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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_605_Библиотеки_им_академика_М_И_Перельмана.pdf
Preconditions of Successful (Gastrointestinal) Surgery
Figure 4.23 (A) Stationary system; (B) mobile operating table. All from MITI.
81
table top is brought to it using the transporter. Mobile systems are compact units integrating each of the three modules (
Fig. 4.23B).
Each has their own particular advantages and disadvantages. Stationary
systems provide larger leg space to the OR team, are favorable in regards to
hygiene, and are better suitable for intraoperative diagnostic procedures.
4.3.4 Typical Surgical Positions in Visceral Surgery
In visceral surgery, the standard position is prone (on the back)
(
Fig. 4.24A). If access to the anorectum is necessary, the so-called lithot-
omy position is required (Fig 4.24B). Surgical operations on the spleen,
the pararenal glands, etc. need a side position. In (laparoscopic) surgery,
the Antitrendelenburg position is preferable.
In special cases, a stomach position is preferable (
the OR table is required as well, in particular horizontally (
A few surgeries even need a left- or right-lateral position (e.g., thorax,
retroperitoneum) (
Fig. 4.24F).
Most of the older OR tables were manually controlled by mechanical
or hydraulic operations. Today, remote control is the standard. Advanced
control handsets even give the operator information regarding the condition of the table and the position of the respective segments (
The table function is an important module of the future integrated OR
environment (see Chapter 14: Visceral Surgery of the Future: Prospects
and Needs).
Fig. 4.24C). Tilting of
Fig. 4.24D,E).
Fig. 4.25).
4.3.5 Maximum Load
The average patient is becoming increasingly obese.
Surgical tables are rated to support patients up to 150, 230, or 450 kg
in the “normal” patient orientation. These values are considerably lower
with side tilt or in a Trendelenburg/Antitrendelenburg position
[8].
82
Biomedical Engineering in Gastrointestinal Surgery
Figure 4.24 (A) Surgical positions: standard prone position. The majority of all
abdominal surgeries can thus be performed. (B) Lithotomy position; (C) stomach
position; (D) Trendelenburg position; (E) Antitrendelenburg (often used in laparoscopic operations); (F) lateral position: To give good access to the thorax and retroperitoneum, the table has to be bent. All from MITI.
The problem is even more relevant in hybrid ORs when the table has to
be shifted horizontally.
4.3.6 Cleaning and Disinfection
Though antisepsis is not required, OR tables have to be cleaned and disinfected after each single surgery. This is mostly done by hand, but at least
in larger surgical units dedicated washing machines are preferable.
Preconditions of Successful (Gastrointestinal) Surgery
Figure 4.25 (A) Remotely controlled OR table: graphical display of selection of function;
(B) the modification is indicated. Courtesy: TRUMPF Medical, Puchheim, Germany.
83
Figure 4.26 Currently available lamp systems: (A) TRUMPF: multiple LED in a twohalved body; (B) multiple lamp bodies; (C) central light source with cone-shaped
reflector. All from MITI.
4.3.7 Operating Lights
In the preelectrical era, adequate illumination during surgery was always
critical. The entrance of electric lights into the OR improved this significantly. Today, the surgeon expects a brilliant illumination even in deep
cavities without shadowing effects. As soon as it is switched on, the illumination should promptly reach its full intensity (e.g., in case of an emergency conversion in laparoscopic surgery).
The standard requirements for surgical lightheads are defined by the
document IEC60601241 of the International Electrotechnical
Commission (IEC): the amount of visible light (lux) should be between
40,000 and 160,000 lux in the center of the beam (central illuminance).
To meet the requirements a multitude of different designs have been
developed (
Most lamps can be moved by sterilized handles on the body of the
light ensemble.
Fig. 4.26).
84
Biomedical Engineering in Gastrointestinal Surgery
Figure 4.27 In modern integrated operation rooms, (A) remote lamp control is provided; (B) the parameters illustrated by icon are shown on the right. Courtesy:
TRUMPF Medical, Puchheim, Germany.
In R&D, a recognizable trend seems to be to replace conventional
lamp systems attached to a boom by static ceiling light systems. The
direction and intensity of the light beam is electronically modified instead
of a mechanical change of the position of the light source (
Fig. 4.27).
4.3.8 Peripheral Devices
Though the OR table, the surgical lamp, and the anesthesia equipment
play a central role, many more items are required to perform the operation,
such as the electrocautery machine (see Section 6.2: Electrosurgery), laparoscopy cart, the C-arm for intraoperative imaging, and instrument tables.
4.3.9 Structural Preconditions
The highly specialized workplace “surgical OR” requires the consideration of hygienic, climatic, energy-providing, etc. aspects
Electrical power supply plays a central role in modern hospitals, since
most devices are electrically powered and must be ready for operation
with highest availability. Therefore, already hospitals of average size are
supplied with high-voltage current directly from the electricity supplier.
To guarantee the safety of the patients and for retention of the functional capability of the hospital, technical arrangements are required by
law to ensure that essential devices can still operate for at least 24 hours
with loss of the central electric power
[10]. The most reliable electrical
power supply is necessary for OR lamps and all medical-technical devices
which are necessary for maintaining vital functions
cally two different emergency power systems are installed in hospitals:
[9].
[11]. Therefore, typi-
Preconditions of Successful (Gastrointestinal) Surgery
Figure 4.28 (A) Battery- or generator-based current can be identified by the red signal color (arrows); (B) terminal wall outlets (gases). All from MITI.
85
Figure 4.29 Central gas supply of a modern hospital with an easy to reach channel
of supply for big trucks. From MITI.
uninterruptible power supply (UPS, battery-based) and generators, usually
diesel engine driven.
The battery backup provides uninterrupted power to critical lifesaving
devices while the generator needs about 15 seconds to start up. To reduce
load on the UPS, in hospitals red colored outlets indicate that they are on
the battery backup current supply (
Fig. 4.28A).
Contemporary ORs are equipped with piped medical gas and vacuum
systems. The supply of oxygen, nitrous oxide, and carbon dioxide comes
from cylinder batteries whose size is based on the individual requirements. The central gas supply is typically located in an area where fresh
supply from the provider can be carried out easily (
Fig. 4.29) [12].
86
Biomedical Engineering in Gastrointestinal Surgery
Compressed air is generated with compressors, driven by electric motors,
additional dryers then withdraw the humidity. Filters and catalytic converters ensure an oil-free, medically pure compressed air. Finally, a pressurerelief valve reduces the air pressure to the required operating pressure.
The gases are passed through a branched pipe network. Gas outlets are
either fitted flush on walls or as overhead booms (
Fig. 4.28B). The termi-
nal gas outlets are labeled and the connection probe assembly differs to
avoid false connections. For the continuity of patient care with medical
gases, pressure monitoring with optical and acoustical alarms is provided
in all rooms connected to the central gas supply.
REFERENCES
[1] Miki´c Z. The gloves of love. Med Pregl 2010;63(12):1337 [in Serbian].
[2] Gastmeier P, Breier AC, Brandt C. Influence of laminar airflow on prosthetic joint
infections: a systematic review. J Hosp Infect 2012;81(2):738.
[3] Rutala WA, Weber DJ. Disinfection, sterilization, and antisepsis: an overview. Am J
Infect Control 2016;44(5 Suppl):e16.
[4] Sohn HM, Ryu JH. Monitored anesthesia care in and outside the operating room.
Korean J Anesthesiol 2016;69(4):31926.
[5] Ball L, Dameri M, Pelosi P. Modes of mechanical ventilation for the operating
room. Best Pract Res Clin Anaesthesiol 2015;29(3):28599.
[6] Da B, Buxbaum J. Training and competency in sedation practice in gastrointestinal
endoscopy. Gastrointest Endosc Clin N Am 2016;26(3):44362.
[7] Stahl JE, Sandberg WS, Daily B, Wiklund R, Egan MT, Goldman JM, et al.
Reorganizing patient care and workflow in the operating room: a cost-effectiveness
study. Surgery 2006;139:71728.
[8] Razavian S., Thurn J. On the tipping point of disaster: operating room surgical
table tips with obese patients,
07_tabletipdanger.htm
[9]
Scherrer M. Hygiene and room climate in the operating room. Min Invas Ther
Allied Technol 2003;12(6):2939.
[10] DIN VDE 0558-507:2008-12 “Battery based central safety power supply systems for
medical electrical equipment.”
[11] IEC 60364-5-56:2009 “Low-voltage electrical installations Part 5-56: Selection
and erection of electrical equipment Safety services.”
[12] IEC 60364-7-710:2002 “Electrical installations of buildings Part 7-710:
Requirements for special installations or locations Medical locations.”
; 2013 [accessed 30.08.16].
http://www.apsf.org/newsletters/html/2013/spring/
CHAPTER 5
Diagnostic Procedures
Surgery is a therapeutic discipline. Nevertheless, the diagnostic workup of
a surgical patient prior to the operation is an essential part of the surgeon’s obligations. For centuries, surgical examination was confined to
so-called “physical examination.” Physical examination, which is still
today mandatory, encompasses:
a. Visual inspection
Optical impressions provide valuable information about the general
state of the patient, including the nutritional state, etc.
b. Auscultation (
Listening to the internal sounds of the body gives valuable information about its function. The physiological movement of the bowel
(peristalsis) produces typical sounds which may be altered by inflammation (subtotal), obstruction, or other pathological conditions. If the
bowel is paralyzed, nothing is heard any longer (“deathly silence”).
Though auscultation of the abdomen is generally not as sophisticated
as cardiac auscultation, it requires sufficient experience.
The characteristic tool for auscultation is the stethoscope. Today,
electronic stethoscopes are available with signal enhancement and
noise reduction.
c. Percussion (
Striking the body with sharp blows of the finger s produces a sound
more or less specific to the density of the underlying anatomy. In the
abdomen, percussion is helpful to determine the size of the liver or to
estimate the air content of the bowel.
d. Palpation (
For palpation, the hands are used to feel the position, size, and consistency of internal organs. In the abdomen, liver and spleen are palpable as
well as tumors. Palpation may be difficult in obese patients. Nonetheless,
it is a basic component of the surgical exploration since the patient’s
complaints (pain) give valuable information upon the underlying disease
(e.g., lower right quadrant: appendicitis; upper right quadrant: cholecystitis; epigastrium: ulcer disease; and lower left quadrant: sigmoiditis).
Fig. 5.1A)
Fig. 5.1B)
Fig. 5.1C)
Biomedical Engineering in Gastrointestinal Surgery. © 2017 Elsevier Inc.
All rights reserved.
87
88
Biomedical Engineering in Gastrointestinal Surgery
Figure 5.1 (A) Auscultation: Bowel motility (peristalsis) produces a typical noise
which may be irregular or completely absent in the case of impaired transit;
(B) percussion: characteristic sound is produced by percussion which helps to determine the underlying tissue; (C) palpation: organs and their borders or atypical
masses can be felt with experienced fingers. All from MITI.
If performed by experienced clinicians, the sensitivity and specificity
of these tests together with clinical observation is rather high
[1].
Nonetheless, they do not reach the precision of modern technical diagnostic procedures. The detection of X-rays was a first breakthrough.
Roentgenographic tools were continuously improved (dynamic fluoroscopy computed tomography, etc.) and complimentary approaches were
invented [e.g., ultrasonography, magnetic resonance imaging (MRI)].
Further developments are in the pipeline. This chapter gives an overview.
5.1 CONVENTIONAL RADIOLOGY
X-rays are electromagnetic, indirectly ionizing radiation. They are
situated between ultraviolet and gamma rays with wavelengths between
26
10
Medical X-ray imaging is a noninvasive and painless method to
diagnose diseases and monitor therapies. It further helps to support the
planning of medical and surgical treatment. Unfortunately, due to the
high energy of the ionizing radiation, X-rays can potentially cause
damage to DNA, which can lead to the development of cancer.
Accordingly, the use must be strictly limited.
The objective of medical X-ray imaging is to provide information
about pathologies of the body structure or function. The image quality is
influenced by the properties of the object examined, hardware components of the imaging system, and the imaging technique used. The image
quality is affected by contrast, spatial resolution, and noise. Contrast
means the amount of the measured signal differences between the point
and 10
210
cm and frequencies in the range of 1010and 1014MHz.
Diagnostic Procedures
89
of interest and the surrounding area. The ability of an X-ray detector to
display different anatomical features within the imaged object is described
by the spatial resolution. The noise represents defective variances of the
true measured signal in the image. For the quantification of contrast, spatial resolution, and noise, and their relationships to each other, the parameters contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR),
modulation transfer function, noise power spectrum, and the detective
quantum efficiency are used
[2].
5.1.1 Technical Aspects
A radiographic system or an X-ray unit consists of an X-ray tube with a
generator, a collimator, an X-ray detector, and a device to ensure the
geometrical arrangement of patient, tube, and detector
tube generates the X-radiation, wh ichisshapedbythecollimatorand
passes through the human body thus creating a latent image in the
image plane. This image was formerly detected by X-ray film, an image
intensifier, or today by a set of X-ray detectors (digital radiography)
(
Fig. 5.2).
[3].TheX-ray
Figure 5.2 (A) Plain X-ray of the thorax. The X-ray source on the right side (not visible). The patient is positioned against the flat detector (posterioranterior X-ray); (B)
conventional dynamic fluoroscopy suite: 1, stretcher; 2, C-arm; 3, steering unit; 4,
video screens. The patient’s bed and the C-arm can be moved in all required degrees
of freedom independently of each other. All from MITI.
90 Biomedical Engineering in Gastrointestinal Surgery
5.1.2 Generation and Detection of X-Rays
The generation of X-rays occurs inside an X-ray tube where fast moving
electrons emitted by a heated cathode are suddenly decelerated by impinging on an anode material. The electron beam is concentrated to form a
small spot on the anode. The X-rays emerge in all directions from this
spot, which can be considered as a point source for the radiation. When
the electrons strike the target, only a small part of their energy is converted
into X-rays and the rest is dissipated in the form of heat. This condition
makes materials with a high melting point and a cooling system for the
X-ray tube necessary. The influencing factors for the wavelength of X-rays
are the anode material and the velocity of the electrons hitting the anode.
The intensity of X-rays depends on the current inside the tube. Typical for
diagnostic purposes are target voltages in the range of 30150 kV, while
the current is in the range of several hundred milliampere.
A detector registers the radiation behind the human body. In the past,
X-ray film delivered the typical shadowgraph. Today, detection of X-rays
is achieved either by a directly converting semiconductor or by a scintillation material followed by a light sensor such as a photodiode. In both
methods, radiation is ultimately converted into an electrical signal. The
sensitive area of a detector is divided into an array of detector elements.
Each delivers a signal representing the amount of absorption. There are
two different options to use the signal. It is called integrating detection if
the signal is integrated over a certain time. When every single event is
analyzed individually, it is called counting detection
tion of the performance of X-ray detectors is usually made by the modulation transfer function and the detective quantum efficiency
X-ray detectors can be subdivided into gas ionization, scintillation,
semiconductor, direct conversion or flat panel, charge-coupled device
(CCD), and photon-counting detectors.
A gas ionization detector measures the beam flux instead of individual photons. It is normally used as an int egrating detector, and consists
of a gas cell with a small entrance and exit windows. Several X-rays in
the beam interact with the chamber gas to produce photoelectrons and
photons. These electrons generate additional electronion pair s by
inelastic collisions, and t he photons either escape or are absorbed in a
photoelectrical way. Electrons and ions are then collected at the plates.
The efficiency of this detector depends on the X-ray absorption
cross-section, the active length of the chamber, and the properties of the
chamber gas.
[4]. The quantifica-
[5].