Device for measuring pulmonary function parameters

Abstract

A device for measuring pulmonary function parameters using quiet exhalation has a flow tube having a mouthpiece end and an outlet, a shutter covering the outlet of the flow tube, a controllable latch for closing and releasing the shutter, a flow sensor for measuring the flow rate in the flow tube after the shutter is released, a pressure sensor for measuring the pressure in the flow tube before the shutter is released, a latch controller connected to the pressure sensor and the controllable latch, and a check valve disposed in the flow tube or the shutter to allow inhalation while the shutter is closed, thereby allowing the device to be used for at least one complete inhalation and exhalation cycle.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 824,393, filed March 27, 2019, the contents of which are incorporated herein by reference.

[0002] This application relates to medical diagnostic and monitoring devices, and more particularly to devices that measure respiratory parameters such as airway resistance. [Background technology]

[0003] The diagnosis of respiratory diseases and monitoring of their progression is based on the measurement of respiratory parameters. One such medically valuable parameter is airway resistance.

[0004] The interrupter or shutter measurement method is one of the techniques for determining airway resistance that requires minimal cooperation from the subject. In this method, the subject breathes through a breathing tube. At a certain moment, usually during expiration, the opening of the breathing tube is briefly closed by a shutter. Within a short period of time after closure (typically about 100-150 ms), the air pressure in the mouth and in the breathing tube rises to a level that is considered to correspond to the alveolar pressure at the moment of airflow interruption. The measurement of airflow just before the shutter is closed, and the accumulated pressure, are used to determine the airway resistance. One variant of the interruption technique, known as the "opening" interruption method, uses a different measurement sequence. The flow rate is measured immediately after the opening of the shutter, rather than before the interruption of airflow. In this method, a longer interruption period provides a more complete equilibrium between alveolar and mouth pressures, thereby improving the accuracy of the airway resistance measurement. According to this method, interruptions are made only during inspiration and in the middle part of the inspiratory phase. The mouth pressure is measured immediately before the opening, while the airflow is averaged over a period of 15 to 35 seconds after the opening of the shutter (K. van der Plas, P. Vooren, "The ''opening'' interruptor. A new variant of a technique for measuring respiratory resistance", Eur. J. Respir. Dis. 1982 63, 449-458).

[0005] Another variation of the operation of the pause technique during breathing is disclosed in applicant's pre-grant U.S. Patent Application Publication No. 2016 / 256073, where the subject begins breathing into a flow tube that is initially closed by a shutter. Applicant calls this device and technique Relaxed Occlusion Expiration Monitoring (REOM). After the accumulated pressure exceeds a certain threshold, the shutter is opened and a flow spike is detected by the shutter. open The airway resistance is measured during the first 100-150 ms after the occlusion. Airway resistance in the upper and lower airways is determined by analysis of the shape of the flow waveform. Airway resistance measurements can be made after a single expiratory cycle that includes the occlusion phase and a brief post-occlusion flow spike. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] K.van der Plas, P.Vooren "The''opening''interruptor.A new variant of a technique for measuring respiratory resistance'', Eur.J.Respir.Dis.1982 63,449-458 Summary of the Invention

[0007] The applicant has found that with REOM, there may be some hesitation among the user or patient due to the mouthpiece of the device not being properly placed in the mouth prior to the start of a non-forced exhalation, resulting from the act of inhaling and then placing the mouthpiece in the mouth. In the present invention, an improvement to this technology is proposed below.

[0008] Switching from a single exhalation (with one interruption event) to spontaneous breathing (where multiple interruptions occur at the beginning of each subsequent exhalation) makes the breathing maneuver easier for the subject. The subject can maintain his / her mouth shape and continue to inhale and exhale in a relaxed or unforced manner. Spontaneous breathing is more natural than a single exhalation when the subject is focused on one attempt and may unwillingly try to control his / her exhalation, resulting in an obstruction phase that is too fast or too slow, and distortions of the flow waveform caused by extra efforts that are different from the efforts applied during spontaneous breathing.

[0009] In prior art REOM devices, the shutter is hinged or can simply fall off the flow tube. If the shutter is operated in continuous mode, it returns to the blocking position. Applicant has open For flow measurement for a period of about 200 ms after openIt has been found that if the shutter is positioned so that it offers little impedance afterwards, the measurements are not affected by the shutter. At that point, if the shutter starts to return during exhalation, resistance to expiratory flow rate need not be an issue. As soon as exhalation stops and inhalation begins, there is enough time for the shutter to return to and latch into the occluded position.

[0010] In some embodiments, a device for measuring pulmonary function parameters using quiet exhalation includes a flow tube having a mouthpiece end and an outlet, a shutter covering the outlet of the flow tube, closing the shutter, open A controllable latch for controlling the open a flow sensor for measuring the flow rate in the flow tube afterwards; open A device is provided having a pressure sensor for measuring the pressure in the flow tube prior to inhalation, a latch controller connected to the pressure sensor and a controllable latch, and a check valve disposed in the flow tube or the shutter to allow inhalation while the shutter is closed, thereby allowing the device to be used for at least one complete inhalation and exhalation cycle.

[0011] Multiple shutter openings at the beginning of each exhalation can improve the accuracy of the measurement by: - Acquisition of interruption flow / pressure data from multiple interruption events; -Rejecting certain interruption events if forced effort is detected or if the flow waveform is distorted due to vocalization or other artifacts: Averaging of airway resistance measured across multiple interruption events, or - Averaging multiple post-obstruction flow waveforms and further calculating airway resistance on the averaged flow waveform.

[0012] The present invention will be better understood from the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0013] [Figure 1A] FIG. 1 shows a prior art design of a flow tube with a shutter for airway resistance measurement using a Pitot tube to measure expiratory flow and a single sensor to measure both flow and pressure. [Figure 1B] FIG. 1 shows a prior art design of a flow tube with a shutter for measuring airway resistance using a flow sensor port and baffle device for measuring expiratory flow and a single sensor for measuring both flow and pressure. [Figure 1C] FIG. 2 is a cross-sectional view of the pipe at the location of the baffle along line AA. [Figure 2A] FIG. 13 is a schematic diagram of the flow tube design with the shutter closed at the start of exhalation. [Figure 2B] FIG. 13 is a schematic diagram of the flow tube design with the shutter open during exhalation. [Figure 2C] FIG. 13 is a schematic diagram of the flow tube design with the shutter closed during inhalation with the valve open. [Figure 2D] FIG. 13 is a schematic diagram of an alternative design of the flow tube with the shutter closed during inhalation, where the flow tube has an additional port and sensor for measuring inhalation flow rate. [Diagram 3] FIG. 13 shows a shutter design with a tilted axis of rotation. [Figure 4] FIG. 2 shows a flow tube mouthpiece. [Figure 5A] FIG. 13 shows one embodiment of the device having an alternative location for the valve integrated with the flow tube. [Figure 5B] FIG. 1 is a schematic block diagram of one embodiment of a device in combination with a smartphone or computing device. [Figure 6] FIG. 2 is a schematic flow diagram illustrating the operation of the device. [Figure 7] FIG. 13 shows the output signal of the pressure sensor at the end of the occlusion phase and the beginning of the post-occlusion flow spike after the shutter is opened. [Figure 8] FIG. 2E is a schematic diagram of a modified design similar to that of FIG. 2D of the flow tube with the shutter closed during inhalation, where the flow tube has a shutter guard. [Figure 9] FIG. 9 is a front view of the embodiment of FIG. 8 showing the shutter guard. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A prior art design of a flow tube with a shutter in a respiratory device for airway resistance measurement is shown in Figures 1A-1C. The device performs the measurement of airway resistance based on a single interruption event at the beginning of one exhalation. The position of the shutter at the end of the post-occlusion spike is not critical and has not been determined. The shutter can be fully open and closed. The only requirement is that the shutter must be fully closed to provide an undistorted flow waveform necessary to calculate airway resistance. open The shutter remains open for a first period of about 100-150 ms after the occlusion, however, it will be appreciated that the shutter does not prevent measurement of post-occlusion flow spikes.

[0015] The transition from a mode of operation of the breathing device based on a single interruption event to one based on multiple interruption events at the beginning of subsequent expiratory cycles can provide an easier, more natural and more convenient breathing maneuver. The subject can breathe spontaneously in a relaxed state, without concentrating on a single exhalation and without trying to control the expiratory effort. {j} Therefore, the results may be more representative of the patient's true lung capacity.

[0016] To implement an operating mode of the respiratory device based on a plurality of interruption events, the shutter includes: a) a shutter; open a) free exhalation immediately after and during the remainder of the inhalation, b) blocking of the flow tube at the start of exhalation and during the occlusion phase, which means that the shutter can be returned to its initial closed position at the start of each exhalation.

[0017] FIG. 2A shows one possible embodiment of the flow tube 1 with a shutter 4. The position of the shutter 4 corresponds to the start of exhalation when the flow tube 1 is blocked. The shutter 4 can have one or more openings 10 closed by a check valve 12, which can be made from a soft and flexible material such as rubber or silicone. A magnet 15 can attract a metal piece 14 of the shutter 4, such as a ferromagnetic metal clip or insert, to prevent the shutter from opening during occlusion when the pressure in the flow tube 1 rises to reach a desired threshold. If the shutter 4 is made of a suitable metal material, a separate metal piece 14 is not needed. A metal clip 15 can be used to hold the shutter 4 and open Other types of latching mechanisms can be used to close the opening 10 in the shutter 4. At this stage, a flexible check valve film 12 can block the opening 10 in the shutter 4. It will be further understood that the check valve 12 can be replaced by any other means of controlling the opening to allow air flow during inhalation while preventing air flow during exhalation, such as using an electronically controlled valve that operates based on sensor readings.

[0018] After the accumulated pressure exceeds a certain threshold, the solenoid 16 pushes the shutter 4 away from the magnet 15. open As the distance between the magnet 15 and the metal piece 14 of the shutter 4 increases, the magnetic attraction force decreases rapidly and further opening of the shutter 4 is achieved by the compressed air accumulated during the closing phase. If other forms of latching mechanisms are used, different triggers or open A mechanism can be used (for example, an electromagnet can be used instead of the magnet 15, and the shutter 4 open The mechanism may include de-energizing an electromagnet).

[0019] Full opening of the shutter 4 may take approximately 10 ms with minimal distortion of the airflow. Figure 7 shows a typical output signal of the sensor 8 measuring the pressure in the air channel 2 of the flow tube 1. A positive signal corresponds to the pressure during the occlusion phase (zero flow rate) and a negative signal corresponds to the flow rate after the shutter is released. It may take approximately 8 ms to open the shutter 4 and reduce the built-up pressure to zero. When the port 7 is placed downstream of the baffle, or in the Pitot tube, the expiratory airflow through the tube 1 causes a negative pressure and a negative output signal of the sensor 8. The maximum absolute value of the signal may be reached approximately 10 ms after the shutter opens and corresponds to the peak flow rate.

[0020] The shutter 4 is a single flap type valve that opens outward as shown, and is therefore propelled by and moves with the air flow leaving the flow tube 1. Two or more flaps may be attached to the end of the flow tube 1. open It will be appreciated that the occlusion may be arranged to provide a possible obstruction. open The movement of the flap by the air does not adversely affect the measurement of the flow rate in the pipe 1 by the sensor 8 .

[0021] The measuring device is the latch openIt will be appreciated that the device may include circuitry for controlling the sensor 8, measuring the pressure and flow rate in the tube 1 from the readings of the sensor 8, and optionally calculating values ​​such as airway resistance and / or lung compliance from the readings. Such circuitry is described in the applicant's pre-grant publication US2016 / 256073, the disclosure of which is incorporated herein by reference. For example, this may include a microcontroller associated with the sensor 8, and data processing may be performed using an associated program or app on a connected device (e.g. Bluetooth) such as a smartphone or other convenient computing device. This may reduce the cost of data processing from the measurement device. Recording such measurements may include collecting measurements over several "trials" or exhalations performed as the user inhales and exhales normally without any forced effort, as described in more detail below with reference to FIG. 6, and the data may be averaged and / or edited as desired.

[0022] In some embodiments, the method of measuring airway resistance includes measuring flow in the range of about 100-150 ms after the shutter is opened. After this time interval, the position of the shutter 4 may not be important to the measurement. Preferably, the shutter 4 is closed once open When the shutter 4 is opened, it should not prevent spontaneous exhalation of the subject. FIG. 2B shows the shutter 4 in a position of maximum opening, which can be limited by a buffer or damper 11. The buffer 11 can provide an abutment against the shutter 4 as it swings open to determine the maximum opening angle of the shutter 4. The opening angle can be an important parameter of the device, which is described below. It will be appreciated that the buffer 11 can take a variety of different forms to provide the function of limiting the opening angle.

[0023] An external return force can be applied to the shutter 4 to push it to its initial closed position. This force can be generated by a spring or by using electrostatic and magnetic principles. Gravity can also be used, as demonstrated in this embodiment. After opening and colliding with the buffer 11, the shutter 4 may return to its initial position, interrupting the opening of the flow tube 1 and preventing the subject from normally exhaling. To eliminate this possibility, the solenoid 16 is left on, preventing the shutter 4 from contacting the magnet 15 and leaving a gap between the shutter and the flow tube wide enough for exhalation. The buffer 11 can also provide some elastic energy to return the shutter 4 to the closed position if desired, thus aiding, for example, gravity or a spring mechanism.

[0024] The onset of inhalation can result in a significant negative pressure inside the flow tube 1 that can be detected by the sensor 8. Immediately after inhalation is detected, the solenoid 16 can be turned off and the shutter 4 can be attached to the magnet 15 (latch closed). The check valve 12 is open, thereby allowing the subject to inhale through the flow tube 1. The position of the shutter 4 during inhalation is shown in Figure 2C.

[0025] After the subject finishes inhaling and begins exhaling, the positive pressure in the flow tube 1 closes the check valve 12 and a new occlusion phase begins.

[0026] FIG. 2D shows an embodiment where an additional port 7′ can be added in front of the flow baffle located in front of port 7. The port 7′ can be positioned as shown so that the inhalation flow can be measured using a sensor 8″. The sensor 8″ is shown as connected to measure the differential pressure over the baffle in the flow tube, and therefore the sensor 8″ measures both the inhalation and exhalation flow rates. It will be understood that other configurations for measuring inhalation are possible and measuring inhalation is optional if only the exhalation flow rate is of interest. By measuring the inhalation and exhalation flow rates over one or more respiratory cycles, the device can measure further pulmonary parameters such as tidal volume, slow vital capacity, etc. When measuring slow vital capacity (SVC), the shutter can be left open as desired. Various arrangements of flow sensors can be used. A single sensor can be used to measure forward and reverse flow rates and another sensor can be used to measure pressure. Measuring respiratory flow / volume parameters may require the shutter 4 to be permanently fixed in an open position and the airway resistance measurement mode to be temporarily disabled.

[0027] 3 shows a front view of one embodiment in which a shutter 4 with a hinge 9 rotates about an axis 6 inclined at an angle α to the direction of the gravitational acceleration. The dynamics of opening and closing of the shutter 4 can then depend on the following parameters: -angle α; -Mass of Shutter 4: The position of the buffer 11 which limits the opening angle of the shutter 4.

[0028] It will be appreciated that without the hinge, the shutter would need to be placed in a closed position prior to use, whereas the check valve allows the patient to begin use of the device by first completing a quiet inhalation before commencing a quiet exhalation. The stability of the quiet exhalation and resulting measurement can be improved by initiating operation with an inhalation.

[0029] In the embodiment of FIG. 3, when performing SVC, it is possible to rotate the flow tube so that gravity keeps the shutter 4 open.

[0030] By adjusting these three structural parameters, the following condition can be satisfied: the time interval between the shutter opening and its collision with the flow tube may exceed the observation time required to measure the post-occlusion flow waveform, i.e., about 150 ms. If the collision between the shutter and the flow tube occurs faster than the aforementioned time, the disturbance of the flow caused by this collision may disturb the measurement of the device.

[0031] In one particular case of device embodiment, the damper or buffer 11 can be positioned such that the opening angle of the shutter 4 is about 150°. The angle α between the axis of rotation and the direction of gravitational acceleration can be selected to be about 75°. The experimentally measured time interval from the shutter opening to its impact with the flow tube is about 250 ms, which is long enough to perform undistorted flow waveform measurements to determine airway resistance.

[0032] After the user begins to inhale, a negative pressure is created inside the flow tube 1 , which can be detected by the sensor 8 .

[0033] It will be appreciated that the use of gravity to return the shutter 4 to the closed position can be replaced or assisted by the use of a light spring or biasing member. If gravity or a biasing force cannot seal the shutter 4 against the end of the flow tube 1, it will be appreciated that subsequent suction will help close the shutter until the check valve 12 opens, and even then, there will be a small negative pressure inside the tube 1 which will help keep the shutter 4 closed during suction.

[0034] After detecting inhalation, the solenoid 16 can be turned off (usually open The mechanism is a shutter. openThe shutter can be attached to a magnet 15. The oil film of the check valve 12 can be deflected inwards by the negative pressure in the flow tube 1 generated during inhalation, opening the hole 10 in the shutter 4 to allow air to flow through the flow tube 1. The check valve 12 can be open until the end of inhalation. When the subject starts to exhale, the check valve 12 is closed and the occlusion phase begins.

[0035] Figure 4 shows an example of a mouthpiece 3 connected to the air channel 2 of the flow tube 1. The mouthpiece 3 includes an optional tongue depressor 5, which fixes the position of the tongue to prevent it from possibly obstructing the opening of the flow tube 1, distorting the air flow and adversely affecting the measurements of the breathing device. Such a mouthpiece 3 can be disposable. It can also be an integral part of the flow tube 1, and the entire flow tube 1 joined with the mouthpiece 3 can be disposable. The mouthpiece 3 can also be integrated with a bacteriological filter.

[0036] 5A shows an alternative embodiment of the device in which a check valve 12 closes an opening 10 in the body of the flow tube 1. In this configuration of the device, the check valve 12 is attached to the shutter 4, eliminating the need to drill a hole 10 in the shutter 4.

[0037] Also shown in FIG. 5A is the option of splitting the sensor 8 into two separate sensors 8 and 8' for expiratory flow and pressure, respectively, instead of using one sensor that works for both flow and pressure. FIG. 5A also shows that the device may include a latch that is triggered based on the pressure measurement. open 5A also illustrates that data from the sensor 8 can be transmitted to another device for processing using a data transmitter such as a wireless link, cable link, or the like.

[0038] Although not shown, an external processing device can be used to monitor pressure during shutter closure and signal unlatch. If inhalation flow is also to be measured, flow sensors 7', 8'' should be placed at port 10.

[0039] In Fig. 5B, a system is shown comprising a device in combination with a computing device such as a smartphone. The computing device may comprise a processor, a memory for storing a computer program for the device 1, a data transmitter for communicating with the device 1, and optionally a network interface for conveying data and / or receiving settings from a remote party. The device may comprise a microcontroller or microprocessing semiconductor unit that may include a wired or wireless transmitter for communicating with the computing device. Thus, functions such as shutter control, collection control using indicators on the device or a user interface on the computing device, data collection and storage, raw and / or compliance calculations, etc., may be accomplished using either the processing capabilities of the device or the processing capabilities of the computing device as desired.

[0040] In the exemplary embodiment of FIG. 5B, the device controls the shutter based on a pressure threshold. open The shutter speed is configured to control the shutter speed, the value of which may be set, for example, by software and / or user interface settings on the computing device. The computing device may include software for communicating results from the device to a healthcare professional (HCP), open The pressure setting can be set by the FICP if desired, or the shutter release can be controlled from a computing device, in which case the device sends a pressure reading to the computing device every few milliseconds.

[0041] FIG. 5B also shows that the computing device can perform a flow spike waveform consistency analysis. This analysis is optional and can also be performed by the device's processor if desired. The consistency analysis can be a comparison of flow spike waveforms (e.g., post-occlusion flow data, typically up to about 150 ms after peak flow) against each other. Since measurements can be taken every exhalation, it is easy to obtain multiple waveforms. If a waveform is significantly different from the others, perhaps due to forced effort, coughing, phonation, etc., it can be disregarded. The occlusion can then be determined. open Sometimes measurements can be made using several consistent waveforms and their associated flow tube pressures.

[0042] Optionally, the device or smartphone can signal the user that data acquisition has ended because a period or number of exhalations has elapsed and / or several consistent waveforms have been collected. The stop signal (e.g., audible or visual) can be issued by an indicator on the device or via the smartphone or computer.

[0043] The software in the device or computer can also be configured to perform a slow vital capacity measurement. This measurement can be initiated by the user selecting the measurement or by the device and / or computer indicating to the user that such a measurement should be initiated. The user inhales slowly and completely, followed by a slow exhalation, engaging the muscles to expel the air completely from the lungs. The device can measure the flow rate during this exhalation and record the volume of air exhaled as the SVC measurement. If the device also measures inhalation flow, the SVC measurement can include measuring the inhalation and exhalation volumes to confirm the SVC measurement by using both the inhalation and exhalation data. Thus, the presence of a shutter and its open Pressure does not adversely affect SVC measurements.

[0044] It may be preferable to separate the systems between the device and the smartphone as a way to provide a better user interface and reduce the cost of the device, but it will be appreciated that the device can incorporate the user interface and can incorporate network connectivity such that the device is completely independent of any smartphone or computer.

[0045] FIG. 6 shows a block diagram of one possible embodiment illustrating the operation of the breathing device during one breathing cycle.

[0046] First, when the subject inhales, the shutter 4 closes and the check valve 12 opens (see FIG. 2C). The transition from inhalation to exhalation is accompanied by a change in pressure in the flow tube 1 from negative to positive, which can be detected by the sensor 8. The check valve can close automatically when the start of exhalation begins.

[0047] In a next step, the sensor 8 can measure the accumulated pressure during the occlusion phase. The solenoid 16 can be powered on when the accumulated pressure in the flow tube 1 reaches a predetermined threshold. The solenoid 16 can push the shutter 4, thereby quickly opening the flow tube 1. As mentioned above, other latching mechanisms can be used without departing from the teachings of the present disclosure.

[0048] The flow rate after closure is Shutter 4 open The airway resistance can be calculated based on the data obtained during the period of about 100-150 ms after the shutter is opened and when the shutter is wide open.

[0049] After the shutter 4 is opened, an external return force can be applied to the shutter 4 to return it to its initial closed position. This force can be generated, for example, by a spring or by gravity. Other sources of external return force are also possible, such as electrostatic or magnetic. A second force counteracting the return force prevents the shutter 4 from closing completely, thereby allowing the patient to continue exhaling. The second counteracting force can be, for example, Solenoid16. Solenoid 16 remains powered on to maintain a gap between the shutter and the edge of flow tube 1. Normally, during exhalation, when the shutter is partially closed, the pressure in flow tube 1 is positive.

[0050] The transition from exhalation to inhalation is accompanied by a change in air pressure in the flow tube 1 from positive to negative. After such a transition is detected, for example by the sensor 8, the counteracting force can be switched off (e.g. Solenoid When the power is turned off (power off 16), an external return force can fully close the shutter 4. The shutter 4 can be attached to a magnet 15. Negative pressure in the flow tube 1 can bend the check valve 12 inwards, so that the hole 10 opens, allowing air flow through the tube 1 during inhalation.

[0051] Calculation of airway resistance and / or lung compliance using post-occlusion non-forced expiratory flow waveforms and occlusion pressures is described in applicant's pre-grant patent publication U.S. Patent Application Publication No. 2016 / 256073, published September 8, 2016. The measured raw data regarding the interruption event can (optionally) be transmitted to a computer or smartphone at this stage. Alternatively, data can be transmitted continuously during all stages of the respiratory cycle if the electronic hardware supports such a mode of operation.

[0052] Once the computer or smartphone receives the measurement data, a decision regarding the acceptability of the measurement can be made in real time. For example, an abnormally short occlusion time may indicate the application of excessive expiratory effort that may not be acceptable during non-forced airway resistance measurements. Distortion of post-occlusion flow spikes, e.g. caused by phonation or other artifacts, can also be detected. Such data can be rejected. After the execution of several interruption events, an averaged flow spike waveform can be calculated. Flow waveforms that deviate from the averaged waveform by more than a certain percentage and do not meet the repeatability criteria can be excluded from further analysis.

[0053] As one possible option, airway resistance can be determined for each single interruption event. An average airway resistance can then be calculated over the course of multiple interruption events. Alternatively, an averaged post-occlusion flow waveform can be calculated excluding single interruption events that do not meet the repeatability criteria. Airway resistance can then be calculated from the averaged flow waveform.

[0054] When a desired number of acceptable interrupt events have been generated and measured, the measurement procedure can be automatically terminated.

[0055] The shutter may be made of a thin plastic or metal material and therefore may be prone to being knocked open or broken if struck by a foreign object. In Figs. 8 and 9, a guard ring is shown as being added to the end of the flow tube to prevent the shutter from being knocked as a result of careless storage with the flow tube. This guard ring is positioned so as not to significantly interfere with the movement of the shutter or the flow rate of air exiting the flow tube. Although a ring is shown, it will be appreciated that the shutter guard may take different forms and may include, for example, several protrusions positioned around the distal end of the flow tube. Such alternative arrangements may provide even less interference to the air flow at the distal end of the flow tube. The shutter guard may be further designed to protect the shutter in both the closed and open positions.

Claims

1. 1. A device for measuring pulmonary function parameters, comprising: a flow tube having a mouthpiece end and an outlet; a shutter covering the outlet of the flow tube; a hinge connecting said shutter to said flow tube such that said shutter opens outwardly to be propelled by and move with the air flow leaving said flow tube; Equipped with - when the device is in an operational position for measuring the lung function parameter, the hinge is mounted with its axis of rotation at an angle to the vertical such that gravity returns the shutter to a closed position, or - providing a biasing member for returning the shutter towards the closed position; The device further comprises: a controllable latch for closing and opening said shutter; a flow sensor for measuring a flow rate in the flow tube after the shutter is opened, the shutter being positioned such that a mass of the shutter and one of the angle of the hinge and the position of the biasing member provide little impedance for measuring a flow rate in the flow tube after the shutter is opened, such that a measurement of a flow rate in the flow tube is not obstructed by the shutter; a pressure sensor for measuring pressure within the flow tube prior to the opening of the shutter; a latch controller connected to the pressure sensor and the controllable latch; a check valve disposed in the flow tube or the shutter to allow inhalation while the shutter is closed, whereby the device can be used for at least one complete inhalation and exhalation cycle; A device comprising:

2. The device of claim 1 , further comprising a calculator connected to the flow sensor and the pressure sensor for calculating a pulmonary function parameter.

3. 3. The device of claim 2, wherein the calculator calculates the pulmonary function parameter using data from the flow sensor for a period from peak flow until 150 ms after the opening of the shutter.

4. The device of claim 3 , wherein the pulmonary function parameter is airway resistance.

5. 5. The device of claim 2, wherein the calculator calculates the pulmonary function parameter from a plurality of interruption events at the start of a subsequent expiratory cycle.

6. The device of claim 1 , further comprising a data transmitter for transmitting data from the device to a computing device for calculating pulmonary function parameters using data obtained from the flow sensor.

7. 7. The device of claim 6, wherein the data includes the flow sensor measurements from a peak flow rate after the opening of the shutter to 150 ms after the peak flow rate.

8. The device of claim 1 , wherein the flow sensor is additionally configured to measure inhalation flow.

9. The device of claim 8 , wherein the flow sensor comprises separate flow sensors for inhalation and exhalation.

10. 10. The device of claim 1, wherein the latch controller connected to the controllable latch and the pressure sensor is configured to open the shutter at the start of exhalation when pressure in the flow tube begins to rise without exertion.

11. 11. The device of claim 1, wherein the latch controller opens the controllable latch at a predetermined pressure.

12. The device of claim 11 , wherein the predetermined pressure is defined by an external computing device.

13. The device of claim 1 , wherein the check valve is disposed within the shutter.

14. 14. The device of claim 1, further comprising a calculator connected to the flow sensor, wherein the expiratory flow is measured over a period of complete expiration to completely expel air from the subject's lungs, and for calculating slow vital capacity from the complete expiration after the opening of the shutter.

15. 15. The device of claim 1, further comprising a shutter guard attached to the outlet of the flow tube.

16. In combination, a device for measuring lung function parameters according to any one of claims 1 to 15, said device comprising a data transmitter and a computing device comprising a corresponding data transmitter and a memory storing a computer program for communicating with said device and for providing a user interface for controlling said device.

17. 17. The device of claim 16, wherein in combination, the computing device further comprises a calculator for calculating the pulmonary function parameter from at least one interruption event at the start of a subsequent exhalation cycle.

18. 15. A device according to any one of claims 1 to 14, wherein the mass of the shutter, the angle of the hinge and / or the biasing member, and the position of a buffer limiting the opening angle of the shutter are adjusted to provide little impedance after opening.

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