Articles for the protection of living tissue

An article for the protection of humans, animals and other articles from damage due to undesired exposure to lasers comprising a tubular element comprising at least one layer comprising a xerogel comprising at least one water-insoluble hydrophilic polymer wherein if said tubular element comprises at least three layers the layer adjacent the distal side, relative to the laser beams, of said xerogel layer comprises a metallic layer the proximal surface of which may be reflective or nonreflective of the laser beams and wherein said xerogel layer may further comprise a pigment. In addition, the layer on the distal side of said metallic layer may be a xerogel. During use of the articles of the invention the xerogels thereof are in a hydrated condition, i.e., they are hydrogels.

BACKGROUND OF THE INVENTION 
This invention relates to articles for the prevention of undesired exposure 
of humans, animals and articles to laser beams. More particularly, it 
relates to protective barriers such as protective clothing, sheaths for 
instruments, surgical drapes, endotracheal tubes, vaginal dilators and the 
like, for use in or during laser-effected surgery or therapy which are 
useful in the protection of such humans, animals and articles from said 
undesired exposure to said lasers, said barriers being comprised of 
hydrophilic xerogels or hydrogels and, if desired, additional additives 
such as salts, colorants, pigments and medications. 
Lasers have recently made a significant breakthrough as a preferred, in 
some, and the only modality, in other surgical and therapeutic areas. 
These areas of increasing use of lasers in surgery and other treatments 
include, e.g., otolaryngology, gynecology and ophthalmology. 
Amongst the main advantages of lasers, in surgery, are their ability to 
incise and/or remove precisely controlled areas of tissue while permitting 
visual assessment of the procedure through use of an operating microscope. 
This visual assessment is facilitated by reduction of bleeding and absence 
of other instrumentation, which might block the surgeon's view, in laser 
surgery when compared to conventional surgical techniques. 
Furthermore, if the blood vessels are sufficiently small they are sealed, 
by the laser, after incision. If some bleeding were to occur, for 
instance, in the case of larger blood vessels it can be efficiently 
stopped by coagulation using a defocused beam, the defocusing being 
accomplished by partial retraction of the focusing tip, i.e., by 
increasing the working distance of the laser beam. 
Additional advantages of using lasers in surgery are the limitation of the 
area of undesirable tissue destruction and the zone of devitalized tissue, 
fewer post-operative complications and less post-operative pain and scar 
formation which might hinder healing. As a consequence hospitalization 
time is reduced. 
Nevertheless, the use of lasers, in medical treatments and surgery, is not 
without disadvantages and hazards, chief among which are the danger of 
fire and the destruction of viable tissue on the margins, or periphery, of 
the operative site. 
As a consequence normal drape procedures commonly used in lasser surgery 
and treatment are of limited value and potentially dangerous. For 
instance, a fire hazard is especially present when wet Cottonoids (cotton 
gauze pads wet with saline) which are used to protect the surrounding 
tissues and organs from exposure to extraneous laser beams, whether direct 
or reflected, dry out and ignite due to the high inflammability of dry 
cotton or cellulosics. This is an always present danger due to the high 
levels of energy associated with laser beams. Thus, it is necessary for 
the surgical team to be constantly aware of that possibility and to keep 
the gauze moistened at all times. 
Yet other problems arise in the use of drapes on compound surfaces, i.e. 
surfaces that are not smooth but rather have cavities and ridges, whereby 
the usual drapes do not conform to the surface topography thereby 
permitting gaps to be formed between the tissue surface and drape. These 
gaps permit the gathering of gases and/or heat therein which ultimately 
result in undesireable tissue damage. 
Furthermore, stray beams may impinge on personnel and articles within the 
operating arena with concomitant damage thereto, e.g., burning the skin of 
said personnel, charring of clothing, melting of plastic articles, 
ingnition of flammable materials, overheating of equipment, and the like. 
A. H. Andrews, Jr., and Polanyi, T. G., "Hazards and Safety Considerations 
When Using the CO.sub.2 Laser" in A. H. Andrews, Jr. (ed.): Microscopic 
and Endoscopic Surgery With the CO.sub.2 Laser, Boston, MA., John 
Wright--PSG. Inc., pp 75-6, 1982. 
An additional aspect of the fire hazard is that the laser beam will burn 
through most plastics or rubbers of which tubes for insertion into body 
cavities, e.g., endotracheal tubes and vaginal drapes or dilators, are 
constructed. Thus, the use of plastic or most rubber endotracheal tubes is 
usually contraindicated when surgery employing lasers is contemplated. 
Therefore red rubber tubing or steel, which are less sensitive to lasers, 
are used, e.g., in the construction of endotracheal tubes. However, 
because endotracheal tubes prepared from such materials lack built-in 
cuffs, they do not make completely air-tight seals with the organ walls. 
To get around that problem it has been necessary to place a separable, 
inflatable cuff over the distal end of the tube which has, therefore, 
resulted in the addition of a balloon-filling tube, passed through the 
larynx, to an already crowded lumen. Furthermore, if the beam impacts upon 
such a cuff it usually creates a hole or holes therein whereby the 
inflating medium escapes with a resultant deflation of the cuff and 
undesirable and potentially dangerous mixing of the environments normally 
separated by the cuff. 
A method to prevent such an occurrence by disposing a thermal shield, 
comprising a plurality of laser-reflecting petals extending from the outer 
walls of said tubes to the inner walls of the cavity, between the cuff and 
the portion of the cavity wherein the surgery or treatment is to be 
performed, is taught in U.S. Pat. No. 4,378,796. 
However, as the above shield functions by "reflecting" the laser beam its 
use would be diadvantageous to the patient in that the reflected beam may 
then impact upon healthy tissue, rather than on the surgical site, with 
deleterious effects thereto. 
Additional protection against such undesired impact by the "laser beam [may 
be provided] by wrapping the tube with an aluminum adhesive tape". . . 
However, [a]lthough the aluminum tape provides protection, it should not 
be relied on heavily. . . The tape is only a safety factor and is not 
absolute." Ibid, p. 77. 
Another problem, the destruction of viable tissue near the operative site 
is due to the fact that, during surgery using lasers, it is often 
impossible to concentrate the laser exactly and exclusively on the 
surgical site. For instance, the incident beam may have a larger diameter 
than the surgical site or part of the beam may be dispersed or reflected, 
although at a lower intensity, to a distance from the surgical site. This 
results in undesireable destruction of healthy tissue at the periphery of, 
and/or at a distance from, the surgical site. The damage occurs in the 
same manner as the surgery is effected, i.e., by ablative removal of the 
water (about 90%) and organic matter of which the tissue is comprised. 
It has now been found that the articles of the instant invention obviate 
the above problems thereby providing for enhanced protection of humans, 
animals and articles during laser-effected surgery and treatments whereby 
healing of the wounds is facilitated. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide articles for the 
protection of humans, animals and other articles from damage due to 
undesireable exposure to stray or reflected laser beams used during 
laser-effected surgery. 
It is yet another object of the invention to provide an article for the 
protection of humans, animal and articles from damage due to exposure to 
laser beams during treatment or surgery using lasers said article 
comprising a hydrophilic xerogel. 
Yet another object of the invention to provide a laser-resistant tube, to 
be utilized by passage of laser beams therethrough or externally thereof, 
for insertion into body cavities, whereby unwanted exposure to said beams, 
directly or indirectly, is prevented. 
According to another object of the invention there is provided a tube as 
described above comprising at least two layers at least the one proximal 
to the laser beams comprising a xerogel. 
In accordance with yet another object of the invention there is provided a 
tube as described above wherein the layer on the distal side of said 
metallic layer also comprises a xerogel. 
According to still another object of the invention there is provided a tube 
as described above comprising a tube which is encircled near its distal 
end by an expandable cuff, said tube and cuff comprising at least one 
hydrophilic xerogel and water. 
Yet another object of the invention is to provide a tubular article 
comprising at least one layer comprising a hydrophilic xerogel as 
described above said tube further comprising at least one metallic layer 
adjacent the xerogel layer proximal the incident laser beam. 
Another object of the invention is to provide an article as described above 
wherein the surface of said metallic layer adjacent said xerogel layer is 
non-reflective of said laser beams. 
Yet another object of the invention is to provide an article as described 
above wherein said xerogel layer further comprises pigments to absorb the 
unwanted radiation. 
Another object of the invention provides a protective artiocle as described 
above wherein the xerogel layer thereof further comprises pigments to 
absorb, and the metallic layer comprises a surface non-reflective of said, 
undesired radiation. 
These and other objects of the invention will be in part discussed and in 
part apparent upon consideration of the detailed description of the 
preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In accordance with the invention it has now been found that humans, animals 
and articles may be protected from damage due to undesired exposure to 
laser beams by disposing protective barriers, comprising at least one 
xerogel, between said laser beams and the item to be protected said 
xerogel comprising at least one hydrophilic water-insoluble polymer. 
Thus, in accordance with this invention there is provided an article for 
the protection of humans, animals and articles from damage due to 
undesired exposure to laser beams comprising 
A. A hydrophilic xerogel comprising at least one water-insoluble 
hydrophilic polymer; 
B. Water; 
and C. If desired, at least one additive such as a medication, colorant, 
pigment or moisturizer. 
The hydrophilic polymers useful in accordance with the invention are those 
which are inherently water-insoluble and those which may be rendered so by 
crosslinking. 
Examples of inherently water-insoluble hydrophilic polymers include 
copolymers of hydrophobic monomers, such as acrylonitrile, acrylates, 
(e.g., methyl and ethyl) methacrylates, (such as methyl and propyl) and 
styrene with hydrophilic monomers such as, acrylamide and acrylic and 
methacrylic acids. Other inherently water-insoluble hydrophilic polymers 
may be exemplified by hydrophobic polymers such as silicone, acrylate, 
methacrylate and urethane polymers whose surfaces have been rendered 
hydrophilic by treatments such as partial hydrolysis of e.g., ester and 
amide groups and by grafting of hydrophilic monomers or other functional 
groups to the hydrophobic backbones. 
The inherently water-insoluble hydrophilic polymers useful in the practice 
of the instant invention include the acrylonitrile-acrylamide copolymers 
described in U.S. Pat. No. 4,331,783 (issued 5/25/82) and the modified 
acrylonitrile-acrylamide copolymers described in U.S. Pat. No. 4,337,327 
(issued 6/29/92), both patents being incorporated herein for reference. 
Other polymers of this nature include block copolymers of poly(ethylene 
oxide) and relatively hydrophobic materials such as polyurethanes which 
are described, e.g., by E. W. Merrill and E. W. Salzman in their article 
"Poly(ethylene oxide) as a Biomaterial" (Am. Soc. for Artificial Internal 
Organs Journal, April/June 1983, pp. 60-64). Such materials are 
exemplified by Polyox.TM., a crosslinked poly(ethylene oxide). 
Water-soluble polymers which may be rendered insoluble by crosslinking 
include polymers of hydrophilic monomers such as those mentioned above, 
hydroxyalkyl acrylates and methacrylates and alkylene oxides such as those 
of ethylene and propylene. Such crosslinked hydrogels are described in, 
e.g., U.S. Pat. No. 3,320,960 (issued 11/30/65) and U.S. Reissue Pat. No. 
Re27,401 (6/20/72). 
Preferred insoluble hydrophilic polymers useful in the practice of the 
invention are the acrylonitrile-acrylamide and poly(ethylene oxide) 
copolymers described above. 
The particular choice of water-insoluble hydrophilic polymers for use in 
the articles according to the invention will depend on the specific 
purpose to which the article is to be applied. For instance, if the 
article is to be used extracorporeally, e.g., as an article of clothing, 
the polymer type is unlimited, whereas if the article is to be used in 
contact with the body, e.g., in an endotracheal tube the type of polymer 
will depend on, for instance, the pK.sub.a thereof and any other factors 
which could affect biocompatability with the specific body part in contact 
with the protective article. 
Crosslinking may be effected by addition of crosslinking compositions, such 
as those which decompose into free radicals and polyfunctional materials; 
by exposure to radiation and by other means known to those skilled in the 
art. 
Examples of compositions which decompose to form free radicals are 
azonitriles, such as azobis(isobutyronitrile): peroxides, such as benzoyl 
peroxide; and hydroperoxides, such as cumene hydroperoxide. 
Polyfunctional materials useful in crosslinking hydrophilic polymers 
include the acrylates and methacrylates of polyhydric compounds such as 
diols, e.g., ethylene glycol; triols, such as glycerol and 
1,1,1-tris(hydroxymethyl)propane; tetraols, e.g., pentaerythritol and 
polyhydric polymers such as epoxy resins. Other crosslinking agents which 
may be used in the practice of the invention, as well known in the art, 
include zinc oxide, organotin compounds, N,N'methylenebisacrylamide and 
diallylidene pentaerythritol. 
Radiation-induced crosslinking may be effected by actinic radiation such as 
UV and visible light; .gamma.-radiation; and electron beams. 
As the sources of laser light provide light of varying wavelengths (e.g., 
the CO.sub.2 laser at 10.6.mu., the Argon laser at 0.48.mu. [i.e., in the 
blue region of the spectrum] and the ruby laser in the red region at 
0.69.mu.) it is often necessary to add colorants to the hydrogel to 
prevent transmission of the laser beams therethrough. Added colorants are 
not needed only in the case of the CO.sub.2 laser, whose light is strongly 
absorbed by water and, therefore, all tissues. 
If the article is to be used in contact with the body the particular 
crosslinking method must be such as will yield a product which will not 
depolymerize or decompose, to yield products which are water-soluble, when 
exposed to the body environment in which they are used or the operating 
media. 
The protective article may be of any shape or form known in the art such 
as, sheets, sheaths, tape, dressings, fiber optic tubes, surgical drapes, 
including laser-transmitting tubes, such as vaginal dilators and 
retractors, and the like, and endotracheal tubes. The particular form to 
be used at any one time would depend upon the requirements of the user. 
The protective articles may be adhesive or non-adhesive to the surface to 
be protected and the adhesion may be effected through autoadhesion or 
adhesives. 
In accordance with this invention there is provided a laser barrier 
comprising a hollow tubular element comprising two layers with the 
provisos that 
(1) if the laser is to be used by passing it through the lumen of said 
element at least the innermost layer comprises said xerogel; 
and (2) if said laser is to be used opposite the outer wall of said element 
at least the outermost layer comprises said xerogel. 
Another aspect of the above embodiment provides for an at least three 
layered structure wherein at least one of said layers is metal composition 
disposed between 
(1) said innermost xerogel layer and the first non-xerogel outer layer when 
the laser is to be used by passing it through the lumen of said element; 
or (2) said outermost xerogel layer and the first non-xerogel inner layer 
when the laser is to be used opposite the outer wall of said element. 
According to a modification of the above aspect the layer on the distal 
side of the metallic layer also comprises a xerogel. 
It has been found that if the lasers are improperly used, e.g., by an 
excessive period of exposure, they may burn through the hydrogel layer. 
The damage resulting therefrom may be reduced or eliminated by further 
modification of the above embodiments. 
Thus, in another modification of the invention the proximal surface of the 
metallic layer is made non-reflective to the laser beams. The methods for 
preparing such surfaces is known to the art and will not be described 
further. 
It has also found that the consequences of such improper use may be abated, 
especially in the absence of such metallic layers, by dispersing pigments 
throughout the xerogel layer. 
Pigments useful in the practice of this aspect of the invention include 
inorganic and organic pigments wherein the inorganic pigments are selected 
from the group comprising TiO.sub.2, ZnO, the basic white carbonates, 
sulfates, and silicates of lead, ZnO, lithopone, Sb.sub.2 O.sub.3, 
CaCO.sub.3, silicates of Mg and Al, pyrophillite, bentonite, mica, pumice, 
BaSO.sub.4, CaSO.sub.4, MgO, SiO.sub.2, diatomite, and powders of Al, Cu, 
Zn, Pb, Au, Ag, Ni and their alloys, bronzes and Stainless Steel. 
Preferred pigments for use in this aspect of the invention may be selected 
from the group comprising TiO.sub.2, ZnO, Sb.sub.2 O.sub.3, silicates of 
Mg and Al, pyrophillite, bentonite, mica and pumice and powdered Al. 
A most preferred pigment for use in the practice of this aspect of the 
invention is TiO.sub.2. 
As required for specific uses the articles according to this embodiment of 
the invention will also comprise means for inserting, removing and 
manipulating same, e.g., handles in the case of vaginal dilators, means 
for hydrating the xerogels, to form hydrogels, e.g., such as those 
described for passing inflating gases to the inflatable balloons described 
in, for example, U.S. Pat. Nos. 4,378,796 and 4,489,722. 
In accordance with another embodiment of the invention there is provided an 
article comprising a tube for use in laser surgery or treatment, 
comprising at least one layer comprising a a xerogel comprising any of the 
afore-mentioned water-insoluble hydrophilic, polymers which is on its 
inner surface plated to a mirror finish which will reflect any extraneous 
laser beams incident thereon. (Of course, in the case where the polymers 
are not initially water-insoluble crosslinking must occur concurrently 
with, or after, formation of said tube.) Any beams which pass through said 
inner surface are absorbed in the tube walls and the energy thereof 
dissipated. 
Another aspect of the above embodiment provides for such a tube which is 
filled with a silver halide material as transmitter of the laser beam. The 
silver halides useful in the practice of the invention are well known in 
the art and will not be discussed further. 
The metallic layer may be applied to one of said inner layers while in 
adhesive or non-adhesive contact therewith and with the layer on its 
opposite surface, in the form of a sheet or tape wound around said xerogel 
layer. It may also be used in the form of concentric tubes, including 
segmented tubes such as "BX" cable, which may be in contact with one or 
both layers adjacent thereto or spaced therefrom. If desired, the metal 
may also be applied to the inner layer in the form of a powder dispersed 
through a binder matrix by any of the means known to one skilled in the 
art. 
Other methods of using the protective articles will be determined by one 
skilled in the art in accordance with the specific application. 
The metals useful in the practice of this embodiment are selected from the 
group comprising aluminum, gold, titanium, silver, their alloys, and the 
like. Preferred metals for use in accordance with the invention are 
aluminum and gold and their alloys. The most preferred metal for use in 
accordance with the invention is aluminum. 
It is believed, although the theory is not essential to the practice of the 
invention, that the article protects the covered portions of the tissue by 
absorption of the energy of the laser beam incident thereon in the 
contained water which dissipates the absorbed energy by evaporation. A 
portion of the energy is also believed dissipated by scission of the 
organic portion of the article and ablation thereof. 
In yet another embodiment of the invention there is provided a method of 
applying laser light to a desired tissue site, without undesirable damage 
due to stray or reflected laser beams, for treatment or surgery, by 
transmission of said light through a tubular instrument (e.g., a fiber 
optic) which focuses said light on the operative site and does not permit 
escape of extraneous reflected or dispersed light to the atmosphere or by 
transmission of gases, such as anesthetics and/or oxygen, or passage of 
instruments through the tube while the treatment or surgery is performed 
opposite the outer wall of the tube, said tubular instrument, comprising 
at least one layer comprising 
A. A hydrogel comprising 
1. At least one hydrophilic xerogel; 
and 2. Water 
and B. If desired, at least one additive such as a medication, colorant or 
moisturizer. 
The hydrogels and additives useful in the practice of this embodiment of 
the invention may be selected from those described above. 
In another modification of the above embodiment the tube comprises a 
multilayered structure wherein 
(a) if the article is to transmit the laser at least the innermost layer 
comprises said hydrogel; 
and (b) if the article is to transmit gases at least the outermost layer 
comprises said hydrogel. 
The multilayered structure may be formed by coextrusion of the layers or 
the layers may be caused to bond to each other adhesively by means of 
separate adhesives or self-adhesively. 
In the case of gas transmitting tubes, such as endotracheal tubes, the 
outer hydrogel layer may be placed upon the inner tube as a lengthwise 
incised sheath or slipped over the inner layers as a seamless tube. 
Adherence of the tubes to each other may be adhesive, as in the above 
indicated embodiment, or non-adhesive. 
If the laser beams are to be applied through the tube the inner xerogel 
layer may be inserted into the hollow formed by the outer layers and 
retained therein either by force fitting or adhesively. 
Furthermore, in accordance with another aspect of this embodiment of the 
invention the tubular element is plated on its inner surface to a mirror 
finish which will reflect most of the extraneous laser beams incident 
thereof and absorb the energy of any beams not reflected. 
If desired, the above tube may be filled with a silver halide as a 
transmitting medium. Silver halides for use in accordance with the 
invention are well known in the art and will not be discussed further. 
In the gas transmitting mode when the tube comprises more than one layer at 
least the outermost layer comprises said hydrogel. 
In another modification of this embodiment a metallic layer is disposed 
(a) in the gas transmitting mode between said outermost layer and the gas 
transmitting path; 
and (b) in the light transmitting mode between said innermost layer and 
said organ wall. 
In a multilayered structure the metallic layer may be any of the layers 
other than 
(a) the outermost in the gas transmitting mode; 
or (b) the innermost in the light transmitting mode. 
The metals useful in this embodiment may be any of those described above or 
known in the art and their method of application may be any of those known 
in the art. 
Throughout the application the metal surface in the path of the stray beams 
may, as desired, be reflective or non-reflective of the laser beams. 
Referring now to FIG. 1, there is shown an embodiment 30, of the invention, 
comprising a hydrophilic xerogel tube 32. The laser beam 32 passes through 
said tube to the site to be lased. 
In modifications of the above embodiment the inner wall 34 of said tube may 
be plated to reflect stray beams and/or the tube may be filled with 
laser-transmitting materials, such as silver halides, and sealed at both 
ends with laser-transmitting end caps and/or handles for manipulating said 
tubes may be attached to the proximal edges 33 thereof. 
FIG. 2 shows an alternate embodiment 40 of the laser-transmitting tube of 
FIG. 1 comprising two concentric tubes 42 and 43 wherein the inner tube 42 
comprises a hydrophilic xerogel. The outer tube 43 comprises any material 
known, in the art, for such purposes, such as metals and rigid or 
semi-rigid plastics or rubbers. Said tube may also comprise a hydrophilic 
xerogel. The xerogels of tubes 42 and 43 may be the same or different. The 
tubes may be joined, at their interface, adhesively or non-adhesively. 
Said tubes may be coextruded or the hydrophilic tube 42 may be inserted 
into tube 43 after formation thereof. 
In another embodiment (not shown) when the laser is to be used externally 
of the tubular element the tube 43 would have to comprise said xerogel. 
In yet another alternate embodiment, not shown, of the tube of FIG. 2 a 
third hydrophilic xerogel tube may be placed on the outside of tube 43. 
Said tube may be applied as indicated above or as a sheath cut lengthwise 
for application, or a seamless tube to be slipped over, the inner layers 
of the tubular element 40. 
FIG. 3 illustrates another aspect of the invention comprising a 
laser-resistant tube 50 comprising a hydrophilic xerogel tube 52 and an 
expandable hydrophilic xerogel cuff 53 encircling and adhesively joined to 
said tube 52 near its distal end. The laser beam 51 is directed to the 
desired site opposite the outer wall of tube 50. 
In FIG. 4 there is illustrated an alternate embodiment 60 of the tube of 
FIG. 3 comprising two concentric tubes 62 and 63. Tube 62 comprises a 
hydrophilic xerogel and tube 63 materials selected from the group 
comprising metals, flexible rubbers and plastics and hydrophilic xerogels. 
The hydrophilic xerogels of tubes 62 and 63 may be the same or different. 
Tube 62 terminates at the expandable cuff 64 which encircles tube 63. 
FIG. 5 illustrates an expandable cuff 70 for any of the above tubular 
elements comprising an expandable sponge 71. If the sponge 71 comprises a 
hydrophobic porous material it is enclosed within a water-impermeable 
covering 72. If, however, sponge 71 comprises a hydrophilic xerogel said 
covering is not necessary. 
In FIG. 6 there is shown an alternate embodiment 80 of the cuff of FIG. 5 
comprising a water-expandable sponge 81 and a water-impermeable covering 
82. In order to decrease the possibility of formation of holes, resulting 
in leakage of the inflating medium and deflation of the cuff, due to 
inadvertent impact of the laser beams on the cuff there are disposed, 
between said sponge 81 and said covering 82 a plurality of particles 83 
comprising at least one hydrophilic xerogel. 
In another alternate embodiment, as illustrated in FIGS. 13-15, of the 
tubular element of FIG. 4 the tube 62 is terminated in a plurality of 
flaps 120, formed by a series of longitudinal incisions in the distal end 
of said tube, said flaps overlying and thereby protecting the cuff 64 from 
being impacted by stray laser beams. This is especially desirable when 
said cuff comprises a hydrophobic porous sponge and a water-impermeable 
covering. 
In the practice of the invention the hydrophilic xerogels are hydrated, by 
either water or aqueous solutions of the aforementioned additives, prior 
to, or after, insertion of said tubes whereby the xerogels of the tubes 
and cuffs form hydrogels and the cuffs of the endotracheal tubes expand to 
close the passages into which the tube has been inserted. 
Here again, as required, water or an aqueous solution of the additives may 
be applied to the protective article to replace any water lost during the 
treatment, e.g., by ablation due to the laser energy absorbed and/or 
evaporation to the environment. 
Methods for preparing the articles of the invention are known to the art 
and will not be discussed further. 
With respect to FIGS. 7 to 12 it is seen that the laser beams are 
transmitted, as in the use of a vaginal dilator, through the tubular 
element. It is to be understood that similar configurations are applicable 
where the laser beams are used externally to the tubular element, e.g., in 
the case of an endotracheal tube. In that instance the relative positions 
of the layers are the same as in the prior case and only their spatial 
positions are reversed. 
FIGS. 7 and 8 illustrate a three layered tubular element 90 wherein at 
least the inner layer 94 comprises a xerogel as described above. The 
middle layer 93 may comprise a metal composition or any other composition 
indicated by the user's needs. 
FIGS. 9 and 10 show another aspect of the tubular element of FIGS. 7 and 8 
wherein the middle layer 93 comprises a metal composition the proximal 
surface of which is non-reflective of the laser beams. 
In FIGS. 11 and 12 the inner, xerogel, layer further comprises at least one 
pigment dispersed therethrough. 
In another aspect (not shown) the tubular element of FIGS. 7 and 8 may, if 
desired, comprise an inner tube 94 through which said pigment is dispersed 
and a middle layer 93, comprising a metal, whose proximal surface is 
non-reflective. The outer layer 92 will comprise any of the materials of 
construction known in the art. 
In the practice of using the protective article of the invention the 
tubular element is inserted into the body cavity within which the laser 
surgery or therapy is to be effected. Prior to insertion the xerogel layer 
will be comprised of the additives if any. 
The xerogel is converted to a hydrogel by hydration with water or an 
aqueous solution, e.g., of the additives, if any, prior to application of 
the laser. The hydration step may, as desired, precede or follow 
insertation of the article. 
In most cases the hydration will precede insertion of the article to 
increase lubricity and, therefore, insertion thereof. 
However, there may be instances, e.g., when the orifices are small, when it 
will be desireable to insert the dry tubular element into the cavity and 
then effect the hydration. The user will, of course, decide this on a 
case-by-case basis. 
Changes may be effected with respect to the details of construction and use 
of the invention without departing from the spirit and scope thereof as 
defined in the appended claims.