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62
W. F. A. Miles et al.
TAMIS
There are a number of exible ports that utilize
the TAMIS technique currently available. They
are discussed below.
GelPOINT Path Transanal Access Platform
The GelPOINT path transanal access platform
(Fig. 7.3) (Applied Medical, Rancho Santa
Margarita, California) is perhaps the most commonly used access channel for transanal surgery
and, with the aid of the surgeons who developed
TAMIS, was designed specically for this purpose. The single-use, disposable device comprises
of a deformable semirigid access channel with a
proximal ange and a distal ange supported by a
metal ring. The access channel can be introduced
into the anus with gentle pressure. The second
part of the device, a gel cap, is attached to the distal end of the channel. Three, or if required four,
ports are inserted through the gel. This provides a
semirigid gastight support for the camera and
instruments. The gel cap has two luer lock connections for insufation and evacuation of gas. A
recent development of the GelPOINT path system
has been the incorporation of a special high ow
port to be used with the insufation stabilization
bag (ISB; see below). The access channel is available in three lengths and with or without the proximal ange. Of the experts performing taTME,
91% utilize the GelPOINT path as the access
channel of choice [43].
SILS
The Covidien (Medtronic, 710 Medtronic
Parkway, Minneapolis, Minnesota, USA) SILS
port (Fig.7.4) is a foam port which is seated in
the anal canal and is sutured in place. This has
three preformed holes which allow the insertion
of three ports (usually one 10mm and two 5mm
ports) to allow rectal access and insufation. The
SILS port was the platform used to perform the
initial report of TAMIS surgery as reported in the
literature [30].
OCTO Port
The OCTO port (DalimSurgNET, B1401Woolin
Blue Nine, 583, Yangcheon-ro, Gangseo-gu,
Seoul, Korea) is a anged sleeve which can be
inserted into the anal canal and a plate carrying
multiple access ports attached. In Europe and
North America, it is not commonly used, and its
use was supported by only 21.6% of the St.
Gallen expert group – although availability of
this platform may limit its use by this group and
the port itself has not been compared to other
TAMIS ports in a meaningful way. There are a
number of other ports suitable for TAMIS including the Dapri-Port (manufactured by Karl Stortz)
(Fig. 7.5) and the KeyPort ex (Richard Wolf)
(Fig.7.6).
Fig. 7.3 GelPOINT path Fig. 7.4 SILS port (Covidien)
7 Operative Equipment and Insufflator Options
Fig. 7.5 D-port manufactured by Karl Storz (KARL
STORZ Endoscopy (UK) Ltd. 415 Perth Avenue, Slough,
Berkshire, United Kingdom)
Fig. 7.6 KeyPort ex Richard Wolf (Richard Wolf
GmbH, Pforzheimer Strasse 32, 75,438, Knittlingen,
Germany)
Robotic-Assisted TAMIS
There is very limited data regarding the use of
any form of robotic assistance to perform TAMIS
or taTME surgery although it has been shown to
be possible to perform transanal surgery with the
assistance of a robot [44, 45]. The current generation of surgical robots are bulky, and their multiarm instruments and mounting systems are not
well suited to transanal surgery. There are, however, indications that a wristed or exible robotic
instrument may improve the utility of transanal
surgery. Furthermore, the current design of the
available robots makes docking in the transanal
position difcult. Notwithstanding, there are pioneering centers which have shown that robotic
TAMIS can be achieved [46–50]. In the future,
robotic access may offer a number of signicant
advantages specically the elimination of clashing of the camera and instruments which is a cur-
63
rent limitation to the utility of transanal surgery.
While clashing can be avoided with experience,
this forms a signicant part of the learning curve
and adds to the fatigue of the operators. The
development of a robotic device with stereoscopic, 3D optics and articulating effector arms
specically for transanal surgery is likely to be
the next signicant step change in the advancement of transanal surgery [51]. For the time
being, however, it is possible but not common to
use a robot to perform transanal surgery.
Transanal Instrumentation
Ordinary Laparoscopic Instruments
With utilization of the TAMIS technique, the
majority of transanal surgery can be completed
with normal laparoscopic instruments on standard laparoscopic colorectal tray. Additional
instruments might include two needle holders,
curved graspers, and various curved instruments,
but these are considered optional.
Modified Instruments
There are a number of modied instruments
which have been developed by Richard Wolf specically for use with the TEM equipment. These
include right- and left-handed angled graspers
and needle holders which make suturing more
straightforward. Instruments with angled shafts
designed for single-incision laparoscopic surgery
(SILS) have not generally found favor among the
majority of transanal surgeons who use the
TAMIS approach. However, the use of angled
instruments may in some circumstances make
performing certain tasks less arduous. Likewise,
articulated instruments are not in general use
with TAMIS as, for the most part, straight instruments are sufcient for local excision.
Suturing Devices
There have been a number of automated suturing
devices which have been developed which accelerate the suturing process when closure is performed
64
W. F. A. Miles et al.
after local excision. While preferred by some
TAMIS experts, automated suturing devices are
generally not in widespread use due to cost limitations. Furthermore, for most closures of rectal
wall defects after full-thickness excision of rectal
neoplasia, a laparoscopic needle holder and
absorbable suture are sufcient to reapproximate
most defects in the rectal wall. Endoluminal
suturing is however made more straightforward
by the use of a self-locking, barbed suture such as
the V-Loc suture (Medtronic, 710 Medtronic
Parkway, Minneapolis, Minnesota, USA,) or the
STRATAFIX suture (Ethicon, Bridgewater, New
Jersey).
Diathermy
Monopolar diathermy is the most commonly
used option for transanal surgery. The choice of
instrument tip, hook, spatula, or needle knife is
very much dependent on the operator. The
advantage of monopolar diathermy, as a method
of tissue division, is that the energy released
leads to tissue vaporization with separation of
the tissue [52]. This causes a release of the anatomical planes allowing them to separate. In
comparison, energy devices such as ultrasonic
shears or other tissue-sealing devices tend to
seal the anatomical planes together. The diathermy effect may be adjusted to provide more
or less hemostasis by blending the “pure cut”
current with the “coagulation” current. As the
dissection is predominantly in an avascular
plane, there is usually no need for advanced
energy devices. Most experts prefer low-energy
settings for electrosurgery to minimize the accumulation of smoke and to lessen the effect of
tissue charring. The use of foot switch or nger
switch to operate the diathermy machine based
upon surgeon’s preference although foot switching may allow more accurate dissection with
less fatigue [53] .
Bipolar energy is not generally used for transanal surgery although it may be used to control
troublesome bleeding from venous channels on
the pelvic side wall, presacral veins, or the prostate gland’s neurovascular bundles. It is not used
in general dissection. The St. Gallen consensus
meeting reached 94.6% consensus on the statement that monopolar and bipolar diathermy were
the energy source of choice [43] and vesselsealing devices for transanal access, although
used, are less preferred for both local excision
and more advanced procedures.
Energy Devices
Ultrasonic dissection is most suited for fullthickness dissection of the rectal wall and close
dissection of the rectal wall from the mesorectum when performing proctectomy for inammatory bowel disease. The ultrasonic dissector
has the advantage of providing division of tissue with simultaneous hemostasis. This is an
advantage when dividing the full thickness of
the rectal wall including the rectal mucosa.
These layers of tissue have a robust blood supply and may bleed especially during full-thickness excision of a large polyp or an early rectal
cancer.
In some circumstances however, the sealing
process can also seal the tissue planes together
causing the dissection to pass unnoticed by the
surgeon from one tissue plane to another. This is
particularly so during taTME.This sealing effect
can impede the surgeon’s attempts to stay within
the correct anatomical planes.
Advanced energy devices use a low voltage
and a high electrical current between bipolar
electrodes along with pressure to plasticize and
fuse tissue. The overall effect is similar to the
effect created by an ultrasonic dissector.
Advanced energy devices can be used in a similar
way to ultrasonic dissectors to complete dissection. There are no published data to suggest
which may be more effective. As mentioned
above, the close dissection of the rectum during
proctectomy for inammatory bowel disease is
facilitated by using either an ultrasonic dissector or any commercially available advanced
energy device. Advanced energy devices are not
commonly used for local excision or rectal neoplasia or advanced procedures such as taTME
dissection [54].
KPV=×
Pressure in cm of water
Pressure volume non-compliant
High volume Low volume Very low volume
7 Operative Equipment and Insufflator Options
65
Insufflation and Billowing
The Gas Laws
In order to understand insufation, it is important
to understand the basic physical laws that apply
to the gas which is used and the materials which
form the walls of space into which the gas is
insufated. CO2 is by far the most commonly
used insufation gas, and the remainder of this
chapter assumes that this is the gas being used.
For the purpose of this discussion, we will consider CO2 as an ideal gas [55].
There are a number of physical laws which
apply to gasses, and perhaps one of the most
important of these is Boyle’s law [56] which is
stated as follows:
Whereby, P represents the pressure of the gas,
and V is the volume within which it is contained
and K the amount of gas (the number of molecules of the gas). We must also be careful to
understand the difference between what we mean
when referring to the insufation rates and the
volume of gas within the abdomen. One liter of
CO2 delivered by the insufator at atmospheric
pressure (1020cm of water) has a slightly lower
volume when compressed within the abdomen at
a pressure of 20cm of water (atmospheric pressure+20cm water).
One liter of CO2 at atmospheric pressure
becomes 1020/1040 x1 liters=0.98 liters of CO2
when compressed within the abdomen with a
pressure of 20cm of water. For the purposes of
this chapter, we will ignore temperature as the
changes to volume or pressure which occur over
a physiological temperature range are small
enough to be considered negligible.
Because the changes in pressure δP are very
small and so the changes in volume with pressure
δV are also very small, it is reasonable to assume
that 1 liter of gas delivered to by the insufator is
equal to 1 liter of gas within the abdomen or rectum. During insufation when gas is added to the
abdomen, both the pressure and the volume
change. The abdomen does not behave like a box
of a xed volume– if it were as such, then the
pressure within the abdomen would be directly
related to the volume of gas insufated. This is
not the case within the human body as many of
the tissues have a degree of elasticity and the
structures are compliant. It is important to understand compliance in relation to insufation.
Compliance
In the previous section, we have discussed the
relationship between K the amount of gas, its
pressure P, and the volume within which it is contained V as being a constant linear relationship.
This is true when there is no compliance. It is possible to draw the relationship between different
pressure and volume when gas is introduced into
spaces of different volumes (Fig. 7.7) [57]. The
tissues of the body are, however, compliant (i.e.,
they exhibit elasticity). This means that the relationship between the pressure of the gas in the
abdomen and volume of the abdomen at the
beginning of insufation is different to the relationship between the pressure of the gas and the
volume of the abdomen at the end of insufation.
At the beginning of insufation, the abdomen
is very compliant in that with the addition of an
amount of gas (K) there will be a very small
change in the pressure within the abdomen and a
very large change in the volume of the abdomen.
16
14
12
10
8
6
4
2
0
0 0.5 1 1.5 22.5 33.5 44.5 5
Insufflated volume
Fig. 7.7 Linear pressure-volume graphs for high- and
low-volume non-compliant spaces
66
Volume
Pressure in cm water
Volume pressure curve none compliant
Volume
Pressure in cm water
Volume pressure curve compliant
Volume of isufflated gas within the abdomen
Intra-abdominal pressure in cm water
Volume pressure curve normal laparoscopy
D
n
Non compliant
30
15
Fig. 7.8 Pressure-volume graph for a non-compliant
space during insufation
30
15
Fig. 7.9 Pressure-volume curve during insufation of a
compliant space (the abdomen) to the point of
non-compliance
However at the end of insufation the addition of
the same amount of gas (K) will produce a very
large change in the pressure within the abdomen
for only a very small change in the volume [57].
If the abdomen was non-compliant, then the
pressure- volume curve might look like that
shown in Fig.7.8. However, since the abdominal
wall is compliant, then the pressure-volume
curve will look like that shown in Fig.7.9.
W. F. A. Miles et al.
[58]. Almost all insufators in current use are
pressure and ow rate controlled [59, 60]. The
insufator is set to a pressure which creates sufcient distension of the abdomen to create a
working space [61] and a ow rate which
replaces any lost gas at a rate which is greater
than the rate of loss. The increasing volume of
the abdomen is resisted by the weight of the
abdominal wall (or its nonelastic compliance)
and the elastic tension of the abdominal wall
structures.
There is a very complex relationship between
the amount of gas introduced into the abdomen,
the working volume, the tension in the abdominal
wall, and the compliance of the abdominal wall.
The walls of the abdominal cavity are not uniform; parts of the abdominal wall are more elastic than others. The abdominal wall is also
dynamic and may contract if the patient is not
completely paralyzed [62, 63]. Because of this,
the physical equations which govern the relationship between the volume, pressure, and tension
are complex. This complex relationship has been
explored by Becker etal. [57], who have shown
that the pressure-volume relationships vary from
patient to patient. The compliance curve for normal laparoscopy should appear as shown in
Fig.7.10. In Fig.7.10, the insufation pressure is
within the compliant phase of the distension of
the abdomen, and so an increase in the volume of
gas produces a modest increase in pressure. This
diagram could be redrawn to show the volume of
the abdomen in relation to the volume of gas
added (Fig.7.11).
30
phase of
inflation
Normal working pressure
15
Deflation
eflatio
Inflation
Inflation
Insufflation
The insufator increases the amount of gas in the
abdomen until the required pressure is reached
Compliant phase of inflation
Fig. 7.10 Compliance curve for normal laparoscopy
Volume of isufflated gas within the abdomen
Volume of the adomen
Volume pressure curve normal laparoscopy
t
Volume of isufflated gas within the rectum
Intraluminal pressure in cm water
Volume pressure curve small volume non-compliant
I
n
Volume of isufflated gas within the rectum
Volume of the rectum
Volume pressure curve for the rectum
t
7 Operative Equipment and Insufflator Options
Deflation
Non complian
phase of
Normal working pressure
Compliant phase of inflation
Inflation
Fig. 7.11 Volume of gas insufated and the change in the
measured volume of the abdomen
30
Non compliant
phase of
inflation
15
Fig. 7.12 Volume-pressure curve of the insufated rectum, a small volume of insufated gas leads to a high
pressure in the rectum
Normal working pressure
Inflation / deflation
nflation / deflatio
Compliant phase of inflation
inflation
The situation in the pelvis is more complex.
The bony anatomy of the pelvis forms a solid
truncated cone with either end of the cone covered by an elastic membrane. It is bound by the
pelvic oor inferiorly and the abdominal peritoneum and pelvic contents superiorly. The dynamics of insufation are quite different in this
situation. As a smaller proportion of the inated
volume of the pelvis is compliant and the volume
of the pelvis is very small, the rate of change of
pressure for a given amount of insufated gas
will be greater (Fig.7.12).
As the insufated volume decreases and the
overall compliance of the insufated volume
decreases, the change in pressure for any volume
67
30
Compliant phase of inflation
15
Normal working pressure
Inflation / deflation
Fig. 7.13 Volume of insufated gas against the volume
of the insufated rectum
Non complian
phase of
inflation
of gas added increases. This is the situation at the
beginning of a TAMIS for local excision or
TAMIS for taTME immediately following placement of the purse string [40]. Figure 7.12 can
also be redrawn to show the change in volume of
the rectal working space for a given change in
volume of gas added (Fig.7.13).
At this point, the insufated volume is less
than 200ml and may be as small as 62ml (e.g.,
this is the baseline internal volume of the
GelPOINT path platform prior to initiating insufation). The compliance of the system is very
low as the access channel is rigid and only the gel
cap and the closed rectum are elastic. If it were
assumed that both the sutured rectum and the gel
cap of the GelPOINT path TAMIS port were
rigid, then the pressure in the rectum would rise
in direct proportion to the amount of gas added (a
non-compliant system). In this situation the rise
in pressure can be calculated. If it is assumed that
the whole system does not exhibit elasticity and
the total volume of the system is 100ml, then, for
each 100 ml of gas at atmospheric pressure
added, the pressure will increase. As an example,
when P =1 and V=100ml and K =amount of
gas in the rectum equates to 100 ml of CO2 at
atmospheric pressure.
Expressed mathematically: 1(atmospheric
pressure)×100ml (rectal volume) =100ml CO2
at atmospheric pressure. This can be rewritten as
P=amount of CO2 added in ml at atmospheric
pressure divided by rectal volume in ml or
P=100/100=1. If a further 100ml of CO2 at
68
Delivery Sensing Delivery Sensing Delivery Sensing
Luminal pressure
Delivery sensing cycle
W. F. A. Miles et al.
atmospheric pressure is added, then P=200/100
P= 2. That is, the pressure in the rectum would
rise to 2x atmospheric pressure or 1020 cm of
water above atmospheric pressure.
Clearly, this does not happen invivo, and, in
fact, two things do happen. First, in the example
using the GelPOINT path TAMIS port, the volume
of the system is not xed, and so the gel cap and
the rectum both stretch. Second, only a small
amount of gas is added before the insufator
senses an increase in pressure and stops delivering
additional gas. It can be seen that in these circumstances the pressure in the rectum increases almost
in direct relation to the amount of gas added. The
smaller and less compliant the insufated volume,
the larger the pressure rise for a given amount of
gas insufated. With very small non-compliant
volumes such as a rectal access device in a closed
rectum, there can be very rapid and large change in
pressure for only a small amount of gas added. The
rate of change of pressure is directly related to the
rate of insufation of the gas. It is this relationship
between pressure, volume, insufation rate, and
the method of control of the insufator that leads
to billowing and overpressure in the rectum [64].
Insufflators and Insufflation Control
The earliest versions of what we would now recognize as a laparoscopic insufator began to
appear in the 1960s and have largely been attrib-
uted to the work of Dr. Kurt Semm (1927–2003).
Semm, an experienced toolmaker and gynecologist, had developed a device for controlled CO2
insufation of the fallopian tubes. This was the
basis of his electronically controlled CO2 insufation device for laparoscopy produced by the
Wisap Company in the 1960s (Wisap® Medical
Technology GmbH, Fichtenstrasse 27, 85,649
Brunnthal/Hofolding, Germany).
The most simple insufation control circuit
allows insufation and pressure sensing to occur
through a single tube connected to the laparoscopic port which has been inserted into the
abdomen. This is the delivery and sensing cycle
(Fig. 7.14) [65]. The controls of the insufator
allow the rate of insufation (as measured in
liters per minute) and maximum pressure (as
measured by cm of water) to be set before insufation begins. Typically, the insufator will display the preset pressure and the actual
intra-abdominal pressure measured by the insufator, the preset ow rate and the actual ow rate,
and the volume of gas which has been delivered.
The sensing and insufation cycle is governed by
a control algorithm within the device (Fig. 7.15).
In order to achieve insufation in a reasonable
time and with the restriction imposed by insufation being achieved via a standard luer lock connections to the insufation tube and laparoscopic
port, during insufation, the pressure in the delivery tubing will be much higher than the set pressure of the insufator. With a single tube
Fig. 7.14 The delivery
and sensing cycle of the
most simple insufator
control system
Average pressure Collapsing pressureGas delivery
Outflow to
High pressure CO
Simplified insufflation control after Semm
7 Operative Equipment and Insufflator Options
69
insufation system, it is not possible to measure
the pressure in the abdomen during insufation,
and so insufation is briey suspended and the
pressure in the delivery tube allowed to equilibrate with the abdominal pressure. Then the true
abdominal pressure can be measured. The insufator employs a control algorithm to allow it to
reach the preset intra-abdominal pressure by
cycling between gas delivery and pressure sensing until the required set pressure is reached.
Once this has occurred, sensing continues and
insufation is suspended when the set pressure is
reached. Should the abdominal pressure fall for
any reason, then the insufation process will
resume. Should the abdominal pressure increase
above the preset value, the insufator will automatically vent gas from the system, retrograde
via the insufation tube, until the pressure again
reaches the preset value [66].
In this system, it is not possible to simultaneously deliver gas and sense the pressure in the
abdomen. This is the basis of the control circuit
employed by the majority of simple insufators
used for laparoscopy. While the simple insufation control circuit is suitable for basic laparoscopy, by the nature of its design, it is not possible
to maintain the abdominal pressure at exactly the
set pressure all of the time. It is always an approximation. Furthermore, as the ow rate increases
and the volume and compliance of the space
decrease, there is a greater deviation from the set
pressure. In these circumstances, very high pressures compared to the set pressure can be
achieved (Fig.7.16).
As discussed previously, the commonly used
insufation devices have a single channel to both
insufate the abdomen and measure the pressure
in the abdomen. There is a brief pause in insufation during the sensing phase, and then insufation is resumed. This continues until the set
pressure is reached. The intermittent nature of the
insufation is not generally noticeable during
abdominal laparoscopy because the volume of
the abdomen is high and the changes in the volume of gas are small as a percentage of the total
volume. The insufator is working in the compliant phase of the pressure-volume curve of the
abdomen (see above). The damping effect caused
by the compliance of the abdomen creates the
impression that the insufation pressure is stable.
This compliance also moderates any changes in
volume related to a small change in pressure.
This is not the case when the insufated volume
is small, such as in the closed rectum, and when
the compliance is low, with a rigid or exible
access channel. When this is the case, insufation
of a small volume of gas can lead to very large
changes in the pressure and almost no change in
volume of the rectum.
In the majority of current systems, insufation is achieved via a standard luer lock connector and small bore tubing. The dimension of the
Fig. 7.15 Diagrammatic
representation of the
control systems of a
simple laparoscopic
insufator
Primary
pressure reduction valve
Emergency over pressure
vent
2
Insufflation control valve
patient
Pressure sensorInsufflation control and
emergency venting
70
Delivery Sensing Delivery Sensing Delivery Sensing
Luminal pressure
Delivery sensing cycle
Fig. 7.16 Delivery and
sensing cycle during
abdominal laparoscopy
W. F. A. Miles et al.
Average pressure Collapsing pressureGas delivery
luer lock connector is governed by an international standard (ISO 80369) which requires that
the internal diameter of the male connector be
2.7mm in diameter. This is generally the smallest diameter pipe in the system although the
valves have a similar internal diameter. This narrow point in the gas pathway provides a signicant restriction to ow. To overcome this and to
deliver a sufcient volume of gas in a short time,
the pressure difference across these restrictions
must be high. To produce a ow rate of 20L/pm
would require a pressure difference across the
connector of 60mmHg. This, in turn, can lead to
high pressures within the inated volume once it
has reached its maximum capacity. In the abdomen, the maximum volume is governed by the
compliance of the abdominal wall and diaphragm and the compressibility of any intraabdominal organs. As discussed above, this
creates a compliant system, and so there may be
a relatively small change in pressure with quite
large changes in the volume of gas within the
abdomen. This is not however the situation when
inating the rectum within the connes of the
bony pelvis where the volume is constrained
[67]. The rectal volume within the pelvis is relatively small and the compliance is low.
Insufating a small volume of gas can lead to
very large changes in pressure. This is most
apparent with a standard insufator during the
initial step of taTME. In this situation, after
placement of the purse string suture, the insufated volume of the access channel and rectum
may be as small as 62 ml as discussed previously. During insufation especially at high ow
rates, the pressure in the delivery tubing is much
higher than the pressure in the rectum. As the
rectum begins to ll, the pressure in the rectum
rises. During the sensing phase of the insufation sensing cycle, the rectal pressure equilibrates to the pressure in the delivery tubing. As
the pressure in the rectum nears the set pressure
on the insufator, one of three things can
happen:
1. The insufator senses that the rectal pressure
is lower than the set pressure and resumes
insufation.
2. The insufator senses the rectal pressure has
reached the set pressure and pauses
insufation.
3. As the pressure in the insufation tubing
equilibrates with the rectum, the pressure is
higher than the set pressure and the system
vents.
In the third scenario, as the system vents CO
, the
2
pressure in the rectum can fall below the set pressure,
and so the sensing insufation cycle resumes.
Persistent overshooting of the set pressure and subsequent venting is observed as billowing. The overshoot
of the set pressure can be substantial [68] and may be
exaggerated if there is a constant loss from the system
due to smoke extraction or suction. Billowing may
also occur without overshooting of the set pressure if
losses from the system are high (Fig.7.17).
Delivery Sensing Delivery
Sensing Delivery Sensing
Luminal pressure
Delivery sensing cycle
7 Operative Equipment and Insufflator Options
Fig. 7.17 Intraluminal
pressure in the rectum
during billowing
Average pressure Collapsing pressureGas delivery
71
Billowing
During billowing, rectal pressure falls below
the collapsing pressure of the rectum (the pressure at which the rectal distension is no longer
maintained). It is at this point that movement of
the rectum is observed. It is also possible that
unintentionally high pressures may occur, dependent on the insufator settings and design, as the
insufator attempts to achieve the set pressure.
The resultant movement can be a very signicant
impediment to safely continuing the operation.
Billowing is most prominent when the inated
volume is very small. Billowing can occur with
any of the currently available TAMIS ports when
used with a standard insufator. Billowing occurs
infrequently with the TEM-specic insufator
and rarely when the AirSeal® insufator
(ConMed, Inc. Utica, New York) is employed
together with a TAMIS port, as discussed in the
following sections.
Smoke extraction can require rapid exchange
of the gas in the rectum. These high ow rates
demand high pressures to overcome the resistance of small bore insufation tubing but more
so the luer lock connections which are found universally on both ports and anal access channels.
The need for high pressure to create enough ow
to overcome leakage and the suction used to
evacuate smoke can lead to overpressure of the
system. Overpressure occurs when the insufator
continues to insufate despite the luminal pressure reaching the set pressure on the insufator.
Depending on the type of device being used, the
set pressure, its ow settings, and the sensitivity
of its pressure control systems, these periods of
overpressure can be small and short-lived or
more prolonged and more severe. It is possible
that overpressure in the rectum could drive CO2
into the blood stream and thus a potential cause a
CO2 embolus, a rare but serious complication of
taTME surgery [64, 69].
The TEM Insufflator
It was the problems with the simple insufation
system that spurred Professor Buess to pursue the
development of the TEM insufator (Wolf
GmbH). In this system there are four separate
connections to the TEM apparatus. They are as
follows:
1. Gas delivery
2. Pressure sensing
3. Smoke evacuation
4. Camera washing
In this system, gas delivery is continuous apart
from very brief periodic interruptions when the
machine has to recalibrate. Pressure sensing is
also continuous as is smoke evacuation. Camera
washing is via a separate channel and is controlled by the operator and does not take part in
the insufation circuit. The rate of smoke evacuation never exceeds the rate of gas delivery, and
the evacuated smoke is lost from the system
(Fig.7.18). Because both the delivery and loss of