CA1108505A - Method and apparatus for weaning patient from continuous mechanical ventilation - Google Patents
Method and apparatus for weaning patient from continuous mechanical ventilationInfo
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- CA1108505A CA1108505A CA295,689A CA295689A CA1108505A CA 1108505 A CA1108505 A CA 1108505A CA 295689 A CA295689 A CA 295689A CA 1108505 A CA1108505 A CA 1108505A
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Abstract
ABSTRACT OF THE DISCLOSURE
A continuous mechanical ventilator system includes a ventilator known in the art with a pneumatic circuit connec-table to the patient and operating in the normal manner. A bag and bag valve are interposed within the pneumatic connection such that when the valve is closed, the patient is on full as-sisted breathing from the ventilator. When the bag valve is opened, gas from the ventilator passes into the bag from which it may be drawn freely by the patient in an unassisted manner.
Electronic controls provide means for varying the proportion of breaths to be assisted by the ventilator to the breaths from the bag which, of course are unassisted. The exhalation valve normally provided, is normally operatively connected to the ventilator in the usual way, when the device is in the assisted mode. However, during the unassisted mode, the exhalation valve is isolated from the rest of the circuit so that no pressure pulses can be fed to the exhalation valve during this time. By utilizing the bag and bag valve, both assisted and unassisted breaths consist of gas from the ventilator with the same amount of humidity and oxygen components.
A continuous mechanical ventilator system includes a ventilator known in the art with a pneumatic circuit connec-table to the patient and operating in the normal manner. A bag and bag valve are interposed within the pneumatic connection such that when the valve is closed, the patient is on full as-sisted breathing from the ventilator. When the bag valve is opened, gas from the ventilator passes into the bag from which it may be drawn freely by the patient in an unassisted manner.
Electronic controls provide means for varying the proportion of breaths to be assisted by the ventilator to the breaths from the bag which, of course are unassisted. The exhalation valve normally provided, is normally operatively connected to the ventilator in the usual way, when the device is in the assisted mode. However, during the unassisted mode, the exhalation valve is isolated from the rest of the circuit so that no pressure pulses can be fed to the exhalation valve during this time. By utilizing the bag and bag valve, both assisted and unassisted breaths consist of gas from the ventilator with the same amount of humidity and oxygen components.
Description
BACXGROUND OF THE INVENTION
This inventionlrelates to new and useful improvements ' in methods and apparatus for weaning patients from continuous mechanical ventilators.
There are two methods to wean a patient with ventila-tory failure away from continuous mechanical ventilation. The oldest method involves simply taking the patient off the venti-lator for increasing periods. While off the ventilator, oxygen ;, ~
... ~ .. , . . , . _ 11~85~5 and humidity to the patient is provided by a heated nebulizer requiring a second ventilator circuit and equipment.
A newer method called intermittent mandatory ventila-tion (IMV) essentially combines the action of both circuits and while allowing the patient to breathe at his own rate and depth, occasionally at a preset rate superimposes large mandatory breaths from the ventilator. I.M.V. is useful in patients with airways obstruction or neurological problems but requires com-plex tubing connections, there is assynchrony between patient and ventilator and there is difficulty in monitoring rate and volume of each breath. A variation of this method of weaning is synchronized I.M.V. (S.I.M.V.) whereby the mandatory large breath is synchronized to the patient's inspiratory effort.
An ideal method of weaning should allow synchrony between the patterns of breathing of the patient and ventilator, it should use the ventilator to provide oxygen and humidity for both the assisted and unassisted breaths, and it should allow monitoring of the breathing pattern that results.
SUMMARY OF THE INVENTION
-The system we have devised uses a bag and valve and an electronic and pneumatic controller connected to the conven-tional ventilator to provide for a variable proportion of breaths to be assisted (controlled) by the ventilator while the rest are due solely to patient effort. The system described herein is an improved method fo S.I.M.V.
In accordance with the invention there is provided in a conventional ventilator which supplies assisted or unassisted ~ 8535 breaths to a patient including a pneumatic connection extend-ing from said ventilator, an exhalation valve operatively con-nected to said pneumatic connection, patient connection means extending from said exhalation valve, an exhalation valve con-trol line operatively connected between the ventilator and theexhalation valve and means operatively connected to said exha-lation valve to monitor exhaled breaths; the improvement com-prising an attachment, said attachment comprising means to pro-vide assisted breaths from the ventilator when in an "assisted"
mode, means to by-pass breaths from said ventilator when in an "unassisted" mode and means operatively connected to the means to monitor the exhaled breaths whereby the ratio of "assisted"
and "unassisted" breaths may be varied within limits, said means to provide "unassisted" breaths including a low resistance bag valve in said pneumatic connection, a bag connected to the bag valve, a one-way valve operatively connected between said bag and said exhalation valve providing one-way flow from said bag to said exhalation valve, the operation of said ventilator in-cluding means to open and close said bag valve whereby breaths from said ventilator are conveyed directly to said patient con-nection means when said bag valve is closed and said ventilator is in the "assisted" mode, and to the bag and thence to said patient connection means as required, when said bag valve is open and said ventilator is in the "unassisted" mode, said means operatively connected to said means to monitor the exhaled breaths whereby the ratio of "assisted" and "unassisted" breaths may be varied within limits, including a pressure sensor in said exhalation valve control line, a signal generator opera-tively connected to said pressure sensor and operated thereby each time the exhalation pressure within said control line exceeds a predetermined pressure, assisted breath counter means, and unassisted breath counter means, means operatively connecting said signal generator to said assisted breath counter means when in the "assisted" mode and to said unassisted breath counter means when in the "unassisted" mode, means to vary the ratio of connection of said signal generator to said assisted and un-assisted counter means, a bag valve solenoid operatively connect-ed to said bag valve and means to operate said bag valve sole-noid operatively extending from said unassisted breath counter means to said solenoid.
Another aspect of the invention is to provide a de-vice in which the gas or air utilized by the patient, may con-tain the same components whether the device is in the assisted or unassisted mode.
Another aspect of the invention is to provide a de-vice of the character herewithin described in which the ratio of assisted breaths to unassisted breaths may be varied within limits.
A still further aspect of the invention is to provide a device of the character herewithin described which is relative-ly simple in construction, economical in manufacture, easy to attach to any ventilator, and otherwise well suited to the pur-pose for which it is designed.
!
With the foregoing in view and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, our invention ~s consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:
DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of the bag and valve portion of the pneumatic circuit.
Figure 2 is an overall schematic diagram of a ventila-tor as normally used.
Figure 3 is an overall schematic diagram for a ven-tilator with the weaner circuitry added thereto.
Figure 4 is a schematic diagram of the pneumatic cir-cuit.
Figure 5 is a block diagram of the weaner circuitry.
Figure 6 is a circuit diagram of the power supply.
Figure 7 is a logic timing diagram.
Figure 8 is a circuit diagram of the counter portion.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
Proceeding therefore to describe the invention in de-tail, reference should be made to the drawings in which the pneumatic circuit consists, in this embodiment of a 3 litre bag 10 into which a ventilator 11, may deliver gas unrestricted and freely when the patient's breath is to be spontaneous or unassisted. The bag can be closed off with a lower resistance powered valve 12 when the patient is to receive an assisted breath from the ventilator 11. These two modes are called "unassisted" (or spontaneous) when the valve 12 is open and "assisted" when the valve 12 is closed. A one-way valve 13 downstream from the bag prevents exhaled gas from going into the bag.
A control box 43,that the ventilator senses or con-trols, counts each breath. Switches 37 and 38 allow the ratio of "assisted" to "unassisted" breaths to be varied from 9/1 to 1/40 in a preferred embodiment. The patient may thus receive, although other ratios may be chosen, 90% of his ventilation under power from the ventilator or at the end of his weaning, may receive only one breath in forty. (Not all ratios from 9/1 to 1/40 are required however.) The control box contains 20 solenoid valves 41 and 40 which control the bag valve 12 and the exhalation valve 17 attached to the ventilator 11 respec-tively.
Ventilation is actually sensed by the ventilator 11 which may be any assist-type or triggered ventilator. It is important that even small inspiratory efforts are sensed, thus the sense tube 14 in the pneumatic circuit should be connected close to the patient. When the ventilator trips "on", the be-ginning of the development of pressure in the exhalation line 38~
18A is sensed by a pressure sensor 18 which drives switch 26 in the control box and depending on the state of the counter, the breath is controlled to be either assisted or spontaneous (unassisted).
The patient receives exactly the same oxygen concen-tration during unassisted or assisted breaths. Humidity is provided by the heated bypass humidifier 16 of the ventilator.
All the gas leaving through the exhalation valve 17 is normally exhaled volume and therefor can be monitored easily. In case of a failure in either the ventilator or the weaner system, an external monitor 44 will produce an alarm.
The powered bag valve 12 should be in the closed position normally and should open under power. Failure of the control box would produce the fail-safe result of the patient's going back on assisted ventilation.
Provision is made for the weaner to function whether or not the ventilator is set to provide a positive end expira-tory pressure (PEEP) feature.
The overall schematics are shown in Figure 2 for a ventilator as normally used, and in Figure 3 with our weaner circuitry added.
CIRCUIT DESCRIPTIONS
1. Pneumatic Circuit (see Figure 4) -A pressure sensor 18 generates logic signals corres-ponding to patient inspiration and expiration. It will sense positive pressure on the exhalation line 18A from the ventilator 11. The trip point, nominally of the order of 20 cm H20, was chosen so that the ventilator 11 can operate with positive end expiration pressure (PEEP), if required, during the "ventilation"
or "assisted" mode. (Nominal values of PEEP are usually less than 15 cm H20, so exhalation control pressure is chosen to be greater in order to achieve positive shutoff). Solenoid valve 40 isolates the exhalation valve 17 from any pressure from the ventilator 11 and connects it to atmosphere or to a PEEP pres-sure. During the "assisted" mode this solenoid 40 is energizedand the exhalation valve 17 operates normally. During the "unassisted" mode the exhalation valve 17 is isolated from the rest of the circuit. This was done so that no pressure can re-main on the exhalation valve control line 18B during "unassisted"
time. (The sources of pressure are positive end expiration pressure if selected, and exhalation drive pressure.) The bag valve 12 should be of the normally closed type in order to be fail safe. During "assisted" time this valve offers a resistance of ~ 0.5 cm H20/L/S in the line 15 from the ventilator to the patient. During "unassisted" time this valve offers a resistance of <0.5 cm H20/L/S between the bag lO and the patient.
The bag 10 is relatively flaccid and is formed from a flexible material such as rubber, synthetic plastic or the like. The one-way valve 13 acts as a resistance to flow to the patient so that when the bag valve i2 is open, gas from the ventilator 11 normally passes to the bag 10, and the patient draws air from the bag during the "unassisted" time or mode.
8~.5 When the bag valve 12 is closed, the patient receives air from the ventilator during this "assisted" time or mode. It will be noted in both the "assisted" and "unassisted" modes, the gas or air is the same with the same humidity and oxygen content inasmuch as it is derived from the ventilator in both cases.
This inventionlrelates to new and useful improvements ' in methods and apparatus for weaning patients from continuous mechanical ventilators.
There are two methods to wean a patient with ventila-tory failure away from continuous mechanical ventilation. The oldest method involves simply taking the patient off the venti-lator for increasing periods. While off the ventilator, oxygen ;, ~
... ~ .. , . . , . _ 11~85~5 and humidity to the patient is provided by a heated nebulizer requiring a second ventilator circuit and equipment.
A newer method called intermittent mandatory ventila-tion (IMV) essentially combines the action of both circuits and while allowing the patient to breathe at his own rate and depth, occasionally at a preset rate superimposes large mandatory breaths from the ventilator. I.M.V. is useful in patients with airways obstruction or neurological problems but requires com-plex tubing connections, there is assynchrony between patient and ventilator and there is difficulty in monitoring rate and volume of each breath. A variation of this method of weaning is synchronized I.M.V. (S.I.M.V.) whereby the mandatory large breath is synchronized to the patient's inspiratory effort.
An ideal method of weaning should allow synchrony between the patterns of breathing of the patient and ventilator, it should use the ventilator to provide oxygen and humidity for both the assisted and unassisted breaths, and it should allow monitoring of the breathing pattern that results.
SUMMARY OF THE INVENTION
-The system we have devised uses a bag and valve and an electronic and pneumatic controller connected to the conven-tional ventilator to provide for a variable proportion of breaths to be assisted (controlled) by the ventilator while the rest are due solely to patient effort. The system described herein is an improved method fo S.I.M.V.
In accordance with the invention there is provided in a conventional ventilator which supplies assisted or unassisted ~ 8535 breaths to a patient including a pneumatic connection extend-ing from said ventilator, an exhalation valve operatively con-nected to said pneumatic connection, patient connection means extending from said exhalation valve, an exhalation valve con-trol line operatively connected between the ventilator and theexhalation valve and means operatively connected to said exha-lation valve to monitor exhaled breaths; the improvement com-prising an attachment, said attachment comprising means to pro-vide assisted breaths from the ventilator when in an "assisted"
mode, means to by-pass breaths from said ventilator when in an "unassisted" mode and means operatively connected to the means to monitor the exhaled breaths whereby the ratio of "assisted"
and "unassisted" breaths may be varied within limits, said means to provide "unassisted" breaths including a low resistance bag valve in said pneumatic connection, a bag connected to the bag valve, a one-way valve operatively connected between said bag and said exhalation valve providing one-way flow from said bag to said exhalation valve, the operation of said ventilator in-cluding means to open and close said bag valve whereby breaths from said ventilator are conveyed directly to said patient con-nection means when said bag valve is closed and said ventilator is in the "assisted" mode, and to the bag and thence to said patient connection means as required, when said bag valve is open and said ventilator is in the "unassisted" mode, said means operatively connected to said means to monitor the exhaled breaths whereby the ratio of "assisted" and "unassisted" breaths may be varied within limits, including a pressure sensor in said exhalation valve control line, a signal generator opera-tively connected to said pressure sensor and operated thereby each time the exhalation pressure within said control line exceeds a predetermined pressure, assisted breath counter means, and unassisted breath counter means, means operatively connecting said signal generator to said assisted breath counter means when in the "assisted" mode and to said unassisted breath counter means when in the "unassisted" mode, means to vary the ratio of connection of said signal generator to said assisted and un-assisted counter means, a bag valve solenoid operatively connect-ed to said bag valve and means to operate said bag valve sole-noid operatively extending from said unassisted breath counter means to said solenoid.
Another aspect of the invention is to provide a de-vice in which the gas or air utilized by the patient, may con-tain the same components whether the device is in the assisted or unassisted mode.
Another aspect of the invention is to provide a de-vice of the character herewithin described in which the ratio of assisted breaths to unassisted breaths may be varied within limits.
A still further aspect of the invention is to provide a device of the character herewithin described which is relative-ly simple in construction, economical in manufacture, easy to attach to any ventilator, and otherwise well suited to the pur-pose for which it is designed.
!
With the foregoing in view and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, our invention ~s consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:
DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of the bag and valve portion of the pneumatic circuit.
Figure 2 is an overall schematic diagram of a ventila-tor as normally used.
Figure 3 is an overall schematic diagram for a ven-tilator with the weaner circuitry added thereto.
Figure 4 is a schematic diagram of the pneumatic cir-cuit.
Figure 5 is a block diagram of the weaner circuitry.
Figure 6 is a circuit diagram of the power supply.
Figure 7 is a logic timing diagram.
Figure 8 is a circuit diagram of the counter portion.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
Proceeding therefore to describe the invention in de-tail, reference should be made to the drawings in which the pneumatic circuit consists, in this embodiment of a 3 litre bag 10 into which a ventilator 11, may deliver gas unrestricted and freely when the patient's breath is to be spontaneous or unassisted. The bag can be closed off with a lower resistance powered valve 12 when the patient is to receive an assisted breath from the ventilator 11. These two modes are called "unassisted" (or spontaneous) when the valve 12 is open and "assisted" when the valve 12 is closed. A one-way valve 13 downstream from the bag prevents exhaled gas from going into the bag.
A control box 43,that the ventilator senses or con-trols, counts each breath. Switches 37 and 38 allow the ratio of "assisted" to "unassisted" breaths to be varied from 9/1 to 1/40 in a preferred embodiment. The patient may thus receive, although other ratios may be chosen, 90% of his ventilation under power from the ventilator or at the end of his weaning, may receive only one breath in forty. (Not all ratios from 9/1 to 1/40 are required however.) The control box contains 20 solenoid valves 41 and 40 which control the bag valve 12 and the exhalation valve 17 attached to the ventilator 11 respec-tively.
Ventilation is actually sensed by the ventilator 11 which may be any assist-type or triggered ventilator. It is important that even small inspiratory efforts are sensed, thus the sense tube 14 in the pneumatic circuit should be connected close to the patient. When the ventilator trips "on", the be-ginning of the development of pressure in the exhalation line 38~
18A is sensed by a pressure sensor 18 which drives switch 26 in the control box and depending on the state of the counter, the breath is controlled to be either assisted or spontaneous (unassisted).
The patient receives exactly the same oxygen concen-tration during unassisted or assisted breaths. Humidity is provided by the heated bypass humidifier 16 of the ventilator.
All the gas leaving through the exhalation valve 17 is normally exhaled volume and therefor can be monitored easily. In case of a failure in either the ventilator or the weaner system, an external monitor 44 will produce an alarm.
The powered bag valve 12 should be in the closed position normally and should open under power. Failure of the control box would produce the fail-safe result of the patient's going back on assisted ventilation.
Provision is made for the weaner to function whether or not the ventilator is set to provide a positive end expira-tory pressure (PEEP) feature.
The overall schematics are shown in Figure 2 for a ventilator as normally used, and in Figure 3 with our weaner circuitry added.
CIRCUIT DESCRIPTIONS
1. Pneumatic Circuit (see Figure 4) -A pressure sensor 18 generates logic signals corres-ponding to patient inspiration and expiration. It will sense positive pressure on the exhalation line 18A from the ventilator 11. The trip point, nominally of the order of 20 cm H20, was chosen so that the ventilator 11 can operate with positive end expiration pressure (PEEP), if required, during the "ventilation"
or "assisted" mode. (Nominal values of PEEP are usually less than 15 cm H20, so exhalation control pressure is chosen to be greater in order to achieve positive shutoff). Solenoid valve 40 isolates the exhalation valve 17 from any pressure from the ventilator 11 and connects it to atmosphere or to a PEEP pres-sure. During the "assisted" mode this solenoid 40 is energizedand the exhalation valve 17 operates normally. During the "unassisted" mode the exhalation valve 17 is isolated from the rest of the circuit. This was done so that no pressure can re-main on the exhalation valve control line 18B during "unassisted"
time. (The sources of pressure are positive end expiration pressure if selected, and exhalation drive pressure.) The bag valve 12 should be of the normally closed type in order to be fail safe. During "assisted" time this valve offers a resistance of ~ 0.5 cm H20/L/S in the line 15 from the ventilator to the patient. During "unassisted" time this valve offers a resistance of <0.5 cm H20/L/S between the bag lO and the patient.
The bag 10 is relatively flaccid and is formed from a flexible material such as rubber, synthetic plastic or the like. The one-way valve 13 acts as a resistance to flow to the patient so that when the bag valve i2 is open, gas from the ventilator 11 normally passes to the bag 10, and the patient draws air from the bag during the "unassisted" time or mode.
8~.5 When the bag valve 12 is closed, the patient receives air from the ventilator during this "assisted" time or mode. It will be noted in both the "assisted" and "unassisted" modes, the gas or air is the same with the same humidity and oxygen content inasmuch as it is derived from the ventilator in both cases.
2. Weaner Block Diagram (see Figure 5 and 7) -The pressure sensor 18 and logic generates a logic signal 33 every time the ventilator exhalation drive line pres-sure exceeds 20 cm H20, as an example i.e. for each vent or spont breath. All breaths are counted when they end.
After switch 28 is reset which starts the cycle, the vent counter is enabled. The spont counter is not enabled.
The system is put in the vent mode by the action of solenoid drives 30 and 31. Vent breaths occur until the number equals that selected by the vent counter. The end of the last vent breath enables the spont counter. The vent counter is now not enabled. The system is put in the spont mode by the action of solenoid drives 30 and 31. Spont breaths occur until the num-ber equals that selected by the spont counter. The end of the last spont breath creates a reset enable. At the initiation of the following breath, a reset is generated. The cycle now starts again.
The logic blocks 21 and 22 are composed of the switches, gates, and associated circuit components which are connected with the counters 19 and 20 to form an electronic logic circuit as discussed in detail below.
After switch 28 is reset which starts the cycle, the vent counter is enabled. The spont counter is not enabled.
The system is put in the vent mode by the action of solenoid drives 30 and 31. Vent breaths occur until the number equals that selected by the vent counter. The end of the last vent breath enables the spont counter. The vent counter is now not enabled. The system is put in the spont mode by the action of solenoid drives 30 and 31. Spont breaths occur until the num-ber equals that selected by the spont counter. The end of the last spont breath creates a reset enable. At the initiation of the following breath, a reset is generated. The cycle now starts again.
The logic blocks 21 and 22 are composed of the switches, gates, and associated circuit components which are connected with the counters 19 and 20 to form an electronic logic circuit as discussed in detail below.
3. Circuit Diagram (see Figure 8 & Power Supply Diagram Figure 6) In a preferred embodiment, all of the circuitry is solid state with CMOS circuits used for the logic. The sole-noid valves 40 and 41 are run from 110V A.C. supplied from an isolation transformer 23. The regulated supply comprising +15 V Zener diode 23A and associated components for the logic is also derived from this transformer. Equivalent controls of other types are within the scope of this invention. The sole-noids 40 and 41 are activated by triacs 24 and 25, respectively, which are controlled by 15 volt logic signals 31 and 32 from the control logic (Figure 8).
The pressure sensor 18 may be a diaphragm which moves under pressure to activate a micro switch 26. This switch (single pole double throw) is buffered with a flip-flop 42 to produce no-bounce logic signals. Both outputs Q and Q of the flip-flop are used in the logic. Because breaths(l) are count-ed just as they end, and the reset pulse is generated at the be-ginning of a breath, the start of a cycle is sometimes during a breath. After the start of a cycle when that breath is fin-ished, the positive going output of the flip-flop is differen-tiated 34 by resistor-diode-capacitor combination 30 and applied to the clock input of both counters 19 and 20, which are made up of 4017 decade counters (2).
The vent counter 19 is enabled and will count breaths until the selected output goes high (see Figure 7). During this time solenoid 40 is continuously energized and solenoid 41 is energized 32 when the ventilator is delivering air. On the S
switch 37, which selects the number of assisted breaths there are two additional positions. One is "vent" which holds the weaner in the "assisted" mode, the other is "wean" which holds it in the "spont" mode. When the selected output of the "vent"
5 counter goes high it will disable itself. The inverse of this signal is used to enable the "spont" counter 20. There is an R.C. delay 29 in the enable circuit to the "spont" counter 20 so that it doesn't count the last assisted breath. The follow-ing breaths will now be counted on the "spont" counter. Dur-10 ing this time solenoids 40 and 41 are not activated. When theselected output of the "spont" counter 20 goes high NAND 1 (27) is enabled. This happens at the end of the last unassisted breath. At the beginning of the next breath, when the Q output of the flip-flop 42 goes positive, it is differentiated through 15 network 45 and gated through NAND 1 (27) and through NAND 2 (28) and resets both counters to zero. This will start the whole cycle over again.
Also included in the logic are switch decks 35 and 36, one on each of the "spont" (38) and "vent" (37) counter switches.
20 Whenever either switch 37 or 39 is changed these additional decks 35 and 36 will produce a reset pulse. This prevents the weaner from going through an illogical sequence. For example, without this feature: if the "spont" counter switch 38 were set on "3" breaths and the spont counter 20 counted to "2", chang-25 ing counter switch 20 to "1", passing through "2", would not re-sult in a reset because the end of a breath must occur to gen-erate the reset logic. The spont counter would then have to count through its whole sequence resulting in far too many un-assisted breaths having to be generated by the patient.
~8.5Q5 LED (light emitting diodes) indicators 39 and 39A
are included to indicate to the operator what state the weaner is in. The appropriate LED lights when the ventilator 11 is delivering air. To indicate if the breath is "assisted" or "unassisted".
47 is a box or container within which the bag may operate. The purpose of this box or container is to provide a positive pressure around the bag so that there is no resistance in breathing from the bag when there is positive end expiratory pressure (PEEP) in the breathing circuit.
Pressure in the box is maintained at the same level as the end expiratory pressure by means of a pressure line 48 which connects the box 47 to the line from the ventilator to the patient, immediately downstream from the one-way valve 13.
The breath counter idea herein described is not the only way in which the breathing bag concept can be utilized.
It is also appropriate for use with the "time window" and re-lated approaches (as typified by mechanizations in the Bennett MA-l and Monaghan 225 ventilators).
(1) To avoid confusion as to whether a patient in-spires or the ventilator expires, we speak of the ventilator delivering air or just breaths. Note that the term "unassisted breath" is used interchangeably with "spontaneous breath" or SPONT. Equally "assisted breath" is equivalent to "ventilated breath" or VENT.
(2) The diagram shows nine switch positions since ~85t~i it was felt that more than nine would be too cluttered for simple operation. Additional steps can, of course, be added, as may be useful for a given application. The value of each step is taken from the appropriate output of the counters 19 and 20.
(3) The term "solenoid" is used here as a short form of "solenoid powered pneumatic valve".
Since various modifications can be made in our in-vention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying speci-fication shall be interpreted as illustrative only and not in a limiting sense.
The pressure sensor 18 may be a diaphragm which moves under pressure to activate a micro switch 26. This switch (single pole double throw) is buffered with a flip-flop 42 to produce no-bounce logic signals. Both outputs Q and Q of the flip-flop are used in the logic. Because breaths(l) are count-ed just as they end, and the reset pulse is generated at the be-ginning of a breath, the start of a cycle is sometimes during a breath. After the start of a cycle when that breath is fin-ished, the positive going output of the flip-flop is differen-tiated 34 by resistor-diode-capacitor combination 30 and applied to the clock input of both counters 19 and 20, which are made up of 4017 decade counters (2).
The vent counter 19 is enabled and will count breaths until the selected output goes high (see Figure 7). During this time solenoid 40 is continuously energized and solenoid 41 is energized 32 when the ventilator is delivering air. On the S
switch 37, which selects the number of assisted breaths there are two additional positions. One is "vent" which holds the weaner in the "assisted" mode, the other is "wean" which holds it in the "spont" mode. When the selected output of the "vent"
5 counter goes high it will disable itself. The inverse of this signal is used to enable the "spont" counter 20. There is an R.C. delay 29 in the enable circuit to the "spont" counter 20 so that it doesn't count the last assisted breath. The follow-ing breaths will now be counted on the "spont" counter. Dur-10 ing this time solenoids 40 and 41 are not activated. When theselected output of the "spont" counter 20 goes high NAND 1 (27) is enabled. This happens at the end of the last unassisted breath. At the beginning of the next breath, when the Q output of the flip-flop 42 goes positive, it is differentiated through 15 network 45 and gated through NAND 1 (27) and through NAND 2 (28) and resets both counters to zero. This will start the whole cycle over again.
Also included in the logic are switch decks 35 and 36, one on each of the "spont" (38) and "vent" (37) counter switches.
20 Whenever either switch 37 or 39 is changed these additional decks 35 and 36 will produce a reset pulse. This prevents the weaner from going through an illogical sequence. For example, without this feature: if the "spont" counter switch 38 were set on "3" breaths and the spont counter 20 counted to "2", chang-25 ing counter switch 20 to "1", passing through "2", would not re-sult in a reset because the end of a breath must occur to gen-erate the reset logic. The spont counter would then have to count through its whole sequence resulting in far too many un-assisted breaths having to be generated by the patient.
~8.5Q5 LED (light emitting diodes) indicators 39 and 39A
are included to indicate to the operator what state the weaner is in. The appropriate LED lights when the ventilator 11 is delivering air. To indicate if the breath is "assisted" or "unassisted".
47 is a box or container within which the bag may operate. The purpose of this box or container is to provide a positive pressure around the bag so that there is no resistance in breathing from the bag when there is positive end expiratory pressure (PEEP) in the breathing circuit.
Pressure in the box is maintained at the same level as the end expiratory pressure by means of a pressure line 48 which connects the box 47 to the line from the ventilator to the patient, immediately downstream from the one-way valve 13.
The breath counter idea herein described is not the only way in which the breathing bag concept can be utilized.
It is also appropriate for use with the "time window" and re-lated approaches (as typified by mechanizations in the Bennett MA-l and Monaghan 225 ventilators).
(1) To avoid confusion as to whether a patient in-spires or the ventilator expires, we speak of the ventilator delivering air or just breaths. Note that the term "unassisted breath" is used interchangeably with "spontaneous breath" or SPONT. Equally "assisted breath" is equivalent to "ventilated breath" or VENT.
(2) The diagram shows nine switch positions since ~85t~i it was felt that more than nine would be too cluttered for simple operation. Additional steps can, of course, be added, as may be useful for a given application. The value of each step is taken from the appropriate output of the counters 19 and 20.
(3) The term "solenoid" is used here as a short form of "solenoid powered pneumatic valve".
Since various modifications can be made in our in-vention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying speci-fication shall be interpreted as illustrative only and not in a limiting sense.
Claims
WHAT WE CLAIM AS OUR INVENTION IS:
(1) In a conventional ventilator which supplies assisted or unassisted breaths to a patient including a pneu-matic connection extending from said ventilator, an exhalation valve operatively connected to said pneumatic connection, patient connection means extending from said exhalation valve, an exha-lation valve control line operatively connected between the ventilator and the exhalation valve and means operatively con-nected to said exhalation valve to monitor exhaled breaths;
the improvement comprising an attachment, said attachment com-prising means to provide assisted breaths from the ventilator when in an "assisted" mode, means to by-pass breaths from said ventilator when in an "unassisted" mode and means operatively connected to the means to monitor the exhaled breaths whereby the ratio of "assisted" and "unassisted" breaths may be varied within limits, said means to provide "unassisted" breaths in-cluding a low resistance bag valve in said pneumatic connection, a bag connected to the bag valve, a one-way valve operatively connected between said bag and said exhalation valve providing one-way flow from said bag to said exhalation valve, the oper-ation of said ventilator including means to open and close said bag valve whereby breaths from said ventilator are conveyed directly to said patient connection means when said bag valve is closed and said ventilator is in the "assisted" mode, and to the bag and thence to said patient connection means as re-quired, when said bag valve is open and said ventilator is in the "unassisted" mode, said means operatively connected to said means to monitor the exhaled breaths whereby the ratio of "assisted" and "unassisted" breaths may be varied within limits, including a pressure sensor in said exhalation valve control line, a signal generator operatively connected to said pressure sensor and operated thereby each time the exhalation pressure within said control line exceeds a predetermined pressure, as-sisted breath counter means, and unassisted breath counter means, means operatively connecting said signal generator to said as-sisted breath counter means when in the "assisted" mode and to said unassisted breath counter means when in the "unassisted"
mode, means to vary the ratio of connection of said signal gen-erator to said assisted and unassisted counter means, a bag valve solenoid operatively connected to said bag valve and means to operate said bag valve solenoid operatively extending from said unassisted breath counter means to said solenoid.
(2) The invention according to Claim 1 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the system in the "assisted" breath mode.
(3) The invention according to Claim 1 in which said means operatively connected to said means to monitor the exhaled breaths to vary the ratio of assisted and unassisted breaths also includes an exhalation valve solenoid operatively connected between said exhalation valve and said exhalation valve control line, and means to operate said exhalation valve solenoid oper-atively connected between said assisted breath counter means and said solenoid whereby said exhalation valve control line is open between said ventilator and said exhalation valve and said valve operates normally when said ventilator is in the "assisted"
mode and said exhalation valve control line is closed between said ventilator and said exhalation valve when said ventilator is in the "unassisted" mode thereby isolating said exhalation valve from the exhalation valve control line.
(4) The invention according to Claim 3 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the system in the "assisted" breath mode.
(5) In a continuous mechanical ventilation system which includes a conventional ventilator which supplies assist-ed and unassisted breaths to a patient, a pneumatic line oper-atively extending from said ventilator, an exhalation valve operatively connected to said pneumatic line and an exhalation valve control line extending between said ventilator and said exhalation valve, patient connection means extending from said exhalation valve; means to assist in weaning patients away from said ventilator, said means including a bag valve in the pneu-matic line between said ventilator and said exhalation valve, a bag connected to said bag valve, a one-way valve operatively connected between said bag and said exhalation valve providing one-way flow from said bag valve to said exhalation valve, means to actuate said bag valve whereby breaths from said ventilator are conveyed to said patient connection means when said bag valve is closed and said ventilator is in the "assisted" mode and to said bag and thence to said patient connection means as required, when said bag valve is open and said ventilator is in the "unassisted" mode, and means operatively connected to said means to actuate said bag valve, to vary the ratio of the number of breaths directly to said patient connection means and the number of breaths to said patient connection means via said bag, within limits, said means to vary the ratio of the number of breaths directly to said patient connection means and via said bag, including a pressure sensor in said exhalation valve con-trol line, a signal generator operatively connected to said pressure sensor and operated thereby, each time the exhalation pressure within said control line exceeds a predetermined pres-sure, assisted breath counter means, unassisted breath counter means, means operatively connecting said signal generator to said assisted breath counter means when in the "assisted" breath mode and to said unassisted breath counter means when in the "unassisted" mode, means to vary the ratio of connection of said signal generator to said assisted and unassisted counter means, a bag valve solenoid operatively connected to said valve and means to operate said bag valve solenoid extending from said unassisted breath counter means to said solenoid.
(6) The invention according to Claim 5 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the system in the "assisted" breath mode.
(7) The invention according to Claim 5 which also includes an exhalation valve solenoid operatively connected be-tween exhalation valve and said exhalation valve control line, and means to operate said exhalation valve solenoid operatively connected between said assisted breath counter means and said solenoid whereby said exhalation valve control line is open be-tween said ventilator and said exhalation valve and said valve operates normally when said ventilator is in the "assisted"
mode and said exhalation valve control line is closed between said ventilator and said exhalation valve when said ventilator is in the "unassisted" mode thereby isolating said exhalation valve from the exhalation valve control line.
(8) The invention according to Claim 7 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the ventilator in the "assisted" breath mode.
(1) In a conventional ventilator which supplies assisted or unassisted breaths to a patient including a pneu-matic connection extending from said ventilator, an exhalation valve operatively connected to said pneumatic connection, patient connection means extending from said exhalation valve, an exha-lation valve control line operatively connected between the ventilator and the exhalation valve and means operatively con-nected to said exhalation valve to monitor exhaled breaths;
the improvement comprising an attachment, said attachment com-prising means to provide assisted breaths from the ventilator when in an "assisted" mode, means to by-pass breaths from said ventilator when in an "unassisted" mode and means operatively connected to the means to monitor the exhaled breaths whereby the ratio of "assisted" and "unassisted" breaths may be varied within limits, said means to provide "unassisted" breaths in-cluding a low resistance bag valve in said pneumatic connection, a bag connected to the bag valve, a one-way valve operatively connected between said bag and said exhalation valve providing one-way flow from said bag to said exhalation valve, the oper-ation of said ventilator including means to open and close said bag valve whereby breaths from said ventilator are conveyed directly to said patient connection means when said bag valve is closed and said ventilator is in the "assisted" mode, and to the bag and thence to said patient connection means as re-quired, when said bag valve is open and said ventilator is in the "unassisted" mode, said means operatively connected to said means to monitor the exhaled breaths whereby the ratio of "assisted" and "unassisted" breaths may be varied within limits, including a pressure sensor in said exhalation valve control line, a signal generator operatively connected to said pressure sensor and operated thereby each time the exhalation pressure within said control line exceeds a predetermined pressure, as-sisted breath counter means, and unassisted breath counter means, means operatively connecting said signal generator to said as-sisted breath counter means when in the "assisted" mode and to said unassisted breath counter means when in the "unassisted"
mode, means to vary the ratio of connection of said signal gen-erator to said assisted and unassisted counter means, a bag valve solenoid operatively connected to said bag valve and means to operate said bag valve solenoid operatively extending from said unassisted breath counter means to said solenoid.
(2) The invention according to Claim 1 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the system in the "assisted" breath mode.
(3) The invention according to Claim 1 in which said means operatively connected to said means to monitor the exhaled breaths to vary the ratio of assisted and unassisted breaths also includes an exhalation valve solenoid operatively connected between said exhalation valve and said exhalation valve control line, and means to operate said exhalation valve solenoid oper-atively connected between said assisted breath counter means and said solenoid whereby said exhalation valve control line is open between said ventilator and said exhalation valve and said valve operates normally when said ventilator is in the "assisted"
mode and said exhalation valve control line is closed between said ventilator and said exhalation valve when said ventilator is in the "unassisted" mode thereby isolating said exhalation valve from the exhalation valve control line.
(4) The invention according to Claim 3 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the system in the "assisted" breath mode.
(5) In a continuous mechanical ventilation system which includes a conventional ventilator which supplies assist-ed and unassisted breaths to a patient, a pneumatic line oper-atively extending from said ventilator, an exhalation valve operatively connected to said pneumatic line and an exhalation valve control line extending between said ventilator and said exhalation valve, patient connection means extending from said exhalation valve; means to assist in weaning patients away from said ventilator, said means including a bag valve in the pneu-matic line between said ventilator and said exhalation valve, a bag connected to said bag valve, a one-way valve operatively connected between said bag and said exhalation valve providing one-way flow from said bag valve to said exhalation valve, means to actuate said bag valve whereby breaths from said ventilator are conveyed to said patient connection means when said bag valve is closed and said ventilator is in the "assisted" mode and to said bag and thence to said patient connection means as required, when said bag valve is open and said ventilator is in the "unassisted" mode, and means operatively connected to said means to actuate said bag valve, to vary the ratio of the number of breaths directly to said patient connection means and the number of breaths to said patient connection means via said bag, within limits, said means to vary the ratio of the number of breaths directly to said patient connection means and via said bag, including a pressure sensor in said exhalation valve con-trol line, a signal generator operatively connected to said pressure sensor and operated thereby, each time the exhalation pressure within said control line exceeds a predetermined pres-sure, assisted breath counter means, unassisted breath counter means, means operatively connecting said signal generator to said assisted breath counter means when in the "assisted" breath mode and to said unassisted breath counter means when in the "unassisted" mode, means to vary the ratio of connection of said signal generator to said assisted and unassisted counter means, a bag valve solenoid operatively connected to said valve and means to operate said bag valve solenoid extending from said unassisted breath counter means to said solenoid.
(6) The invention according to Claim 5 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the system in the "assisted" breath mode.
(7) The invention according to Claim 5 which also includes an exhalation valve solenoid operatively connected be-tween exhalation valve and said exhalation valve control line, and means to operate said exhalation valve solenoid operatively connected between said assisted breath counter means and said solenoid whereby said exhalation valve control line is open be-tween said ventilator and said exhalation valve and said valve operates normally when said ventilator is in the "assisted"
mode and said exhalation valve control line is closed between said ventilator and said exhalation valve when said ventilator is in the "unassisted" mode thereby isolating said exhalation valve from the exhalation valve control line.
(8) The invention according to Claim 7 in which said bag valve is normally closed thereby acting as a fail safe mechanism and placing the ventilator in the "assisted" breath mode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,689A CA1108505A (en) | 1978-01-24 | 1978-01-24 | Method and apparatus for weaning patient from continuous mechanical ventilation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,689A CA1108505A (en) | 1978-01-24 | 1978-01-24 | Method and apparatus for weaning patient from continuous mechanical ventilation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1108505A true CA1108505A (en) | 1981-09-08 |
Family
ID=4110631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA295,689A Expired CA1108505A (en) | 1978-01-24 | 1978-01-24 | Method and apparatus for weaning patient from continuous mechanical ventilation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1108505A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4747402A (en) * | 1985-09-13 | 1988-05-31 | Reese David M | High frequency ventilation method |
| WO2000041757A1 (en) * | 1999-01-15 | 2000-07-20 | Resmed Limited | Method and apparatus to counterbalance intrinsic positive end expiratory pressure |
| AU2003259632B2 (en) * | 1999-01-15 | 2007-03-15 | ResMed Pty Ltd | Method and Apparatus to Counterbalance Intrinsic Positive End Expiratory Pressure |
| AU2007202796B2 (en) * | 1999-01-15 | 2010-06-10 | ResMed Pty Ltd | Method and Apparatus to Counterbalance Intrinsic Positive End Expiratory Pressure |
| EP3020438A1 (en) | 2014-11-13 | 2016-05-18 | Linde AG | Device for ventilating a patient and method for operating a device for ventilating a patient |
-
1978
- 1978-01-24 CA CA295,689A patent/CA1108505A/en not_active Expired
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4747402A (en) * | 1985-09-13 | 1988-05-31 | Reese David M | High frequency ventilation method |
| WO2000041757A1 (en) * | 1999-01-15 | 2000-07-20 | Resmed Limited | Method and apparatus to counterbalance intrinsic positive end expiratory pressure |
| US6588422B1 (en) | 1999-01-15 | 2003-07-08 | Resmed Ltd. | Method and apparatus to counterbalance intrinsic positive end expiratory pressure |
| AU764874B2 (en) * | 1999-01-15 | 2003-09-04 | ResMed Pty Ltd | Method and apparatus to counterbalance intrinsic positive end expiratory pressure |
| US6854462B2 (en) | 1999-01-15 | 2005-02-15 | Resmed Limited | Method and apparatus to counterbalance intrinsic positive end expiratory pressure |
| US6915803B2 (en) | 1999-01-15 | 2005-07-12 | Resmed Limited | Method and apparatus to counterbalance intrinsic positive and expiratory pressure |
| AU2003259632B2 (en) * | 1999-01-15 | 2007-03-15 | ResMed Pty Ltd | Method and Apparatus to Counterbalance Intrinsic Positive End Expiratory Pressure |
| US7270128B2 (en) | 1999-01-15 | 2007-09-18 | Resmed Limited | Method and apparatus to counterbalance intrinsic positive end expiratory pressure |
| AU2007202796B2 (en) * | 1999-01-15 | 2010-06-10 | ResMed Pty Ltd | Method and Apparatus to Counterbalance Intrinsic Positive End Expiratory Pressure |
| EP3020438A1 (en) | 2014-11-13 | 2016-05-18 | Linde AG | Device for ventilating a patient and method for operating a device for ventilating a patient |
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