U.S. patent number 3,757,776 [Application Number 05/148,580] was granted by the patent office on 1973-09-11 for ventilator for an anesthesia gas machine.
Invention is credited to Jack Bauman.
United States Patent |
3,757,776 |
Bauman |
September 11, 1973 |
VENTILATOR FOR AN ANESTHESIA GAS MACHINE
Abstract
Located adjacent an anesthesia gas machine is a pair of opposed,
concave paddles, relatively movable toward and away from each
other, alternately squeezing and releasing a conventional,
flexible, breathing bag interposed between the paddles. The
frequency of the paddle opening and closing cycle can be
controlled; and a warning mechanism monitors and indicates
excessive back pressure during bag compression, thereby alerting
the anesthetist to a change in the patient's responses.
Inventors: |
Bauman; Jack (Los Angeles,
CA) |
Family
ID: |
22526385 |
Appl.
No.: |
05/148,580 |
Filed: |
June 1, 1971 |
Current U.S.
Class: |
128/202.22;
128/205.13; D24/164 |
Current CPC
Class: |
A61M
16/0057 (20130101) |
Current International
Class: |
A61M
16/00 (20060101); A61m 016/00 () |
Field of
Search: |
;128/188,145.8,145.5,145.6,145.7,202 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Dunne; G. F.
Claims
What is claimed is:
1. A ventilator for an anesthesia gas machine having a flexible gas
reservoir bag connected thereto at one end and laterally exposed
comprising:
a. a frame;
b. a pair of paddles;
c. means for cantilevering one of said paddles on said frame to
project therefrom into lateral abutment with one exposed side of
said bag;
d. means for movably cantilevering the other one of said paddles on
said frame to project therefrom into lateral abutment with the
other exposed side of said bag;
e. a rotary actuating means on said frame including an electric
motor; and,
f. means including a crank and pitman for connecting said actuating
means to drive said other paddle repeatedly to and fro and toward
and away from said one paddle.
2. A ventilator as in claim 1 including a housing mounted on said
frame, said one paddle projecting upwardly from said housing in a
substantially vertical attitude, and said other paddle projecting
upwardly from said housing and being movable between a first
position approximately 40.degree. to the vertical and a second
position approximately vertical.
3. A ventilator according to claim 1 including a pivot mounting on
said frame for said one of said paddles, a stop on said frame, and
yielding means on said frame and engaging said one paddle for
urging said one paddle toward said stop and toward said other one
of said paddles.
4. A ventilator as in claim 3 further including warning means
effective upon deflection of said one paddle resulting in
compression of said yielding means.
5. A ventilator as in claim 4 wherein said warning means includes a
signal member, and a pressure responsive switch connected to said
signal member and closed by said deflection of said one of said
paddles.
6. A ventilator as in claim 5 wherein said warning means includes
adjustable means for controlling the extent of deflection of said
one of said paddles required to actuate said signal member.
Description
The invention relates to improvements in accessories for anesthesia
apparatus and, more particularly, to improvements in the operation
of the flexible gas reservoir, or breathing bag, customarily used
as a part of the lung ventilating system.
Heretofore, the anesthetist has alternately applied manual pressure
to the bag and released the bag, to help the patient breathe during
the administration of anesthesia. The bag is squeezed during
inhalation and released during exhalation.
Manipulation of the bag by the application of hand pressure affords
a valuable indication as to whether proper lung ventilation is
taking place, according to the "feel" provided by the bag. That is
to say, the bag pressure along with other indicators reveals to an
experienced anesthetist whether lung ventilation is proceeding in a
satisfactory manner. However, it is often difficult to time the
rate of respiration so as to provide the optimum pattern, wherein
each cycle of respiration, timewise, consists of approximately
one-third inhalation time and two-thirds exhalation time plus a
short pause after each. So also, the extent of the pressure
manually exerted is subject to fluctuation, depending upon fatigue,
degree of concentration and similar subjective factors.
It is therefore an object of the invention to provide a ventilator
for an anesthesia gas machine which can be regulated so as to
operate at a predetermined optimum pattern of respiration, at a
predetermined pressure and at a predetermined optimum respiration
rate, or respiratory frequency.
It is another object of the invention to provide a ventilator which
affords a warning when a predetermined back pressure threshold is
exceeded, thereby alerting the anesthetist that operation of the
machine or ventilation of the patient has departed from the norm,
such as might be occasioned, for example, from a bronchial spasm,
an obstruction in the ventilation flow path or decreased compliance
of the patient.
It is yet another object of the invention to provide a ventilator
in which aseptic techniques can more readily be applied owing to
the ease with which the bag can be removed, cleaned and
replaced.
It is a further object of the invention to provide a ventilator
which is relatively economical, both with respect to original
acquisition as well as upkeep costs, yet which is reliable, sturdy
and long-lived.
It is still a further object of the invention to provide a
ventilator which functions in a manner such that its operation can
readily be learned.
It is yet a further object of the invention to provide a ventilator
which is readily accessible and which enables the anesthetist to
resume manual operation at any time or to place the bag in the
device substantially instantaneously and without pause in the
respiration cycle.
It is another object of the invention to provide a generally
improved ventilator for an anesthesia gas machine.
Other objects, together with the foregoing, are attained in the
embodiment described in the following description and illustrated
in the accompanying drawings in which:
FIG. 1 is a perspective view of the ventilator shown in a typical
environment adjacent an anesthesia gas machine providing, as a part
of the lung ventilation system, a flexible, gas reservoir breathing
bag;
FIG. 2 is a fragmentary perspective view, to an enlarged scale, of
the housing and paddle structure, portions of the housing being
broken away to reveal details of the paddle drive mechanism;
FIG. 3 is a fragmentary sectional view to an enlarged scale, of the
warning signal switch mechanism, the section being taken on the
line 3--3 in FIG. 2; and,
FIG. 4 is a diagram of the electrical system.
While the ventilator of the invention is susceptible of numerous
physical embodiments, depending upon the environment and
requirements of use, substantial numbers of the herein shown and
described embodiment have been made, tested and used, and all have
performed in an eminently satisfactory manner.
The ventilator of the invention, generally designated by the
reference numeral 12, is customarily located adjacent a
conventional anesthesia gas machine 13 in an operating room. The
machine 13 is provided with the usual compressed gas bottles 14,
conduits 15, pressure relief valve 20, pressure gauge 16, flow
meters 17, filter cannister 18, and flexible tubing 19 and 21
leading to and from the face mask 22 applied to the patient's face
during ventilation. The customary valves within easy reach of the
anesthetist afford control of gas pressures and volumes.
Connected to the ventilation system through a duct 23 is the
customary flexible breathing bag 24, or reservoir, ordinarily of an
elastomeric material. As stated above, the anesthetist has
heretofore been required alternately to squeeze and release the
bag, in cyclical fashion, whenever it was deemed necessary to
assist the patient's own efforts in inhaling and exhaling during
the lung ventilation process.
To assist the anesthetist, cyclical compression and release of the
reservoir 24 is effected herein by a pair of paddles 27 and 28. The
paddles are formed with concave faces in opposed, facing relation,
thereby conforming somewhat to the curved surfaces of the bag 24
when it is interposed between the paddles.
The paddles are moved, relatively, toward and away from each other;
and preferably, one of the paddles, such as the paddle 27, is
substantially fixed, although pivotable through a slight distance
for signal control purposes, as will subsequently be described, and
the other paddle, 28, is movable. The movable paddle 28 rocks to
and fro between a substantially vertical attitude, in close
juxtaposition to the substantially fixed paddle 27, and an inclined
attitude approximately forty degrees from vertical, in which
position all pressure on the interposed bag is released.
Rocking of the movable paddle 28 is effected by a crank mechanism,
generally designated by the reference numeral 31, mounted on a
frame 32 comprising a bottom plate 33, supported on a pedestal
structure 34, and a vertical mounting wall 36 having a bottom
flange 37 appropriately secured to the plate 33. Actuating the
cranking mechanism in a conventional variable speed electrical
motor 41 controlled as to speed by an exteriorly located knob 42.
The knob 42, for accessability, is on top of a top closure plate
43, the plate 43 having depending pairs of side walls 44 and end
walls 46 which, with the bottom plate 33 define a box-like housing
47 encompassing the actuating mechanism and electrical components.
Around the base of the speed control knob 42 are indicia 48 such as
the words "Respiratory Increase" with a corresponding arrow 49
indicating the direction in which the control is turned to effect
an increase in the rate of respiration, i.e., the number of
inhalation-exhalation cycles per minute.
The speed of the motor shaft is reduced by connection to a
conventional gear box 51 from which protrudes a drive shaft 52
journaled in an opening in the mounting plate 36. Mounted on the
end of the shaft 52 is a crank arm 53 driven by the drive shaft in
the clockwise direction indicated by the arrow 56 in FIG. 2.
Pivotally mounted on the distal end of the crank 53, as by a pin
57, is a lever 58, the remote end of which is pivotally connected
by a pin 59 to the lower end of the rocker arm 61 of the movable
paddle 28. The rocker arm 61, in turn, is pivotally mounted on a
pivot pin 62 secured to the adjacent mounting wall 36.
The rocker arm 61 extends upwardly through an elongated opening 66
in the top closure plate 43, the edges of the opening being guarded
by a rubber grommet 67. The upper portion of the rocker arm 61
affords means for detachable connection with the concavo-convex
paddle 28, as by fastenings 70.
With the crank mechanism 32 in the position shown in FIG. 2, the
movable paddle 28 is in a substantially vertical posture, parallel
to the vertical substantially fixed paddle 27 and in close
juxtaposition thereto in order to effect a substantially complete
expulsion of the contents of the bag interposed therebetween as in
FIG. 1.
When the crank arm 53 has revolved, in the clockwise direction 56,
through 180.degree. from the position shown in FIG. 2, the right
hand portion of the lever 58 overlies the crank arm 53, and the pin
59 has moved toward the right a distance equal to twice the throw
of the crank, thereby rocking the arm 61 about the fulcrum 62 and
causing the arm 61 and the paddle 28 to incline toward the left and
upwardly at an angle of approximately 40.degree. from the vertical,
the paddle in this position allowing the bag to expand to its
maximum extent.
Continued rotation of the crank returns the movable paddle to
upright position, the relative closure of the paddles again
squeezing the interposed bag 24 (see FIG. 1) to substantially empty
condition.
The cycle is continued until the ventilator is shut off by rotation
of the control knob 42 in a counter-clockwise direction to "OFF"
position. A pilot lamp 50 adjacent the knob 42 indicates whether
the device is in "OFF" or "ON" condition.
Occasionally, a back pressure will build up in the ventilation
system caused, for example, by an obstruction which has developed
in the system or, more seriously, from a bronchial spasm or
decreased compliance on the part of the patient. Where the
anesthetist is effecting compression of the bag by hand, this back
pressure is felt. Similarly, in the present machine, provision is
made for sensing the back pressure and affording a warning, such as
by a buzzer, which immediately alerts the anesthetist to a change
in the system requiring attention.
The monitoring device, generally designated by the reference
numeral 71, comprises a block 72 secured by fastenings 73 to the
mounting wall 36. The block 72 extends upwardly through an
elongated grommeted slot 74 in the top plate 43, the slot 74 also
accommodating the vertical rod 76 to which the paddle 27 is
detachably connected, by fasteners 70, the bottom end of the rod 76
being pivotally mounted by a suitable fastening 77 to the mounting
plate 36.
Formed in the upper portion of the block is a through bore 81
oriented so as to intersect the vertical axis of the rod 76 of the
paddle 27. An adjustment knob 82 carries a threaded stem 83 in
threaded engagement with the adjacent tapped portion 84 of the
through bore 81. The distal end of the threaded stem 83 engages the
adjacent end of a helical spring 86 biasing in a left-hand
direction (as appears in FIGS. 2 and 3) a plunger 87 abutting the
vertical rod 76 carrying the paddle 27.
The plunger, in other words, biases the rod 76 in a
counterclockwise direction, movement in such direction being
opposed, however, by a limit stop pin 88 mounted on the wall
36.
The fastening 77 at the bottom end of the vertical rod 76 affords a
pivoting movement to the rod, but since the limit stop 88 prevents
further movement in a counterclockwise direction (see FIGS. 2 and
3) and the spring bias effected by the plunger 87 opposes movement
in a clockwise direction, the vertical attitude of the rod 76 can
be deemed as substantially fixed in nature, at least with respect
to movable paddle 28.
Nevertheless, the spring 86 will yield when a supervening force is
applied against the plunger 87 in excess of the amount of the
spring urgency. Such a force is exerted when an excessive amount of
back pressure arises in the breathing bag during the compression
(inhalation) portion of the respiration cycle. In this situation,
the rod 76 is tilted slightly in a clockwise direction, about the
pivot 77, owing to the force exerted by the movable paddle in
swinging against the interposed breathing bag having excess back
pressure, the bag, in turn, forcing the paddle 27 in a clockwise
direction, as appears in FIGS. 1 and 2. In tilting slightly to the
right (see FIG. 3), the rod 76 deflects the adjacent tip 91 of the
spring leaf 92 of a microswitch 93 and depresses the customary
button 94 into closed position, thereby sounding an alarm, such as
a buzzer 96. By appropriate adjustment of the signal control knob
82, the anesthetist can set the mechanism to monitor back pressure
and to provide the warning signal whenever the back pressure
crosses a selected pressure threshold.
As appears most clearly in FIGS. 2 and 4, the power supply
originates at a plug 101 and extends through conductors 102, 103
and 104, leading into a terminal box 106 to and from which extend
various conductors, as will be described.
The conductor 102 is a common bus which extends through the switch
110 controlled by knob 42, and which not only affords "ON-OFF"
capabilities but which also provides control of the motor speed
("Respiratory Rate") by means of a conventional phase angle control
circuit, generally designated by the reference numeral 108. The
control circuit 108 includes, as shown in FIG. 4, identical diodes
109 and 111 (1N 4003) and a silicon controlled rectifier 112 (2N
4443). The SCR 112 is connected in series in the bus 102 and the
gate terminal 113 of the SCR 112 is connected to a junction 114 of
a conductor 116 attached to the diode 111 and a conductor 117
extending through a resistor 118 (47 ohms) and to the motor 41. A
potentiometer 121 is mechanically connected, as indicated by the
broken line 122, to the "ON - OFF" switch 110.
Appropriate resistors 123 (3.9K ohms), 124 (250 ohms) and 126 (0 to
300 ohms according to what is preferred with respect to lowest, or
threshold motor speed) are connected in the line 13, and a line
resistor 132 (6.2K ohms) is also placed in the conductor 133
including the back pressure microswitch 93 and buzzer 96.
The conductor 133 and attendant elements are in shunt not only with
the conductor 136 containing the pilot lamp 50, but also with the
motor circuit. The AC ground 104 is grounded to the motor frame, as
shown.
The capacitors 137 and 138 (both 0.05 mf.) between the bus 102 and
ground 104, and between the conductor 103 and ground 104,
respectively provide a filter effect which is most desirable in
affording a nice degree of motor control.
In order to start the machine 12, the knob 42 is rotated a short
distance in a clockwise direction to turn on the switch 110,
further rotation in a clockwise direction being effective to
increase the respiratory rate deemed most suitable by the
anesthetist for the particular patient. The breathing bag 24 is
thereupon inserted between the relatively reciprocating paddles so
as to assist in ventilation. Should mechanical blockage, bronchial
spasm or decreased compliance occur, the anesthetist is immediately
alerted by an audible signal which is detected regardless of the
attention being paid to the ventilating machine at the time. Prompt
remedial action can thereupon be taken.
Removal of the bag, if necessary, and reinsertion thereof is
readily accomplished, and the accessibility of all controls affords
the user a conveniently operated ventilator machine.
In the usual case, the operation of the automatic ventilator is as
follows. First, establish anesthesia with any of the standard
anesthesia gas machines, such as the machine 13, using a 2 or 3
liter capacity reservoir bag with a gas flow rate of 2 to 6 liters
per minute, as desired. Next, position the reservoir bag 24 between
the paddles 27 and 28, as shown in FIG. 1, and adjust the
appropriate respiratory rate valves as required for the particular
patient. Also adjust the pressure relief valve 20 to allow proper
filling of the patient's lungs as well as the proper escape of
excess gas. The pressure gauge 16 will, under these conditions,
ordinarily attain a peak water pressure of about twenty
centimeters, but will vary according to compliance, respiratory
rate and other factors. The bag 24 must empty sufficiently to avoid
pressure during the expiratory phase of the cycle. As previously
indicated, the signal alarm 71 can be set to sound when pressures
exceed the desired level. Tightening the thumb screw increases the
pressure necessary to sound the alarm.
The paddles can be actuated by an electric motor, as heretofore
indicated, or by suitable mechanism, not shown, operated by
compressed gas or liquid.
It can therefore be seen that I have provided an automatic
ventilator for use in an operating room, in conjunction with a
conventional anesthesia gas machine, which is versatile, safe,
hygienic and easy to apply and use.
* * * * *