United States Patent 3918447

Apparatus is described for the ventilation of mammals which utilizes a linear arrangement of cylinder, piston and delivery-volume control means to reduce the size of the ventilator. The preferred embodiment is suitable particularly for the ventilation of neonates and infants.

Inkster, John S. (Gosforth Newcastle-upon-Tyne, 3, EN)
Burn, Norman (Newcastle upon Tyne, EN)
Application Number:
Publication Date:
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Primary Class:
Other Classes:
International Classes:
A61M16/00; (IPC1-7): A61M16/00
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US Patent References:
3530873FLUID DELIVERY DEVICE1970-09-29Arp
3166068Automatic apparatus for artificial respiration1965-01-19Kuban
3158152Mouth to mouth resuscitator1964-11-24Bloom
1371702Respirating device1921-03-15Lyon

Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Recla, Henry J.
Attorney, Agent or Firm:
Dhuey, John A.
What is claimed is

1. A ventilator comprising a cylinder having a piston reciprocally movable therein between a first position and a second position, sealing means disposed between said cylinder and said piston, said sealing means and said piston defining a first compartment and a second compartment within said cylinder, piston guide means having a first tube attached to said piston and a second tube attached to said cylinder, said tubes being concentric, and said first tube being reciprocally movable within said second tube, biasing means within said first compartment urging said piston toward said first position, said biasing means consisting of a coil spring connected to said first tube and to said second tube, said spring being within said first tube and said second tube, and adjustable piston stop means within said first compartment defining said first position, said first compartment being operably connected to a source of driving gas to move said piston from said first position to said second position and said second compartment being operably connected to a source of breathing gas and to a patient airway.

2. A ventilator as in claim 1, wherein said second tube is movable relative to said cylinder and engagable therewith, whereby said second tube operates as said piston stop means and defines said first position.

3. A ventilator as in claim 2, wherein said sealing means is an annular diaphram having its outer periphery attached to said cylinder and its inner periphery attached to said piston.

The present invention is concerned generally with mechanical ventilators. More particularly, it is concerned with mechanical ventilators for delivery of a pre-determined volume of gas to a mammal, wherein the ventilator is of such configuration that the overall size is minimized.

Conventional ventilators are generally large units capable of ventilating adults. The large volumes of breathing gas involved in those systems often make them unsuitable for the ventilation of pediatric patients. Thus, it is an object of this invention to provide a ventilator which can be used for the ventilation of pediatric patients. It is a further object of this invention to provide a ventilator which is of such size that it may be placed inside an incubator for the ventilation of neonates.

A better understanding of the present invention and of its many advantages will be had by referring to the following drawings, in which:

FIG. 1 is a perspective view of the ventilator;

FIG. 2 is a partial sectional view of the ventilator;

FIG. 3 is a cross-sectional view of the breathing gas inlet and outlet valve plate;

FIG. 4 is a top view of the breathing gas inlet and outlet valve plate; and

FIG. 5 is a bottom view of the cylinder end plate.

With reference to those figures, the present invention comprises a cylinder 10 substantially closed at the upper end by cover flange 38 and at the bottom end by cover flange 33, a movable piston 11 dividing the cylinder 10 into two compartments, a driving gas connection 12 to one compartment, breathing gas inlet 13 and outlet 16 connected to the other compartment, valves 20 and 29 associated with said breathing gas inlet and outlet connections, respectively, to direct the flow of breathing gas from the inlet connection 13 to the outlet connection 16, and volume control means defining the relative volumes of the two compartments.

The ventilator further may be provided with a valve 15 through which expired gas from the animal must pass, the valve requiring a pre-determined and adjustable gas pressure to allow flow of expired gas through it, thereby maintaining a residual pressure within the lungs of the patient. Also, a pressure relief valve 34 and a condensate drain 35 may be provided in bottom cover flange 33.

The ventilator of the present invention is a unit capable of providing a pre-determined volume of respiratory gas to an animal while minimizing the amount of dead space in the system, which dead space contains breathing gas which will not be delivered to the patient during the normal delivery cycle of the ventilator. The ventilator is conveniently driven by the gas supply from a conventional respiratory ventilator or from an auxilliary unit capable of providing the necessary gas pulses.

In a particularly preferred embodiment of this invention as described with reference to FIGS. 2-5, the ventilator comprises cylinder 10, substantially closed at the top end by cover flange 38 and at the bottom end by cover flange 33. Clyinder 10 is divided into two major compartments, first compartment 18 and second compartment 19, by movable piston 11 reciprocally mounted therein and gas-tight seal 17 disposed between cylinder 10 and piston 11. A driving gas connection 12 in fluid communication with first compartment 18 is provided in cover flange 38, and second compartment 19 is in fluid communication through inlet valve 20 with breathing gas inlet 13 and in fluid communication with breathing gas outlet 16 through outlet valve 29. Outlet 16 is connected to the subject to be ventilated via a patient airway.

A positive gas pressure provided by the driving unit, not shown, enters first compartment 18 through its driving gas connection 12 and forces piston 11 along cylinder 10 thereby enlarging first compartment 18 and reducing the volume of second compartment 19. This movement of piston 11 and consequent increase in breathing gas pressure in second compartment 19 over the inlet breathing gas pressure closes inlet valve 20 on the gas inlet to the second compartment 19 and opens an outlet valve 14 to permit breathing gas to pass through gas outlet 16 to the patient.

Volume control means are provided which adjust the starting position of piston 11 whereby the volume of gas to be displaced by piston 11 can be selected. Such means conveniently includes a first tube 21 attached to the center of piston 11 and disposed along the axis of first compartment 18. Tube 21 is movable within second tube 22 passing through the center of cover flange 38. Tube 22 is movable through and engagable with cover flange 38. In particularly preferred embodiment, tube 22 extends through third tube 36 which is attached to cover flange 38. Tube 36 preferably is threaded on its outer surface and engagable with ring 37, which is threaded on its inner surface. The threaded portion of ring 37 and tube 36 are generally tapered and the threaded portion of tube 36 is segmented, whereby threading ring 37 on tube 36 draws the segmented portions of tube 36 into contact with tube 22 and holds tube 22 stationary at a selected position. Alternative engagement means may be provided, however. For example, a conventional O-ring seal between tube 36 and tube 22 may be provided.

By releasing ring 37, tube 22 may be slidably moved within tube 36 to adjust the position of the end of second tube 22 within first compartment 18. The end of tube 22 functions as a piston-stop means when ring 37 is retightened to prevent movement of tube 22 within tube 36, thereby defining the volume of second compartment 19 and the corresponding volume of breathing gas which will be supplied to the patient.

The necessary biasing means to return piston 11 to its normal stop position after driving gas pressure has been removed from compartment 18 is conveniently provided by a spring arrangement which provides a return force to return piston 11 to the starting position. For example, a suitable coil spring 23 may be attached to outer end 25 of second tube 22 and to the piston end of first tube 21. Displacement of piston 11 by means of positive pressure within the first compartment 18 extends spring 23 such that on removal of the positive pressure, spring 23 returns piston 11 to its initial resting position. After removal of the driving gas pressure, reversal of direction of movement of the piston results in increase of the volume of the second compartment 19. The outlet valve 24 in the second compartment therefore closes and inlet valve 20 opens, allowing entry of further respiration gas via gas inlet 13 through inlet valve 20 into the second compartment.

The expired gas from the patient may be passed directly into the atmosphere. However, particularly with neonates and infants, it is advantageous to provide a residual pressure against which the patient must breathe. Thus, there is provided valve 15 through which the expired gas from the animal must pass, requiring a pre-determined gas pressure to allow the flow of the expired gas. Valve 15 conveniently consists of a short tube which rises above the bottom plane of valve plate 30 to contact diagram 27 retained between valve plate 30 and bottom end cover flange 33. Expired gas from the patient passes through expiration inlet 14, thereby raising the diaphram 27 away from the end of the tube of valve 15 and allowing expired gases to pass through valve 15. Diaphram 27 may be held in a closed position over the end of the tube position by means of spring 28 passing through the center of valve 15. The tension on spring 28 is adjustable to increase or decrease the pressure required to allow expired gas to pass diaphram 27. It is then possible to select a pressure at which the expired gas is able to lift the diaphram and permit exhaustion of the expired gas. Simple pressure valves of other kinds may be used. However, it can be appreciated that the above described arrangement is advantageous in minimizing the overall size of the ventilator.

Piston 11 of the ventilator must be freely movable within cylinder 10. Conventional sealing rings may be used on the circumference of the piston, but such rings may prevent the relatively free movement of the piston. It is therefore preferred to use a gas-tight seal of the so called rolling sock type seal, as the one known under the registered trademark of Bellofram (Bellofram Corporation). The outer periphery of such a rolling sock seal 17 is attached to the wall of first compartment 18 of cylinder 10 and the inner periphery of the seal is attached to the inner and narrower end of piston 11. This gas-tight seal 17 allows the relatively free movement of piston 11 along the whole length of cylinder 10. Piston 11 is guided in its movement within cylinder 10 by means of tube 21 which passes reciprocally within tube 22. Furthermore, the axial location of spring 23 within tube 22 and tube 21 provides a force tending to keep piston 11 centrally located within cylinder 10.

It will be appreciated that this novel arrangement of piston stop means, piston guide means, volume control means and piston return means, all being substantially contained within the cylinder of the ventilator, greatly minimizes the required size of the ventilator. Furthermore, the novel arrangement of valves 20 and 29 on valve plate 30 and valve 15 in communication with expired gas outlet 14 also reduces the necessary space required for the ventilator. As seen in FIGS. 3 and 4, valves 20 and 29 conveniently are mushroom shaped and extend over a plurality of vents 31 and 32 in valve plate 30, which is sealed to cylinder 10 by O-ring 26 and to cover flange 33 by diaphram 27. Opening 39 through valve plate 30 provides space into which diaphram 27 may intrude when diaphram 27 is moved away from the raised mouth of valve 15 by the pressure of expired gas. Thus, a ventilator may be produced having a size large enough to ventilate adults yet small enough to ventilate neonates and infants.

The ventilator may be constructed of materials which make it capable of being cleaned and sterilized. It may also be constructed that it can be dismantled by unskilled personnel. The inlet and outlet valves may be simple mushroom valves constructed of synthetic rubber. These, together with the rolling sock seal may be removed and discarded after each use of the ventilator. Construction of the cylinder piston end and the wall of the first compartment, with suitable materials, allows the whole assembly to be heat sterilized by conventional means, together with the end wall of the second compartment, the gas inlet and outlet and the residual pressure valve. Following sterilization, the ventilator may be re-assembled with new, steril inlet and outlet valves and the rolling sock seal. The cylinder may be, for example, constructed of glass and the end walls of chrome-plated brass or stainless steel. The piston should be light and be capable of being autoclaved, a suitable material being poly-carbonate.

The dimensions of the ventilator depend upon the use to which it is to be put. A particular advantage of the present invention is that the ventilator may be constructed to provide a very small volume of respiratory gas required by neonates and infants. For example, a total volume of between 10 ml. and 250 ml. may be provided by a simple unit. An adjustable residual pressure valve for such a ventilator may provide a residual pressure of between 0 and 5 cm. of water.

The simple design of the present ventilator allows construction of a compact device. In use as a pediatric ventilator, the device may therefore be incorporated inside the incubator in which the child is maintained. Air provided by the ventilator is taken from the atmosphere of the incubator and is therefore already humidified and warmed. Alternatively, it is possible to provide suitably humidified air to the ventilator and to heat the face plate of the incubator through which the respiratory gas passes. The temperature of the air may be monitored at the infant and the temperature of the face plate adjusted to maintain the correct temperature. It is possible to provide an enclosure for the ventilator and a jacket for an inhalation tube to the subject, through both of which is passed warmed, humidified air, thus maintaining the gas supplied from the subject at the correct humidity and temperature.

The foregoing description of the preferred embodiments of the present invention is presented for illustration and is not intended to limit the invention thereto. Various modifications will be apparent to those skilled in the art without departing from the spirit or scope of this invention.