Field

The invention relates to a portable respiratory airway obstruction measuring apparatus. Background

Measurement of specific airway resistance/conductance with body plethysmography utilizes a sealed chamber in a laboratory, which is a complicated and expensive solution requiring trained nurses.

US 6,287,264 discloses a system for measuring respiratory function with respiratory inductance plethysmography including elastic bands around a rib-cage and a pneumotachograph coupled to an endotracheal tube (or a microphone in contact with the skin, or a directional microphone in a stream of an air flow). US 7,094,206 discloses a similar system for detecting a respiration restriction condition effecting sleep.

However, a need remains for a cheap, portable, easy-to-use respiratory airway obstruction measuring apparatus.

Brief description

The present invention seeks to provide an improved portable respiratory airway obstruction measuring apparatus.

According to an aspect of the present invention, there is provided a portable respiratory airway obstruction measuring apparatus as specified in claim 1.

According to another aspect of the present invention, there is provided a computer readable medium as specified in claim 15. List of drawings

Example embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which Figure 1 illustrates example embodiments of a portable respiratory airway obstruction measuring apparatus;

Figures 2 and 3 illustrate further example embodiments of the apparatus and its use;

Figures 4 illustrate further example embodiments of apparatus;

Figure 5 is a flow chart illustrating example embodiments of data processing; and

Figure 6 illustrates an example embodiment of measuring a time delay between a respiration-related movement and an airflow. Description of embodiments

The following embodiments are only examples. Although the specification may refer to "an" embodiment in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

Let us study Figures 1 and 5 illustrating example embodiments of a portable respiratory airway obstruction measuring apparatus 100 and data processing therein.

The apparatus 100 comprises an inertial measurement unit 102 configured to measure 502 a respiration-related movement 160 of a frontal upper body 156 of a subject 150 during a breathing of the subject 150 in order to generate motion data 168.

The inertial measurement unit 102 may comprise one or more of the following: an accelerometer, a gyroscope, a magnetic orientation sensor, each measuring parameters (acceleration, orientation and angular velocity, magnetic field) at maximum in three dimensions. With the motion data 168, for example with acceleration data measured in three dimensions (and taking into account Earth's gravitation), the respiration-related movement 160 of the frontal upper body 156 may be measured and detected. The frontal upper body 156 may comprise frontal chest and/or upper abdomen. The frontal upper body 156 in the vicinity of the sternum, or, more precisely, in the vicinity of the processus xiphoideus is an appropriate location for a contact with the inertial measurement unit 102, although other locations may be applicable as well.

The apparatus 100 also comprises a microphone 104 configured to measure 504 through an ambient air 190 an airflow 162 of a mouth 154 of the subject 150 caused by the breathing in order to generate airflow data 166. The microphone 104 may measure sounds of the airflow 162 in order to generate the airflow data 166. As the measurement of the airflow 162 is made through the ambient air 190, a certain kind of noise (from clothes, for example) may be avoided, but the ambient noise may need to be filtered out with known filtering methods.

The microphone 104 may be an apparatus-internal microphone, or an apparatus-external microphone such as a condenser microphone coupled in a physical port of the apparatus 100 and enabling a more precise measurement of the airflow 162.

The apparatus 100 also comprises means 110 for obtaining 506 an ambient barometric pressure 170 around the subject 150. The means 110 for obtaining the ambient barometric pressure 170 may be a barometric pressure sensor (such as in a sports watch by Suunto®), or it may be a user interface 108 command with which an obtained ambient barometric pressure 170 is set, or the ambient barometric pressure may be obtained from some data source, for example.

The apparatus also comprises a processing unit 106 coupled with the inertial measurement unit 102 and the microphone 104.

The processing unit 106 may be implemented with one or more processors (such as a microprocessor) and software, or as an application-specific integrated circuit (AS1C), or as any other way of implementing a device that is capable of processing data. At least a part of the signal processing may also be performed in an integrated circuit of the inertial measurement unit 102.

The processing unit 106 is configured to analyze 508 the motion data 168 and the airflow data 166 in order to measure a time delay 122 between the respiration-related movement 160 and the airflow 162.

The processing unit 106 is configured to define 510 a cycle length 124 of the breathing (or a respiratory cycle) based on the motion data 168 and/or the airflow data 166.

The processing unit 106 is configured to compute 512 a specific airway resistance/conductance 126 of the subject 150 based on the time delay 122, the ambient barometric pressure 170, and the cycle length 124.

Note that the term 'specific airway resistance/conductance’ 126 refers to the specific airway resistance and/or the specific airway conductance as mathematically the specific airway conductance is the reciprocal of the specific airway resistance (and vice versa, of course) .

The time delay 122 depends on an airway obstruction as it increases with the specific airway resistance and, thus, with the muscular work required to move the air mass in the airway. The main airway obstructions occur in almost all cases in the lungs and/or in the nose ln the prior art, measurements are made in the whole-body plethysmograph in which the whole body is enclosed in an airtight container and the breathing is performed through a spirometer according to a specially designed protocol. Both respiratory airflow and the pressure changes in the container are simultaneously recorded, and finally used for computing the specific airway resistance. The inverse to the resistance is the conductance, which is usually reported to the user. The specific airway conductance relates to the openness of the airways and most recent literature reports reference values for clinical significance.

The specific airway resistance sR _aw may be calculated:

sRaw = [(Ti + T _E ) / (2 X TT)] x (Patm - PH2O) x tan [2 x p x dT / (Ti + T _E )], (1) wherein: sR _aw = specific airway resistance;

Ti = inspiratory time in seconds;

TE = expiratory time in seconds;

Patm = atmospheric pressure;

P _H 2 _O = water vapor pressure at body temperature; and

dT = time delay (lag) between nasal and thoracoabdominal flows in seconds.

Further information about Formula 1 may be obtained from the following two publications, incorporated herein by reference in those jurisdictions where applicable:

Pennock B.E., Cox C.P., Rogers R.M., Cain W.A., and Wells J.H., "A noninvasive technique or measurement of changes in specific airway resistance", J Appl Physiol (1979) 46(2):399-406.

Yasumitsu R., Hirayama Y., lmai T., Miyayasu K., and Hiroi J., "Effects of specific tachykinin receptor antagonists on citric acid-induced cough and bronchoconstriction in unanesthetized guinea pigs", European Journal of Pharmacology (1996) 300(3):215-219.

As was explained earlier, the specific airway conductance sG _aw may be calculated:

Figure 6 illustrates an example embodiment of measuring the time delay 122 between the respiration-related movement 160 and the airflow 162.

The airflow 162 is captured as a sound signal 600, and the respiration related movement 160 is captured as a motion signal 602. The inspiration 1NS and expiration EXP are detected from both signals 600, 602, and the time delay 122 is measured at an end of an inspiration, whereby ti denotes the end of the inspiration in the sound signal 600, and t ₂ denotes the end of the inspiration in the motion signal 602. The time delay dT may be calculated:

dT = t - 1 (3) The portable apparatus 100 may comprise also other parts and functionalities, a power source such as a rechargeable battery 114 and a user interface 108. ln an example embodiment, the user interface 108 is configured to implement exchange of graphical, textual and/or auditory information with a user of the apparatus 100. The user interface 108 may be used to perform required user actions and presentation of the measurement results. The user interface 108 may be realized with various techniques, such as a (multi-touch) display, loudspeaker, keyboard/keypad/push buttons/rotary buttons, speech recognition system enabling audio control, cursor control device (mouse, track ball, arrow keys, touch sensitive area etc.), haptic feedback technology, etc.

As shown in Figure 2 the portable apparatus 100 offers a very convenient way of measuring daily variations of the obstruction: it may be made anytime, anywhere (also in home). The subject 150 sits on a chair 200 and may be instructed to hold the apparatus 100 so that the microphone 104 is facing away from the contact with the frontal upper body 156 so that possible friction sounds are minimized. The sitting position of the subject 150 may be advantageous as a backrest 202 of the chair 200 stabilizes the position of the subject 100, which may make the measurement data 160, 162 processing more accurate.

Figures 1 and 2 further illustrate that the inertial measurement unit 102, the microphone 104 and the processing unit 106 are integrated within a housing 116 of the portable apparatus 100. The housing 116 provides protection against dust, water and external mechanical influence, whereby portability and hygiene of the apparatus 100 are enhanced.

Figure 3 illustrates that it is feasible to perform the measurement also in a standing position (also other positions such as a lying position are applicable).

Figure 3 also illustrates two auxiliary example embodiments ln an example embodiment, the apparatus 100 further comprise an auxiliary inertial measurement unit 300, which is placeable on the frontal upper body 156 and is communicatively couplable (preferably in a wireless fashion) with the processing unit 106 in order to generate the motion data 168. The auxiliary inertial measurement unit 300 may be attached to clothing worn by the subject 150, or it may be attached by suitable fixing means (glue, tape, elastic band around the chest) in the upper frontal body 156, for example. The measurement accuracy may be enhanced with such a solution, but it may also provide easier long-term measurements.

ln an alternative or additional auxiliary embodiment, the apparatus 100 further comprises an auxiliary microphone 302 placeable in the vicinity of the subject 150 and communicatively couplable with the processing unit 106 in order to generate the airflow data 166. This may also enhance measurement accuracy and/or provide easier long-term measurements. As shown in Figure 3, the auxiliary microphone 302 may be a part of a wireless hand-free setup attachable around ear, but also other configurations are possible such as a condenser microphone attached with a cable to the apparatus 100.

An example embodiment illustrated in Figure 1 provides a computer readable medium 180 comprising computer program code (or software), which, when loaded into the processing unit 106 and executed by the processing unit 106 causes the apparatus 100 to perform the following:

measuring 502 with the inertial measurement 102 unit the respiration-related movement of the frontal upper body 156 of the subject 150 during the breathing of the subject 150 in order to generate motion data;

measuring 504 with the microphone 104 through the ambient air the airflow of the mouth 154 of the subject 150 caused by the breathing in order to generate airflow data;

obtaining 506 the ambient barometric pressure around the subject 150;

analyzing 508 the motion data and the airflow data in order to measure the time delay between the respiration-related movement and the airflow;

defining 510 the cycle length of the breathing based on the motion data and/or the airflow data; and computing 512 the specific airway resistance/conductance of the subject 150 based on the time delay, the ambient barometric pressure, and the cycle length.

The computer-readable medium 180 may comprise at least the following: any entity or device capable of carrying the computer program code to the portable apparatus 100, a record medium, a computer memory, a read-only memory, an electrical carrier signal, a telecommunications signal, and a software distribution medium ln some jurisdictions, depending on the legislation and the patent practice, the computer-readable medium 180 may not be the telecommunications signal ln an example embodiment, the computer-readable medium 180 may be a computer-readable storage medium ln an example embodiment, the computer-readable medium 180 may be a non-transitory computer-readable storage medium.

Figure 4 illustrates an example embodiment, wherein the portable apparatus 100 is configured to transmit the motion data 168 and the airflow data 166 to a networked server apparatus 400 in order to distribute a part of the data processing to the networked server apparatus 400. lntermediate results, final results, updates, and other such data 430 related to the operation of the apparatus 100 may be transferred between the apparatus 100 and the networked server apparatus 400.

ln the distributed implementation, the portable apparatus 100 is capable of producing the specific airway resistance/conductance 126 independently, but the networked server apparatus 400 is capable of even better accuracy or to some added functionality.

ln an example embodiment, the portable apparatus 100 and the networked server apparatus 400 operate according to a client-server architecture, a cloud computing architecture, a peer-to-peer system, or another applicable computing architecture.

The communication couplings 166, 168, 430 may be implemented with appropriate wired/wireless communication technologies and standard/proprietary protocols. ln an example embodiment, the wireless communication is implemented with a suitable cellular communication technology such as GSM, GPRS, EGPRS, WCDMA, UMTS, 3GPP, 1MT, LTE, LTE-A, etc. and/or with a suitable non-cellular communication technology such as Bluetooth, Bluetooth Low Energy, Wi-Fi, WLAN, Zigbee, etc. ln this example embodiment, the portable apparatus 100 comprises a wireless transceiver 112. The communication traffic may also be transported (in an encrypted form, for example) in the lnternet.

ln an example embodiment, the networked server apparatus 400 is capable of managing a plurality of portable apparatuses 100: manage the collected data, communicate (instructions for use, treatment/medication instructions) with the users 150, collect holistic data from the use of the portable apparatuses 100 (data about effect of medications / environmental factors on the respiratory airway obstruction).

The treatment may have been tailored for the subject 150 by a therapist 420. The therapist 420 may be a physician, nurse, or some other authorized person for administering the treatment lt is also feasible that the apparatus 100 may support the treatment performed by the subject 150 in a self- help fashion, i.e., not necessarily guided by the therapist 420. As shown in Figure 4, the therapist 420 may generate and receive patient data 432 with a terminal 410 communicating (in a wireless or wired fashion) with the networked server apparatus 400.

ln an example embodiment, the portable apparatus 100 and/or the networked server apparatus 400 is communicatively coupled with a database 440, which may comprise measurement data, reference measurement data (collected from a plurality of users 150), and the networked server apparatus 400 is further configured to analyze the measured data 166, 168 in view of the reference measurement data to produce an assessment of a condition of the subject 150.

Now that the basic measurement configuration has been explained, let us study measurements and processing in more detail with reference to Figures 1 and 5. ln an example embodiment, the processing unit 106 is configured to measure the time delay 122 at an end of an inspiration of the subject 150. The end of the inspiration seems to be an easily detectable phase of the breathing. The end of the inspiration is illustrated with time ti and time t ₂ in Figure 6.

ln an example embodiment, the portable apparatus 100 further comprises a synchronization mechanism 120 with which the motion data 168 and the airflow data 166 are synchronized to a common timeline. This may be necessary so that the internal delays of the portable apparatus 100 are removed, and the real time delay 122 may be obtained ln Figure 5, time ti and time t ₂ are presented in the common timeline, by the use of a common real-time clock circuit, for example.

ln an example embodiment, the processing unit 106 is configured to compute 512 the specific airway resistance/conductance 126 of the subject 150 as a median of a plurality of specific airway resistances/conductances 126 computed for different respiratory cycles. The different respiratory cycles may have been measured in one measurement session. For example: five specific airway resistances/conductances of the subject 150 are arranged into an ascending or descending order, and the middle one (= the third one) of the values is selected as the specific airway resistance/conductance 126 of the subject 150 ln an example embodiment, the user interface 108 is configured to output 516 instructions to block the nose 152 before the measurements and measure 504 the airflow 162 of the mouth 154 in order to obtain the specific airway resistance/conductance of the lower airways (mainly lungs).

ln an example embodiment, the user interface 108 is configured to output 516 instructions to shut the mouth 154 before the measurements and measure 504 the airflow 164 of the nose 152 in order to obtain the specific airway resistance/conductance of the total airways.

With the help of these two previously described example embodiments, a third example embodiment may be realized: the processing unit 106 is configured to compute the specific airway resistance/conductance of the nose 152 by subtracting the specific airway resistance/conductance of the lower airways from the specific airway resistance/conductance of the total airways.

Note that this subtraction operation (and other later described substraction operations) works for the specific airway resistances, whereas if the parameters are specific airway conductances their inverses need to be used for the subtraction.

ln a further example embodiment, the specific airway resistance/conductance 126 may be measured for each nostril separately. The user interface 108 is configured to output 516 instructions to shut the mouth 154 and block only one nostril of the nose 152 before the measurements, and measure 504 the airflow 164 of the nose 152 through the other nostril in order obtain the specific airway resistance/conductance of the total airways with only one nostril, and the processing unit 106 is configured to compute the specific airway resistance/conductance of the other nostril of the nose 152 by subtracting the specific airway resistance/conductance of the lower airways from the specific airway resistance/conductance of the total airways with only on nostril.

This nostril measurement may first be made for the left or right nostril, and then for the not yet measured nostril.

Another way, if the specific airway resistance of the nose sR _aw is known, is to measure just one nostril and calculate its specific airway resistance sR _aw l, and then calculate the specific airway resistance of the other nostril sR _aw 2 from Formula:

1/sR aw ^— 1/sR aw 1 + 1/sR aw2 (4)

With help of Formula 4, it is also possible to calculate the specific airway resistance of the nose based on specific airway resistances of both nostrils.

ln an example embodiment, the processing unit 106 is configured to identify related marker points both in the motion data 162 and the airflow data 160, and to measure the time delay 122 between the identified marker points. As was explained earlier, one such marker point may be the end of the inspiration, but also other marker points may be used. ln an example embodiment, the processing unit 106 is configured to detect a phase difference between a continuous motion signal defined by the motion data 168 and a continuous airflow signal defined by the airflow data 166, and to utilize the detected phase difference in order to obtain the time delay 122.

lt will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention is not limited to the example embodiments described above but may vary within the scope of the claims.