Abstrict Disclosed herein is a peak expiratory flow meter capable of measuring
continuous expiratory flow. The peak expiratory flow meter includes
a lower casing unit (110), an air expansion unit (130) and an upper
casing unit (150). The lower casing unit (110) includes a first
body (112) having an open top and open opposite sides and having
a first end in which a first expiratory flow entrance (114) is formed,
a plurality of rails (118), and a movable plate (122). The air expansion
unit (130) includes a pressure transfer tube (132), an elastic plate
(136), and a pressure spring (140). The upper casing unit (150)
includes a second body (152) adapted to define the air expansion
unit and provided with a first end in which a second expiratory
flow entrance (154) is formed, and a measurement slot (156), and
a scale indicator (160) having a "T" shape.
Claims 1. A peak expiratory flow meter capable of measuring continuous
expiratory flow, comprising: a lower casing unit including a first
body formed to have an open top and open opposite sides and to have
a first end in which a first expiratory flow entrance is formed
to be integrated with the first body so as to allow an asthma patient
to hold the first expiratory flow entrance in his or her mouth,
a plurality of rails arranged on a top of the first body adjacent
to a second end of the first body, and a movable plate fitted on
the rails; an air expansion unit including a pressure transfer tube
arranged on a side of the first expiratory flow entrance, an elastic
plate fitted on the pressure transfer tube, and a pressure spring
comprised of a first end that is mounted to the elastic plate and
a second end that is mounted on a first side surface of the movable
plate; and an upper casing unit including a second body coupled
with the first body, adapted to define the air expansion unit and
provided with a first end in which a second expiratory flow entrance
corresponding to the first expiratory flow entrance is formed to
be integrated with the second body, and a measurement slot formed
on a side of the second expiratory flow entrance and extended to
a portion of the second body adjacent to a second end of the second
body, and a scale indicator formed to have a "T" shape
and to have an upper portion exposed to outside of the measurement
slot, and hung on a top of the second body and a lower portion supported
on an upper portion of a second side surface of the movable plate
(122), the scale indicator being moved by the movable plate (122).
2. The peak expiratory flow meter according to claim 1 wherein
the rails have ends that are fixedly arranged by supporting projections
(120) vertically extended from a bottom surface of the first body.
3. The peak expiratory flow meter according to claim 1 wherein
the first expiratory flow entrance has a pressure transfer hole
that is formed on a side thereof to penetrate through a bottom surface
of the first body.
4. The peak expiratory flow meter according to claim 3 wherein
the pressure transfer tube includes a first transfer tube that is
formed to have a closed top and an open bottom to penetrate from
the top of the first body through the pressure transfer hole, and
a second transfer tube that is extended from an outer circumference
of the first transfer tube, arranged in the first body, to be radially
broadened towards the movable plate while communicating with the
first transfer tube, and then mounted to the elastic plate, the
pressure transfer hole being tightly fitted around the first transfer
tube, which passes therethrough, without circulation of air therebetween.
5. The peak expiratory flow meter according to claim 4 wherein
the first transfer tube extended to an outside of the first body
is selectively connected to any one of a typical pressure sensor
and a typical electronic circuit for signal analysis, thus performing
spirometry.
6. The peak expiratory flow meter according to claim 4 wherein
the elastic plate includes a mounting cavity that is formed in a
portion thereof to allow an extending part of the second transfer
tube to be fitted into the mounting cavity, the second transfer
tube being tightly fitted into the mounting cavity without circulation
of air therebetween.
7. The peak expiratory flow meter according to claim 1 wherein
the measurement slot is formed to penetrate through the top of the
second body, the second body having a scale indicated to both sides
of the measurement slot.
Description TECHNICAL FIELD
[0001] The present invention relates, in general, to a peak expiratory
flow meter being used by asthma patients, and a peak expiratory
flow meter, which is capable of measuring continuous expiratory
flow.
BACKGROUND ART
[0002] Generally, asthma is a chronic respiratory disease, and
an asthmatic attack narrowing the respiratory tract is a respiratory
disease capable of causing a patient to die (A. Greening, "General
principles", In: Manual of asthma management, pp. 331-337
Ed. by P. M. O'byne, N. C. Thomson, W. B. Saunders, New York, 2001).
Therefore, an asthma patient must monitor himself or herself, typically
performs a forced expiration using a conveniently portable Peak
Expiratory Flow Meter (PEFM), and measures Peak Expiratory Flow
(PEF) at that time. Typically, the asthma patient recognizes his
or her status on the basis of a peak expiratory flow value measured
by the PEFM, and then determines whether to go to hospital.
[0003] The above-described conventional PEFM is operated on the
basis of the principles of FIG. 1 in which one end of a spring
11 having elasticity is fixed to a respiration tube 10 {circle around
(s)} within the respiration tube 10 and the other end thereof is
connected to a movable plate 12 movably arranged in the respiration
tube 10. Further, an indicator 13 extending through the wall of
the expiration tube 10 is arranged to be in contact with the movable
plate 12. In FIG. 1 when the expiratory flow F of a patient does
not exist, that is, when the PEF is not used, the movable plate
12 is placed at a location {circle around (1)} shown in FIG. 1
and the indicator 13 is made to be in close contact with the movable
plate 12. When the patient starts to expire, a force of expiratory
flow F is applied to the movable plate 12 so that the movable plate
13 starts to move to the right side of the drawing. As a push force
F obtained by the expiratory flow increases, a movement distance
L is lengthened, and the indicator 13 moves together with the movable
plate 12. Simultaneously, the movable plate 12 pulls the spring
11 so that an elastic force is generated and maintained in the
spring 11. A patient forcibly expires as in spirometry, which corresponds
to a standardized respiratory function examining method of allowing
the patient to apply a mouth to the expiration tube 10 and expire
as rapidly as possible and as much as possible, after maximally
inhaling air. If the value of the push force F, generated by the
expiratory flow during the forcible expiration of the patient, starts
to decrease from a peak value, the movable plate 12 starts to move
to the left side of the drawing due to the elastic force of the
spring 11 and consequently returns to {circle around (p)} its original
location {circle around (1)}. However, since the indicator 13 having
moved {circle around (m)} while being in close contact with the
movable plate 12 is not connected to the movable plate 12 the
indicator 13 moves by the right maximum movement distance L of the
movable plate 12 and then remains at a location {circle around (2)},
so that peak expiratory flow is measured by visually measuring the
maximum movement distance L.
[0004] The above-described peak expiratory flow meter is widely
utilized medical instrument, because it allows an asthma patient
to conveniently carry and occasionally measure peak expiratory flow
if necessary. For the prior arts related to the peak expiratory
flow meter, there are patents disclosed in UK Pat. No. 1463814 and
U.S. Pat. No. 5224487.
[0005] The peak expiratory flow meters disclosed in the above prior
arts are portable and convenient to use, but they can measure only
a peak expiratory flow value in a spirometry process executed while
a patient forcibly expires. However, typically, the evaluation of
the respiratory function of a chronic respiratory disease patient,
such as an asthma patient, is possible only when an expiratory flow
signal is continuously measured during the forcible expiration and
then important index values, such as Forced Vital Capacity (FVC)
and Forced Expiratory Volume at 1 sec (FEV.sub.1.0), are obtained
together from the measured signal waveform (R. E. Kanner, and A.
H. Morris, "Forced expiratory spirogram", In: Clinical
pulmonary function testing, pp. I-7.about.10 Intermountain Thoracic
Society, Salt Lake City, 1975). However, the above-described conventional
peak expiratory flow meters are limited in the evaluation of the
respiratory function because they provide only a peak expiratory
flow value, which is the maximum value of the expiratory flow.
[0006] Further, when FVC, FEV.sub.1.0 and PEF, which are important
and essential indexes to evaluate the respiratory function, are
required to be simultaneously obtained, an expensive spirometer
must be used, which has a construction completely different from
that of the PEFM in an entire operating structure including the
principles of measurement of an expiratory flow signal. Therefore,
when an asthma patient desires to currently evaluate the respiratory
function thereof, there is a problem in that he or she must measure
only a PEF value using the PEFM, or utilize a separate spirometer.
DISCLOSURE OF THE INVENTION
[0007] Accordingly, the present invention has been made keeping
in mind the above problems occurring in the prior art, and an object
of the present invention is to provide a peak expiratory flow meter
capable of measuring continuous expiratory flow, which improves
the construction of a peak expiratory flow meter having a miniatured
air expansion chamber therein to obtain a pressure signal corresponding
to a continuous flow signal through the peak expiratory flow meter,
so that an actual spirometer function is provided, thus enabling
the present invention to be used as a typical peak expiratory flow
meter at ordinary times, and allowing a signal accumulation and
analysis circuit to be connected to the peak expiratory flow meter
to execute spirometry if necessary.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a view schematically showing the operating principles
of a conventional peak expiratory flow meter;
[0009] FIG. 2 is a perspective view showing the coupling state
of a peak expiratory flow meter capable of measuring continuous
expiratory flow according to the present invention;
[0010] FIG. 3 is an exploded perspective view of the peak expiratory
flow meter of FIG. 2;
[0011] FIG. 4 is a view schematically showing the operating principles
of the peak expiratory flow meter according to the present invention;
[0012] FIG. 5 is a graph showing the characteristics of pressure
and flow; and
[0013] FIG. 6 is a graph showing an example of the comparison of
standard flow with measured flow.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014] The present invention provides a peak expiratory flow meter
capable of measuring continuous expiratory flow, comprising a lower
casing unit including a first body formed to have an open top and
open opposite sides and to have a first end in which a first expiratory
flow entrance is formed to be integrated with the first body so
as to allow an asthma patient to hold the first expiratory flow
entrance in his or her mouth, a plurality of rails arranged on a
top of the first body adjacent to a second end of the first body,
and a movable plate fitted on the rails; an air expansion unit including
a pressure transfer tube arranged on a side of the first expiratory
flow entrance, an elastic plate fitted on the pressure transfer
tube, and a pressure spring comprised of a first end that is mounted
to the elastic plate and a second end that is mounted on a first
side surface of the movable plate; and an upper casing unit including
a second body coupled with the first body, adapted to define the
air expansion unit and provided with a first end in which a second
expiratory flow entrance corresponding to the first expiratory flow
entrance is formed to be integrated with the second body, and a
measurement slot formed on a side of the second expiratory flow
entrance and extended to a portion of the second body adjacent to
a second end of the second body, and a scale indicator formed to
have a "T" shape and to have an upper portion exposed
to outside of the measurement slot, and hung on a top of the second
body and a lower portion supported on an upper portion of a second
side surface of the movable plate, the scale indicator being moved
by the movable plate.
[0015] As described above, the present invention is advantageous
in that it improves the construction of a peak expiratory flow meter
having a miniatured air expansion chamber therein to obtain a pressure
signal corresponding to a continuous flow signal through the peak
expiratory flow meter, so that an actual spirometer function is
provided, thus enabling the present invention to be used as a typical
peak expiratory flow meter at ordinary times, and allowing a signal
accumulation and analysis circuit to be connected to the peak expiratory
flow meter to execute spirometry if necessary.
[0016] Hereinafter, embodiments of the present invention will be
described in detail with reference to the attached drawings.
[0017] FIG. 2 is a perspective view showing the coupling state
of a peak expiratory flow meter capable of measuring continuous
expiratory flow according to the present invention, and FIG. 3 is
an exploded perspective view of the peak expiratory flow meter of
FIG. 2.
[0018] Referring to FIGS. 2 and 3 a peak expiratory flow meter
100 capable of measuring continuous expiratory flow according to
the present invention includes a lower casing unit 110 an air expansion
unit 130 and an upper casing unit 150.
[0019] First, the lower casing unit 110 includes a first body 112
and rails 118. The first body 112 is formed to have an open top
and open opposite sides. A first expiratory flow entrance 114 which
radially narrows to allow an asthma patient to hold the entrance
114 in his or her mouth, is formed at one end of the first body
112 to be integrated with the first body 112. A pressure transfer
hole 116 penetrating through the bottom surface of the first body
112 is formed on a side of the first expiratory flow entrance 114.
In the meantime, the rails 118 are arranged on the top surface of
the first body 112 adjacent to the other end of the first body 112.
Such rails 118 are arranged to be spaced apart from each other by
a certain distance around the pressure transfer hole 116 and extended
to the other end of the first body 112 respectively. The ends of
the respective rails 118 are fixedly arranged by supporting projections
120 vertically extended from the bottom surface of the first body
112. A movable plate 122 having a vertical planar shape is slidably
fitted on the rails 118. The air expansion unit 130 and the upper
casing unit 150 are mounted on the lower casing unit 110 formed
as described above.
[0020] The air expansion unit 130 includes a pressure transfer
tube 132 and an elastic plate 136. The pressure transfer tube 132
includes a first transfer tube 134a and a second transfer tube 134b.
The first transfer tube 134a is extended from the top of the body
112 to the outside of the first body 112 through the pressure transfer
hole 116. At this time, the top of the first transfer tube 134a
is closed, and the bottom thereof is opened to allow any one of
a typical pressure sensor 136 and an electronic circuit for signal
analysis to be selectively mounted on the bottom. The second transfer
tube 134b is extended from the outer circumference of the first
transfer tube 134a, arranged inside of the first body 112 to the
movable plate 122 so that the second transfer plate 134b is radially
broadened. That is, the second and first transfer tubes 134b and
134a communicate with each other. The elastic plate 136 may be formed
to have a vertically arranged disk shape. A mounting cavity 138
is formed in a portion of one side surface of the elastic plate
136 so that the extending part of the second transfer tube 134b
can be fitted into the cavity 138 and one end of a pressure spring
140 is mounted on the other side surface of the elastic plate 136.
At this time, the other end of the pressure spring 140 is mounted
on one side surface of the movable plate 122.
[0021] In the meantime, the upper casing unit 150 includes a second
body 152 and a scale indicator 160. The second body 152 is formed
to have an open bottom and open sides to be coupled with the first
body 112. A second expiratory flow entrance 154 corresponding to
the first expiratory flow entrance 114 is formed at one end of the
second body 152. A measurement slot 156 extending to a portion of
the second body 152 adjacent to the other end of the second body
152 is formed on a side of the second expiratory flow entrance 154
to penetrate through the top of the second body 152. In this case,
a scale 158 is indicated to both sides of the measurement slot 156.
The scale indicator 160 is formed in an approximate "T"
shape. The upper portion of the scale indicator 160 is exposed to
the outside of the measurement slot 156 and hung on the top of the
second body 152 and the lower portion thereof is supported on the
upper portion of the other side surface of the movable plate 122.
That is, the scale indicator 160 moves with the movable plate 122
and the air expansion unit 130 arranged in the first body 112 is
defined to be between the first and second bodies 112 and 152 by
the second body 150.
[0022] Hereinafter, the operating state of the peak expiratory
flow meter 100 formed as described above is described briefly.
[0023] First, the air expansion unit 130 is mounted on the lower
casing unit 110 having the first body 112 in which the movable plate
122 is slidably fitted on the rails 118. In this case, the first
and second transfer tubes 134a and 134b of the pressure transfer
tube 132 of the air expansion unit 130 are fitted into the pressure
transfer hole 116 and the mounting cavity 138 of the elastic plate
136 respectively. In this case, the first transfer tube 134a and
the second transfer tube 134b are tightly fitted into the pressure
transfer hole 116 and the mounting cavity 138 respectively, to
prevent the circulation of air therebetween. The other end of the
pressure spring 140 mounted on the elastic plate 136 is mounted
to one side surface of the movable plate 122.
[0024] As described above, when the air expansion unit 130 is mounted
on the lower casing unit 110 the upper casing unit 150 having the
second body 152 in which the scale indicator 160 is installed,
covers the top of the lower casing unit 110 thus closing the top
of the lower casing unit 110. At this time, the lower portion of
the scale indicator 160 is arranged to be in close contact with
the other side surface of the movable plate 122 thus enabling the
scale indicator 160 to react to the movement of the movable plate
122.
[0025] In the peak expiratory flow meter 100 formed as described
above, when the expiratory flow F passing into the flow meter 100
through the first and second expiratory flow entrances 114 and 154
pushes the movable plate 122 to stretch the pressure spring 140
an elastic force is generated in the pressure spring 140 to pull
the elastic plate 136 so that the expansion of air occurs in both
the elastic plate 136 and the pressure transfer tube 132 thus forming
a vacuum pressure, that is, a negative pressure. Further, the movement
distance of the movable plate 122 varies with the level of the expiratory
flow F, and the elastic force varies in proportion to the movement
distance, so that the pressure P formed in the air expansion unit
130 is proportional to the expiratory flow F and reflects the continuous
variations of the expiratory flow F, and the pressure spring 140
is fixedly connected to the air expansion unit 130 reacting to the
pressure spring 140 thus obtaining a pressure signal proportional
to the expiratory flow F.
[0026] Further, in the peak expiratory flow meter 100 the movable
plate 122 can safely move along the plurality of symmetrically arranged
rails 118. If the expiratory flow F flows from the first and second
expiratory flow entrances 114 and 154 the movable plate 122 is
moved, and the elastic plate 136 is pulled together as the pressure
spring 140 is pulled, so that the negative pressure proportional
to the expiratory flow F is formed. In the meantime, the negative
pressure is continuously measured by the pressure sensor 136 connected
to the outside of the flow meter 100 through the pressure transfer
tube 132 so that a flow signal can be continuously measured during
the forcible expiration of the patient.
[0027] Moreover, with respect to the present invention as described
above, the characteristics of pressure and expiratory flow were
calculated using the mechanism and method proposed in Korean Pat.
Appl. No. 2002-1151 filed by the present applicant.
[0028] FIG. 5 is a graph showing the characteristics of pressure
P and expiratory flow F obtained through stroke experiments carried
out six times. A mathematical formula between the pressure P and
the expiratory flow F can be almost exactly expressed in the form
of a quadratic function (correlation coefficient=0.99996). The reason
that the pressure P and the expiratory flow F are not simply proportional
to each other is due to the fact that the operation of a mechanism
using a frictional force and inertia is not ideal, so the formula
deviates from a theoretical proportional relationship. However,
if the solution of a quadratic equation is obtained after the pressure
P is measured, the expiratory flow F is obtained, and then it can
be seen that there is no practical problem. For example, the pressure
P is continuously measured to obtain the expiratory flow F (measured
flow: Fm), which is compared to a standard flow signal (standard
flow: Fs), which is actually applied, so that the comparison results
therebetween are shown in FIG. 6. In this case, it can be seen that
Fm and Fs are almost equal to each other, which experimentally proves
the usefulness of the peak expiratory flow meter 100 capable of
measuring continuous expiratory flow according to the present invention.
INDUSTRIAL APPLICABILITY
[0029] As described above, the peak expiratory flow meter 100 capable
of measuring continuous expiratory flow according to the present
invention is advantageous in that a movable plate 122 for moving
a scale indicator 160 is fitted on a plurality of rails 118 thus
enabling the scale indicator 160 to exactly move without being shaken.
[0030] Further, the present invention is advantageous in that,
since any one of a pressure sensor 136 and an electronic circuit
(not shown) is mounted to a first transfer tube 134a of a pressure
transfer tube 132 spirometry can be performed using a suitable
method, so that the peak expiratory flow meter 100 has excellent
flexibility and is manufactured at low cost, thus increasing a customer's
desire to purchase the peak expiratory flow meter 100.
[0031] Although the preferred embodiment of the present invention
has been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and substitutions
are possible, without departing from the scope and spirit of the
invention as disclosed in the accompanying claims. |