Non-newtonian fluid spray applicator and method

Details Non-newtonian fluid spray applicator and method Non-newtonian fluid spray applicator and method

2000-05-08

2002-08-13

Walberg, Teresa (Department: 3742)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

Reexamination Certificate

active

06432084

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Continuation Status Not Claimed
This application discloses subject matter related to our copending U.S. patent application Ser. Nos. 08/838,078 and 08/839,614 both filed Apr. 14, 1997, to patent application Ser. No. 08/946,364 filed Oct. 7, 1997 and to patent application Ser. No. 09/037,160 filed Mar. 9, 1998, to a patent application Ser. No. 09/302,726 filed Apr. 30, 1999 and entitled “GAS-DRIVEN SPRAYING OF MIXED SEALANT AGENTS” all naming Gordon H. Epstein as first inventor, and to an international PCT patent application in the name of the assignee of all interest of the instant application, Biosurgical Corporation, Application No. PCT/US99/09663 also entitled “GAS-DRIVEN SPRAYING OF MIXED SEALANT AGENTS”. The disclosures of the aforementioned United States patent applications, and one international PCT patent application, “the related applications”, are hereby incorporated herein by reference thereto. Continuation status is not claimed.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not applicable.)
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an applicator and method for spray application of a non-Newtonian fluid to a work surface. The invention is particularly, although not exclusively, useful for applying tissue sealant agents containing a polymer such, for example, as fibrinogen, to biological tissue to effect hemostasis or achieve other therapeutic results. More particularly, it relates to spray application of tissue sealants from a hand-held applicator.
2. Description of Related Art Including Information Disclosed under 37 CFR 1.97 and 37 CFR 1.98
Use of tissue sealants and other biological materials is an important emerging surgical technique, well adapted for the operating room or field environments such as the doctor's office or mobile medical units. Preferred sealants include fibrin sealants which are formed from blood plasma components and comprise, on the one hand, a first agent containing fibrinogen and Factor XIII and on the other hand a second agent which usually includes thrombin, and calcium ions. The fibrinogen is capable of a polymerizing and being cross-linked to form a solid fibrin clot when the agents are mixed. The necessary additional factors to simulate relevant portions of the natural blood coagulation cascade are suitably distributed between the fibrinogen and thrombin agents.
High levels of protection against transmission of infections or induction of immunological reactions can be assured by using an autologous or single-donor source for both agents. Such sealants are highly effective, are biologically degraded without residue and may promote wound healing.
They may be dispensed from hand-held applicators which can generally be classified as droplet applicators or spray applicators. Droplet applicators dispense a continuous stream or single line of droplets from a cannula, or other dispensing tube. Spray applicators generate one or more patterns of atomized fluid that can be applied to a work surface so as to cover a wider area than the output from droplet applicators. In many cases the applicators comprise dual syringes providing reservoirs for two sealant agents which are dispensed by manually operated plungers which drive the fluids out of the reservoirs to be mixed internally or externally. Some examples of such applicators, especially ones that address the problems of mixing sealant agents internally, are disclosed in the related applications.
Capozzi et al. U.S. Pat. No. 5,116,315 discloses a spray applicator that outputs a mixture of two sealant agents which applicator is provided with replaceable spray orifices so that when they become clogged with sealant, the user can remove the clogged orifice and replace it with a new one. Changing the clogged orifices is inconvenient and may be difficult and inconvenient during surgery. Fibrin sealants can coagulate very quickly, in a matter of seconds. Accordingly, such a spray applicator can easily become clogged between applications if it is set down for a minute or two. The need to change the spray orifices during a surgical procedure, and to have replacement orifices available, may be quite disruptive or impractical.
Furthermore, the momentum of the spray droplets leaving the applicator is derived from manually applied pressure to the sprayed liquid. Naturally, the pressure with which the liquid is applied to the spray orifice, and therefore the momentum with which the droplets are discharged from the spray orifice, is subject to variation, caused by the mechanics of the dispensing mechanism or simple inability of a human operator to apply constant pressure throughout a range of manual movement. Accordingly with the Capozzi spray applicators, it is difficult to produce an even spray having a consistent spray pattern. It is also difficult to discharge the droplets from the applicator with a constant momentum, as would be desirable for consistent application of materials such as a surgical sealant.
Another approach to this problem has been to entrain the individual sealant agents in separate gas streams, providing overlapping spray patterns, with the intention that the agents will mix in the air or on the tissue surface. Thus, for example, Redl U.S. Pat. No. 4,359,049 discloses a dual syringe tissue adhesive applicator for dispensing two adhesive agents, which applicator employs a disposable mixing needle to provide a mixed sealant output a in the form of a liquid stream or a series of droplets. To provide a spray output, FIGS. 4 and 5 of Redl disclose the use of two pressurized gas streams emerging from outlets 50,51 in the region of the valves 43,44 of conveying channels 41,40 which separately supply adhesive agents from syringe bodies 1 and 2. (See column 3, lines 45-47.) Two spray patterns are generated and, according to Redl “unite at a distance of about 10 to 20 cm, rapidly forming a thin uniform adhesive film on the surface to be adhered or sealed.”, see column 4 lines 1-3. As taught in the related application filed Apr. 30, 1999 application Ser. No. 09/302,726, such external mixing of separate sprays provides ineffective mixing and the resultant sealant may lack adhesive or cohesive strength.
Furthermore, depending upon the potency of the particular formulations employed, coagulation of the sealant may take place very rapidly, once the necessary sealant agents are mixed, yielding a gel within perhaps 5 or 20 seconds of mixing. Though often desirable for surgical reasons, such fast-acting properties may aggravate difficulties with atomization, when a mixed sealant is sprayed, and can lead to fouling or clogging of the spray applicator.
Surprisingly, we have found that many known spray applicators exhibit poor spray quality when applying fibrinogen, even spray applicators specifically intended for fibrinogen application, such as those referenced above. Studies we have conducted, pursuant to the present invention, have shown that a fibrinogen agent tends to stream instead of spray when dispensed through conventional spray applicator nozzles, which is wasteful and ineffective. Such drawbacks may render the applicator quite unsuitable for surgical use. The possibility of such streaming is particularly unsatisfactory for many surgical applications where a thin film of sealant is desired. In some cases, thick layers of sealant can be a barrier to the blood supply of connected tissues. To meet the need for a thin layer of deposited sealant, it is desirable for a spray applicator to be capable of generating a consistent, fine spray.
Pursuant to our studies, it appears that because the fibrinogen agent is a polymer solution containing a dissolved long-chain polymer, the fibrinogen molecule, a molecule which has a molecular weight of about 400,000 daltons, the fluid characteristics of the fibrinogen agent may be non-Newtonian. Thus, the viscosity of the fibrinogen agent fluid may vary with shear rate. In particular, the elongational viscosity, which is the resistance of the fluid to being stret

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