Endoscopes for Gastroenterology Procedures
Endoscopes are a valuable diagnostic and therapeutic tool in clinical gastroenterology. They are used to examine the lower esophageal sphincter, stomach, small intestine and large intestine.
The insertion tube of an endoscope has to be flexible (i.e., inserted deep into the body cavity). In order to reduce the burden on patients and prevent body fluids from entering the insertion section of an endoscope, an outer cover is provided on the outer periphery of a structural body of a flexible tube.
Deflection control
The deflection control feature of an insertion tube endoscope allows the insertion tube to be manipulated without damaging the more fragile components. This feature is particularly useful when a rigid tube has been used to construct the body of an endoscope. It is important to ensure that the insertion tube is able to be flexed without causing damage to the more delicate internal components, such as CCD wires and fiberoptic strands.
To achieve this, an angled slot is formed on each of the two control knobs that can be rotated to one of the four “hard” positions or to the “soft” position (e.g., to the “up” or “right” position). When a pawl is seated in this hard position it causes the slide pin on the end of the pull wire to stretch and place heavy tension on the coil wire surrounding the pull wire. The result is a significant increase in stiffness of the insertion tube (Fig. 3.4).
A variable stiffness mechanism is also used to make the insertion tube more rigid at will, allowing for a smoother and more controlled procedure. This is achieved by varying the mixture of soft and hard resins in the polymer base layer, which creates a relatively stiff and elastic endoscope. The insertion tube may then be further stiffened by rotating the stiffness control ring, which also controls the angulation of the tip.
Deflection control is typically found in small-diameter endoscopes, such as bronchoscopes and urethroscopes. However, gastrointestinal endoscopes have four-way angulation (i.e., up, down, left, and right), which is required for effective navigation of the gastrointestinal tract.
In addition to this, the bending section of the endoscope is deflected in one or two planes, depending on the type of insertion tube. Deflection in one plane is sufficient for many procedures, but gastrointestinal endoscopes with four-way angulation are preferred because they allow the endoscopist to deflect the tip of the insertion tube in more than one direction simultaneously.
A number of different accessories and ancillary instruments can be added to an endoscope system to enhance its functionality, diagnostic or therapeutic capability, and documentation of findings. These include sheaths and instruments for biopsy, grasping, aspiration, fluid infusion, cytologic sampling, electrosurgery, and laser surgery; pumps for suction, insufflation, and irrigation; and image management systems for recording, printing, and digital storage or transmission of still photographs and video.
Insufflation channel
The insertion tube endoscope is a long, flexible instrument that has an integrated air pump and light source. The air is sucked from the light source box through an air pump and pumped into the air pipe of the endoscope (Fujifilm, Pentax), or into an air/water channel (Olympus).
The distal tip of the insertion tube contains a water-jet nozzle that can be used to wash debris away from the objective lens or to insufflate the patient’s GI tract. This is an important safety feature.
Some colonoscopes also have an additional water tube and a nozzle on the distal end that can insertion tube endoscope be used to wash the mucosa. This is an additional safety feature that should be checked regularly to ensure it is functioning properly.
When the nozzle is clogged with blood, mucus, or stool, it can break away and contaminate the patient’s GI tract. If this occurs, it can result in perforation of the bowel and infection.
For this reason, it is important to use a disinfectant that will not cause any damage to the nozzle or the air/water valves. This can be done by following the manufacturer’s instructions for sterilization.
It is also a good idea to have a regular cleaning program to prevent odors, dirt, and bacteria from building up on the nozzle or in the air/water channels. This is an easy and safe way to keep your scope working efficiently.
A more rigid insertion tube is best for the examination of fixed anatomy, while a more floppy (nonrigid) one is more useful for the colon, which has tortuous structures that can be easily pulled back into the correct position. This combination of flexibility, elasticity, column strength, and torquing ability is the key to getting the best performance from your insertion tube.
The flexibility of the insertion tube is typically a compromise between these ideal characteristics, confirmed by months of clinical testing. The distal portion of the tube is typically significantly more flexible than the proximal section, but this does not run the entire length of the insertion tube. It is achieved by changing the formulation of the outer polymer layer as it is extruded over the wire mesh during manufacturing. This layer is initially soft and gradually replaced by a harder resin within a transition zone near the middle of the insertion tube.
Irrigation nozzle
Irrigation of the viewing window is an important component of most endoscopic procedures. This cleaning method eliminates the problem of dirt and body fluids sticking to the viewing window causing a blockage in the endoscope.
An insertion tube endoscope is usually equipped with an irrigation nozzle at the distal tip for spraying water onto the endoscopic view window. The water is sprayed at a low angle and does not cause damage to the surrounding tissue. It is also used to clean the endoscopic view window and reduce the risk of infection.
Several nozzles can be used with the endoscope; however, it is best to select the correct one for your procedure. A few factors that should be considered before selecting a nozzle include the location of the nozzle, its angle and the distance between the water nozzle and the patient.
In some nozzles, water is sprayed in a horizontal direction. This may be more suitable in flat areas, but it is not recommended if the area is sloped or has mounds.
This type of nozzle can be found on the Prisms 930 and 935 insertion tube endoscopes. It is also available as a disposable version.
The bending section of the insertion tube is controllable from a proximal side by four angulation wires attached to the tip at various positions. Pulling on a wire at 12 o’clock causes the bending section to curl up, while pulling the other three wires cause the bending section to deflect down or to the left.
Alternatively, the bending section can be controlled by a pull rope extending from the insertion tube to the distal end of the bending portion. The pull rope is guided in the bending portion to pivot the bending portion relative to the insertion tube.
In addition, the sleeve of the bending portion has a separating element arranged for dividing the cross-section of the sleeve into two separate chambers. The separating element may be a spring element, which imparts elasticity and bending stiffness to the sleeve.
The vapor barrier between the outer sheath and the interior space of the insertion tube provides a protective coating against passage of hydrogen peroxide or other sterilants into the inner space of the insertion tube. This prevents the contamination of the internal space of the insertion tube and allows for repeated sterilization of the insertion tube without affecting the inner tube.
Accessory channel
The accessory channel (also called a biopsy channel) in an insertion tube endoscope provides a passageway for accessories such as snares, probes and other tools. It also provides the air/water and suction valves that control these accessories. This channel is positioned close to the objective lens on the distal tip of the insertion tube and determines how accessories appear in the image as they pass into the visual field.
A one-way valve is present in this system to prevent the flow of air back into the nozzle on the distal tip, up the water channel and out the hole in the air/water valve when the operator removes his or her finger from the valve. This feature also allows the use of a disposable instrument to comply with infection control policies in many countries.
In addition to this antireflux valve, the endoscope’s air/water and suction valves are controlled by a knob on the control section of the endoscope. This knob is operated by the physician’s left hand and may be used to alternately control the valves.
When the blue air/water valve is covered, it feeds air from the nozzle at the distal tip to clean the objective lens. Full insertion tube endoscope depression of the valve flushes water to clear the lens.
Once the air/water valve is depressed, a suction pump connected to the light source connector of the endoscope generates suction through the biopsy channel. This suction is then directed to the gastrointestinal tract to distending the tissue and to allowing room air to enter the mucosa, enabling the examination of the viscus.
Several of the other features that are part of the control section of an insertion tube endoscope also are located in this portion of the instrument, including the up-and-down angulation knob. This knob is manipulated by the physician’s left thumb.
A channel-opening valve is also present to close the proximal opening of the biopsy channel and prevent room air from being drawn into the suction collection system. This valve is accompanied by a manometer that is attached to the valve and is used to monitor the pressure level of the insertion tube.
