Note: Descriptions are shown in the official language in which they were submitted.
WO 94113349 PCT/US93111935
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COMPhIANCE METER FOR RESPIRATORY THERAPY
Eackg~round of the Invention
t
1. Field of the Invention
The present invention relates to the field of
respiratory therapy. More particularly, the invention
concerns a respiratory apparatus operable for delivering
a breathable gas to the airway of a patient and includes
a status monitor for determining the status of usage of
the unit by the patient and a timer for determining the
accumulated time of usage of the unit by the patient.
2. Description of the Prior Art
In the treatment of obstructive sleep apnea, for
example, it has been found that the application of
pressurized ambient air to the nasal passages of a
patient provides a pneumatic splint that maintains the
patency of the airway. This type of respiratory therapy
can be implemented by a home therapy device having a
blower unit, a nasal mask, and a pneumatic hose intercon-
necting the two. When the patient is ready to retire for
the night, the mask is placed in position over the
patient's nose and the blower activated to deliver the
prescribed therapeutic pressure regimen to the patient's
airway. The prescribed therapy may include continuous
positive air pressure (CPAP), intermittent positive air
pressure (IPAP) , or a variety of other pressure regimens,
depending upon the needs of the patient.
As those skilled in the art appreciate, the effec-
tiveness of an apnea therapy device depends upon its
usage. In order to determine usage, some prior art
devices have incorporated a timer which indicates
accumulated operational time of the device. Such prior
art devices, however, do not determine whether the device
has actually been used by the patient. Even though the
therapy device has been turned on, the patient may not
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have used the device or the nasal mask may have become
dislodged during the sleep session.
Sutt~nary of the Invention
The present invention solves the prior art problems
discussed above and provides a distinct advance in the
state of the art. More particularly, the present
invention determines the accumulated time of the actual
usage of a respiratory apparatus.
Accordingly, the present invention provides a
respiratory apparatus comprising:
a gas delivery unit including coupling means for
coupling with the airway of a patient and delivery means
for delivering a breathable gas thereto during usage of
said unit by the patient; and
a compliance circuit in communication with said gas
delivery unit and that senses a parameter indicative of
the status of usage of said unit by the patient, said
compliance circuit including an adjustable pressure
SWltCh, a hose pneumatically interconnecting said
coupling means and said switch, timer means for measuring
an accumulated time of usage of said unit by the patient
and logic means generating logic signals responsive to
patient breathing cycles and for communication with said
adjustable pressure switch to activate and deactivate
said timer means.
The present invention also provides a respiratory
apparatus comprising:
a breathing gas supply;
a patient connector in fluid communication with said
breathing gas supply;
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a meter configured to accumulate time of usage of
gas supply by the patient; and
logic means for generating a signal indicative of
usage of said breathing gas supply by a patient said
logic means including first means for generating a logic
signal corresponding to patient exhalation and second
means responsive to said logic signal for activating and
de-activating said meter.
The present invention also provides a respiratory
apparatus comprising:
an ambient air blower:
a pneumatic hose in fluid communication with said
blower;
a nasal mask in fluid communication with said
pneumatic hose and said blower;
a pressure sensor for generating a signal indicative
of connection of said nasal mask to a patient;
a timer activated by said pressure sensor, said
timer being configured to accumulate an amount of time
said nasal mask is connected to the patient; and
logic means for generating logic signals responsive
to patient breathing cycles and for communicating with
said pressure sensor to activate and deactivate said
timer.
The present invention also provides a respiratory
apparatus comprising:
supply means for delivering breathable gas below a
selected pressure for at least a portion of a respiratory
cycle of a patient;
a patient connector in fluid communication with said
supply means, said patient connector including means for
coupling with a nasal passage of the patient;
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timer means including a selectively activatable,
accumulated time meter;
logic means for generating a signal indicative of
said patient connector being coupled to the nasal passage
of the patient, said signal responsive to patient
breathing cycles; and
means for activating and deactivating said timer
'means in response to the signal from said logic means.
In a further aspect, the present invention provides
a compliance meter for use with a respiratory apparatus
including a breathing gas supply and a patient connector
in fluid communication with the gas supply, the
compliance meter comprising:
a meter configured to accumulate time of usage;
first means for generating a logic signal
corresponding to exhalation of a patient through said
respiratory apparatus; and
second means responsive to the logic signal of said
first means for activating and de-activating said meter.
In a further aspect, the present invention provides
a compliance meter for use with a respiratory apparatus
including a blower, a nasal mask and pneumatic hose, the
compliance meter comprising:
a pressure switch for generating logic signals
responsive to patient breathing cycles;
a timer capable of being activated and de-activated
in response to the logic signals; and
wherein the pressure switch is in fluid communication with a
nasal mask of the respiratory apparatus, wherein said
pressure switch activates said timer when a prescribed
pressure is maintained at the nasal mask and wherein said
pressure switch deactivates said timer when the
prescribed pressure is not maintained at the nasal mask.
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In a still further aspect, the present invention
provides a method for measuring the compliance of a
patient using a respiratory apparatus, the method
comprising:
providing a breathing gas supply and a patient
connector in fluid communication with the breathing gas
supply;
generating a first and a second logic signal, said
first logic signal corresponding to patient exhalation
indicative of usage of the breathing gas supply by the
patient; and
said second logic signal corresponding to nonusage
of said gas supply by the patient;
activating a meter in response to said first logic
signal to accumulate time of usage of the breathing gas
supply by the patient; and
de-activating said meter in response to said second
logic signal.
The present invention also provides a method for
measuring the compliance of a patient using respiratory
apparatus, the method comprising:
delivering breathing gas under a selected pressure
for at least a portion of a respiratory cycle of a
patient;
providing a patient connector in fluid communication
with the breathing gas, the patient connector including
means for coupling with a nasal passage of the patient;
generating a logic signal indicative of the patient
connector being coupled to the nasal passage of the
patient, said signal responsive to patient breathing
cycles; and
activating and deactivating an accumulated time
meter in response to the logic signal.
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The present invention also provides a respiratory
apparatus comprising:
a gas delivery unit for providing gas flow, said gas
delivery unit including a blower motor having a
measurable current;
a patient connector in fluid communication with said
gas delivery unit, said patient connector configured to
provide gas flow to a patient;
a compliance circuit including a meter, said
compliance circuit responsive to at least one input
signal, said meter configured to accumulate time of usage
of said gas delivery unit; and
a current monitor coupled with said blower motor, said at
least one input signal varying with the current of said
blower motor, wherein the current provides an indication
of patient respiration through said patient connector.
Brief Description of the Drawings
Figure 1 is a schematic representation of the
preferred respiratory apparatus;
Fig. 2 is an electrical schematic diagram of the
compliance circuit of Fig. 1; and
Fig. 3 is an electrical schematic of a second
embodiment of the preferred compliance circuit.
Detailed Descri tion of the Preferred Embodiment
Referring initially to Fig. 1, preferred respiratory
apparatus 10 includes gas delivery unit 12, and
compliance circuit 14. Gas delivery unit 12 includes
pressure
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supply device 16 and patient connector 18: Pressure
supply device is preferably a conventional respiratory
therapy device operable for delivering ambient air at a
selected pressure such as the COMPANION 3I8~ nasal CPAP
system available from Puritan-Bennett of Lenexa, Kansas.
The preferred patient connector 18 is known as an ADAM
circuit also available from Puritan-Bennett and further
includes connection hose 20 and nasal mask 22.
Fig. 2 illustrates compliance circuit 14, which
includes adjustable pressure switch 24 (P/N MPL-500-P-G
40 available from Micro Pneumatic Logic Co.), hose 26
pneumatically interconnecting mask 22 and switch 24, and
timer circuit 28. Circuit 28 includes capacitor C1 (0.1
uF), voltage regulator 30 (type 7508), capacitor C2 (0:1
uF), capacitor C3 (10..0 uF), resistor R1 (500 Ohms),
light emitting diode (LED), and time meter 32 (P/N
T33BM733-DC from ENM Co.). .
In use, pressure switch 24 is adjusted to close at
a pressure level just below that of the CPAP pressure
prescribed for the patient. When device 16 is turned on
and mask 22 properly fitted, pressure at the prescribed
level is delivered to the patient and also delivered by
way of hose 26 to switch 24, which closes. In this way,
hose 26 and switch 24 present an effective means for
sensing the pressure at nasal mask 22, which is a
parameter indicative of the status of usage of unit 12 by
the patient. More particularly, pressure above the
pressure switch setting indicates that the patient is
using apparatus 10, and pressure below this setting
indicates the status of non-usage.
With switch 24 closed, power at 12 VDC (supplied by
device 16) is delivered to capacitor C~1 and to the input
of voltage regulator 30, which supplies a regulated
output at ~-5 VDC to capacitors C2, C3, resistor R1, and
meter 32. With this supply voltage, meter 32 is ac-
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WO 94/13349 PCTlUS93/11935
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tivated as is the LED by way of resistor R1. While
activated, meter 32 records accumulated time.
If mask 22 becomes dislodged or not properly seated
thereby presenting excessive leakage, the pressure inside
mask 22 drops substantially below the set point pressure. '
When this occurs, switch 24 opens to de-energize timer
circuit 28 and deactivate meter 32.
Fig. 3 illustrates circuit 34 which is a second
embodiment of the preferred compliance circuit. The
input to this circuit is provided at terminal 36 and is
preferably in form of logic signals such as a voltage at
+9 VDC during exhalation of a patient and at 1.0 VDC
during patient inhalation. Such an input can be pro-
vided, for example, by a conventional flow transducer
placed in connection hose 20 with appropriate interface
circuitry to provide the desired logic signals corre-
sponding to patient exhalation and inhalation. With such
an arrangement, air flow through hose 20 provides an
indication of whether the patient is respirating, at
least in part, through hose 20. The desired input
signals could also be provided through other means
responsive to patient respiration such as a pressure
transducer in mask 22, a current monitor coupled with the
blower motor of device 16, a heat sensor in the mask, or
a position sensor coupled with a control valve that might
be used to control the pressure delivered to the patient.
Circuit 34 includes network 38 composed of resistors
R2 (1K), R3 (iM), diode D2 (type 4148) and capacitor C4,
inverter network 40, inverter network 42, ffield effect
transistor T1 and meter 32. Networks 40 and 42 include
operational amplifiers Al and A2 respectively intercon-
nected with various resistors as shown in Fig. 3 so that
these respective networks function as simple inverters.
In the operation of circuit 34, a logic high input
at +9 VDC at terminal 36 corresponds to patient ex
halation. This input rapidly charges capacitor C4
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through resistor R2 and diode D2. Amplifier A1 inverts
this signal to a logic low input to amplifier A2 which
again inverts to provide a logic high output to the gate
of transistor T1, which turns on and thereby activates
meter 32.
When the input at terminal 36 goes low (+1 VDC)
during patient inhalation, capacitor C4 discharges slowly
through resistor R3. More particularly, the time
constant of resistor R3 and capacitor C4 is about 10
seconds which maintains the logic high input to amplifier
A1 during normal patient inhalation (lasting less than 10
seconds). The next patient exhalation results in rechar-
ging of capacitor C4. In this way, the operation of
meter 32 is maintained during the entire respiratory
cycle of the patient and thereby accurately accumulates
the usage time of apparatus 10 by the patient.
If the patient removes mask 22, or excessive leaks
develop, a subsequent exhalation signal is not provided
at terminal 36 to recharge capacitor C4. After 10
seconds, the input voltage to amplifier A1 is suf-
ficiently low so that a logic high output is provided to
amplifier A2 which in turn provides a logic low output to
the gate of transistor T1 which turns off and de-ener-
gizes meter 32.
As those skilled in the art will appreciate, the
present invention encompasses many variations in the
preferred embodiments described herein. For example, the
invention finds utility in the context of CPAP, IPAP, and
other pressure regimens. Additionally, a wide variety of
inputs can be provided indicative of patient usage of the
therapeutic apparatus so that the actual time of usage
can be determined. Having thus described the preferred
embodiments of the present invention, the following is
claimed as new and desired to be secured by Letters
Patent:
