Irrigation tubing set having compliant sections

An irrigation system including a pump that regulates the supply of fluid to an endoscopic surgical site, and a tubing set for supplying the fluid. The tubing set comprises an inflow line for supplying fluid to the surgical site, and an outflow line for draining fluid from the surgical site. At least one of the inflow and outflow lines includes an expandable compliant tubing segment that expands to accommodate changes in the rate of fluid flow through the surgical site to reduce variations in fluid pressure in the surgical site. The fluid volume within the compliant tubing segment increases in response to increasing fluid pressure within the compliant tubing segment. The system is particularly designed for use in small joint arthroscopy (e.g., of the wrist) where the fluid volume in the surgical site is relatively small.

BACKGROUND OF THE INVENTION 
The invention broadly relates to endoscopic surgical procedures, and more 
particularly to an irrigation system and tubing set for use in irrigating 
an endoscopic surgical site. 
A trend in modern medicine has been to treat the body without invasive 
procedures if at all possible, because invasive procedures inflict a 
certain trauma of their own on the patient, and because when the skin is 
broken the risk of infection of the patient, or others by the patient, 
increases substantially. When surgery must be performed, it is currently 
considered desirable to use "minimally invasive" procedures as much as 
possible. A specific known example of a class of such techniques is 
arthroscopic surgery, wherein joints (most commonly the knee) and their 
supporting structures are treated through small incisions using tools to 
visualize the interior of the body. 
During such surgery, irrigation of the joint is necessary for the following 
reasons: 
(1) Inflation of the joint is desirable for better visualization and access 
achieved by an increased joint or tissue separation. This is accomplished 
by application of pressure through the medium of the irrigation fluid or 
gas. 
(2) Flow of the irrigation fluid through the joint keeps the field of view 
clear and eliminates loose debris. 
(3) The fluid keeps the joint lubricated and replaces lost body fluids. 
Co-assigned U.S. Pat. No. 4,650,462 (DeSatnick et al.) discloses an 
irrigation system particularly adapted for the control of such irrigation, 
and which allows independent control of both the pressure and the flow. 
The DeSatnick '462 patent shows an expansion chamber connected to an 
outflow line for dampening pressure variations. Co-assigned U.S. Pat. No. 
4,820,265 (DeSatnick et al.) discloses a tubing set particularly adapted 
to deliver irrigation fluids as part of such a system. An irrigation 
system generally as disclosed in the Desatnick et al. patents has been 
available as Model 8300 under the trade designation "3M ARTHROSCOPY PUMP" 
from Minnesota Mining and Manufacturing Company, St. Paul, Minn. 
U.S. Pat. Nos. 4,604,089 (Santangelo et al.), and 4,940,457 (Olson), and 
PCT Publication No. WO 86/00534 show other irrigation systems for use 
during arthroscopy. 
While irrigation systems of the type described above have enjoyed success 
in helping to carry out surgery on large joints such as the knee, it would 
be desirable to have an irrigation system that is particularly designed to 
control the irrigation of small joints such as the wrist. The small volume 
in such joints makes controlling the pressure a more difficult task, since 
relatively small amounts of flow can translate into large pressure spikes 
within the joint space. 
SUMMARY OF THE INVENTION 
The invention provides an irrigation system and tubing set that are 
particularly useful in irrigating an endoscopic surgical site having a 
relatively small internal volume, such as an arthroscopic surgical site in 
a small joint (e.g., a wrist). The irrigation system and tubing set are 
particularly adapted to reduce the amplitude of pressure peaks and control 
the fluid pressure of the irrigating fluid. The invention also includes a 
cannula that is designed for use in the irrigation system, and which is 
designed for use in small joint arthroscopy. The invention normally 
includes the use of a pump for regulating the flow of irrigating fluid 
through the tubing set. 
Generally, the tubing set of the invention comprises an inflow line for 
supplying fluid to the surgical site, and an outflow line for draining 
fluid from the surgical site. The inflow line is adapted for mounting an 
inflow cannula in fluid communication with the inflow line to supply fluid 
to the surgical site, and for connection to a source of fluid in fluid 
communication with the inflow line so that fluid from the source of fluid 
can be directed through the inflow cannula. The outflow line is adapted 
for mounting an outflow cannula in fluid communication with the outflow 
line to drain fluid from the surgical site. The inflow and outflow lines 
define a fluid pathway through the surgical site. Inline compliance means 
is provided in at least one of the inflow and outflow lines for 
accommodating changes in the rate of fluid flow through the surgical site 
to reduce variations in fluid pressure in the surgical site. The inline 
compliance means includes means for increasing the fluid volume within the 
inline compliance means in response to increasing fluid pressure within 
the compliance means thereby reducing variations in fluid pressure. 
Preferably, the inline compliance means is provided at least in the inflow 
line, although it is most preferred to provide the compliance means in 
both the inflow and outflow lines. The compliance means preferably 
comprises a resilient tubing segment defining a portion of the inflow 
line. The tubing segment has a cross section that is resiliently 
expandable in response to increasing fluid pressure within a range to 
increase the volume of fluid within the tubing segment. 
The tubing set preferably includes a means associated with the tubing set 
for transmitting information about fluid pressure within the surgical 
site. For example, the means for transmitting information about fluid 
pressure within the surgical site may comprise a fluid pressure sensing 
line adapted to be connected in fluid communication with one of the inflow 
cannula, outflow cannula or a separate pressure sensing cannula. In this 
case, the pressure sensing line would include: (a) an elongate tubular 
pressure chamber in the pressure sensing line having a distal end adapted 
to be connected to one of the inflow cannula, outflow cannula or a 
separate pressure sensing cannula, and a proximal end mounted in pressure 
transmitting communication with the remainder of the pressure sensing 
line; and (b) a pressure transmitting resiliently flexible diaphragm 
within the pressure chamber, the diaphragm defining a fluid seal within 
the pressure chamber precluding passage of fluid from the surgical site 
through the proximal end of the pressure chamber. The remainder of the 
pressure sensing line defines a column of pressure transmitting fluid 
(e.g., air) responsive to but segregated from the fluid from the surgical 
site, and the end of the pressure sensing line opposite the pressure 
chamber is adapted to be connected in fluid communication with a mechanism 
for sensing pressure. 
The method of irrigating an endoscopic surgical site in a patient with 
fluid generally comprises providing an irrigation system comprising (1) a 
tubing set comprising (a) an inflow line for supplying fluid to the 
surgical site, the inflow line being adapted for connection to a source of 
fluid; (b) an outflow line for draining fluid from the surgical site; and 
(c) compliance means provided in at least one of the inflow and outflow 
lines for accommodating changes in the rate of fluid flow through the 
surgical site to reduce variations in fluid pressure in the surgical site, 
the compliance means including means for increasing the fluid volume 
within the compliance means in response to increasing fluid pressure 
within the compliance means; and (2) a pump adapted to receive a portion 
of the inflow line to pump fluid through the inflow line. Inflow and 
outflow cannulae are connected to the inflow and outflow line 
respectively, and the inflow and outflow cannulae are inserted into the 
patient to establish a fluid pathway through the surgical site with the 
tubing set. The irrigation fluid is introduced into the surgical site via 
the inflow line and cannula, and the irrigation fluid drained out from the 
surgical site through the outflow cannula and line. The fluid volume is 
allowed to increase within the compliance means in response to increasing 
fluid pressure within the compliance means, and to decrease within the 
compliance means in response to decreasing fluid pressure within the 
compliance means. 
Other features will be in part apparent and in part pointed out hereinafter 
.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
As illustrated in FIG. 1, the arthroscopy tubing set 10 of the invention 
functions as a component of an irrigation system in arthroscopic 
procedures. The tubing set 10 channels a flow of saline solution from 
hanging bags or bottles 12 through an arthroscopy pump 14 to the joint or 
site 16 of the procedure, at a flow rate and pressure set on the pump 14. 
The pump 14 may be of the "positive displacement" type which normally pump 
a fixed volume of fluid through each pumping cycle or revolution of a 
peristaltic pumping roller mechanism 44. Ultimately, the flow discharges 
to an appropriate collector 18. 
In order to facilitate handling of the tubing set 10, it is preferred that 
the tubing set 10 be of a trilumen configuration with three parabounded 
PVC tubes separated at their ends to form three functionally different 
lines, an inflow line 20, a pressure sensing line 22 and an outflow line 
24. Co-assigned U.S. Pat. Nos. 4,650,462 and 4,820,265 (DeSatnick et al.), 
which disclose an irrigation system and tubing set of the general type 
described herein, are incorporated herein by reference. 
As described in U.S. Pat. No. 4,820,265, the inflow line 20 includes a 
capped male luer fitting 26 at the patient end. The luer fitting 26 is 
adapted for connection to an inflow cannula 27. The inflow cannula 27 may 
be of the general type (although possibly scaled down for small joint 
surgery) as disclosed in co-assigned U.S. Pat. No. 5,037,386, which is 
incorporated herein by reference. The fitting 26 is bonded into a delivery 
tube 30, which is in turn attached to one end of a novel high compliance 
tubing segment 100 that is described in more detail below. The other end 
of the high compliance tubing segment 100 is attached to a polyvinyl 
chloride (PVC) header tube 32. 
The header tube 32 connects to a "Y" connector 34 normally formed or cast 
from plastisol. Two duplicate PVC supply tubes 36 extend from the "Y" 
connector. A hand manipulable shut-off clamp 38 mounts on each supply tube 
36, and the terminal end of each of the supply tubes 36 is bonded to a 
separate bag spike 40. Each of the bag spikes 40 is provided with a cap or 
protector 42 which is removed prior to a piercing engagement of the spike 
40 into one of the saline containers 12. 
The header tube 32 is engageable about the rollers 44 of the peristaltic 
unit 46 of the pump 14 to pump fluid through the inflow line 20. The 
rigidity or stiffness and diameter of the header tube 32 are important to 
the proper operation of the rollers 44 of the peristaltic pump 14. 
Preferably, the header tube 32 has a durometer of approximately 68 on the 
Shore A scale, an inside diameter of approximately 0.375 inches (9.5 mm) 
and an outside diameter of approximately 0.5 inches (12.7 mm). 
The pressure sensing line 22 includes a capped male luer pressure retaining 
fitting 50 bonded into one end of an elongate tubular PVC pressure chamber 
54. The pressure chamber 54 contains a resiliently collapsible elongate 
balloon diaphragm 56 of an appropriate elastomer such as natural or 
synthetic latex or silicone rubber. The diaphragm 56 is a pressure 
transmitter and fluid barrier, and is bonded to and in fluid communication 
with a length of pressure-transmitting tube 58 projecting from the end of 
the pressure chamber 54 remote from the luer fitting 50. The end of the 
pressure-transmitting tube 58 remote from the pressure chamber 54 is 
provided with a cap 60, and is adapted for connection to a mechanism for 
sensing pressure, such as a pressure transducer (not shown) in the pump 
14. This pressure-transmitting tube 58 functions as a pressure tube 58 to 
transmit sensed pressure, that is, it defines a column of pressure 
transmitting fluid (e.g., air) responsive to but segregated from the fluid 
from the surgical site. 
The luer fitting 50 of the pressure tube 58 would be provided with a capped 
female luer fitting bonded thereto (not shown), and is adapted to be 
connected in fluid communication with one of a separate pressure sensing 
cannula, a pressure sensing inflow cannula, or the pressure sensing 
outflow cannula 200 shown in FIGS. 1 and 4-5. The pressure sensing line 22 
is basically dry, restricting liquid to the diaphragm-containing chamber 
54 immediately adjacent the operating site. Fluid pressure sensing line 22 
constitutes one embodiment of a means associated with the tubing set 10 
for transmitting information about fluid pressure within the surgical 
site. 
The outflow line 24 includes a tubular elastomeric adapter 64 of natural or 
synthetic latex or silicone rubber at the patient end, which is adapted 
for connection to an outflow cannula, such as the pressure sensing outflow 
cannula designated by the reference numeral 200. The outer or free end of 
the adapter 64 is provided with a protective cap 66 of a distinctive 
color, preferably blue, providing an easily distinguished visual 
indication of the patient end of the tubing set 10. The elastomer adapter 
64 is bonded to a drain tube 68, which is in turn is bonded a plastisol 
"Y" connector 70, the two branches of which are bonded to a pair of 
parallel tubes. The first tube 72 is an elastomer tube, for example of 
latex or silicone rubber, and the second tube 74 is PVC tubing with a 
durometer of 39 on the Shore A scale. The two parallel tubes 72 and 74 are 
rejoined by a second plastisol "Y" connector 76 which in turn is bonded to 
and in communication with a discharge tube 78. The free remote end of the 
discharge tube 78 is provided with a distinctively colored cap 80, 
preferably red and easily distinguished from the opposed end cap 66, again 
to provide a ready and immediate identification of each end of the tubing 
set 10. 
Approximately 30 inches (760 mm) from the capped end of the tube 78, the 
discharge tube 78 is provided with one complete coil 82. The coil 82 
defines a "pigtail" configuration forming a liquid seal. An appropriate 
cable tie or the like 84 is wrapped around the coil to retain the 
configuration thereof. Preferably, the diameter of the discharge tube 78 
immediately downstream (toward the remote end at 80) of the coil 82 is 
larger than the diameter of the discharge tube 78 along the coil 82 and 
upstream of the coil. For example, the inside diameter of the discharge 
tube 78 along the coil 82 and upstream from the coil may be approximately 
1/8" (3.2 mm), and the inside diameter of the discharge tube 78 downstream 
of the coil 82 may be approximately 3/8" (9.5 mm). 
The preferred arrangement is that the parallel branches or tubes 72 and 74 
are positioned upstream relative to the coil 89. As described in U.S. Pat. 
No. 4,820,265, the parallel tubes 72 and 74 in the outflow line 24 
constitute a portion of a pressure control and relief assembly, and are 
respectively engaged by a mechanical pressure relief valve 86 and a 
solenoid control valve 88. 
The inflow line 20, outflow line 24 and pressure sensing line 22 are 
preferably joined along a substantial portion thereof in substantially 
parallel, non-communicating relationship. For example, the three lines 20, 
22 and 24 may include portions that have been co-extruded to form one 
trilumen tube (not shown), or in the case of PVC tubing, the joined 
portions may be solvent bond with cyclohexanone, for example. It is 
believed that by joining substantial portions of the tubing set 10 
together, confusion during use and set-up is reduced. 
A novel inline compliance means (e.g., flattened tubing segments 100 and 
102) is provided in at least one of the inflow and outflow lines 20 and 24 
for accommodating changes in the rate of fluid flow through the surgical 
site to reduce variations in fluid pressure in the surgical site. The 
inline compliance means includes a means for increasing the fluid volume 
within the compliance means in response to increasing fluid pressure 
within the compliance means. Preferably, the inline compliance means is 
provided in both the inflow and outflow lines 20 and 24, although it is 
also contemplated that the compliance means might be provided in only one 
of the inflow or outflow lines 20 or 24, in which case it would be 
preferred to have the compliance means provided in the inflow line 20. 
The compliance means conveniently comprises a "first" resilient tubing 
segment 100 defining a portion of the inflow line 20. The ends of the 
resilient tubing segment 100 may be bonded to separate portions of the 
delivery tube 30 to form a part of the delivery tube 30, or one end of the 
tubing segment 100 may be bonded to the end of the delivery tube 30 and 
the other end of the tubing segment 100 may be bonded to the downstream 
end of the header tube 32 as illustrated in FIGS. 1 and 2. The compliant 
tubing segment 100 should be downstream from the header tube 32 so that in 
use the tubing segment 100 is along the fluid pathway between the pump 14 
and the endoscopic surgical site. 
The first compliant tubing segment 100 has a cross section that is 
resiliently expandable in response to increasing fluid pressure within a 
range to increase the volume of fluid within the tubing segment 100. This 
feature helps to minimize variations in fluid pressure. For example, the 
cross-section of the compliant tubing segment 100 may be generally 
flattened, rectangular, oval-shaped or dumbbell-shaped when not expanded 
by relatively high fluid pressure as indicated in FIG. 3a and 3c. The 
cross sectional configurations shown in FIGS. 3a and 3c are believed to be 
particularly desirable because the cross sectional area can be increased 
by flexing the tube wall outwardly without substantial stretching of the 
tube wall. In other words, the cross section shown in FIGS. 3a and 3c are 
believed to provide a more responsive tubing segment 100 as far as 
increasing fluid volume in response to increasing pressure is concerned. 
The "second" resilient compliant tubing segment 102 defines a portion 102 
of the outflow line 24, and is of a design similar to the first compliant 
tubing segment 100. As is the case with the first tubing segment 100, the 
second tubing segment 102 has a cross section that is resiliently 
expandable in response to increasing fluid pressure within a range to 
increase the volume of fluid within the second tubing segment 102. The 
cross sectional configuration of the second tubing segment 102 when 
unexpanded is preferably as illustrated in FIGS. 3a and 3c, and of similar 
dimensions and materials as the first tubing segment 100. 
As shown in FIG. 2, the second tubing segment 102 can be bonded to the 
drain tube 68 to form a section 102 of the drain tube 68. Preferably, 
however, the downstream end of the drain tube 68 is bonded to the upstream 
end of the high compliance tubing segment 102, and the downstream end of 
the tubing segment 102 is directly bonded to the "Y" connector 70. The 
preferred arrangement reduces the number of bonds required by one. The 
compliant tubing segment 102 should, however, be positioned between the 
patient and the Y connector 70 for optimal operation of the irrigation 
system. This arrangement is important for the second tubing segment's 
optimum response to pressure variations between the patient and the 
mechanical relief valve 86 and solenoid control valve 88. 
Most preferably, the first tubing segment 100 has a length along the inflow 
line 20 approximately fifty percent longer than the length of the second 
tubing segment 102 along the outflow line 24 so that, assuming equal cross 
sectional areas, the amount of the increase in volume within the first 
tubing segment 100 is approximately fifty percent greater than the amount 
of the increase in volume within the second tubing segment 102 in response 
to the same increase in pressure within the first and second tubing 
segments 100 and 102. For example, the first tubing segment 100 may have a 
length of approximately 90 cm, and the second tubing segment 102 may have 
a length of approximately 60 cm. 
The resilient tubing segments 100 and 102 are formed of elastomeric 
material (e.g., polyvinyl chloride (PVC)) having a durometer of less than 
60 on the Shore A scale, preferably within the range of approximately 
50-60 on the Shore A scale. For example, the resilient tubing segments 100 
and 102 may have a durometer on the Shore A scale of approximately 55. In 
this example, the lumen 104 of the tubing segment 100 (102) may have a 
generally oval or rectangular cross section as shown in FIG. 3a when 
unexpanded, with a dimensions of the lumen being approximately 12 mm by 3 
mm and the wall thickness of the tubing segments 100 and 102 being about 
0.75 mm. In this example, the length of the first tubing segment 100 is 90 
cm and the length of the second tubing segment 102 is 60 cm. 
The outflow cannula 200 is adapted to be inserted in a patient into the 
surgical site, and connected in fluid communication with the outflow line 
24. The outflow cannula 200 shown in FIGS. 4 and 5 is a double sheathed 
pressure sensing cannula 200 having (a) an inner sheath 202 defining an 
inner lumen 204, which is intended to be in fluid communication with the 
outflow line 24, and (b) an outer sheath 206 defining an outer lumen 208 
that receives the inner sheath 202. The portion of the outer lumen 208 not 
occupied by the inner sheath 202 defines a pressure transmitting 
passageway (at 208) adapted for fluid communication with the pressure 
sensing line 22. The inner and outer sheaths 202 and 206 are formed of 
stainless steel. 
The inner and outer sheaths 202 and 206 comprise generally cylindrical 
hollow shafts. The outer sheath 206 has an enlarged distal end portion 210 
that is inserted into the patient to drain the irrigating fluid from the 
surgical site. The distal end portion 210 of the outer sheath 206 has a 
tapered portion 212 that is tapered in the distal direction (right in 
FIGS. 4 and 5) to facilitate insertion into the patient. The distal end 
portion 210 also has a rounded portion 214 proximally of the tapered 
portion 212. The rounded portion 214 is generally rounded in the proximal 
direction radially inwardly toward the remainder of the shaft 206 to help 
retain the distal end portion 210 within the patient while permitting 
intentional removal of the outflow cannula 200 from the patient. The 
distal end portion 210 of the cannula 200 may be considered to be 
generally acorn shaped. 
The distal end portion 210 of the outer sheath 206 includes walls in the 
tapered portion 212 that form a plurality (e.g., 4) of openings 216 in 
fluid communication with the pressure transmitting passageway 208. The 
openings 216 are preferably arranged in an equally spaced circumferential 
array in a second or proximal section 212B of the tapered portion 212. As 
illustrated in FIG. 5, the distal end of the tapered portion 212 converges 
toward the inner sheath 202 to substantially close the distal end of the 
outer lumen 208 to fluid communication except through the openings 216. 
This feature, in combination with preferred design in which the distal end 
217 of the inner sheath 202 extends distally (rightwardly in FIGS. 4 and 
5) slightly beyond the distal end of the outer sheath 206, helps to 
isolate the pressure transmitting passageway 208 from the flow of fluid 
through the inner lumen 204 of the outflow cannula 200. 
The tapered portion 212 preferably has two tapered sections 212A and 212B, 
including a first tapered section 212A extending substantially to the 
distal end of the outer sheath 206, and a second tapered section 212B 
extending between the rounded portion 214 and the first tapered section 
212A. The angle of taper of the first tapered section 212A is most 
preferably substantially steeper than the angle of taper of the second 
tapered section 212B. For example, the included angle defined by the first 
tapered section 212A may be approximately 43 degrees and the included 
angle of the second tapered section 212B may be approximately 15 degrees. 
The cannula 200 would be provided with a suitable introducer or obturator 
(not shown) for facilitating insertion of the cannula 200 into the 
patient. The obturator is inserted into the inner lumen 204 of the cannula 
200, and should extend slightly beyond the distal end 217 of the inner 
sheath 202. The obturator and proximal end of the inner sheath 202 are 
preferably adapted for a threaded connection between them. 
The inner sheath 202 conveniently has a hub 218 generally adjacent its 
proximal end 219. The hub 218 includes a suitable releasable locking 
mechanism, such as a the bayonet mechanism illustrated in FIG. 5, for 
locking the inner sheath 202 in position in the outer sheath 206. For 
example, the pin portion of the bayonet mechanism is provided by an inward 
extension of a lever or handle 220 provided on the hub 218 for manually 
turning the inner sheath 202 relative to the outer sheath 206 to lock them 
together. An L-shaped, pin-receiving channel is provided in the hub 222 of 
the outer sheath 206 to complete the bayonet mechanism. An O-ring seal 224 
is provided in the hub 222 of the outer sheath 206 to form a seal between 
the hubs 218 and 222. 
As illustrated in FIG. 2, the proximal end 219 of the inner sheath 202 is 
adapted for connection to the upstream end of the outflow line 24. The 
side port 226 is adapted for connection of the pressure sensing line 22 in 
order to bring the fluid side of the pressure chamber 54 into fluid 
communication with the pressure-transmitting passageway 208. 
OPERATION 
In installing the tubing set 10 prior to commencing the arthroscopic 
procedure, the pump 14 is initially put in the off position and saline 
bags 12 hung just above the level of the pump 14. Using sterile 
techniques, the tubing set 10 is delivered to the scrub nurse. The scrub 
nurse, in turn, will pass the red-capped equipment end of the tubing set 
10 to the circulating nurse. The scrub nurse will then secure the excess 
tubing and the blue-capped patient end of the tubing to the sterile field 
on the draped patient. The circulating nurse will close the clamps 38 on 
the inflow line 20. The inflow line 20 will then be connected to the pump 
14 by engaging the header tube 32 around the pump rollers 44. To 
facilitate this installation, flow direction indicating arrows can be 
provided on the pump 14. The bag spikes 40 will be connected to the saline 
bags 12. 
The pressure sensing or monitoring line 22 will be connected to the 
appropriate port on the pump 14 and subsequently connected to the patient 
cannula 200. If the pressure sensing outflow cannula 200 is being used, 
the pressure sensing line 22 is connected to the side port 226, and the 
blue-capped patient end of the outflow line 24 is connected to the 
proximal end 219. The downstream end of the inflow line 20 is connected to 
the appropriate port of an inflow cannula 27, which may be of the type 
that is adapted to receive an optical scope (not shown) suitable for use 
with a video display terminal (not shown). 
With regard to the outflow line 24, and in particular the pressure control 
and relief assembly comprising the parallel lines 72 and 74, the 
relatively stiffer PVC control tube 74 is mounted in operative position 
within the solenoid valve assembly as. The relatively more flexible 
elastomer pressure relief tube 72 is in turn inserted in operative 
position within the mechanical relief valve unit 86. Directional arrows 
may be provided in conjunction with the valve units to insure proper 
directional positioning of the tubes 72 and 74. 
Finally, the discharge tube 78 is placed within an appropriate collector or 
liquid collecting receptacle 18 open to the ambient air. The irrigation 
system, with a new sterile tubing set 10 installed, is now ready for use. 
In use, the inflow and outflow cannulae 27 and 200 are inserted into the 
patient to establish a fluid pathway through the surgical site. Irrigation 
fluid (e.g., saline solution) is then introduced into the surgical site 
via the inflow line 20 and inflow cannula 27, and drained from the 
surgical site through the outflow cannula 200 and outflow line 24. 
Pressure within the surgical site is indicated at the pump 14 as 
transmitted through the pressure sensing line 22. 
During operation of the irrigation system, the fluid volume is allowed to 
increase within the compliant tubing segments 100 and 102 in response to 
increasing fluid pressure, and the fluid volume within the compliant 
tubing segments 100 and 102 is allowed to decrease in response to 
decreasing fluid pressure. This is accomplished by allowing the cross 
section of the resilient tubing segments 100 and 102 to expand in response 
to the increasing fluid pressure within a range of expansion. The 
flattened portions of the tubing segment 100, 102 expand away from each 
other to increase the fluid volume within the tubing segment 100, 102 in 
response to increasing pressure. 
Example 1 
A tubing set 10 generally as shown in the figures was prepared, with the 
compliant tubing segments 100 and 102 formed of polyvinyl chloride 
compounded to a durometer of 55 on the Shore A scale. The tubing was 
fabricated by extrusion. The interior lumen of the compliant tubing 
segments 100 and 102 was formed in the shape of an oval, and the 
dimensions of the cross section of the lumen were 12 mm by 3 mm. The wall 
thickness of each of the compliant tubing segments 100 and 102 was the 
same (0.75 mm). The length of the compliant tubing segment 100 in the 
inflow line 20 was 90 cm, and the length of the compliant tubing segment 
102 in the outflow line 24 was 60 cm. 
The tubing set 10 was connected to a Model 8300 "3M ARTHROSCOPY PUMP" 
commercially available from Minnesota Mining and Manufacturing Company, 
St. Paul, Minn. The bag spikes 40 were used to pierce and engage bags 12 
of normal saline solution. Arthroscopic surgery was performed on the wrist 
joint of a fresh cadaver. Fluid pressure within the joint was observed to 
be within the norms expected of standard tubing sets operating on larger 
joint spaces. Excessive pressure spikes were not observed. 
As various changes could be made in the above constructions and methods 
without departing from the scope of the invention, it is intended that all 
matter contained in the above description or shown in the accompanying 
drawing be interpreted as illustrative and not in a limiting sense.