any other suitable type of electrical conductor. 
         [0041]    In another embodiment, instead of having two nasal thermal sensors  16  and  18 , there can be only one nasal thermal sensor  17  that extends such as to receive air flowing out of either of the nasal openings  306 . 
         [0042]    The tail portion  8  can have defined therein a hole  26  that can be used to receive a cooperating part of a connector adapted to connect the electrodes  28  to the aforementioned measurement apparatus. The hole  26  receiving the cooperating part of the connector can help secure the electrodes  28 , and the tail portion  8  to the connector. 
         [0043]    The substrate  310  also defines the tab  14 , which, as shown at  FIG. 1 , can be used to secure the thermal sensor assembly  300  to the cannula  10 . The tab  14  is shown as extending perpendicularly from the intermediate portion  6 ; however, this need not be the case. For example, in another embodiment, the tab  14  can extend obliquely from the intermediate portion  6  and away from the sensor portion  308 . Such an embodiment would also allow the oblique tab to secure the thermal sensor assembly as in the previous embodiment; however, in applications where it may be desired to remove the thermal assembly sensor  300  from the cannula  10 , the oblique tab can facilitate the removal of the thermal sensor assembly  300  from the cannula  10  in that it can be easier for a technician to grab the end of the oblique tab for removal of the tab from the cannula  10 . In yet another embodiment there can be no tab  14 . 
         [0044]    Further, the nasal sensor portion  308  of the thermal sensor assembly  300  has defined therein holes  32  and  34 , which can receive the nasal prongs  307  of the cannula  10 . The holes  32  and  34  define an alignment feature of the substrate  310  and of the thermal sensor assembly  300 . The nasal prongs  307  define an alignment feature of the cannula  10 . The alignment feature of the cannula (the prongs  307 ) cooperate with the holes  32  and  34  to align the thermal sensor assembly  300  to the cannula. As such, the thermal sensor assembly  300  is self aligning with respect to the cannula  10 . That is, a technician placing the thermal sensor assembly  300  onto the cannula  10  only needs to place the nasal prongs  307  into the holes  32  and  34  and to join the thermal sensor assembly  300  to the cannula  10 . By doing so, the nasal thermal sensors  16  and  18  are aligned to receive air from the nasal openings  306 . 
         [0045]    The substrate  310  also defines a substrate oral portion  314  which has the oral thermal sensor  22  formed thereon. The substrate oral portion  314  can have tabs  24  which can be used to secure the substrate oral section  314  to the cannula oral section  110 . 
         [0046]    The nasal thermal sensors  16  and  18 , and the oral thermal sensor  22  can be thermocouple sensors, thermistor sensors, bead sensors, or any other suitable type of sensor that allows for the measurement of temperature. Additionally, the nasal thermal sensors  16  and  18 , and the oral thermal sensor  22  can be made of thin deposits of electrically conductive ink. An electrically insulating, thermally conductive protective layer (e.g., a bio-compatible electrically insulating epoxy) can be formed over the nasal thermal sensors  16  and  18 , the oral thermal sensor  22 , and the electrically conductive traces  312  to allow proper temperature measurement of the air coming out of the patient and to avoid any extraneous electrical signal being picked up by the sensors and the conductive traces. An bio-compatible electrically insulating epoxy such as Loctite HYSOL M-31CL could be used. 
         [0047]    The side of the substrate shown in the thermal sensor assembly  300  of  FIG. 2  is the sensor side of the substrate. That is, the side of the substrate  310  that has the thermal sensors formed thereon. 
         [0048]    The side of the substrate opposite to the sensor side (the backside) can have an adhesive layer portion secured thereto. The adhesive layer portion allows the thermal sensor assembly  300  to be secured to the cannula  10 . The side of the substrate opposite to the sensor side can also have a stiffener secured thereto, to facilitate the electrical connection of the electrodes  28  to a measurement apparatus through an electrical connector and to protect the electrodes against excessive bending.  FIG. 3  shows such a stiffener  38  formed at the tail portion  8  and an adhesive layer portion  36  formed at the sensor portion  308 . As will be understood by the skilled worker, the adhesive layer portion  36  need not be applied over the entire backside of the sensor portion of the thermal sensor assembly  300 . The stiffener  38  can be made of any suitable rigid or semi-rigid material such as, for example plastic. As another example, a double layer of substrate material, or a thicker layer of substrate material could be used as a stiffener. The stiffener  38  can be secured to the substrate  310  with any suitable adhesive or through any other suitable means. 
         [0049]      FIG. 4  shows a side view thermal sensor assembly  300 , which is shown with the stiffener  38  secured to the substrate  310 , the adhesive layer portion  36  formed on the substrate  310 , and a peel-way backing  44  that protects the adhesive layer  36  until the thermal sensor assembly  300  is ready to be secured to the cannula  10 . Also shown in  FIG. 4  are the nasal thermal sensors  16  and  18 , and the oral thermal sensor  22 . Additionally, a layer of electrically insulating, thermally conductive material is shown, at reference numeral  46 , formed over the nasal thermal sensors  16  and  18 , and the oral thermal sensor  22 . An example of material that can be used at  46  is Loctite® HYSOL™ M-31CL. Any other suitable material can be used. 
         [0050]    The thermal sensor assembly  300  is such that, when secured to the cannula  10  and with the cannula being secured to a patient (individual), the nasal thermal sensors  16  and  18 , and the oral thermal sensor  22  line-up with the nasal openings  306  and with the mouth of the patient  302 . Further, the tab  14 , which has the adhesive portion  36  formed thereon, facilitates the connection of the thermal sensor assembly  300  to the cannula  10  and can provide relief of strain applied at the tail portion  8 . The thermal sensor assembly being secured to the cannula and the cannula being secured to the individual can be referred to as the thermal sensor assembly installed position or simply as the installed position. 
         [0051]    To secure the thermal sensor assembly  300  to the cannula  10 , the user (technician, clinician, etc.) first removes the peal-away backing  44  to expose the adhesive layer portion  36 . The user then slides the nasal prongs  307  of the cannula into the holes  32  and  34  to begin securing the sensor portion  308  to the nasal portion  304  of the cannula  10  by adhering the sensor portion  308  to the cannula  10 . This is shown in a front view at  FIG. 5 , and in a rear view at  FIG. 6 . 
         [0052]    Subsequently, the user can wrap the tab  14  to the cannula  10  and back onto itself, as show in front and rear views at  FIGS. 7 and 8  respectively. 
         [0053]    If the thermal sensor assembly  300  is used with a nasal-only cannula, the tabs  24  may be cut off as shown in front and rear views at  FIGS. 9 and 10  respectively. As such, the oral thermal sensor  22  dangles from the cannula  10  and faces the mouth of the patient  302 . The electrically insulating, thermally conductive material  46  mitigates interference from any contact of the oral thermal sensor  22  with the patient. 
         [0054]      FIGS. 11 and 12  show respectively a front view and a rear view of the thermal sensor assembly  300  being secured to an oronasal cannula  10  prior to the tab  14  being secured to the cannula  10 .  FIG. 11  also shows an oral section  110  of the cannula  10  and  FIG. 12  an opening  120  for the oral pressure wave. The thermal sensor assembly  300  can be dimensioned such that, when the thermal sensor assembly is secured to the oronasal cannula  10 , the oral thermal sensor  22  does not occlude the opening  120 . For example, in the view shown at  FIG. 12 , the oral thermal sensor  22  lies above the opening  120  and does not occlude the opening  120 . 
         [0055]      FIGS. 13 and 14  show respectively a front view and a rear view of the thermal sensor assembly  300  secured to an oronasal cannula  10  with the tab  14  wrapped around the cannula  10 . 
         [0056]      FIGS. 15 and 16  show respectively a front view and a rear view of the thermal sensor assembly  300  secured to an oronasal cannula  10  with the tabs  24  wrapped adhered to the cannula  10 . Although the tabs  24  are shown extending parallel to the intermediate portion  6  shown at  FIG. 2 , this need not be the case. The tabs  24  can be at any suitable angle to the intermediate portion  6  without departing from the scope of the present disclosure. 
         [0057]      FIG. 17  shows another embodiment of a thermal sensor assembly of the present disclosure. The thermal sensor assembly  500  of  FIG. 17  has one elongated opening  502 , which can also be referred to as an alignment aperture or feature, that can fit over nasal prongs of a cannula to align and secure the thermal sensor assembly  500  the cannula in question. 
         [0058]      FIG. 18  shows another embodiment of a thermal sensor assembly of the present disclosure. The thermal sensor assembly  504  of  FIG. 18  has one opening  506 , and a slot  508 , both of which can also be referred to as alignment apertures or alignment features, that can fit over nasal prongs of a cannula to align and secure the thermal sensor assembly  504  the cannula in question. 
         [0059]      FIG. 19  shows another embodiment of a thermal sensor assembly of the present disclosure. The thermal sensor assembly  510  of  FIG. 19  has recesses  512 , both of which can also be referred to as alignment apertures or alignment features, that can fit over nasal prongs of a cannula to align and secure the thermal sensor assembly  510  the cannula in question. 
         [0060]    The views of the thermal sensor assemblies of  FIGS. 17 to 19  are bottom views. That is, the thermal sensors of the thermal sensor assemblies are on the opposite side of the side shown in  FIGS. 17 to 19 . 
         [0061]    In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details are not required. 
         [0062]    The above-described embodiments are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope, which is defined solely by the claims appended hereto.