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.
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%.
The American Academy of Sleep Medicine'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.
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's flow of air (i.e., can interfere with the patient'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's skin. All of these effects will cause errors in the thermal sensor signal, which can lead to incorrect diagnostics.
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'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's comfort.
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.
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.
Furthermore, sleep laboratories are looking towards medical devices that are single patient use for the diagnosis of OSA on patient'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.
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.
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.
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.
Therefore, improvements in thermal sensors for cannulae are desirable.
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.
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.
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.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.
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.
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.
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.
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.
The substrate 310 also defines the tab 14, which, as shown at
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.
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.
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.
The side of the substrate shown in the thermal sensor assembly 300 of
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.
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.
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
Subsequently, the user can wrap the tab 14 to the cannula 10 and back onto itself, as show in front and rear views at
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
The views of the thermal sensor assemblies of
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.
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.
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.
Number | Date | Country | |
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61449358 | Mar 2011 | US |