Abstract:
The flow measurement device of the present invention incorporates numerous novel features. For example, the device includes a displacement measuring device to measure the position of a movable plate member, a self-oscillation dampener to dampen oscillations of the plate member, one or more stiffening members engaging or incorporated into the plate member to increase the resonant frequency of the plate member and reduce flutter, and a conduit providing for differing directions of air flow at different points along its length to eliminate the effects of gravity on flow measurements.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to devices and methods for measuring gas flow parameter(s) and specifically for measuring air flow parameter(s) for diagnosing lung performance. 
     BACKGROUND OF THE INVENTION 
     Mechanical and electronic peak flow meters are used to monitor lung performance of patients having respiratory ailments, such as asthma. Mechanical peak flow meters in particular are used by patients to self-monitor lung performance. In such applications, lung performance parameters, such as peak air flow, are periodically recorded in a diary. If lung performance falls below a certain level or if the diary shows a deterioration in lung performance, the patient seeks medical assistance. 
     Mechanical peak flow meters are typically a spring-loaded device having a peak flow pointer attached to a plate-like spring that is displaced or slid laterally by the exhaled air of the patient to indicate the peak flow rate. Although such devices are inexpensive, the devices provide only a Peak Expiratory Flow Rate (PEFR) measurement and are unable to measure other desirable and important parameters, such as Forced Expiratory Volume in one second (FEV 1 ) (the total volume of air exhaled by the patient over a one second interval) or Forced Expiratory Volume in 6 seconds (FEV 6 ) (the total volume of air exhaled by the patient over a six second interval). The accuracy of such devices is often poor and typically deteriorates over time due. Mechanical devices are also unable to track peak flow measurements by writing the measurements to an electronic memory. The measurements must be manually recorded in the diary. 
     Electronic devices typically have a fixed or variable orifice and a pressure transducer located on one or both sides of the orifice. A fixed orifice is a reduced diameter passage (which can have any shape) having a fixed cross-sectional area that is independent of air flow rate. A variable orifice is a reduced diameter passage (which can have any shape) having a cross-sectional area that is dependent on air flow rate (e.g., the cross-sectional area increases as the flow rate increases). In either case, the orifice typically causes a back pressure to form in front of the orifice in response to air flow through the orifice. By measuring the back pressure and determining the pressure downstream of the orifice (which is typically ambient pressure), the pressure differential across the orifice can be obtained. The pressure differential permits not only the peak flow to be determined but also FEV 1  and FEV 6 (when the pressure differential is measured as a function of time). Due to the use of expensive pressure transducers and associated electronics, electronic devices are typically too costly for individual patients in self-monitoring applications. As a result, patients are unable to monitor important lung performance parameters, such as FEV 1  or FEV 6 . 
     SUMMARY OF THE INVENTION 
     These and other needs are addressed by the devices and methods of the present invention. The present invention is directed generally to an inexpensive device and method for measuring an (expiratory) air flow parameter, such as PEFR, FEV 1 , FEV 6 , Forced Vital Capacity (FVC), and Mid Expiratory Flow Rate (FEF 25-75). The device can be simple to use and portable and/or hand held. 
     In a first embodiment, a device is provided that includes: 
     (a) a conduit having an inlet (or mouthpiece) for exhaled air and an outlet (or flow chamber) for the exhaled air; 
     (b) a plate (or orifice or closure or sensing) member (or vane) movably disposed in the conduit between the inlet and outlet, the plate member at least partially blocking the conduit and moving in response to the passage of the exhaled air through the conduit; and 
     (c) a measuring device for measuring, at a plurality of points in time, at least one of (i) a location of the plate member, (ii) a pressure or force applied by the exhaled air against the plate member, and/or (iii) an air flow parameter (e.g., a rate of volume of flow) and generating a plurality of measurement signals. The plate member is typically shaped such that air flow from the inlet end past the member causes the member to move, e.g., rotatably or linearly, away from a rest or starting position to a succession of other open positions forming an ever widening gap between the member and a part or wall of the conduit or passageway. From the position of the plate member or the force applied to the plate member, the pressure applied to the plate (e.g., the back pressure or the pressure or force applied by the air flow) in front of the plate member can be determined. 
     In one configuration, the device measures the force applied to the plate by the mass of air contacting the plate (even though there is no back pressure). The force is directly proportional to the flow rate or the kinetic energy of the air flow. 
     In another configuration, the outlet is at ambient (atmospheric) pressure and therefore the pressure differential across the plate member can be determined. The use of the displacement measuring device thereby eliminates the need for an expensive pressure transducer and related electronics. The device can be designed to comply with the stringent maximum back pressure requirements of the American Thoracic Society (which require the back pressure to be less than about 2.5 cm H 2 O/liter second measured at 14 liters/second airflow (for monitoring applications)) and 1.5 cm H 2 O/liter second measured at 14 liters/second airflow (for diagnostic applications)), but also, by selecting the distance between the displacement member and the outlet of the conduit, the relationship between the pressure and air flow for the device can be predetermined (e.g., the shape of the curve when pressure is plotted against flow rate can be controlled). In this manner, extremely low flow rates can be accurately measured. 
     To permit determination of time dependent parameters, such as FEV 1 , or FEV 6 , the device can further include a processing unit for receiving the plurality of measurement signals and an electronic memory, in communication with the processing unit, for recording the location of or pressure or force applied to the plate member at the plurality of points in time. This permits determination of the flow rates at the differing points in time and, therefore, the volumetric flows over a selected time interval. The contents of the electronic memory can be read by the user through a visual display and/or uploaded to a computer to generate an electronic diary for the patient and/or to forward the information by modem to a physician. Physicians can program the device to set goals or targets using a computer (PC) interconnected via a port to the device or keys on the device. In one configuration, the memory is tamper proof, thereby eliminating errors that frequently are associated with manually logged results. 
     The measuring device can be any suitable device for monitoring the pressure or force applied to the plate member and/or the plate member position as a function of time, such as a strain gauge (e.g., a single, half or full resistor bridge strain gauge), a radiant energy source (e.g., a light or sound energy source) in communication with a radiant energy detector. In one configuration, the device is any type of strain gauge, such as piezoresistive, thin film, semiconductor, and the like, that measures deformation of a plate. A particularly preferred strain gauge has an active circuit and an inactive circuit. By configuring the strain gauge as a half or full resistor bridge, noise as a result of thermal expansion or contraction of the plate member and the like, can be zeroed out. The strain gauge is typically located on an upstream (front) or downstream (rear) surface of the plate member relative to the direction of exhaled air flow. 
     In another embodiment, a method is provided for determining exhaled air flow. The method includes the steps of: 
     (a) exhaling air into an inlet of a conduit; 
     (b) moving a sensing member that is movably disposed in the conduit downstream of the inlet, the sensing member at least partially blocking the conduit and moving in response to the passage of the exhaled air through the conduit; and 
     (c) measuring the location of the sensing member at a plurality of points in time and generating a plurality of location signals. The plurality of location signals can be processed to determine a desired air flow parameter. 
     In another embodiment, a portable device for measuring respiratory air flow is provided that compensates for the effects of inertia of the plate member. The device includes a self-oscillation dampener (or dampening means) that resists movement of the sensing member. In one configuration, the dampener is located behind and movably (e.g., frictionally) engages the sensing member. The self-oscillation dampener dampens the amplitude of oscillations of the sensing member in response to exhaled air contacting the sensing member. The self-oscillation dampener can also increase the resonant frequency of the sensing member such that the resonant frequency exceeds the frequency of any oscillations imparted to the system by the air flow. In one configuration, the self-oscillation dampener is located on the downstream side of the sensing member. In another configuration, the self-oscillation dampener applies a pressure to the sensing member of no more than about 10 gm or no more than about 10% of the pressure applied to the sensing member by the air flow. 
     In yet another embodiment, a device for measuring respiratory air flow is provided that includes: 
     (a) a conduit having an inlet for exhaled air and an outlet for the exhaled air; 
     (b) a plate member movably disposed in the conduit between the inlet and outlet, the plate member at least partially blocking the conduit and moving in response to the passage of the exhaled air through the conduit; and 
     (c) a measuring device for measuring at least one of a pressure or force applied against the plate member by the exhaled air and generating a measurement signal. The measuring device is located on (e.g., adhered or attached to, etched on, etc.) or otherwise engages the plate member. In a particularly preferred configuration, the measuring device is a strain gauge. 
     In a further embodiment, a portable device is provided that increases the plate member&#39;s resonant frequency for the reasons noted above. The device includes (incorporates) or engages one or more stiffening members to impart rigidity to the plate member without significantly increasing the mass of the member. The stiffening members can be located anywhere on the plate member such as on a peripheral edge(s) of the plate member and/or in the central portion of the plate member. By increasing the rigidity of the plate member, the stiffening members also inhibit or minimize flutter of the member in response to air flow. 
     In another embodiment, a portable device for measuring respiratory air flow is provided that substantially eliminates the effect of gravity on the air flow measurement. The device includes 
     (a) a conduit having an inlet for exhaled air and an outlet for the exhaled air; and 
     (b) a sensing member for measuring an air flow parameter (e.g., a pressure transducer, a movable plate). The direction of air flow through the inlet is transverse to the direction of air flow at the sensing member. In one configuration, the direction of air flow through the inlet is substantially normal to the direction of air flow at the sensing member. In this design, the positioning of the device when the patient exhales into the conduit has substantially no effect on the air flow measurement. In one configuration, an axis of sensing member movement is substantially normal or orthogonal to an axis of possible movement of the patient during the respiratory test using the device. 
     In yet a further embodiment, the device includes a detachable or removable head assembly that includes the input conduit, sensing member and outlet conduit. The head assembly is removable for cleaning. In this manner, the device does not require a bacterial filter. 
     The above-described embodiments and configurations are neither complete nor exhaustive. As will be appreciated, other embodiments of the invention are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is perspective view of a user operating the peak flow meter according to one embodiment of the present invention; 
     FIG. 2 is a perspective view of the flow meter with the inlet in the undeployed position; 
     FIG. 3 is a perspective view of the head assembly disengaged or detached from the body of the flow meter; 
     FIG. 4 is a perspective view of the body of the flow meter with the head assembly detached; 
     FIG. 5 is a bottom view of the detached head assembly; 
     FIG. 6 is a side view of the flow meter with the inlet in the undeployed position; 
     FIG. 7 is a side view of the detached head assembly with the inlet in the deployed position; 
     FIG. 8 is a cross-sectional view along line  8 — 8  of FIG. 2; 
     FIG. 9 is an end view depicting the flow meter with a portion of the housing removed to reveal the flow meter interior; 
     FIG. 10 is a side view depicting the interior of the flow meter with a portion of the housing removed to reveal the flow meter interior; 
     FIG. 11 is an end view (opposite the end view of FIG. 9) depicting the flow meter with a portion of the housing removed to reveal the flow meter interior; 
     FIG. 12 is a side view (opposite the side view of FIG. 10) depicting the flow meter with a portion of the housing removed to reveal the flow meter interior; 
     FIG. 13 is a cross-sectional view taken along line  13 — 13  of FIG. 3; 
     FIG. 14 is a schematic view of the inlet and plate member in various positions; 
     FIG. 15 is a top view of the schematic view of FIG. 14; 
     FIG. 16 is an electrical flow schematic of the peakflow meter; 
     FIG. 17A is a plan view of the segmented display; 
     FIGS. 17B-K are flow charts of the software for operating the meter; 
     FIGS. 18A and B are respectively a configuration of a resistor bridge for the measuring device and an electrical flow schematic of the device; 
     FIGS. 19-22 show differing plate member configurations; 
     FIG. 23 depicts an alternative configuration for determining the position of the plate member; 
     FIG. 24 depicts another alternative configuration for determining the position of the plate member; 
     FIGS. 25-26 depict a plate member and a plate member location system according to another alternative configuration, with FIG. 25 being a front view of the plate member and FIG. 26 being a plan view of the system components; 
     FIG. 27 depicts another configuration of a system for determining the location of the plate member and/or a force applied to the plate member by the airflow; 
     FIG. 28 depicts a plate member and self-oscillating dampener according to another embodiment of the present invention; 
     FIGS. 29-30 depict yet another embodiment of a plate member and self-oscillating dampener, with FIG. 29 being a plan view of the system components and FIG. 30 being a side view of the plate member; 
     FIG. 31 is a plan view of a plate member according to another embodiment; and 
     FIG. 32 is a front view of the plate member of FIG.  31 . 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1-12 depict a peak flow meter  100  according to one embodiment of the present invention. The flow meter  100  includes a body assembly  104  and a detachable head assembly  108 . Referring to FIG. 4, the head assembly  108  can be detached from the body assembly  104  by means of a front latch  112   a  activated by pressing a release button  116  located on the front  120  of the body assembly  104 . Rear latch  112   b  is not activated by the release button but simply holds the rear of the head assembly. 
     Referring to FIGS.  4  and  9 - 12 , the body assembly  104  generally includes signal processing circuitry, a processor, and a display, all enclosed within a body housing. The body housing is typically formed from a lightweight rigid material such as plastic. 
     Referring to FIGS. 3,  5 ,  8 - 10 , and  16 , the head assembly  108  generally includes a rotatable (or adjustable) inlet conduit  124 , an outlet conduit  128 , a plate member  132  adjacent to an orifice  136 , and a self-oscillation dampener  140  engaging the plate member  132 , all enclosed by a head housing  144  that is typically formed from the same material as the body housing. 
     Referring to FIGS. 14 and 15, the plate member  132  is movably or rotatably engaged with the head housing  144  to permit exhaled air  148  passing through the inlet conduit  124  and the orifice  136  to displace the plate member  132  away from the orifice  136 . When the plate member  132  is displaced away from the orifice  136 , the exhaled air  148  can pass into the outlet conduit or flow chamber  128  and through the outlet or exhaust  152  into the exterior environment. The clearance between the bent edges of the plate member and the adjacent interior surfaces of the head housing is typically low (e.g., no more than about 0.5 mm to improve measurement accuracy. 
     As the plate member  132  is displaced from a starting position  156   a  to a new position  156   b  (FIGS.  14  and  15 ), a strain gauge  160  located on or etched onto the plate member  132  generates an electrical signal that may be processed by known techniques to determine the force applied to the plate member  132  by the air  148  flowing through the inlet conduit  124 . As will be appreciated, the electrical signal will vary as the length of the resistor in the strain gauge varies in response to deformation of the plate member  132 . If the strain gauge  160  were to be located on the front surface  164  of the plate member  132 , the resistor length increases as the plate member  132  is displaced. If the strain gauge  160  is located on the rear surface  168  of the plate member  132 , the resistor length decreases as the plate member  132  is displaced. As discussed below, the electrical signal can be used to determine directly the pressure or force applied to the plate member by the air flow as a function of time and the resulting waveform integrated over the appropriate time interval to provide FEV 1  or FEV 6 . 
     FIGS. 18A and B depict a configuration of a strain gauge  160  that is particularly useful in many applications. The strain gauge  160  is a full resistor bridge design having resistors R 1  and R 2 . The resistor R 1  is orthogonally oriented to the resistor R 2  to permit background variations or noise (signal “T”) in the electrical signal due to thermal effects to be zeroed out. In other words, the resistors R 1  and R 2  are electrically connected in parallel such that changes in the length of each resistor due to thermal expansion and contraction of the plate member  321  eliminate one another (because the plate member  132  will uniformly expand or contract in all directions). When the plate member  132  is displaced by the air flow through the inlet conduit  124 , the length of the resistor R 2  will remain substantially constant while the length of resistor R 1  will vary to generate, signal “MS” measurement. 
     The strain gauge  160  can be adhered or otherwise attached to the plate member  132  or etched into the plate member  132  (which is typically of metal construction) by known techniques. Typically, the strain gauge will be fabricated separately and later attached to the plate member  132  for reasons of cost. 
     Referring to FIG. 8, the distance Δx between the upstream or front surface  164  of the plate member  132  and the plane of the orifice outlet  172  (when the plate member is at its starting position  156   a  (FIG.  14 )) (i.e., when no air is flowing through the inlet conduit  124 )) can determine the linearity and sensitivity of the response of the system to the air flow through the inlet conduit  124 . For example, if Δx were zero an extremely high gain (or extreme sensitivity at low flow rates) would be realized when the air flow  148  first contacts the plate member. However, the accuracy of the measurement would decrease rapidly as the flow rate increases. As Δx becomes larger, the opposite effect occurs. Although a more linear response is realized at higher Δx&#39;s, the system would have a very low sensitivity at low flow rates. Preferably, Δx is no more than about 5 mm and more preferably ranges from about 0 to about 2.5 mm. 
     The plate member  132  can be composed of any preferably lightweight, noncorrosive, high strength, substantially rigid or rigid material, with metal, such as any 3XX stainless steel alloy  15 - 5 ,  15 - 7 ,  17 - 4 , and  17 - 7  which are sold by major suppliers, being more preferred. 
     It is important to reduce the mass of the plate member  132  to reduce the impact of gravity on the displacement of the plate member  132  by air flow  148  and reduce the severity (frequency and amplitude) of plate member oscillations. If the plate member  132  is too thin, flutter of the plate member  132  can adversely impact the accuracy of the measurement. Preferably, the plate member  132  has a thickness “T” (FIG. 14) ranging from about 0.05 to about 0.5 mm and more preferably from about 0.05 to about 0.25 mm. Typically, the weight of the plate member  132  is no more than about 0.6 gms and more typically ranges from about 0.3 to about 2 gms. 
     To absorb energy imparted to the plate member  132  by the air flow  148  (and thereby reduce the magnitude of oscillations of the plate member  132 ), the self-oscillation dampener  140  resists (typically frictionally) displacement of the plate member  132 . As will be appreciated, oscillations can cause a loss of measurement accuracy, especially at the peaks, which translates into an inaccurate computation of the desired respiratory parameter(s). 
     Referring to FIG. 8, a number of design parameters for the self-oscillation dampener  140  are depicted. Typically, the contact angle θ ranges from about 0 to about 75° and more typically ranges from about 15 to about 65°. The height H CP  of the contact point “CP” between the dampener  140  and plate member  148  typically ranges from about 25 to about 95% of the height H PM  of the plate member  132  above the same datum plane. The length “L SOD ” of the dampener  140  from the contact point to the datum plane typically ranges from about 10 to about 150% of the height H PM  of the plate member  132 . As will be appreciated, the datum plane is the plane containing the rotational axes for the plate member  132  and dampener  140 . The plate member  132  and dampener  140  pass through a common hole  176  to allow freedom of rotation. The dampener  140  typically has a thickness “T 0 ” (FIG. 15) ranging from about 0.05 to about 1 mm and is fabricated of a metal such as the stainless steel alloy referred to above. Typically, the self-oscillation dampener  140  applies a pressure to the plate member  132  of no more than about 10 gm and more preferably ranging from about 2.5 to about 8 gm or no more than about 10% and more typically no more than about 1 to about 7.5% of the pressure applied to the front surface  164  plate member  132  by the air flow  148 . 
     The plate member  132  is preferably designed such that the natural or self-resonant frequency of the plate member  132  is higher than than the frequency of the oscillations that are imparted to the plate member  132  by the air flow  148 . Typically, the plate member  132  is designed to provide a natural frequency of the plate member  132  that is at least about 70 Hz and more typically at least about 75 Hz based on the assumption that the air flow  148  will impart a maximum frequency of 25 Hz to the plate member  132 . In this manner, measurement inaccuracies caused by oscillation of the plate member  132  are maintained at acceptable levels. 
     To provide such a high natural frequency and to significantly reduce flutter of the plate member  132 , the plate member  132  can have one or more stiffening members  180   a,b,  (FIG.  14 ). The stiffening members can be in any shape and any location on the plate member  132  and can be integral with the plate member  132  or nonintegral with and attached in some manner to the plate member  132 . The width “W” (FIG. 15) of the stiffening members  180   a,b  typically ranges from about 0.1 to about 1.0 mm and are typically formed as an integral part of the plate member  132 . 
     FIG. 8 depicts the various interconnected components supporting the plate member  132  and the self-oscillation dampener  140 . The components include inner and outer parts  184   a,b  (which are preferably a lightweight material such as plastic) and inner components  188   a,b  (which are preferably a high strength material such as a metal (e.g., a stainless steel). A fastener, such as a screw  192  and washer or nut  196 , are used to fasten the various components together. A sealant  200   a,b,  such as a silicon sealant, is positioned to block moisture from penetrating into the interior of the head assembly  108  and damaging electrical components contained therein. The various parts of the head housing in the head assembly  108  are attached together by a suitable technique to provide protection from moisture. A particularly preferred technique is ultrasonic welding. 
     To substantially eliminate the effects of gravity on the air flow measurement, the inlet conduit  124  provides a change in the direction of air flow  148  upstream of the plate member  132 . Referring to FIG. 13, the input direction  204  of air flow through the inlet  206  is transverse (typically orthogonal) to the direction  208  of the air flow  148  at the outlet of the orifice  136 . As can be seen from FIG. 1, the positioning of the meter  100  when the patient exhales into the inlet has substantially no effect on the air flow measurement. Stated another way, the direction  220  of plate movement (FIG. 15) is substantially normal or orthogonal to a direction  224  (FIG. 1) of possible movement of the user during the respiratory test. As shown in FIG. 13, this result is accomplished by making the air flow direction  204  at the inlet  206  substantially orthogonal to the air flow direction  208  at the orifice  136  and making the air flow direction  208  substantially normal to the plane of the front surface  156   a  of the plate member  132 . 
     For the convenience of the user, the inlet conduit  124  can be rotated freely between an undeployed position (FIG. 2) for ease of handling and the deployed position (FIG.  7 ). 
     The electronics of the meter will now be discussed with reference to FIGS. 4-5,  8 - 12 , and  16 . The signal from the measurement device  160  is received by an amplifier (which typically has a gain of about 1000) (and in some cases a filter)  250 , amplified (and in some cases filtered to remove noise) and transmitted via three contacts  254   a-c  and  158   a-c  from the head assembly  108  to an analog-to-digital converter  262 . The signal is converted from analog to digital by the converter  262  and processed as set forth below with reference to FIG. 17 by a microprocessor  266 . The microprocessor  266  accesses a nonvolatile memory  270 , such as an Electrically Erasable Programmable Read-Only Memory or EEPROM. The memory can store a variety of information including calibration and operating information. This information can be programmed into the chip at the time of manufacturing. 
     The microprocessor  266  is typically connected to various components. In one embodiment for example, the microprocessor  266  is connected to an audio device  274 , such as a buzzer, to provide a warning signal such as when the air flow rate and/or volume is below a predetermined level. The microprocessor is connected to a system clock  267  for timing information. The clock can access nonvolatile memory  270  to protect data and information. The microprocessor is connected to a display module  278 , such as a Liquid Crystal Display or LCD or a number of Light-Emitting Diodes or LEDs, via a plurality of contacts  282  located on either side of the display. The microprocessor is connected to a display drive  279  for the display module  278 . In one configuration, the display is a segment-type display. The display is covered by lens  286 . The microprocessor is connected to an Infrared Communication or IR ports  290  to upload information from the memory  270  to a peripheral computing device, such as a PC (not shown). The microprocessor is connected to a plurality of keys  294   a-b.  The keys are incorporated into the display module. The keys are hereinafter referred to as the operator key  294   a,  the scroll key  294   b,  and the settings or select key  294   c.    
     A common printed circuit  274  board typically contains the analog-to-digital converter  262 , microprocessor  266 , memory  270 , display drive  279 , and system clock  267 . The PCB is located in the body assembly  104 . 
     A power source  300 , which is typically a small sized battery such as a 2032 lithium cell having a power capacity of 3 Volts, powers the various electrical components. 
     Switches  304   a,b  activate and deactivate the various components. Switches  304   a,b  are activated by the microprocessor  266  as described below. 
     The display module  278  is depicted in FIG.  17 A. Each of the segment indicators  301   a-d  correspond to a zone indicator  302   a  (red zone),  302   b  (orange zone),  392   c  (yellow zone), and  302   d  (green zone). The segment indicators  301   a-d  are activated to indicate which of the colored zones a PEF reading corresponds to. Alarm segment  303  includes three subsegments  305   a-c,  each of which corresponds to a separate alarm setting. When an alarm is triggered, the corresponding subsegment  305   a-c  and center  390  is illuminated along with the exclamation mark segment  306 . The blow segment  307  is illuminated when a blow test is to be initiated. The PEF segment  308  is activated to display the results of a blow test. The reference segment  309  is illuminated to display the percent of the reference PEF to which the PEF measured for the blow test corresponds. The question segment  310  is activated during the symptom score mode when the microprocessor is scrolling through diary questions. The question segments  311   a-f  correspond to medication frequency (inhaler segment  311   a ); coughing severity (cough segment  311   b ); wheezing severity (wheeze segment  311   c ); chest tightening rating (chest clamp segment  311   d ); existence of nocturnal awakenings (True/False) (yawning segment  311   e ); and supplemental questions (medical bag segment  311   f ). The lower display  312  is used to display the time, FEV 1 , FEV 6 , and the ratio of FEV 1 :FEV 6 . The M segment  313  is illuminated to indicate a full memory  270 . The transfer segment  314  is illuminated during the uploading or downloading of information. The check segment  315  is illuminated upon successful completion of the transfer. The lower exclamation segment  316  is illuminated upon unsuccessful completion of the transfer. Finally, the low battery segment  317  is illuminated when the power level falls below a predetermined level. 
     Referring to FIGS. 17A-K, the operation of the device will now be described. Referring to FIG. 17B, the device is typically in the standby mode  301 . In the standby mode, the microprocessor deactivates the switches  304   a,b  to conserve power and awaits instructions from the user. 
     If the operator key is pressed (see decision diamond  414 ), the microprocessor enters into the operating key mode or subroutine which is depicted in FIG.  17 C. Referring to FIG. 17C, the microprocessor determines in decision diamond  415  whether the operator key  194  was pressed and held down for more than three seconds. If so, the microprocessor proceeds to decision diamond  319  in FIG.  17 D. 
     In FIG. 17D, the device is in the symptom score mode or subroutine in which the user can create and/or revise the diary. Referring to FIG. 17D, the microprocessor determines whether a symptom score is going to be entered by waiting for a keystroke within ten seconds. If so, the microprocessor proceeds to decision diamond  321 . If the system score is zero (meaning that the question is disabled), the microprocessor proceeds to decision diamond  322 . In decision diamond  322 , the microprocessor determines if the question number is more than sixteen (the maximum number of diary questions). If so, the microprocessor in box  323  saves the entered system scores. If not, the microprocessor in box  324  increments to the next question and returns to decision diamond  321 . If the maximum value in decision diamond  321  exceeds zero, the microprocessor determines in decision diamond  325  if the operator key  294   a  was held down by the user for more than 2 seconds. If so, the microprocessor proceeds to box  323 . If not, the microprocessor proceeds to decision diamond  326  where the microprocessor determines if the operator key  294   a  was pressed down again after the 2 second interval of decision diamond  325  (i.e., the user is incrementing the symptom score). If so, the microprocessor proceeds to box  322 . If not, the microprocessor proceeds to decision diamond  328  where the microprocessor determines if the operator key was pressed within two seconds of the last pressing of a button or key. If not, the microprocessor saves the symptom score in box  329  and proceeds to decision diamond  330  where the microprocessor determines if the symptom score was entered within 5 minutes of a former symptom score for the same question. If not, the microprocessor returns to decision diamond  322 . If so, the microprocessor replaces the old symptom score in box  331  and then proceeds to decision diamond  322 . Returning again to decision diamond  328 , if the operator key  294   a  was pressed within 2 seconds of the pressing of the previous key, the microprocessor proceeds to decision diamond  332 . In decision diamond  322 , the microprocessor determines if the entered symptom score exceeds the maximum symptom score. If so, the microprocessor in box  333  sets the entered symptom score to zero and displays the new score in segment  312  (to the right of the colon) next to the question number (to the left of the colon) and returns to decision diamond  328 . If not, the microprocessor in box  336  increments to the next count or symptom score and displays the new score in segment  312  and the question number in segment  310  and returns to decision diamond  328 . 
     Returning to FIG. 17C if the operator key  194   a  is held down for less than three seconds, the microprocessor proceeds to decision diamond  425 . If the operator key  194   a  is pressed again while the microprocessor is in the loop of FIG. 17C, the microprocessor returns to decision diamond  425 . Alternatively, if 10 seconds elapse between the pressing of keys, the microprocessor returns to the standby mode  301 . 
     In decision diamond  425 , the microprocessor determines if the sensor is successfully nulled. In this operation, the microprocessor beeps; activates switches  304   a,b;  delays for a specified period without reading the analog-to-digital input to allow the DC supply to the operating amplifier to stabilize; and checks for a valid sensor signal. A valid signal is typically analog-to-digital counts in the range of 60 mv to 140 mv. If a valid signal is not detected, the microprocessor proceeds to decision diamond  426  where it determines whether five seconds has passed. If not, the microprocessor loops back to decision diamond  425 . If five seconds has passed, the microprocessor activates segment  306  to display “!” and returns to the standby mode  301 . Returning to decision diamond  425 , if the sensor is nulled successfully the microprocessor averages the last sixteen counts from the analog-to-digital converter  262  and stores them as the absolute zero baseline. The microprocessor in box  426  activates segment  307  and zeros out segments  308 ,  309  and  312  and provides an audible pattern tone for test initiation. In decision diamond  427  if more than ten seconds has elapsed, the microprocessor returns to the standby mode  301 . If less than ten seconds has elapsed, the microprocessor in decision diamond  428  determines whether an exhalation effort is detected. If not, the microprocessor loops back to decision diamond  427 . If so, the microprocessor proceeds to box  429  (FIG. 17F) and collects data. When the flow signal exceeds the absolute zero baseline by at least 30 counts, segment  307  is deactivated and the time is marked as “TIME ZERO”. The data is collected to memory  270  beginning with the “TIME ZERO” data point. In box  430 , the data is processed by computing the back extrapolation time point, the 80 millisecond peak flow or PEF 80 , the uncorrected FEV 1  and FEV 6 , the back extrapolation volume (BEV), and finally the corrected PEF 80 , FEV 1 , and FEV 6 . The correction can be performed using any known mathematical corrective techniques and empirical data to correct for one or more respiratory, environmental, or other parameters, as will be obvious to those skilled in the art. 
     In decision diamond  431  the microprocessor determines if a cough occurred during the test. This is determined by analyzing the change in flow between adjacent samples from PEF to the first second (first 100 samples). If the change is above a predetermined level (typically greater than about 50% of the flow of the previous sample) a cough is assumed to have occurred. If not, the microprocessor in decision diamond  432  determines if the time interval for FEV 1  is less than one second. If not, the microprocessor determines in decision diamond  433  if there is a back extrapolation error. Such an error is deemed to exist when the back extrapolation (BE) error is equal to or greater than 0.15 Liters. If not, the microprocessor in decision diamond  434  whether the PEF is less than 30% or more than 150% of the reference PEF. If any of the queries for decision diamonds  432 ,  433 , and  434  are true, the microprocessor in box  435  activates segment  306  to indicate an error. After performing box  435  or if the query in decision diamond  434  is false, the microprocessor proceeds to decision diamond  436  and determines if the previous test was done within five minutes. If so in box  437 , the parameters are replaced in memory  270  with the new test results, if no error is identified. If not, the new test results in box  438  are saved to memory  270 . 
     The results are displayed in box  439  for the user after the test. As will be appreciated, the following results are displayed before the test: (a) the PEF 80  result of the previous test in segment  308 ; (b) the percent reference PEF in segment  309 ; and (c) the zone indicator  301   a-d  corresponding to the percent reference PEF. After the test is completed, the new values for these variables are displayed along with the values for FEV 1  and the FEV1 symbol in segment  312 . After three seconds or when the operator key  194   a  is pressed, the display is changed by replacing the FEV 1  value for the FEV 6  value and the FEV1 symbol for the FEV6 symbol in segment  312 . After three more seconds or when the operator key  194   a  is again pressed, the display is changed by replacing the FEV 6  value with the FEV 1 /FEV 6  value and the FEV6 symbol for the FEV1/FEV6 symbol  312 . After three more seconds these steps are repeated in the sequence described and the microprocessor then proceeds to standby mode  301 . 
     FIG. 17G depicts the process used for displaying the proper zone indicator in segments  301   a-d.  In decision diamond  440 , the microprocessor determines if the absolute flag is set. If so, the microprocessor in box  441  compares the measured PEF directly to the values loaded into the zones. As will be appreciated, the reference value can be not only absolute but also the percent of best PEF or the percent of predetermined normal PEF&#39;s. If the absolute flag is not set, the microprocessor loads the percent values rather than absolute values in box  442 . In box  443 , the microprocessor compares (a) the measured PEF to the reference zone value or (b) the ratio of the PEF to a baseline PEF value to a percentage for each zone. The microprocessor then follows the operations set forth in decision diamonds  444   a-h  and action boxes  445   a-d  in activating the correct zone indicator. After completing the pertinent action box  445   a-d,  the microprocessor completes the display sequence described above and ultimately returns to the standby mode  301 . 
     Referring again to FIG. 17B, the microprocessor next determines in decision diamond  446  if the setting key  194   c  has been pressed for more than three seconds. If so, the microprocessor proceeds to the manual setting mode or subroutine depicted in FIG.  17 H. In FIG. 17H, the microprocessor determines in decision diamond  337  if the user has pressed the scroll key  294   b.  If so, the microprocessor in box  341  increments the selected sequence value (e.g., increments to the next hour). If the scroll key  294   b  is held down the display scrolls faster then if the scroll key is intermittently pressed. The microprocessor in decision diamond  338  determines if the scroll key  294   b  is released. If not, the microprocessor loops back to diamond  338 . If so, the microprocessor determines if five seconds has passed in decision diamond  339 . If so, the result from the current sequence is saved in box  340  and the microprocessor proceeds to box  341 . If not, the microprocessor determines in decision diamond  342  if the setting key  294   c  has been pressed. If so, the microprocessor in box  343   a  saves the result from the current sequence and in box  343   b  increments to the next sequence number. If not, the microprocessor returns to decision diamond  337 . Using this subroutine, the clock hour and minute; first, second, and third alarm hour and minute; and the reference PEF are set by the user. 
     Returning to FIG. 17B, the user can enter into a scroll mode or subroutine to scroll through the contents of the memory  270 . When the microprocessor determines in decision diamond  447  that the scroll key  194   b  has been pressed by the user, the microprocessor proceeds to decision diamond  448  in FIG.  17 I. If the user has not pressed the operate key  294   a,  the microprocessor determines if ten seconds has elapsed since the last key was pressed. If so, the microprocessor proceeds to the standby mode  301 . If not, the microprocessor loops back to decision diamond  448 . If the user has pressed the operate key  294   a,  the microprocessor in box  449  decrements one memory location and determines in decision diamond  450  whether the scroll key  194   b  has been pressed. If so, the microprocessor returns to the standby mode  301 . If not, the microprocessor determines in decision diamond  451  whether 10 seconds has elapsed. If so, the microprocessor proceeds to box  301  of FIG.  17 B. If not, the microprocessor returns to decision diamond  448 . 
     In decision diamond  416 , it is determined whether the setting key  94   c  was pressed for less than three seconds. If so, the microprocessor proceeds to decision diamond  417  where the microprocessor determines if the device is in a cradle (not shown) for uploading or downloading of information from or to another computer (not shown). If the device is not in the cradle, the microprocessor in box  302  activates the segment  316  to signify an error and returns to the standby mode  301 . 
     If the device is in the cradle, the microprocessor proceeds to the data transfer subroutine in FIG.  17 E. In FIG. 17E, the microprocessor in box  418  activates the IR amplifiers and checks in decision diamond  419  for the correct pulse. If the correct pulse is not detected, the microprocessor in box  420  deactivates the IR amplifiers and returns to the standby mode  301 . If the correct pulse is detected, the information transfer is initiated in box  421 , and the transfer segment  314  is activated in box  422 . In decision diamond  423 , the microprocessor determines if the transfer is completed. If not, the microprocessor loops back to decision diamond  423 . If so, the microprocessor proceeds to decision diamond  424  where the microprocessor determines if the transfer was good using a checksum or other approach. If the transfer was good, the checkmark segment  315  is activated and the microprocessor returns to the standby mode  301 . If the transfer was not good, the segments  308  and  306  are activated to display ERR!. The microprocessor then returns to the standby mode  301 . 
     If the setting key was not pressed for less than three seconds, the microprocessor proceeds to decision diamond  470  of FIG.  17 B and determines if an alarm should be triggered. Referring to FIG. 17K, when one of the three alarms is activated in box  471 , the microprocessor in box  472  activates the flashing alarm segment  305   a-c  that corresponds to the triggered alarm and center  390 . In box  473 , the microprocessor activates the an audible tone from the buzzer  274 . In decision diamond  474 , the microprocessor determines if the user has pressed the operator key  194   a.  If so, the microprocessor returns to the standby mode  301 . If not, the microprocessor in decision diamond  475  determines if twenty seconds has elapsed. If not, the microprocessor loops back to decision diamond  474 . If so, the microprocessor proceeds to the standby mode  301 . 
     Finally, the microprocessor determines in decision diamond  460  if the battery is low (i.e., the power level is 2.7 volts or less). If so, the low battery segment  317  in box  476  is activated. If not, the microprocessor returns to the standby mode  301 . 
     Referring to FIG. 17J, the process used by the microprocessor when the battery is replaced is depicted. Upon installation or replacement of the battery, the microprocessor in box  344  beeps and turns on switches  304   a,b  for two seconds. The microprocessor in decision diamond  345  then determines if the sensor is nulled. The sensor is nulled when the microprocessor detects a valid signal within two analog-to-digital counts for 16 data points. Before reading the analog-to-digital output, the microprocessor typically waits for a predetermined period to allow the power supply to the amplifier  250  to stabilize. If nulling of the sensor is unsuccessful (e.g., the sensor is not attached, the sensor readings are acceptable, and the reading is stable) the microprocessor proceeds to box  346  activates segments  308  and  306  to display ERR! and returns to decision diamond  345 . If the sensor is nulled, the microprocessor proceeds to decision diamond  347  where the microprocessor determines if the battery is low. If so, in box  348  the segments  308  (to show ERR) and  317  are activated for five seconds and the microprocessor proceeds to decision diamond  349 . Segment  317  remains activated until power is reset. In decision diamond  349 , the microprocessor determines if the memory is full. If so, the M segment  313  is activated in box  350 . In either event, the microprocessor proceeds to box  301 , which is the standby mode. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. 
     By way of example, the plate member can have any number of a plurality of shapes. In FIG. 19, a plate member  400  includes a straight or flat section  404  on one end and a curvilinear section  408  on the other end that moves in direction  412 . FIG. 20 shows a curvilinear plate member  500  that moves in direction  504 . In FIG. 21, a plate member  600  is shown that has a curved section  604  and a flat section  608  that are both displaced in direction  612  in response to air flow  614 . The curved section  604  is further elastically deformed by the air flow as shown by the dotted line. This plate member configuration is depicted in FIG. 22 interacting with an air flow  616  contacting the plate member  600  at a different angle than that depicted in FIG.  21 . 
     The plate member can move not only rotatably but also linearly. FIG. 27 shows a configuration in which the plate member  700  moves linearly in direction  704 . The plate member  700  is engaged with a spring member  708  that is in turn engaged with a strain gauge  712 . As the plate member  700  is displaced by the air flow  716  in direction  704 , the spring member  708  causes an increasing force to be applied to the strain gauge, thereby altering the electrical signal output by the gauge. An outlet  720  is located along a wall of the conduit  724  such that as the plate member  700  moves towards the strain gauge  712 , the air  716  has an increasing area of the outlet available in which to escape from the conduit  724 . 
     Other techniques are available to monitor the position of the plate member as a function of time. In this manner, the force or pressure exerted by the air flow against the plate member or the flow rate can be determined as a function of time. FIG. 23, for instance, shows an ultrasound transmitter  800 , such as one or more piezoelectric crystals, and an ultrasound receiver  804 , which can also be one or more piezoelectric crystals. As will be appreciated, one or more piezoelectric crystals can act as both the transmitter or emitter and receiver or detector. An ultrasound beam  808 , which can be modulated by known techniques, is transmitted towards the plate member  812  in conduit  816  and reflected off of the plate member  812  and the reflected beam  820  received by the receiver  804 . The characteristics of the reflected beam and/or the time duration between signal transmission and reception can be analyzed to determine the distance of the plate member  812  from the ultrasound transmitter  800  and/or receiver (which are typically equidistant from a common plate member surface). FIG. 24 depicts a system in which a light beam  900  is generated and directed by a light emitter  904  towards the plate member  908 . The reflected beam  912  is received by a light detector or encoder  916  on a wall of the conduit  920 . As in the case of the ultrasound beam, the beam can be modulated. The parts of the detector  916  receiving the reflected beam and/or the characteristics of the reflected beam itself can be used to determine the distance from the light emitter  904  or detector (which is typically the same) to the plate member  908 . FIGS. 25 and 26 depict another system using a light beam, which is typically an infrared beam. A bar or interference code  1000  is located on the plate member  1004 . The code  1000  causes a unique, detectable reflection pattern depending upon the distance of the code from the light emitter  1008 . A detector  1012  mounted on the wall of the conduit  1014  receives the reflected beam  1016  and, based upon the reflected light pattern, is able to determine the distance from the light emitter  1008  or detector (which is typically the same) to the plate member  1004 . Additionally, a magnet and a Hall Effect device can be used as described in U.S. Pat. No. 5,277,195, which is incorporated herein by this reference. 
     The self-oscillation dampener can be a variety of other systems. FIG. 28 depicts a plate member  1100  that includes a plurality of holes  1104  passing through the plate member  1100 . As the plate member  1100  moves in response to exhaled air contacting the front surface of the plate member, air will flow from the area behind the plate member (behind the page of FIG.  28 ), through the holes  1104 , and into the area in front of the plate member  1100  (in front of the page of FIG.  28 ). In this manner, the amplitude of oscillation of the plate member  1100  is dampened. The holes typically have a diameter ranging from about 0.01 to about 5 mm. FIGS. 29 and 30 depict a method of dampening the amplitudes of oscillations of a plate member  1200  using an electromagnetic field  1204 . A strong magnet  1208  is positioned in close proximity to the plate member  1200  (which is metal). The field  1204  induces eddy currents in the side members  1212   a,b  of the plate member  1200 . As will be appreciated, the eddy currents will be in a plane that is normal to the direction of movement  1216  of the plate member  1200 . The magnetic field will resist movement of the eddy currents through the field. 
     The stiffening members can be in a variety of configurations. FIGS. 31 and 32 show that the stiffening members can be formed into the plate itself. The members  1300   a,b  are trough-like depressions in the plane of the plate member  1304 . These depressions impart stiffness or rigidity to the plate member  1304 . As will be appreciated, the stiffening members can be any other shape or depth of irregularity in the planarity of the plate surface. 
     The embodiments described herein above are further intended to explain best modes known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.