US1905782A - Manometer - Google Patents

Description

April 25, 1933. s. s AMDURSKY' MANOMETER Filed Oct. 25, 1930 ATTORNEY INVENTOR JWME .s. amm BY Patented Apr. 25 1933 UNITED STATES-- PATENT OFFICE SAMUEL s.amnonsxxornoonnsrsn; new 3073 assrcnon TO TAYLORI'NSTRUMENT comramns'or nocx-rasrnnnnwyonx, A CORPORATION or new YORK MANOM'ETER Application filed October 25, 1930. Serial No. 491,146.

The invention relates to manometers of the type for measuring the pressure conditions of the circulatory system andmore in particular to thatform of manometer wherein the operating pressure is balanced against a column of liquid, usually mercury.

Oneof the great drawbacks of this form of measuring device is the setting up of oscillations of the mercury column due to the rhythmical variations of the pulse wave, which oscillations make it diiiicult to read the values of the static pressure applied for producing the constricting etfectupon the artery. The systolic pressure and the diastolic pressure are determined from the characteristic sounds observed by-means of the stethoscope during the gradual release ofthe pressure from the constricting cuff and it is of the utmost importance that the pressure indicated by the mercury columnis the true pressure causing the constrictive efiect. Since'itis impossible to avoid the rhythm'icreaction's of the blood stream upon the pressure-responsive walls of the constricting cuff and upon the pressure fluid therein, it is necessary to find the true effective-pressure values at which the characteristicsounds are observed.

It is impossible for even the keenest obtween the upper and the lowerlevel of the oscillating mercury column.- The amplitudes of the oscillations vary in proportion to the pulse pressure, the pulse rate and the height of the mercurycolumn, and attimes may be 15 m. m; or more and the: difiiculty of reading is considerably increased bythe changing form of the meniscus.

The amplitudes are the largerth'e more the pulse rate approaches the natural period of oscillation of the mercury column, which oscillation is a damped simple harmonic mot-ion. 1 I a The undesirable character ofthese oscillations was recognized for. many years and 45 attempts were made to eliminate them or at least materially reduce them. Heretofore, the only apparent remedy devised was a resistance to the flow of the mercury from the cistern to the tube or to the flow of air above ,5 the column outof the tube or tothe flow of f the pressure medium. from the cuff into the c stern. lVhile these constricting measures effect a damping out of the oscillations, they accomplish the object only due to a time lag introduced bygthe frictional resistance. Although investigations in this field have not been, completed and the technique is too in tricate to dispose of the different questions in ashort time, theevidence clearlyindicates that for the usual practice of makingthe observations on a decreasing cuff pressure, the readings ofthe mercury columnare materiallyhigher thanthe true pressure in the cuif would call for.. This-errorin the reading varies in proportiouto the rate at which the operator allows the airto leak out of the system :and also in proportion to the height ofthe column when the reading'is'taken;

.Aside from theerrordueto the lag, in general, the ditficulty is thus aggravated by thesetwo variable factors which donot admitof standardization or application of calibration constants. I

The object of the present invention is a mercurial manometer of the class referred to wherein the pulsations tending to main,- tain the ,mercurycolumn in an oscillating condition are damped out or dissipated without causing. any time lag or any appreciable timelag: inthe establishment of a true balance between the weight of the mercuif fy column and the static pressure in the on i Expressed in different form, it is the object of the invention toprovide a mercury nanometer wherein at the. time of a stetho scopic indication the true corresponding valueof the pressure in the bag may be instantly read from the position of the mercury column.

,HFora full understanding of the invention, the principle of operation on which it is based and its advantages, reference is made to theaccompanying drawing wherein Y Fig. 11s a front AVIBWOTE one arrangement embodying the invention; Fig. 2 is: a sectional view of another construction embodymg the invention e Fig. 8 is a section on line 3,3, Fig, 2; and

Fig, t is'a s ct onal view of'what I now consider as a preferred form of the invention.

In Fig. 1, 1 represents a part of the cuff or pneumatic armlet generally placed over the upper arm and held in place by means of a sleeve of inelastic materiah There are two connections 2a and 2b to the cuff, one of which carries the usual hand bulb 2 and the other of which is in fluid connection with the cistern '3 which acts as the pressure chamber for the measuring tube 4, being connected thereto by the bent tube 5. The tube 4, bent tube 5 and cistern are mounted upon a suitable standard 8.

The structure thus far described represents generally the usual form of a mercury sphygmomanometer.

The salient feature of the invention is the interposition between the cuff '1 and the cister-n 3 of a means for damping out vibrations or oscillations transmitted from the cuff toward the tube 4. A very effective means to this end is a vessel 6 which is in fluid connection with the cuff, on the one hand, and with the cistern 3, on the other hand.

The operation is, of course, generally the same as in all usual forms of apparatus of this type. The cuff is pumped up and part of the air flows into the cistern 3 and forces an amount of mercury into the tube corresponding to the pressure in the cut]? 1'.

One of the characteristic features of the invention is the absence ofany form of means tending to impede or retard an equalization of pressures between the pressure medium in the cuif, on the one hand, and the pressure of the mercury column, on the other hand. Thefiuid connection between the cuff and the tube is free of constricting'means and the upper end of the tube is entirely open during measurements or if there is a closure for" preventing the escape of mercury, such closure is of suchconstruction as not to materially aifectthe fiow of air into and out of the tube when themercury column is made torise or fall.

It is the usual practice to pump air into the cufi until the pressure in the systemis greater than the systolic pressure expected in the patient. Then the pressure is gradually decreased by allowing air to escape through the leak valve 7,, until the physician hearsthe characteristic sound indicating the systolic pressure. When. he hears this sound, he notes the reading of the mercury column and, allowing the air to continuously escape, he follo-ws'the column down until he hears the sounds characteristic of the diastolic pressure when he takes another readmg.

In the invention described, the mercury column always in equilibrium with the pressure in the cuff. This effect is obtained,

in; the firs in$tance, by the omissiqn f res strictions in the flow path of the air and the mercury, and secondly, by the damping out of all the vibrations which usually, in the absence of constricting means, set the mer cury column in motion and maintain it in motion. The waves setup by the-pulse beat are leveled out in the body of air in the vessel 6, so that the pressure at the outlet of the vessel 6 and in the reservoir manifests itself solely as static pressure.

Naturally, the larger the body of air in the vessel i. e. the larger the vessel, the greater is the leveling out or damping eifect. However, I have found that a relatively small volume, a volume several times larger than the average volume of the cuff, i. e. of the order of about to 1 liter, gives perfect satisfaction. Having reference'to Figs. 2 and the vessel 10 for damping out the oscillations is mounted on the inside of a cover 11a of the casing 11 containing the apparatus. The cistern 12 is disposed within the vessel 10 and is in fluid connection with the latter through a tube 13 which is so disposed that the mercury cannot escape when the cistern isin a horizontal position. The tube 14;' together with the scale plate 16 is supported directly on the-wall of the vessel 10. A nipple 17, preferably at thebottom of the vessel 10, adjacent to the bent tube laserves to make fluid connection to the interior of the vessel from the I cuff. Arms 18 pivotally interconnecting the lower part-and the upper part of the casing 11 are provided for swinging the latter and the manometer as a unit into an upright position, as indicated in Fig. 2 in dotted lines.

The form of apparatus shown in Fig. 4 is a reduction of the invention to its simplest form. The dampingvessel and; the cistern or reservoir are defined by a single vessel 20 the lower portion 20a of which is preferably funnel-shaped to constitute the cistern from which a bent tube 21 makes fluid connection to the manometer tube 22' on the opposite side of the standard 23; A connection 2i preferably extending through the bottom of the vessel 20 to the top thereof, serves for making fluid connection to the cuflt. The

standard 23 maybe supported similarly to the cover 11a, as a part of a casing or in any other desired manner. l

i The manometer tubemaybe closedat its top in any suit-able manner provided the 010-" sure does not introduce a material. resistance to the flow of air into and out of the tube.

F or the purposes of illustration. I have inwhich septum allows air to freely pass, but

forms a barrier to the flow of the mercury. W In the foregoing I have described the essen al fea u s of my luventwn. 1t 13 un derstood that there are many forms in which the invention may find expression.

I claim:

1. In a manometer of the character described, the combination with a cufi, a pressure chamber, a measuring tube connected to the pressure chamber and a liquid in the pressure chamber and the tube, of a closed vessel in fluid connection with the 01111 and the pressure chamber, said vessel having a volume capacity such as to materially damp out pulsating waves coming from the cuff.

2. In a manometer of the character described, the combination of a cuff, a pressure chamber, a fluid connection between the cufi and the pressure chamber, including a closed vessel having a volume capacity in excess of the volume of the cuff and a measuring tube connected with the pressure chamber, containing a measuring liquid.

3. In a manometer of the character described, a measuring tube. a pressure chamber in fluid connection with the tube, a closed vessel having an inlet therein for communication with a cufl, a fluid connection between the said vessel and the pressure chamber, and a standard for supporting the said vessel, the tube and the pressure chamber in operative relation.

4. In a manometer of the character described, a standard. a measuring tube. a pressure chamber and an air chamber in fluid connection therewith mounted as a unit on the standard, a connection between the tube and the pressure chamber and a cufif in fluid connection with the air chamber.

5. In a manometer of the character described, a measuring tube, a pressure chamber, a connection between the latter and the tube, an air chamber above the pressure chamber, forming an upward extension of the latter, a cufl in fluid connection with the air chamber, and a standard for supporting the said parts in operative relation.

6. In a manometer of the character described, the combination of a cufi', a measuring tube and a fluid connection between the cufl' and the tube, including an air chamber having a volume capacity of such size as to substantially damp out pulsating waves set up in the cuff by the pulse beat.

7. In a manometer of the character described, the combination of a cufl, a measuring tube and afluid connection between the cufl and the tube, including an air chamber having a volume capacity greater than the volume capacity of the cufi.

8. In a manometer of the character described, a standard, a vessel mounted on the standard, a measuring tube in fluid connection with the said vessel at the bottom thereof and disposed in substantially parallel coextensive relation to the vessel, the vessel including at its bottom a part forming a pres sure chamber for the manometer liquid and above the pressure chamber an air space several times larger than the space of the pressure chamber.

9. In a manometer of the character described, the combination of a measuring tube, a vessel defining at its bottom a cistern for the measuring liquid and above the cistern an air space several .times larger than the space of the cistern, a standard for the support of the vessel and the tube, a connection between the tube and the bottom of the said vessel, and a cuff in fluid connection with the air space of the vessel.

In testimony whereof I aflix my signature.

SAMUEL s. AMDURSKY.

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