Patent Application
20050022815
This invention relates in general to devices for mounting upon a compressed oxygen cylinder or liquid oxygen reservoir for controlling the delivery of supplemental oxygen to an ambulatory patient and in particular to an apparatus and method for monitoring the operation of the device.
As the number of aged people in the population increases, there is an increasing number of people who require supplemental oxygen therapy. Many of these people are ambulatory and are capable of leaving the home and hospital. However, they require a portable source of supplemental oxygen in order to remain mobile. In the most basic supplemental oxygen system, compressed oxygen from a tank is supplied to the ambulatory patient through a pressure reducing regulator and a tube connected to a nasal cannula. The difficulty with the basic system is that the oxygen flow must be continuous. This results in an unnecessarily high oxygen consumption. Either the mobile time is severely limited or the patient must carry or push a heavy large capacity oxygen cylinder. The wasted oxygen also increases the expense of oxygen therapy.
Since the normal breathing pattern is to inhale about one-third of the time and to exhale and pause about two-thirds of the time, the constant flow gas delivery devices waste more than two-thirds of the oxygen since the oxygen is delivered to the patient during the exhalation and pause portion of the breathing cycle in addition to the inhalation portion of the cycle. In addition, it has been recognized that a patient's airway includes significant dead air space between the mouth and nose and the oxygen adsorbing portions of the lungs. Only oxygen in the portion of the respiratory gas which reaches the alveoli is absorbed. This oxygen is in the leading portion of the flow of respiratory gas when the patient initially begins to inhale. One recent trend in the design of portable respiratory oxygen management systems is a pulse-type flow controller which delivers a fixed volume or bolus of the respiratory gas only at the initiation of a patient's inhalation cycle. The gas savings permits smaller and lighter portable oxygen systems with increased operating time. An exemplary prior art oxygen flow controller is shown, for example, in U.S. Pat. No. 4,461,293.
The pulse-type gas flow controllers typically use a sensor to determine when the initial point of inhalation occurs. Upon sensing the initiation of inhalation, the device opens a valve to deliver a short, measured dose of oxygen at the leading edge of the inhalation cycle. Since all of this dose finds its way deep into the lungs, less oxygen is required to accomplish the same effect than with the more wasteful continuous flow delivery method. Therefore, with the pulsed delivery method, the respiratory gas supply is conserved while still providing the same therapeutic effect. Typically, an oxygen supply with a pulse flow controller will last two to four times longer than a similarly sized continuous flow oxygen supply. However, the actual oxygen usage will vary depending upon the particular user and the user's activity level. Since the oxygen usage directly affects the frequency of gas cylinder replacement, it would be desirable to monitor the actual usage of the gas supplied by system.
This invention relates to an apparatus and method for monitoring the operation of a device devices for controlling the delivery of supplemental oxygen to an ambulatory.
The present invention contemplates a device adapted to be connected to controller for a gas supply apparatus and at least one storage device connected to said gas usage monitor that is operable able to store said gas usage data. In the preferred embodiment, the device is a microprocessor and the storage device includes at least one electrically erasable programmable read-only memory chip. The device also includes a connector for downloading the stored data to an external device, such as a personal computer.
The present invention also contemplates a method for monitoring a gas supply apparatus comprising the steps of providing a gas usage monitor having at least one storage device. The usage monitor monitors and records gas usage in the storage device. The stored data is then periodically downloaded to an external device, such as a personal computer.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
Referring now to the drawings,
The components of the gas management device 10 are contained within a housing 16. As shown in
The housing 16 is preferably molded from a lightweight and durable material, such as a plastic. It is preferred that the material used for the housing 16 also have flame retardant characteristics since it may be exposed to high oxygen concentration gas. One suitable material which meets these criteria is an ABS such as Cycolac KJW manufactured by General Electric Company. ABS is the material of choice because of its flame retardancy and excellent impact properties. Additional details of a similar gas management device 10 are included in U.S. Pat. No. 5,755,224, which is incorporated herein by reference.
The microprocessor 32 has an output signal port 39 that is electrically connected to the gate of a Field Effect Transistor (FET) 40. The FET 40 is electrically connected between ground and one end of a solenoid coil 42 for the oxygen supply valve. The other end of the solenoid coil 42 is connected directly to the voltage supply 36. Upon receiving a signal from the pressure sensor 38 that the user is inhaling, the microprocessor 32 is operative to cause the FET 40 to apply a voltage to the FET gate. The voltage on the FET gate switches the FET 40 to a conducting state and thereby energizes the solenoid coil 42. Upon energization of the solenoid coil 42, the associated normally closed oxygen supply valve opens to supply pressurized oxygen to the user. When the user stops inhaling, the pressure transducer 38 reverts to its original state which, in turn, causes the microprocessor 32 to remove the voltage applied to the FET gate, returning the FET 40 to an non-conducting state. When the FET 40 returns to the non-conducting state, the solenoid coil 42 is de-energized, allowing the oxygen supply valve to return to a closed position and thereby cutting off the flow of pressurized oxygen to the user. Alternately, depending upon the position of the mode selection switch 23, the solenoid valve may be closed after the elapse of a predetermined time that corresponds to the selected dose flow rate.
As shown in
The control microprocessor 32 has a standby mode in which the microprocessor's oscillator is turned off to conserve battery life. If the microprocessor 32 does not receive an inhalation signal for a predetermined amount of time, the microprocessor 32 enters a “sleep” mode with most of its functions shut off. In the preferred embodiment, the time period is selected as one minute. However, upon receiving a signal from the pressure transducer 38 that the user has drawn a breath, the microprocessor 32 will awaken by restarting the oscillator and provide oxygen in accordance with the setting of the mode selection switch 23.
The control circuit 10 also includes a second data microprocessor 50 that is operative to collect operational data for the device 10. In the preferred embodiment, a PIC 18F627 available from Microchip Technology Inc. is used; however, other microprocessors also may be used. The data microprocessor 50 has a data output port 52 that is connected to the serial data acquisition port of each of a plurality of Electrically Erasable Programmable Read-Only Memory (EEPROM) chips 54 by a Serial Data Acquisition Line (SDA). The EEPROM chips 54 both read and write data. In the preferred embodiment, each of the EEPROM chips 54 are a 24LC256 chip, also available from Microchip Technology Inc.; however, other memory chips also may be used. While four EEPROM chips 54 are shown in
Both the data microprocessor 50 and the EEPROM chips 54 are electrically connected to the output of the voltage protection circuit 34. The data microprocessor 50 has a first data input port 56 that is connected to the gate of the FET 40. Additionally, a second data input port 58 of the data microprocessor 50 is connected to the cathode of the red LED 22B. During normal usage, the data microprocessor 50 receives device usage data at the first data input port 56. However, upon the battery voltage falling below the voltage threshold described above, the data microprocessor 50 will begin receiving device usage data at the second data input port 58. The change of data input ports functions as a low voltage/battery failure signal to the data microprocessor 50. The data microprocessor 50 is responsive to the low voltage/battery failure signal to stop operating and thereby conserve battery life. As will be described below, the data microprocessor 52 operates only during inhalation by the user to further conserve the batteries.
The data microprocessor 50 includes a pair of data output ports 60 and 62 that are connected to a data output interface 64. As shown in
The operation of the data monitoring portion of the device 10 will now be described. In the preferred embodiment, the data microprocessor 50 monitors the input ports 56 and 58 to count the number of breaths taken by the user during a predetermined time period. Again, for the preferred embodiment, the predetermined time period is one minute. Additionally, the duration of the last breath during the time period is measured and the breath duration is used as an average breath duration during the minute. At the end of the predetermined time period, two bytes, representing the number of breaths and breath duration, are serially written to one of the EEPROM chips 54, where the data is stored. The number of breaths and breath duration are coded into 1-8 bits in each byte. If the number of breaths is zero, the duration will also be zero. In this case only one byte would be needed for data; however, the use of one byte would make tracking of the records difficult. Accordingly, when there are no breaths, the microprocessor simply downloads a double zero for zero usage and then advances to the next data storage address. For the circuit 30 shown, it expected that the four EEPROM chips 54 can store 44.5 days of data.
Periodically, the stored data is downloaded into an external personal computer. As the data is downloaded, the EEPROM chips 54 are erased. Thus, upon completion of the data download, the usage monitoring can resume. In the preferred embodiment, the data is downloaded once per month. The personal computer has software for manipulating the downloaded data to produce a device activity and oxygen usage report. In the preferred embodiment, the report can provide hourly and/or daily usage data.
Similar to the control microprocessor 32, the data microprocessor 50 also has a standby mode in which the microprocessor's oscillator is turned off to reduce power use. An external event such as the valve drive line going high re-starts the oscillator and triggers an interrupt in the microprocessor 50 so that the microprocessor only has to be active while it is processing the signal. Another event that can wake the data microprocessor 50 from standby is an internal signal from a counter connected to a 32.768 khz crystal (not shown) that wakes the microprocessor every 4 seconds to keep track of the passage of real time. After every 15 counter events, one minute has elapsed and the accumulated breath and valve on time data is stored to the EEPROM chips 54. The breath and valve on time variables are then cleared for use in accumulating data during the next minute.
While the preferred embodiment has been described as counting the number of breaths each time period and measuring the last breath during each minute, it will be appreciated that the invention also may be practiced to accumulate other data. For example, the duration of each breath during the time period can be measured and the durations averaged. Alternately, the duration of each breath can be measured and then saved; however, the additional storage required to do so will decrease the total time between data downloads. Also, the number of breaths can be counted for a different time period, such as, for example, five or ten minute intervals. Additionally, the EEPROM chips 54 can be configured to construct multiple data tables. The EEPROM chips 54 would then record the number of breaths for each of the flow settings, pulsed or continuous flow mode, in one table and the number of minutes of use at each flow setting in the another table.
A flow chart for an algorithm for implementing the above operation is shown in
In the preferred embodiment, the monitoring device will operate until the memory is full, the batteries are depleted or the data is downloaded. Accordingly, in decision block 76, the algorithm determines whether the memory is full. If the memory is full, the algorithm transfers to functional block 78 where the monitoring device is de-activated pending a memory download and then exits through box 80. If the memory is not full, the algorithm transfers to decision block 82.
In decision block 82, the monitoring device determines whether the battery is low. If the battery is low, the algorithm transfers to functional block 78 where the monitoring device is de-activated pending a memory download and then exits through box 80. If the memory is not full, the algorithm transfers to decision block 84.
In decision block 84, the algorithm determines whether a download condition exists. In the preferred embodiment, the download condition is determined when an external connector is attached to the monitoring device for downloading the data. If, in decision block 84 it is determined that a download condition does not exist, the algorithm returns to functional block 74 and continues to monitor the gas usage. If, in decision block 84 it is determined that a download condition does exist, the algorithm advances to functional block 86.
In functional block 86, the stored data is downloaded into an external personal computer. The personal computer utilizes the data to generate a gas usage report. In the preferred embodiment an Excel™ Computer Program is used to generate the report. Upon completion of the data download, the algorithm continues to functional block 88 where the memory is erased. Alternately, the memory can be erased concurrently with the data download in functional block 86. The algorithm then advances to decision block 90.
In decision block 90, the organization desiring the data determines whether the monitoring is completed. If the monitoring is completed, the algorithm advances to block 92 where the monitoring device is retrieved and then exits trough block 80. If the monitoring is not completed, the algorithm returns to functional block 74 and continues to monitor gas usage.
In addition to the discontinuance of monitoring upon the memory being full or the battery voltage low, the invention also contemplates that the monitoring may be discontinued upon lapse of a predetermined time period. If this option is included, an additional decision block (not shown) would be included after decision block 82 in
While the preferred embodiment has been illustrated and described for delivery of oxygen, it will be appreciated that the invention also may be practiced for delivery of other gases. Also, while two microprocessors 32 and 50 were shown in
The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
This application claims the benefit of Provisional Patent Application Ser. No. 60/482,356 filed Jun. 25, 2003.
| Number | Date | Country | |
|---|---|---|---|
| 60482356 | Jun 2003 | US |
