Device for performing measurements on fluids, directly in the sample container

United States Patent m

Meiattini et al.

[ii] 4,339,317 [45] Jul. 13, 1982

[54] DEVICE FOR PERFORMING

MEASUREMENTS ON FLUIDS, DIRECTLY
IN THE SAMPLE CONTAINER

[75] Inventors: Franco Meiattini, Siena; Giorgio Papeschi, Florence; Paolo Tarli, Monteriggioni; Paolo Neri, Siena, all of Italy

[73] Assignee: Institute Sieroterapico e Vaccinogeno Toscano "Sclavo" S.p.A., Siena, Italy

[21] Appl. No.: 204,220

[22] Filed: Nov. 5,1980

Related U.S. Application Data

[63] Continuation of Ser. No. 52,506, Jun. 27, 1979, abandoned.

[30] Foreign Application Priority Data

Jul. 5, 1978 [IT] Italy 25351 A/78

[51] Int. C1.3 G01N 27/28; G01N 27/30

[52] U.S. CI 204/195 B

[58] Field of Search 204/195 R, 195 B

[56] References Cited

U.S. PATENT DOCUMENTS

2,886,771 5/1959 Vincent 204/195 R

3,224,433 12/1965 von Dalebor 204/195 B

3,497,442 2/1970 Vincent 204/195 R

3,878,830 4/1975 Bicher 204/195 B

Primary Examiner—T. Tufariello

Attorney, Agent, or Firm—Morgan, Finnegan, Pine,

Foley & Lee

[57] ABSTRACT

For taking measurements on fluids, such as biological fluids (e.g. blood and the like), a device is disclosed which is a cylindrical body insertable in a syringe or a similar sampling container and has on the exposed face a set of electrodes or probes which are connected via appropriate electric leads to processing and displaying devices which permit the taking of immediate readings of important parameters such as pH, temperature, partial pressures of gases and so on.

10 Claims, 2 Drawing Figures

4,339,

1

DEVICE FOR PERFORMING MEASUREMENTS
ON FLUIDS, DIRECTLY IN THE SAMPLE
CONTAINER

5

This is a continuation of application Ser. No. 052,506 filed June 27, 1979, now abandoned.

This invention relates to a device adapted to perform analytical check-up operations on samples of various origin. 10

A typical example is the check of the environmental pollution, which requires, as a rule, a special sensitivity and, concurrently, a simple performance of the analytical operations.

Another field of application is that of clinical tests in 15 which there is the necessity of continuously monitoring the trend of certain analytical parameters, such as for example, during progress of certain surgical operations, or in reanimation centers.

The samples of the material to be analyzed must very 20 often be transferred into specially provided containers for being sent to the analysis laboratory. The shortcomings which are generally experienced in such procedures are as follows:

increased occurrence of contamination and/or errors, 25 such as sample-swapping, errors in copying down the sample identification codes and the like.

time waste

increased use up of laboratory vessels a few particular cases, such as for example the case of 30 analysis of gases in the blood, with attendant risk of alteration of the values of the substances to be measured, due to diffusion from and into the environment. This drawback is particularly significant in the case, mentioned above, of the operating 35 rooms and the reanimation centers where, on the basis of the analytical results which are obtained, decisions of vital importance shall be taken. It becomes thus imperative to be able to use a device which permits that these analysis may be performed, if 40 and when possible, without transferring the samples and, preferably, at the very sampling spot.

The subject matter of this invention is a device which permits the taking of readings directly in the sampling container. 45

The device is composed, as shown in FIG. 1 of the accompanying drawings, which does not limit the invention, by a cylinder of an appropriate material 1, which is not prone to attack by the fluids to be analyzed and which can be sterilized if so required, appropriate 50 sensors, 3, 4, 5 and 6 being inserted in said container so as to confront the side 2 of the cylinder which contacts the sample. The cylinder is so shaped as to be capable of acting like a piston in the hollow cylindrical space of the sampling container. The sensors are connected, via 55 appropriate leads, to one or more detecting instruments) which serve for the processing and display of the readings.

FIG. 2 of the accompanying drawings offers an example of a piston of the kind referred to above, inserted 60 in a hypodermic syringe for taking blood samples. In such a syringe (hypodermic) the sample of the blood which is drawn contacts, at very instant of sampling, the sensors housed in the head of the piston and which are specific for measurements of pH, PO2, PCO2 and 65 temperature.

The sensors deliver their signals to the processing instruments which provide to process them and to dis

317

2

play the readings on appropriate display screens and/or printed charts. By so doing, the results of the tests are made immediately available. The example given is by no means a limitation and does not exclude the use for different measurements and on samples other than those exemplified herein. An outstanding asset of the invention is that it becomes possible to effect the readings on reduced volumes of sample since it is by no way necessary to fill the cylindrical space completely, it being necessary and sufficient that the sensors projecting from the piston head are wetted. This fact also facilitates the performance of tests in a rapid sequential order by using a plural-way cock such as in FIG. 2.

As a matter of fact, once the hypodermic needle 1, has been inserted in the artery or the vein, the sample is drawn and, once the measurement has been taken, the sample itself can be discharged without removing the needle upon shifting the stream to the discharge 2 by the two-way cock 3 which is inserted between the needle and the body of the syringe 4. By rotating the cock handle again, the device is in readiness for the next sampling and so forth. In the case in which there is the necessity of introducing in the sample a clot-preventing agent such as heparin, the device can be equipped with a 3-way cock, one way being intended to draw the clot-preventing agent.

A model of the device has been embodied by way of example only by combining in a single piston-cylinder assembly of a plastics material, a microelectrode of iridium and iridium oxide for measuring the pH, a microelectrode for measuring PCO2, a polagraphic-type microelectrode for measuring PO2 and a thermosensitive probe for taking sample temperature readings. This model of pistons can be inserted in a syringe, the latter being possibly surrounded by a thermostatic liner.

As a rule, the electrodes used in the analysis of blood gases are based on the following; operating principles:

. PCO2 electrode:

This is composed by an electrode which is normally made of glass and is responsive to the protonic activity, and is immersed in a solution of NaHC03 in contact with a membrane through which diffusion of CO2 can take place. When the CO2 which is diffused through the membrane is solubilized (I) in the solution held between the electrode surface and the membrane, it shifts the equilibrium (II) towards the right, the protonic activity being consequently increased:

co2 + H2o H2CO3 (I) H2CO3 H+ + CHO3- (H)

Under equilibrium conditions, the partial pressure of CO2 will be the same on both faces of the membrane. Thus, variations of PCO2 outside the membrane will originate equal variations of PC02in the film of solution enclosed between the membrane and the electrode.

The potential of the glass electrode is measured relative to a reference electrode Ag/AgCl which finds the Cl_ ions in the internal solution which contains also the bicarbonate (typical composition NaHCOs: 0.05 M+NaCl: 0.1 M).

The cell is thus constituted as follows:

Ag—AgCl NaHCO3 0.05 M pH electrode
NaCl 0.1 M