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Endoscopic Platforms for NOTES
Pankaj J. Pasricha & Homero Rivas
Stanford University School of Medicine, Stanford, CA, USA
Introduction
Natural orifi ce translumenal endoscopic surgery (NOTES)
represents a potentially signifi cant breakthrough and a paradigm shift in surgery. The adoption of this concept was the
result of the work of a multicenter team of investigators (the
Apollo Group) in the late 1990s [1–4]. Since then, numerous technological advances have been created and implemented in many different areas of interventional endoscopy
and minimal -access surgery while trying to promote NOTES
as a sole technique.
As with any technological or technical innovation, proponents of NOTES need to demonstrate how this technique
can be practically implemented, and whether its effi cacy,
risks, and costs are comparable or better as compared with
the current standards of practice. Only then can we expect
it to cross the chasm from concept to reality and be widely
adopted. Indeed, during the fi rst decade of NOTES, some
critics have said that the approach has fallen short of its
expectations [5]. On the other hand, many clinicians and
innovators have argued the opposite, as numerous endoscopic platforms have been created and successfully implemented as a result of extensive multidisciplinary work in
this fi eld throughout the world [1,6,7].
These endoscopic platforms have been tailored to all different potential points of entry access through natural orifi ces (i.e., mouth, rectum, vagina, etc.) [8–11]. In addition,
some platforms have been designed for hybrid surgical and
endoscopic approaches leveraging on single -port laparoscopy and also on the use of microscopic laparoscopic instrumentation (MAN -OS) [12].
Critical features of an ideal NOTES
platform
There are four fundamental requirements for a NOTES platform [4]:
1 Provide safe entry into the peritoneal cavity.
2 Provide a stable conduit for rapid passage of instrumenta-
tions, including imaging and therapeutic tools.
3 Maintain safe peritoneal distention.
4 Provide quick, easy, and robust closure of the visceral
defect at the end of the procedure.
Safe access entry
In general, two of the most important technical features that
any ideal NOTES platform should include are the safe creation of a translumenal access and its reliable and easy closure
at the end of the procedure. For most clinical applications,
such points of access include the proximal or distal gastrointestinal (GI) tract or through the vagina. Additionally, and
perhaps just as importantly, such platforms should be stable
and may allow use and change of endoscopic instrumentation (including advanced energy, retraction, and suturing
devices) while providing superb optics and excellent access
and visualization of intra -abdominal structures (Table 2.1).
Ideally, all of these features would be easy to master, especially by average endoscopists.
Provision of safe entry to the peritoneal cavity from a
visceral organ is not necessarily a straightforward task. The
most important complication to avoid during this phase is
damage to neighboring organs, and several techniques have
been used to deal with this, including the use of a percuta-
Natural Orifi ce Translumenal Endoscopic Surgery (NOTES): Textbook and Video Atlas, First Edition. Edited by Anthony N. Kalloo, Jacques Marescaux,
Ricardo Zorron.
© 2012 John Wiley & Sons, Ltd. Published 2012 by John Wiley & Sons, Ltd.
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CHAPTER 2 Endoscopic Platforms for NOTES
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Table 2.1 Features of an ideal NOTES platform.
Three -star features (essential)
• Triangulation
• Instrument able to cover the operative fi eld
• Precise and smooth control
• High fl ow regulated insuffl ations
• Good suction and irrigation
• Vigorous retraction
Two -star features (ideal but not absolutely essential)
• Automated imaging
• Complete array of dedicated tools
• Accessory design that is uniform across vendor supply
One-star features (nice to have but not essential)
• Seated interface
• Voice activation
• Multiple optical views
• Wireless operation
• Mobility
• Cost effective
neous endoscopic gastrostomy -like approach [13]. Perhaps
one of the most intuitive forms of safe access, and the one
frequently used clinically in the GI tract, has been to create
a submucosal tunnel, as was fi rst described by Sumiyama
and colleagues from the Apollo Group [14]. This provides a
long submucosal fl ap, which allows entry into the abdomen
while providing an additional defense mechanism against a
leak once the conduit is no longer needed. Inoue et al. have
successfully implemented this technique in a modifi ed way
during their per -oral endoscopic myotomy for achalasia
(POEM) [15,16]. While Inoue ’s technique is not translumenal, it follows the same endoscopic paradigm shift of NOTES.
Other forms of direct transvisceral access without this submucosal fl ap would rely on a primary closure by a number
of different devices, as described later in this chapter.
Stable platform
Attaining a stable platform for access via the GI tract almost
invariably will require the use of an overtube. This would
provide rigidity to the endoscope and facilitate scope
exchanges. Further, additional functionality necessary for
the procedure (such as closure) could be incorporated
into the design of the overtube instead of the endoscope. In
the case of transvaginal NOTES, such an overtube is represented by either a modifi ed laparoscopic port or one with
multiple working channels in addition to an optical one.
Occasionally, such an overtube may not be needed, and only
a simple plastic cap at the end of the endoscope may be suffi cient to allow creation of submucosal fl aps, use of closure
devices, etc.
Peritoneal distention, optimal optics, and
extensive access throughout the abdomen
The techniques of intraperitoneal fl exible endoscopy are
even more demanding than the intralumenal approach,
especially when multi -quadrant evaluations of the abdomen
are required. Maintaining orientation and a sense of direction is essential as the visualization of the surgical horizon
usually is dramatically different than that obtained in conventional laparoscopic surgery. Some platforms, especially
those used for transvaginal access, have mainly relied on
rigid endoscopy, attenuating some of these issues. However,
fl exible endoscopic platforms provide better access to more
locations in the abdomen in comparison to rigid endoscopy
and will probably become the norm if NOTES becomes
widely adopted.
Distention of the peritoneum will probably be important
for many NOTES procedures and ideally will be done using
an inert gas such as carbon dioxide that is easily absorbed
after the procedure. However, overinfl ation presents its own
problems with respect to diaphragmatic and respiratory
mechanics, and intraperitoneal pressures will need to be
monitored and regulated [17].
Safe and reliable closure of access entry
One of the most crucial factors for the success of the NOTES
technique is the safe closure of the site of peritoneal entry
at the end of the procedure. Presently there are already
multiple platforms that allow this, and while they are not
used daily in NOTES they are certainly employed safely and
successfully in clinical practice for other indications. These
include clips, clasps, full -thickness sutures, T -bars, etc.
Ideally, these closure mechanisms should be automated and/
or built into the overtube. To date, this has only been
attained in experimental models, but this may truly push
NOTES into a feasible common practice.
Multifunctional instrumentation
Many of the above features are being incorporated into
practical platforms. Modifi ed laparoscopic carbon dioxide
insuffl ators with feedback pressure regulators that can be
attached to the platform are being developed [18]. Others
are integrating unique and proprietary features into devices
based on the previously mentioned objectives to create
effective translumenal ports that simplify the process of
entering, controlling, and exiting the peritoneal space (as an
example see Apollo Endosurgery, Austin, TX, USA;
www.apolloendo.com ; see also Figure 2.1).
Available endoscopic platforms for NOTES
While reliable access and exit platforms may be forthcoming
in the near future, currently NOTES procedures face an
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Figure 2.1 Apollo Endosurgery platforms
(OverStitch™, FlexShears ™) (Apollo, Austin,
TX, USA) .
additional hurdle: once in the peritoneal cavity, the lack of
effective fl exible tools is a serious obstacle to completing the
desired procedure in a timely and effi cient manner. The
current fl exible endoscope is unable to recapitulate most
surgical maneuvers because of intrinsic problems with its
design [4].
1 Force limitations: the modern endoscope cannot effi ciently transmit forces that are not aligned with its axis.
Further, the fl exibility of the shaft limits the magnitude of
even coaxial forces.
2 The “chopstick” effect (lack of triangulation).
3 Size limitations: there is a physical limit to the overall size
of the instrument determined by the natural orifi ce itself and
it cannot exceed a diameter that is comfortably and safely
tolerated by humans.
These and other limitations and their opposite ideal circumstances have been summarized by the Natural Orifi ce
Surgery Consortium for Assessment and Research (NOSCAR)
meeting [3] (Table 2.1). New NOTES -specifi c platforms have
to overcome these limitations while maintaining their
intrinsic fl exibility. Numerous endoscopic systems are being
designed with this in mind, yet are far from incorporating
all the desired elements. In the following sections, we will
briefl y describe some of the state -of-the-art endoscopic plat-
forms currently available either for clinical implementation
of NOTES or for its evaluation in the animal or dry lab.
NOTES scope
One of the fi rst systems utilized in the NOTES animal lab
was the Olympus R scope (XGIF -2TQ160R Olympus, Tokyo,
Japan). This system was later modifi ed into the NOTES
scope. In a nutshell, this endoscope is a modifi ed dual channel endoscope that has two bending segments, one of
which is lockable. Such segments allow simultaneous vertical lifting and horizontal dissection motion. This endoscope
has standard fl exible endoscopic optics, which are married
to the effectors (Figure 2.2). Overall this is one of the most
rudimentary NOTES systems presently available.
Incisionless Operating Platform
The Incisionless Operating Platform (USGI Medical, San
Capistrano, CA, USA) works on the basis of a fl exible platform, using an overtube, and with a steerable and lockable
shaft with four different operating channels (7 mm, 6 mm,
4 mm, and 4 mm in diameter), one of which allows for the
use of a small fl exible endoscope (N -scope from Olympus,
Tokyo, Japan). The endoscope becomes independent of the
instrumentation, yet this can become challenging for its
14
Figure 2.2 Olympus R Scope (XGIF -2TQ160R)
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(Olympus, Tokyo, Japan) .
CHAPTER 2 Endoscopic Platforms for NOTES
Figure 2.3 Incisionless Operating Platform (USGI Medical, San
Capistrano, CA, USA) .
manipulation. All of the instruments, including the optics,
are in a parallel axis (Figure 2.3).
Apollo Endosurgery platforms ( OverStitch™,
FlexShears™)
The Apollo Endosurgery platforms (Apollo Endosurgery,
Austin, TX, USA) include different technological confi gurations that either couple with a double -channel fl exible
endoscope and/or are utilized via its operating channels. The
main platform (OverStitch ™) allows coupling of a suturing
claw to the tip of the fi berscope. This platform is activated
through a long mechanical wire located immediately to the
side of the endoscope, and with a handle located next to the
primary controls of the endoscope (Figure 2.1). The FlexShears™ allow use of endoscopic shears to the overall system
(Figure 2.1).
EndoSAMURAI
The EndoSAMURAI (Olympus, Tokyo, Japan) was conceived under a hybrid premise of a fl exible and laparoscopic
system. It employs a locking overtube and a remote
working station, which can be used with a more ergonomic
user interface than most fl exible endoscopic platforms.
Distally it has two independent short, fl exible arms in
addition to the working channel, which allows a third
interchangeable instrument. The arms are aligned to
the body of the endoscope upon entry, but act independently with fi ve degrees of freedom and different effectors,
once the endoscope is at the target location. This
endoscope permits several ideal surgical qualities such as
triangulation, traction, counter -traction, tying of knots, etc.
Because of its overtube, it acts as a stable, robust platform
(Figure 2.4).
Direct Drive Endoscopic System
The Direct Drive Endoscopic System (DDES) (Boston
Scientifi c, Natick, MA, USA) is an endoscopic system
also designed under an endoscopic and laparoscopic platform. It provides three different channels for interchangeable 4 mm multifunctional instrumentation. Equally as
important, it permits the implementation of a user interface
for ideal operating ergonomics. The available specialized
tools include graspers, scissors, needle pushers, and diathermy. Its scope acts independently from the end effectors
(Figure 2.5).
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(a)
(a)
(b)
Figure 2.4 EndoSAMURAI (a) user interface and (b) distal end effectors
with scope (Olympus, Tokyo, Japan) .
ANUBIS
The ANUBIS system (Karl Storz GmbH, Tuttlingen, Germany)
is another sophisticated endoscopic platform, with an ergonomic user interface. It allows entry through a single access
point for translumenal, intralumenal, or laparoscopic procedures, and once it reaches its ideal target location, it deploys
three independent end effectors with multiple advanced
functionalities. This platform provides triangulation of end
effectors along their optical fi eld, and it allows the use of
controlled carbon dioxide insuffl ation, which could be used
on laparoscopic cases (Figure 2.6).
Disruptive concepts of endoscopic
platforms for NOTES
While all of these features are essential for any given NOTES
platform, many people are also convinced that NOTES, like
any other innovative technique, should replicate all of the
(b)
Figure 2.5 Direct Drive Endoscopic System (Boston Scientifi c, Natick,
MA, USA) .
surgical steps that conventional surgery (open and laparoscopic) follows. This may be where the true paradigm change
of NOTES may take place, as others would argue that such
replication is not necessary and may hinder its independent
success. If NOTES is a truly disruptive technique then it
should not only provide an alternative route to do the same
kind of surgery as laparoscopy allows, but also it should
encourage the innovation of simpler and more effective
alternatives to achieve the same clinical outcome. The endoscopic myotomy technique fi rst described in animals by Pasricha et al. and then translated into clinical experience by
Inoue is an example of such an innovation [15,16].
Unorthodox ways of maneuverability and anatomic expo-
sure need to be explored further. As a distinctive example,
16
(a)
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CHAPTER 2 Endoscopic Platforms for NOTES
the “snake fi st ” does not rely on appendages but mainly on
fl uid coaxial movements, such as those that could be
achieved with an endoscope. These different styles could
accomplish the same effi ciencies and desired outcomes in
the art of fi ghting. These paradigms may be inspirational to
design more functional platforms for NOTES, likely with as
good or better results as those presently achieved with conventional and sophisticated endoscopic platforms [4].
Conclusions
We have come a long way in our concepts about NOTES and
the kinds of technological platforms required. What was
seen as futuristic may quickly become part of our daily
armamentarium of diagnostic and therapeutic endoscopy.
While NOTES itself has not been widely adopted and replicated, the technological fallout since its inception, especially
of endoscopic platforms, has been substantial. In the future,
even more unorthodox ways in how we do endoscopy and
surgery may be worth exploring, especially by younger
generations.
(b)
(c)
Figure 2.6 ANUBIS (Karl Storz GmbH, Tuttlingen, Germany) .
and following an analogy of Chinese martial arts, two different yet highly effi cient ways to attack are the “eagle claw ”
(Ying Zhao) and the “snake fi st ” (She Quan) (see Videos 2.1
and 2.2). Both rely on fl uid movements of the attacker. The
“eagle claw ” has been described as a collective set of side to
side movements of “108 hands ” (Yue Shi San Shou), while
Chapter video clips
Video 2.1 “Snake fi st ” (She Quan) fi ghting technique of martial
arts.
Video 2.2 “Eagle claw ” (Ying Shao) fi ghting technique.
References
1 Pasricha PJ. NOTES: a gastroenterologist ’s perspective . Gastroin-
test Endosc Clin N Am 2007;17:611.
2 Kalloo AN, Singh VK, Jagannath SB, et al. Flexible transgastric
peritoneoscopy: a novel approach to diagnostic and therapeutic
interventions in the peritoneal cavity . Gastrointest Endosc
2004;60:114.
3 Rattner D, Kalloo A. ASGE/SAGES Working Group on Natural
Orifi ce Translumenal Endoscopic Surgery. October 2005 . Surg
Endosc 2006;20(2):329–33.
4 Mummadi RR, Pasricha PJ. The eagle or the snake: platforms for
NOTES and radical endoscopic therapy . Gastrointest Endosc Clin N
Am 2008;18:279.
5 Maiss J, Zopf Y, Hahn EG. Entrance barriers and integration
obstacles of NOTES . Minim Invasive Ther Allied Technol
2010;19(5):287–91.
6 Pasricha PJ. The future of therapeutic endoscopy . Clin Gastroen-
terol Hepatol 2004;2:286.
7 Shaikh SN, Thompson CC. Natural orifi ce translumenal surgery:
fl exible platform review. World J Gastrointest Surg 2010;2(6):
210–16.
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SECTION 1 Development of the NOTES Concept
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8 Chukwumah C, Zorron R, Marks JM, Ponsky JL. Current status
of natural orifi ce translumenal endoscopic surgery (NOTES) .
Curr Probl Surg 2010;47(8):630–68.
9 Zornig C, Mofi d H, Siemssen L, et al. Transvaginal NOTES hybrid
cholecystectomy: feasibility results in 68 cases with mid -term
follow-up. Endoscopy 2009;41(5):391–4.
10 Lehmann KS, Ritz JP , Wibmer A, et al. The German registry for
natural orifi ce translumenal endoscopic surgery: report of the
fi rst 551 patients . Ann Surg 2010;252(2):263–70.
11 Burghardt J, Buess G. Transanal endoscopic microsurgery
(TEM): a new technique and development during a time period
of 20 years . Surg Technol Int 2005;14:131–7.
12 Lacy , AM, Delgado, S, Rojas, OA, et al. MA-NOS radical sigmoid-
ectomy: report of a transvaginal resection in the human . Surg
Endosc 2008;22:1717.
13 Kantsevoy S, Jagannath S, Niiyama H, et al. A novel safe
approach to the peritoneal cavity for per -oral transgastric endoscopic procedures . Gastrointest Endosc 2007;65(3):497–500.
14 Sumiyama K, Gostout CJ, Rajan E, et al. Pilot study of trans-
esophageal endoscopic epicardial coagulation by submucosal
endoscopy with the mucosal fl ap safety valve technique (with
videos). Gastrointest Endosc 2008;67:497.
15 Inoue H, Minami H, Kobayashi Y, et al. Peroral endoscopic
myotomy (POEM) for esophageal achalasia . Endoscopy
2010;42(4):265–71.
16 Pasricha PJ, Hawari R, Ahmed I, et al. Submucosal endoscopic
esophageal myotomy: a novel experimental approach for the
treatment of achalasia . Endoscopy 2007;39(9):761–4.
17 Meireles O, Kantsevoy S, Kalloo A, et al. Comparison of intraab-
dominal pressures using the gastroscope and laparoscope for
transgastric surgery . Surg Endosc 2007;21(6):998–1001.
18 Bergstrom M, Swain P, Park P. Measurements of intraperitoneal
pressure and the develop development of a feedback control
valve for regulating pressure during fl exible transgastric surgery
(NOTES). Gastrointest Endosc 2007;66(1):174–8.
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Physiology of NOTES
Juliane Bingener & Angela M. Johnson
Mayo Clinic, Rochester, MN, USA
This chapter provides an overview of the physiologic impact
of the natural orifi ce translumenal endoscopic surgery
(NOTES) approach as we understand it today. We review
experimental and clinical studies and compare them with
prior knowledge from laparoscopy, endoscopy, and open
surgery as available. The reader will fi nd that a number of
physiologic parameters of importance will be very similar to
those investigated with the advent of laparoscopy. This especially concerns the choice of insuffl ation gas and insuffl ation
pressures. NOTES resulted from efforts to provide approaches
to the peritoneal and chest cavities that may be even less
invasive than laparoscopy. The theoretical advantages over
open and laparoscopic surgery include less postoperative
pain, decreased wound -related complications, possibly less
adhesions, possibly faster recovery mediated through a
decreased infl ammatory reaction, and improved cosmesis
[1]. To organize the physiologic component of NOTES, we
have subdivided the topic by organ system. We wish to
address the nervous and musculoskeletal systems in regards
to pain, the respiratory system including acid -base changes,
the cardiovascular impact, as well as the physiologic implications for the gastrointestinal (GI) tract, and the hematologic
and immunologic systems.
Why should NOTES be different than
laparoscopy?
In traditional laparoscopy, carbon dioxide is the insuffl ation
gas of choice as it is safe, inexpensive, noncombustible, and
colorless. It is excreted by the lungs and is highly water
soluble, reducing the risk of gas embolism seen with compressed air. Endoscopic compressors do not routinely include
a CO
insuffl ation component but use compressed air.
2
However, a CO
insuffl ator can be provided for the endo-
2
scope and has been used for intraluminal insuffl ation with
good results. Due to the uncontrolled insuffl ation used in
endoscopy, concerns have been voiced regarding high intra abdominal pressures with negative impact on the cardiovascular and respiratory system. In addition, the question of an
infectious component by breaching the GI wall is certainly
a concern that has to be addressed. A number of these concerns were outlined in the White Paper by Kalloo and
Rattner in 2006 [2].
Central and peripheral nervous systems
The central and peripheral nervous systems (CNS, PNS) are
the sites of a major consequence of surgical intervention:
pain. Pain is now recognized as the “fi fth vital sign ” in clinical practice and its impact on recovery is well described. Less
well known are reports that postoperative pain may contribute to more rapid tumor growth [3]. The NOTES approach
seeks to avoid creating pain by utilizing access routes with
limited pain receptors such as the GI tract or the posterior
vault of the vagina [4,5].
Experimentally, this hypothesis is supported by a prospective randomized controlled trial of transgastric oophorectomy in canines [6]. This experimental model measured the
nociceptive threshold of animals undergoing NOTES, laparoscopic, or open procedures using postoperative abdominal
cuff insuffl ation. The nociceptive threshold measurement is
a method to establish an individual subject ’s pain threshold
using standard stimuli. For example, a blood pressure cuff
is infl ated around a subject ’s arm and when the subject
expresses pain, that pressure is recorded as the threshold.
The initial pressure constitutes the baseline and can be compared between individuals and groups. After a painful stimulus, such as a surgery, the threshold for the blood pressure
Natural Orifi ce Translumenal Endoscopic Surgery (NOTES): Textbook and Video Atlas, First Edition. Edited by Anthony N. Kalloo, Jacques Marescaux,
Ricardo Zorron.
© 2012 John Wiley & Sons, Ltd. Published 2012 by John Wiley & Sons, Ltd.
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cuff around the arm to cause pain is usually lower as the
pain fi bers are “wound up. ” In this study, the nociceptive
threshold was measured using abdominal cuff insuffl ation
after surgery. The study reported that the nociceptive threshold of animals undergoing NOTES was decreased less than
those undergoing an open procedure. The NOTES animals
also tolerated signifi cantly higher abdominal cuff pressures
as early as 18 hours postoperatively compared to animals
that underwent laparoscopy or an open procedure. Of note,
the study described a shorter time to gastrointestinal motility
for those animals undergoing NOTES oophorectomy [6].
Clinically, a comparative study by Zorron et al. also
reported a decreased need for pain medication in patients
undergoing transvaginal cholecystectomy. He compared
patients undergoing transvaginal cholecystectomy with
standard laparoscopic cholecystectomy. In the transvaginal
cholecystectomy group, 50% of the patients did not
request any pain medication. Conversely, in the group
undergoing standard laparoscopic cholecystectomy, all
patients requested pain medication [7]. The group led by
Roberts has recently reported similar fi ndings for transvaginal appendectomy [8]. In a series by Horgan et al., the visual
analog pain scale was used with patients undergoing NOTES
procedures. Subjectively, patients reported pain levels less
than 2.5 in the fi rst 24 hours status post NOTES procedures,
which would be below the level at which pain medication,
in general, is offered [9]. Although these preliminary reports
support the decreased pain reaction after NOTES procedures, data from well -designed randomized multicenter
trials are still pending.
Respiratory system and acid-base
disturbance
From comparisons of laparoscopic and open surgery, we
know that the respiratory impact of surgical procedures can
be described in several components: the intra - and peri operative atelectasis resulting from intra -abdominal pressure and positioning, the intraoperative hypoxia and
hypercapnia noticed on the oxygen saturation and blood
gases, and postoperative pain limiting respiratory excursion
with decrease in vital capacity and tidal volume. The postoperative pain has been addressed above. Here we will
review the effects of intra -abdominal and intrathoracic pressure and the acid -base disturbances caused by the insuffl ation gases.
Intra-abdominal and intrathoracic pressure
The intra -abdominal pressures measured by a Veress needle
and endoscope appear to be fairly similar in several studies
[10]. In the chest cavity, however, the pressures measured
with the endoscope and the Veress needle, in a study by von
Delius et al., were 13% higher than the measured endo-
scopic pressure. This has to be taken into account when
relying solely on the endoscopic pressure [11].
Multiple studies have investigated the effect of intra abdominal insuffl ation on the respiratory status comparing
NOTES and laparoscopic procedures. These experimental
procedures did not fi nd any difference in clinically apparent
events between laparoscopy and NOTES groups [12–15].
This applied to studies where pressure -controlled insuffl ation was used, including high intra -abdominal pressures
such as pneumoperitoneum of 20 mmHg. Diverging results
have been reported from studies using on -demand insuffl ation. While studies investigating diagnostic NOTES procedures encountered a decrease in intra -abdominal pressure
recorded during on -demand procedures [16], complex
NOTES procedures revealed that signifi cantly elevated intra abdominal pressures were realized [17]. The pressure readings in the on -demand insuffl ation group in one study
revealed pressures higher than 15 mmHg 20% of the time.
However, with increased intra -abdominal pressure, no clinical differences were noted during the operative procedure
itself.
The intra -abdominal hypertension was associated with a
rise in the peak -inspiratory pressures measured up to
40 mBar. The increased peak -inspiratory pressure indicates
reduced pulmonary compliance and increased pulmonary
resistance. In the control group, with a constant insuffl ation
pressure of 12 mmHg as measured by Veress needle, the
maximum peak -inspiratory pressure was 26 mBar.
Abdominal insuffl ation gas
From a pulmonary and acid -base standpoint, the gas used
to initiate and maintain pneumoperitoneum is important.
Similar to laparoscopy with CO
is noted in the NOTES carbon dioxide groups. This rise is
usually transient and stabilizes, and is reversible with the
cessation of the procedure, similar to laparoscopy. The rise
in pCO
and associated decrease in blood pH was seen in
2
several studies [12,14]. This was avoided with NOTES procedures using air insuffl ation and also with NOTES procedures using lower intra -abdominal pressure, both with air
and CO
. The hypercapnia that resulted from 12 –15 mmHg
2
intraperitoneal pressure with CO
piratory effort, which leads to refl ex tachycardia, vasoconstriction, and a decrease in oxygenation. The decrease in
oxygenation was seen with increased abdominal pressures
(12 mmHg) and the use of CO
groups, this did not become clinically signifi cant in the
experimental setting [12,15].
Postoperatively, no clinically diverging results have been
reported. However, we are not aware of studies examining
vital capacity in the postoperative period for NOTES compared to laparoscopy. A histologic study investigated the rate
of pulmonary abnormalities in experimental swine at
necropsy, 14 days after NOTES or laparoscopy procedures.
, a signifi cant rise in pCO
2
requires an increased res-
2
. Again, in the experimental
2
2
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CHAPTER 3 Physiology of NOTES
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A statistically signifi cantly higher rate of pneumonitis was
seen in swine undergoing laparoscopy compared to swine
undergoing NOTES procedures. Pneumonitis is not infrequent in laboratory swine and all had undergone 14 days of
pre-operative quarantine prior to any operative procedure.
A possible reason for the increased pneumonitis may be the
increased mean intra -abdominal pressure recorded in the
laparoscopic group [18].
Cardiovascular system
Research during the introduction of laparoscopic cholecystectomy revealed that pneumoperitoneum decreases venous
return and subsequently cardiac output. For most clinical
situations and short laparoscopic procedures this effect
is outweighed by the decreased physiologic impact in
other aspects of the approach (pain, respiration, wound
healing). For patients with limited cardiopulmonary reserve
(e.g., septic shock, pulmonary hypertension), a small
decrease in venous return, however, can be detrimental. A
number of studies investigated the cardiovascular effects of
NOTES with CO
or air in comparison to laparoscopy or
2
endoscopy.
Cardiovascular parameters such as heart rate, mean arterial pressure, cardiac index, end diastolic volume, and systemic vascular resistance index were investigated [12,15,19].
Transgastric access
Intra-abdominal pressure during NOTES pneumoperitoneum appeared to affect cardiovascular parameters when
comparing on -demand with high abdominal pressures and
pressure-controlled insuffl ation. During on -demand insuffl ation pneumoperitoneum in experimental animals,
decreased heart rate was observed; cardiac index declined;
minor variations in mean arterial pressure were noted that
did not reach statistical signifi cance; and systemic vascular
resistance index was markedly elevated in three animals and
unchanged in the remainder. Pneumoperitoneum in the
control group was held constant at 12 mmHg. The control
group experienced a similar decrease in heart rate, increase
in mean arterial pressure, increase in cardiac index, increase
in global end -diastolic index, and decrease in systemic vascular resistance index [14].
When on -demand pressure resulted in intra -abdominal
pressures lower than laparoscopy and NOTES with air was
used, the heart rate increased over 90 min in the laparoscopy
group but decreased in the NOTES group [16].
Mean arterial blood pressures were statistically signifi cantly increased across all study groups during pneumoperitoneum; however, this was least pronounced in the NOTES
air insuffl ation group. No statistically signifi cant change was
noted in cardiac index in either NOTES group. A statistically
signifi cant increase in cardiac index, upwards of 17%, was
noted in the laparoscopic group. Likewise, no statistically
signifi cant increase in end -diastolic volume was noted in
the NOTES groups. The laparoscopic group illustrated a
statistically signifi cant increase in end -diastolic volume.
The systemic vascular resistance was noted to be statistically
signifi cantly increased during pneumoperitoneum in the
NOTES carbon dioxide group; this increase was not
statistically signifi cant with NOTES air insuffl ation or
laparoscopy.
In a study comparing NOTES, laparoscopy, and endoscopy, heart rate and diastolic blood pressure were similar for
NOTES and endoscopy.
None of the changes noted in experimental animals
proved to lead to clinically apparent hemodynamic instability; however, one must account for the fact that study
animals were all young and healthy. The marked increase
of systemic vascular resistance index in three animals was
indicative of a stress response [14].
Mediastinal access
Hemodynamic effects of on -demand air insuffl ation during
transesophageal mediastinoscopy have also been investigated [11]. During uncomplicated mediastinoscopy, no correlation was noted between insuffl ation pressure and cardiac
index, systemic vascular resistance, heart rate, and mean
arterial pressure. A statistically signifi cant decrease in cardiac
index during NOTES mediastinoscopy correlated with an
increase in systemic vascular resistance. This may be a stress
response to endoscopic surgery.
No complications were noted regarding access to the
mediastinum through the esophagus and this necessitated a
limited amount of air insuffl ation for visualization. During
endoscopy, however, small tears were made in the parietal
pleura leading to left -sided pneumothoraces in three of eight
study animals. This was unrecognized and fatal in one
animal. Pleural injury was a signifi cant complication in three
of their eight study animals, leading to death in one; therefore, inadvertent parietal pleura injury and resultant pneumothorax is a large risk for this procedure [11].
Transvaginal access
Cardiovascular effects of transvaginal cholecystectomy were
compared to those of traditional laparoscopic cholecystectomy. The peritoneal cavity was insuffl ated with carbon
dioxide in both study arms with pressure -controlled pneumoperitoneum. No hemodynamic instability was noted in
any study animal. No statistically signifi cant change in
hemodynamics was noted in the NOTES or laparoscopic
group [13].
The cardiovascular effects appear to be pressure and gas
related, just as in traditional laparoscopy. Higher intra abdominal pressures lead to larger negative effects and CO
does have a measurable but usually not clinically deleterious
impact.
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