US2494712A - Lung immobilizer - Google Patents

Description

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J LEYENAAR LUNG IMMOBILIZER Jan., 17, 1950 Flled Dec 4, 1947 Jan. 17, 1950 1. L EYENAAR 2,494,712

LUNG IMMOBILIZER Filed Dec. 4, 1947 4 Sheets-Sheet 5 y P1 @J Jan. 17, 1950 .1. LEYENAAR LUNG IMMOBILIZER 4 Sheets-Sheet 4 Filed Dec.' 4, 1947 1&4

Inventor Jawa Le e naar a cf td able features.

Patented Jan. 17,4 195.()

U NITED STATES PATE OF Fl CE 2,494,712 Los@ mmosrnzm J an Leyenaar; Lexington, Mass., assignorto` .L H.

Emerson Company, Cambridge, Mass., a corporation of Massachusettsn Application Deeenrher 4, 1947-; Serial N; 789,597 7 claims. (ci. 12a-3c) l This invention relates toan app'aratus"y for the treatment of pulmonary tuberculosis which periodica'lly forces gas into and removes gas from `the patientls lungs and which: maintains `his `chest and lungs substantially motionless during suchl operation..

The most successful prior art type of such alpparatus includes a chamber tol enclose the patientsbcdy from his feet to his neck, acharn- V ber to enclose his head, a partition which separates these chambers' an'd which provided with an opening to accommodate the patients neck, a slide for varying the size' ofi the opening and either a centrifugal type pump or two impell'er type pumps which@ communicate with thehead enclosing chamber andv which alternately' create 4periods of positive and negative pressuresl therethe slide) the respective amounts of: the pressure l `exerted on the opposite sides ot' the patients thorax and diaphragm` at and7 instant are equalized by delaying` or reducing deg-ree the-amount of the pmessurer the body enclosing chamber compared tothe amount: of: the pressurei inthe" head enclosing chamberasithe positive andi negative pressures are being: built. up"i or diminished, thereby to compensate for the resistance' off' the respiratory passageway toi the gas as it passes inwardly or outwardly therethroug'l-ha It has been found that' if thei pressure Within the body enclosing chamber.` is.` thus maintained at an amount which is approximately 5' cm1.` of water less than the amount' of thei pressure in the head enclosing` chamber during" eachf period` from. maximum negative to?` maximum positive pressures and' approximately 5i cm; of Water greater than the amount. of the pressure in the head enclosing chamberduring eachlperibdffiiom maximum positive to maximum negative pressures, the respective pressures on the outer' and inner surfaces oi the thorax and. diaphragmA are substantially the same and the chestwail and the lungs are accordingly maintained substantially immobile While gas is periodically forced into and Withdrawn from the lungs.. A more complete description of the use of this priori art machine may be found in an article by Dr. Alvan L. Barach in the November-December 1946i issue of the Journal ofthe American Collegefof Chest Physicians, volume XU, number 6;

This prior art machine had several objection- One objection is that with the use oi an impeller type or a centrifugaly type pumplf'or creating periodic periodsof positive andn 2t negative pressures the air transmitted. tcthe head `enclosing chamber is heatedsubstantially,

andzis turbulent,r and for thesereasons is uncomtient fortable to a patient in.1 the apparatus; `turtltlermore each type of apparatusl`s-1neisy-in opera- Anotne'r em'ecticu,y which is particularly truel the use or ani imipeller type pump or pumpsi is that a pul'satiorr is created t-hc air stream each time the impeller completesa rev'olution,` thus: creatina a S^ri`e`sl o'f vibrations or pulsatio'ns` of. the air the ne'adl` enclositrgi char-fiber which are undesirable from a standpoint of noise and also iromithestandpoint of the effectiveness of the apparatus to maintain the- WallsI4 of the chest sullstantially` motionless A further objectionl is that with both o-fsaid GS/'peel of pumps it has* been' impossible to' produce ai uniform and progressive increase in the amount of positive pressure Within the` header-iclosing chamber until it reaches thev predetermined maximum amount,

their ai uniformand'. progressive' decrease in said positive pressure until it returnsltfr atmospheric,

i theny a. uniform and progressive increase intthe amount of negative pressure in the head enclosing chamber untill it reaches the" predetermined maximum and then a unifonn and progressive decrease` in said? negative pressure until it returns to atmospheric, i'. el it hasfbeen impossible tosi'aithiullly reproduce the uniform curve forthe variations; pressure` Within the' head enclosine chamber which is desirable; A- further objection is that the impell'er' type or the centrifugal type pressufrelvarying appara^-tusl is expensive and is difcult to'controlin operation.

It isitll'e oki-teeltr O'f this` nvelltion toprovide an improved pressure creating mechanismL incombifnati'on WitiuaV lung immobilizerw Whittle* isfsi'lple and economical in censtru'ctienf and operatibn and Whiclr iunctionsl to"y provide* a` uniform pressure' varying curve.

A further object iste provide such a irrimoloilizer` wherein" substantial15 l'esshea andf substantiallf` rio turbuiencer orpulsatibns are created ing; chamber may bei controlled" desired.

A further object is to provide a lung ininiobiliter hav-lng apressure creating: mechanism of the reciprocating type wherein bothl the headl enclosing chamber and the pressure creating mechanism are automatically supplied with fresh air from the atmosphere prior to the end of each period of negative pressure and without interfering with the uniformity of the pressure varying curve thereby to insure a supply of substantially fresh air tc be forced into the patients lungs during each period of positive pressure.

A further object is to provide such a lung immobilizer with a pressure creating mechanism of the reciprocating type which is free from pressure actuated spring loaded valves, thereby greatly reducing the size of the pressure varying mechanism and reducing the amount of power required for its operation.

A further object is to provide a lung immobilizer which is simple and economical in construction and operation.

Other objects relate to the construction and to the mode of operation and will be apparent from a consideration of the following description and the accompanying drawings Which exemplify three embodiments of the invention chosen for the purposes of illustration.

In the drawings:

Fig. 1 is a side elevation of a lung immobilizer embodying my invention with the body enclosing chamber slightly separated preparatory to the insertion of a patient;

Fig. 2 is an enlarged elevation looking from left to right at Fig. 1 of the separating partition removed;

Fig. 3 is an enlarged section taken on the line 3-3 of Fig. 1;

Fig. 4 is an enlarged side elevation of the pressure varying mechanism looking at the mechanism from the same side as it is shown in Fig. 1 but with the front wall of the cabinet removed and two side walls shown in vertical section;

Fig. 5 is a section taken on the line 5-5 of Fig. 4 but with the motor removed except for its drive pulley;

Fig. 6 is an enlarged section on the line 6-6 of Fig. 4;

Fig. 7 is an enlarged section on the line 'I-'I` section, showing still another embodiment of they invention.

The head enclosing chamber as illustrated consists of a dome-shaped member I 0, which may be made of any rigid material, for example a transparent plastic, and the body enclosing chamber consists of the two complementary casing members II and I2 also of rigid material, for example metal. When the complementary casing members are moved to end abutting relationship, the flange I3 of the shorter casing member II is held in air-tight or sealed relationship against the flange I4 of the longer casing member I2 by the clamp I5 by rotating the clamp about its pivotal connection I 6 so that its inner curved face engages the side of the pin IIA, this pin being secured to the casing member II. A similar clamp and pin are provided on the opposite side of the machine.

The casing member II and the head enclosing chamber I 0 are supported from the floor by a pair of vertical legs I1, one located at each side of the casing member, and by a pair of casters I8 adapted to roll along the oor as the casing member I I is moved toward or away from the casing member The casing member I2 is supported by two pairs of legs I9 and 20, one pair being located at the front end of the casing and the other pair at the foot end thereof and each leg terminating in a caster 2i which rests upon the floor.

A bed 23 has its head end secured to the casing member II and its foot end supported for sliding movement longitudinally of the interior of the casing member I2, for example by a pair of casters (not shown) which roll upon longitudinally extending tracks (not shown) secured to the inside face of the wall of the casing I2, Thus as the casing member I I is moved outwardly from or inwardly toward the casing member I2, the bed 23 moves with the casing member II and is correspondingly withdrawn from or inserted in the casing.

As shown in Fig. 3, the casing member II is provided with a flange 25 and the dome I0 is provided with a corresponding flange 26. The partition member 28, made of rigid material, for example a transparent plastic, is secured between the flanges 25 and 2S by bolts 29 which pass through perforations 30 (Fig. 2) in the partition member 28 and corresponding perforations in the flanges 25 and 26 and which are secured to the ring washer 34. Rings of compressible material 3|, 32 and 33, for example rubber, are interposed between the partition 28, the flanges 25 and 26 and the ring washer 34 to insure an air-tight seal.

The partition 28 is provided with an opening 35 which is large enough to permit the passage therethrough of the patients head. A head rest 36 is secured to the outer face of the partition 28 by means of brackets 31 and screws 38 which pass through registering perforations (not shown) provided in the brackets and the partition.

A slide 4I is mounted for vertical sliding movement in the two ways 42 which are provided by the inner face of the partition member 28 and two vertical channels formed in the adjacent sides of the members 44, said members being secured to the partition member 28 by screws 45.

The lower end of the rod 4l is detachably secured to the bracket 48 which is secured to the face of the slide 4I by screws 49. The rod 41 eX- tends upwardly through a perforation in the casing member I I and it is provided with a head 50 (Fig. 1). A collar 5I surrounds the rod 5U and is detachably secured to it by the thumb screw 52. Another collar 53 surrounds the rod 41 and is detachably secured to it by the thumb screw 54. By raising or lowering the rod 41 corresponding movement is imparted to the slide 4I and its lower end accordingly functions to enlarge or reduce the effective size of the opening 35 so that the space between the edges of this opening and the neck of the patient may be varied to correspondingly delay or reduce the amount of pressure transmitted from the interior of the head enclosing chamber II! through this space to the interior of the body enclosing chamber. The co1- lars 5I and 53 serve detachably to retain the rod 4l at any desired elevation.

A porthole 6I) is provided to permit the observation of the patients chest.

A water manometer indicated generally by the arrow 6I consists of the usual U-tube manometer member (not shown), one leg of which is connected by the flexible tube 32 and the rigid tube 63 with` thehead. enclosing chamber I and the-other end of which isi connected by the ileirible tube. 6I and the rigid tube `65 tothe interior off thebodt' enclosing chamber. This manometerindicates at all times the difference. in the amounts of." the pressures within the head enclosing chamber I0 anda the body enclosing chamber, and, byiobserving this manometer the required? ad'justmentzof `the slide.4.| may be made. The pressure gauge BB bottom wall 12, topframe members 13.1andfside walls: 14', 1'5, 'Hi4 and 11. On theV top of the `cabinet` an open ended cylinder 80 iswsupported, the upper end being closed by a cover 8|. The'pis'- ton 82l is mounted for reciprocating movement longitudinally of the cylinder 80, thereby to create in the topof the cylinder positive pressure on` the upward stroke and negativev pressure on the downward stroke. The interior of the cylinder 8|!- is connected with the interior ofthe head enclosing chamber I0 by the rigid tubes 84, 85, the longitudinally exible tube 8E, and the rigid tubes 81, 88, the flexible tube 86 detachably connectingV the adjacent ends of theV tubes 85 and 8'1. The other end ofthe tube 81 is connected to the adjacent end of the tube 88 automatically when ange I3 of the casing member I is closed against the face of the ange I4 of the casing member I2 by the clamp I5 and the pin IFA, an air-tight connection being effected by the abutting relationship between the adjacent ends oi'. the tubes 81 and 88 when the clamps I5` are closed, and the ends of. these tubes are provided withrngs of resilient material to insure an airtight connection. The interior of the tube. 88

communicates with the interior of the head enclosing chamber I0 through the opening 90 which is provided in the partition member 28. The tube 88 may be secured to the partition `member 28` by bolts (not shown) which extend belt 99.

The motor is mounted upon a pair of horizontal rods |00 for sliding movement toward or. away :from the shaft 91. Such sliding movement is effected by rotation of the handle I0| which is secured to the horizontal rod |02 located between the rods |00 and having an. exteriorly threaded portion (not shown), the` threads of which engage an interiorly threaded passage (not shown) provided in the vertical ange of one-of the motor supports I 03.

Rotation of the handle |.0I causes the* motor to. be moved longitudinally along; the rods: |100" towards` or away from the the axis: of: the shaft 9.1` and the operative portionA of the belt 99 acting upon the split pulley 96 thereby moves farther-away from or closer to the axis of the shaft 3ft sotliat they speed of rotation ot the shaft 85 The motor pulley 98 is operatively andi the corresponding speed of' rotation ofthe drive shaft 95? thereby may be varied.

Secured. tothe piston 82 (Fig. 5) atthe center thereof is: a1 substantially vertical shaft I-IUL Secured to: therdrive shaft 95 is a crank arm IIIIL. A connecting'rod- I|2 has its'. lower end pivotalty secured to the crank pin |1I3f and its upper end pivotally secured to the lower end of the shaft I lill by means of a cross rod II5.

guide member is formed by theV pair of arms |=f6"andthelpair of rods |I1. Each of the arms Hi8 has one end welded to the rod ||0 and the opposite endi pivotally secured to the ends of the arms |"I1 byla cross rody ||84 (Fig. 4). The other endof each of the rods I|1 is pivotally secured `to a bracket member |20 which is secured to the cabinet 1-0'. The tension spring |22 has one end anchoredto the connecting rod' H2 and. the other end anchored to the cross rod I'I8. This guide member formed by the rods IIB-|11 and the spring |22 functions to maintain the shaft ||0 in substantially vertical position. as itis reciprocated upwardly and downwardly by rota.- tion of the crank arm I |.I by the drive shaft 95, thereby maintaining an air-tight t between the periphery ofthe piston 8'2 and the inner wall of the cylinder 80. On each revolution of the drive shaft 95, the piston 82 is caused to be reciprocated' longitudinally of the cylinder SI1-.a complete stroke, and the interval of time required to'complete such. reciprocation may be variedby moving the motor 94` toward or away from the axisof the shaft 9:1.

TheV tube 84 extends downwardly belowy its junction with the tube and. its lower endr is provided with a flange |25 (Figs. 4, 5 and; Si.) A tube |21 extends from the lower end of thetube 84 downwardly and thence transversely `of the fcabinetwithits outer end passing through the cabinet wall' 14- and freely communicating with `the atmosphere. Its end which isf adjacent to the lower. end of the tube 8,4 is provided with a flange: |28 which is heldin abutment with` the flange |-251byf bolts I 29 (Fig. 6).

A; valve` seat |30 isdetachably secured with'- n the lower end of the tube 84 by the exteriorly threaded.A portion thereof which interengages with, the interiorly" threaded ring I3 I secured to the: interior of the tube 04. The valve 'member r3.5 is.` secured to the rod |36 and this valve is normally held in closed position by the compression spring |31, the lower end of which rests upon the member |38 and theupper end of which engages: the adjacent face of the valve.

The cam |40 (Figs. 5 and- 8) is detachably secured toy thedriver shaft 95. The follower supporting rodi |'|I+|` is' pivotally secured to the support |42; the lower end of which is secured tothe bottom cabinet member 12. One end of the follower supporting rod |4| is pivotally secured to the lower end of the rod |43 (Fig. 5') and the follower |44 isV pivotally supported between the biturcated` portion of the follower supporting rod 'Fhe-turnbuckle |46 adjustably connects the lower end of the rod F36 and the upper end cfthe rod |1435 this turnbuckle and these two rods being thus constructed sothat the distance separating the adjacent ends of these rods may be varied by turning the turnbuckle thus adjusting the length ofthese two rods as represented by the distance between their outer ends;

Upon rota-tion of the drive shaft SI54 thel cam Il correspondingly rotated. The camv F40" is `'misorcontouredthat as it is rotated in the directionl fof the arrow of Fig. 8; (i)V when the fo1lower';|44

is in engagement with the portionsY ab and `celof the cam the valve is maintained, seated or closed by the spring |31, thereby closing all communication between the interior of the tube 84 5 and the atmosphere through this valve; (ii) when the follower is in engagement with the portions vef and gh of the cam the valve |35 is fully opened by rotation of the follower supporting rod I4I about its pivotal connection, thereby compressing the spring |31 and maintaining free communication between the interior of the tube 84 and lthe atmosphere through the tube |21; (iii) when the portions bg and cf of the cam are in engagement with the follower the valve is progressively opened; and (iv) when the portions hd and ea are in engagement with the follower the valve is progressively closed.

Referring to Fig. 7, the tube |21 is lined with felt and this felt lining is faced with wire screening |5| to deaden sounds transmitted through the tube.

A secondary atmospheric conduit extends between the conduit |21 and the junction of the conduits 84 and 85. This secondary conduit |85 .is provided with a valve |88 which is operative to control the effective size of this secondary conduit.

Operation of the apparatus of Figs. 1 to 8 In operation of the embodiment of Figs. l to 8 inclusive, the patient is inserted in the patient enclosing chamber by sliding the casing portion II away from the casing portion I2 far enough topermit the patient to be placed upon the bed 23. The patients head is then inserted through the opening 35 in the partition 28 and placed upon a pillow located on the head rest 3E. y The Acasing portion II is then slid toward the casing portion I2 and these casing sections are sealed in end abutting relationship by rotating'the clamps I5 into contact with the pins I IA. In this condition, the patients body up to his neck is enclosed 1in a substantially air-tight chamber formed by the casing members il and I2 and his head is sup-V ported on the head rest 86 within the substantially air-tight head enclosing chamber formed by the dome I8, and a conduit affording com- ;munication between the head enclosing and the body enclosing chambers is provided by the space between the patients neck and the lower edge of the slide 4| and the lower edge of the opening 35 respectively. Y Closure of the clamps I5 also causes an abuttin relationship between the adjacent ends of the 5 tubes 88 and 81 and thereby provides free communication between the interior of the head en.-

closing chamber lil and the interior of the opera- .tive end of the cylinder through the tubes 88,

81, 86, and 84. The motor 96 is then started and this causes Movement of the crank arm I I the piston progressively increasing positive pressure is created in the upper portion of the cylinder I 80 and on the down stroke of the piston progressively increasing negative pressure is created?.

therein' and these pressures are transmitted through the continuously open tubes 84, 85,:86, 81 and 88 to the head enclosing chamber I8 and thence to the patients lungs through his nose and mouth. These pressures are also transmitted to the body enclosing chamber through the opening in the partition 28 and the size of this opening is adjusted by longitudinal movement of the rod 41 and corresponding sliding movement of the slide 4| so that on the positive pressure stroke, for example, the amount of the pressure in the body enclosing chamber is substantially 5 cm. of Water less than the amount of the pressure in the head enclosing chamber at substantially any given instant. For example, during the instant when the positive pressure in the head enclosing chamber is 45 mm. of mercury, the positive pressure in the body enclosing chamber is 5 cm.

`of water less than 45 mm. of mercury. As appears more clearly from Fig. 9 the pressures in the head land body enclosing chambers are equal shortly after the maximum positive and negative pressures in the head enclosing chamber. This 5 om.

adjustment is accomplished by observing the `manometer El while adjusting the slide 4 I.

The cam |48 is arranged (i) to open the valve I|35 when the piston 82 has completed aboutvesixths of` its upward stroke, (ii) to close the valve |35 when the piston has completed about one'- sixth of its downward stroke, (iii) to re-open the valve |35 when the piston has completed approximately ve-sixths of its downward stroke and (iv) to re-close the valve when the piston has (completed approximately one-sixth of its upward stroke. Thus the head enclosing chamber I0 `and the interior of the cylinder 88 are in communication with the air of the atmosphere during approximately one-third of the length of each upward movement and one-third the length of each downward movement of the piston, and the yvalve is completely closed during about twothirds of the length of each upward movement and two-thirds of the length of each downward movement of the piston.

Stated in terms of elapsed time the valve |35 Yis in partially open and in fully open position approximately one-half of the time required for each stroke and in fully closed position approxi- -mately one-half of the time required for each the curve represents the point where the valve closes on the down stroke of the piston, the point marked 2 represents the point where the valve commences to open on the down stroke of the piston, the point marked 3 represents the point where the valve closes on the upstroke of the piston, the point marked 4 represents the point 'where the valve commences to open on the up- 'fstroke of the piston and the point marked 5 represents the point where the valve closes on the next down stroke of the piston. The points 6 and 1 represent valve openings and closings in 1 the next stroke of the piston corresponding re- 'spectivcly to the points 2 and 3 on the rst stroke. -This chart of Fig. 9 is plotted in elapsed time, .the area 3 4--5-3 being positive pressure and vthe areas |-2--3-I and 5-6-1--5 being negative pressures in the head enclosing chamber,

:As shown the negative pressure created by the downward stroke of the -piston is gradually relieved beginning at the -point `2 until the pressure in the -cylinder til `and in the -head enclosing chamber has been increased to atmospheric at the point 3 and the valve then completely closes, the piston then being at approximately one-sixth of the distance upon its upward'stroke. Th-isaction from the point 2 to the point 3 not `only gradually and progressively increases the pres-` sure in the cylinder 88 and the head end `lf) of the `chamber from the maximum `nega-tive pressure to atmospheric Ibut it also supplies fresh air to the .head enclosing Vchamber `and to the interior oi the cylinder 8|), the `fresh air being admitted through the tubes |21, 84, 85, 86, 81 and. 88. Agradual and progressive decrease from maximum..positive pressure `to atmospheric is `ac-` complished by opening and closing the valveifrom the .point l tothe point 5 and gases are exhausted to the atmosphereduring this period. The resultant `pressure curve shown in Fig. 9 is-a smooth curve. i

Normally the apparatus is .adjusted to create approximately cycles `ei? positive and negative pressure `per minute but the number of cycles per minute may be varied by `moving the motor toward or away from the axis `oi the shaft 9T, such movement being accomplished by rotation of the handle llll.

The maximum amount of the positive pressure within the head enclosing chamber on each cycle is normally limited `to from 40.13055 mm. of mercury, and the maximum amount of negative pres-` sure in the head enclosing chamber is also normally limited to from to 55 mm. of mercury. The maximum positive pressures may be controlled `by means of the valve |86, thereby `in effect creating a controlled leak between the atmosphere and the interior of the head enclosing chamber. This adjustment correspondingly controls the maximum amount of negative pressure created inthe `head enclosing chamber on each strokeo'f'the piston. t

The pressure varying curve of Fig. 9 may `be changed as desired byva'ryingthe contour ofthe cam Ill but in the preferred `embodiment of this invention the valve is nul'ly opened prior to` the end of the downward or `negative pressure stroke of the piston which is also `prior to the beginning of the upward or positive pressure stroke of the piston thereby (i) to prevent a sudden change from maximum negative pressure to atmospheric pressure at the end ofthe downward stroke and at the beginning of the upward stroke of the piston and also (ii) -to permit `sufficient time for the admission of an adequate supply of fresh air prior to the creation of each phase of positive pressure.

The embodiment of Fig. 10

The device illustrated in Fig. 10 is constructed like that of Figs. l to 8 except that a exible diaphragm |18 is substituted for the .piston 82. The diaphragm may be made of leather or other substantially air-tight iiexible fabric. The cylinder 88A is provided with a flange 88B and the edge of the diaphragm is clamped between this flange and the top frame members `'13A of the cabinet. The diaphragm is secured to the end of the shaft |||J by means ofthe metallic discs `I"l| and |12 which engage opposite faces of the valve housing |83 so that it normally-holds the 10 diaphragm. The cover 8|-A is secured across the upper lend of `the cylinder 88A. The tubes 84, |65 `and 85 are `of lthe same construction as the corresponding tubes of `the embodiment of Figs. l .to 8 inclusive, as are all other parts of the apparatus.

In operation the diaphragm is moved between the two` dot-dash positions during reciprocation of the shaft HU, positive pressure being created during upward movement and .negative pressure during downward movement. The operation of the valve |35 and the adjustment of all controls are exactly the same in this embodiment as in the embodiment of Figs. l 1to'8 inclusive.

The embodiment of Fig. 11

formed `through ythe cover `8-| The 'valve lhousing |83 is -detachably secured to Vthe cover and the valve rod |84 is slidably `received by Ethis' Vheus` ing. The valve |82 lis secured to the `rod |84. `The compression spring. 485 has oneL end seated on' valve seated. Four guide flutes |86 are secured to the valve |82` and they serve torguide the lower end of the rod |84 during vertical slidin movements thereof.` i

In this `apparatus the cam |48,` follower |41!` and` follower supporting member I4! of Figs. 1 to 8 are. omitted and the `valve 35 y.permanently obstructs or closes communication `between the tubes `3l!` and 2.11, but the` other parts of the apparatus maybe the same as that of Figs. l to 8 except as4 above` described.

In operation the piston H0 is reciprocated by the drive shaft 95 between the upper and `lower dot-dash positions shown in Fig. 11. `As the piston progresses upwardly from the full line position of Fig. 11 it contacts the lower end `of the rod `"mand elevates it. This `opens the valve |82 and` gases are` exhausted to the atmosphere.

. The valve is maintained `open until the piston has returned to the full line `position at which point -it .is fully closed by the spring |85. This` valve remains closed as Athe piston is moved downwardly and` upwardly until it reaches the full line `position again on its upward` stroke.

As the piston passes downwardly from the intermediate` dot-dash position, communication is opened betweenthe atmosphere and the inte-r rior of the cylinder as the edge of the piston` passes below the upper edges of the perforations |88 and -such communication is maintained `to admit fresh air until, `on the upward stroke, the edge of the piston is elevated to a position above the upper edges of the perforations. The lower dot-dash position of the piston represents the bottom of the stroke.` The length of the lower portion of the rod "|84 and the elevation of the.

perforations |88 controls the opening of the at mospheric communication prior to the negative and prior to the positive pressure strokes respectively.

The maximum amounts of the pressures may be controlled by the valve |66 (Figs. 4 and 5) and the speed reciprocation of the piston may be controlled by the handle IUI (Fig. 4).

From the foregoing it will be apparent that the apparatus of this invention provides an improved immobilizer which is simple and economicalin construction, which provides a uniform pressure varying curve, in which substantially no heatand substantially no air vibrations or pulsations are transmitted to the head enclosing portion in which substantially no noise is created in operation, in which both the head enclosing chamber and the pressure creating mechanism are amply supplied with fresh air from the atmosphere prior to the commencement of each period of positive pressure without interfering with the uniformity of the pressure varying curve and in which the maximum amounts of the positive and negative pressures may be controlled as well as the number of pressure varying cycles per minute, and in which the pressure varying mechanism is of the reciprocating type and is free from spring loaded valves so that the size of the pressure varying mechanism and the amount of power required for its operation is small.

While I have shown and described three desirable embodiments of an apparatus embodying my invention, 'it is to be understood that this disclosure is for the purpose of illustration only and that equivalent forms of the apparatus may be used without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim:

.1.. In a lung immobilizer having a body-enclosing chamber. a head-enclosing chamber, a partition separating said chambers. a conduit affording communication between said chambers at all times` and mechanism for varying the effective size of said conduit, the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate tbe pressure-creating member to create a period of negative pressure within the head-enclosing chamber during each movement of the reciprocasing member in one direction, an atmospheric conduit operative to afford free communication between the head-enclosing chamber and the air of the atmosphere, a movable member operative to control said free communication between the head-enclosing chamber and the air oi' the atmosphere through said atmospheric conduit, and means to actuate said movable member to open said communication through the atmospheric conduit prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure. whereby both the head-enclosing chamber and the pressure-creating mechanism supplied 4with air from the atmosphere through said atmospheric conduit prior to the end of each movement of the reciorocatingr member in a direction to create a period of negative pressure. Y

2. In a lung immobilizer having a body-enclosing chamber, a bead-enclosing chamber, a partition separating said chambers, a conduit affording communication between said chambers at all times, and mechanism' for varying the effective size of said conduit, the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate the pressure-creating member to create a period of negative pressure within the head-enclosing chamber during each movement of the reciprocating member in one direction, an atmospheric conduit operative to afford free communication between the head-enclosing chamber and theair f the atmosphere, a movable valve member to open and close said communication through said atmospheric conduit, a cam to control movement of said valve member, and means to actuate said cam to open said communication through the atmospheric conduit prior to the end 0f each movement of the reciprocating member in a direction to create a period of negative pressure, whereby both the head-enclosing chamber and the pressure-creating mechanism are supplied with air from the atmosphere prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure.

3. In a lung immobilizer having a body-enclosing chamber, a head-enclosing chamber, a par- '.tion separating said chambers, a conduit anording communication between said chambers at all times, and mechanism for varying the eiective size of said conduit, the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate the pressure-creating member to create a period of negative pressure within the head-enclosing chamber during each movement of the reciproeating member in one direction, an atmospheric conduit operative to afford communication between the head-enclosing chamber and the air of the atmosphere, a movable valve member to open and close communication through the atmospheric conduit, a cam to control the movement of said valve member, said cam having a contour such that the valve is opened prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure and is maintained open for a substantial period, and means to actuate said cam, whereby both the head-enclosing chamber and the pressure-creating mechanism. are supplied with air from the atmosphere prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure.

4. In a lung im'mobilizer having a body-enclosing chamber, a head-enclosing chamber, a partition separating said chambers, a conduit affording communication between said chambers at all times, and mechanism for varying the eiTective size of said conduit. the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate the pressure-creating member to create a period of negative pressure within said head-enclosing chamber during each movement thereof in one direction, a primary atmospheric conduit operative to afford :free communication between the head-enclosing chamber and the air of the atmosphere, a movable member operative to control said communication between the head-enclosing chamber and the air of the atmosphere through said atmospheric conduit, means to actuate said movable member to open said communication through the atmospheric conduit prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure, a secondary atmospheric conduit operative to afford communication between the head-enclosing chamber and the air of the atmosphere, and an adjustable member to control the eifective size of said secondary conduit, whereby both the head-enclosing chamber and the pressure-creating mechanism are supplied with air from the atmosphere through said primary atmospheric conduit prior to the end of each movement or" the reciprocating member in a direction to create a period of negative pressure and the maximum' amount oi negative pressure in the head-enclosing chamber is controlled by said adjustable member of said secondary atmospheric conduit.

5. In a lung immobiliser having a body-enclosing chamber, a head-enclosing chamber, a partition separating said chambers, a conduit affording communication between said chambers at all times, and mechanism for varying the eiective size of said conduit, the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate the pressure-creating member to create a period oi' negative pressure within said head-enclosing chamber during each movement of the reciprocating member in one direction and a period of positive pressure during each movement thereof in the other direction, movable means operative to control the communication between the headenclosing chamber and the air of the atmosphere, and means to actuate said movable means prior to the end of each movement of hte reciprocating member in a direction to create a period of negative pressure and prior t the end of each movement of the reciprocating member in a direction to create a period of positive pressure, thereby periodically to open said communication with the air of the atmosphere, whereby both the head-enclosing chamber and the pressure-creating mechanism are supplied with air from the atmosphere prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure and gases are exhausted therefrom to the atmosphere prior to the end of each movement of the reciprocating member in a direction to create a period of positive pressure.

6. In a lung immobilizer having a body-enclosing chamber, a head-enclosing chamber, a partition separating said chambers, a conduit affording communication between said chambers at all times, and mechanism for varying the effective size of said conduit, the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate the pressure-creating member to create a period of negative pressure within said head-enclosing chamber during each movement of the reciprocating member in one direction and a period of positive pressure therein during each movement of the reciprocating member in the other direction, an atmospheric conduit operative to aiord free communication between the head enclosing chamber and the air of the atmosphere, a movable valve member operative to control the communication between the head-enclosing chamber and the air of the atmosphere through said atmospheric conduit, a cam to control the opening and closing of said valve member, said cam having a contour such that the valve is opened prior to the end of each movement of the reciprocating member in a direction to create a period of negative pressure and prior to the end of each movement of the reciprocating member in a direction to create a period of positive pressure, and on each occasion is maintained open for a substantial period of time, and means to actuate said cam, whereby both the head-enclosing chamber and the pressure-creating mechanism are supplied with air from the atmosphere prior to the end of each movement of the reciprocating member in a direction to create a period oi negative pressure and gases are exhausted therefrom to the atmosphere prior to the end of each movement of the reciprocating member in a direction to create a period of positive pressure.

7. In a lung immobiliser having a body-enclosing chamber, a head-enclosing chamber, a partition separating said chambers, a conduit affording communication between said chambers at all times, and mechanism for varying the effective size of said conduit, the improvement comprising a pressure-creating mechanism including a pressure-creating member which is continuously in communication with the head-enclosing chamber, a reciprocating member operative to actuate the pressure-creating member to create a period of negative pressure within said head-enclosing chamber during each movement of the reciprocating member in one direction and a period of positive pressure during each movement thereof in the other direction, movable means operative to control the communication between the headenclosing chamber and the air of the atmosphere, and means to actuate said movable means during the time interval between the end of the first nve sixths of each movement of the reciprocating member in a direction to create a period of negative pressure and the end of the iirst one sixth of each movement of the reciprocating member in a direction to create a period of positive pressure, whereby both the head-enclosing chamber and the pressure-creating mechanism are supplied with air from the atmosphere prior to the commencement of the last iive sixths of each movement of the reciprocating member in a direction to create a period of positive pressure.

JAN LEYENlAAR.

REFERENCES CITED The following references are of record. in the le oi this patent:

UNITED STATES PATENTS Number Name Date 2,060,766 Vinal Nov. 10, 1936 2,263,844 Hammond Nov. 25, 1941 OTHER REFERENCES Pages 521 to 525 of Diseases of the Chest, for November-December 1946, vol. XII, number 6, published by American College of Chest Physicians, 560 North Dearborn Street, Chicago 10, Illinois. Article written by Alvan L. Barach. (Copy in Medical School Library, National Naval Medical Center, Bethesda, Maryland.)

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