The angulation system is what makes the tip articulate when the control handles on the control head are rotated and it can be broken down into three areas:
Either a wire pulley assembly or a chain drive can articulate endoscopes. The wire pulley is the most commonly used on flexible endoscopes. A locking mechanism allows these to be fixed in any position.
The pulley system uses a pair of wire cables wound onto a two slotted pulley and terminaties with a solid stopper. Turning the control handles turns the pulleys that pull the wires as they wind themselves up. Tension is released by feeding out wire to give slack to the opposing side. A shaft in the control head connects the pulleys to the control handles. Endoscopes that have up and down as well as left and right angulation have two pulley systems.
This is a chain and sptocket system similar to a bicycle. The chain wraps around the sprocket and moves in the direction it is turning. the chaing attaches to the angulation wire in the insertion tube.
These are flexible springs attached to the inner wall of the insertion tube. the coil pipes house the angulation wires and direct them in the proper direction. The also offer protection tot he internal elements from the sawing motion of the wires, which are constantly in motion while steering the distal tip.
When an insertion tube snakes into an 'S' shape the coil pipes have become crossed or detached. If the angulation system stiffens there may be a problem related to the coil pipes.
In the bending section several metal bands are hinged together. When the control handles are manipulated the angulation wire is pulled up through the coil pipes. The wire is threaded through a loop on each of the metal bands down to the distal tip where it is attached. As the wire is pulled it causes the distal tip to bend in that direction. A combination of up/down and left/right allows the tip to bend in any direction and be steered through most intricate lumens as far as the instrument's length will allow.
| On a flexible endoscope locate the handles or knowbs which control the angulation system. turn them to make the bending section move in every direction. |
The Elevator Channel on the ERCP endoscope is particularly susceptible to problems. You can understand why when you see the construction of the system.
The elevator raiser is hinged at one end and attached to a wire at the other end. Pressure exerted by the motion of the wire moves the cantilevered raiser up and down. Cleaning access to the cavity in which the raiser moves can only occur by brushing through the instrument channel opening. You need to open or extend the raiser as far as possible before brushing the cavity thoroughly. Then the raiser must be elevated completely to clean behind the raiser. If any debris is left behind it may solidify and impair the elevator operation as well as posing a potential infection risk. Some duodenoscopes have a removable distal cap that makes cleaning the elevator raiser shoe easier.
The wire channel assembly runs the length of the insertion tube and has two components. At the distal end the wire passes through a plastic channel supported by a coil pipe that remains flexible so the tip of the endoscope can move freely. At the control body end the wire runs through the metal sus-pipe. The total length of this channel that must be flushed is approximately 125 cm long and the opening between the elevator wire and the sus-pipe is approximately 0.18 mm. This is why when the channel is flushed it results in only a slow flow of fluid.
The elevator control knob mechanism varies slightly from one model to another. The operator moves either a lever or a wheel. This movement is transferred to the elevator pivot arm that is soldered to the end of the elevator wire. If there is a delay in raiser motion or if it jerks or moves erratically it needs to be sent for adjustment.
The elevator wire channel cleaning tube mount on the body allows fluids forced from a syringe to enter the tube and reach the elevator rod-sealing block. The block has two O-ring seals that allow the elevator rod to move in and out while allowing fluids to flow down the channel without entering the interior of the endoscope. A major difficulty in designing automated reprocessors is to devise a method to flush the elevator wire channel. Too little pressure doesn't produce enough flow to adequately reprocess; too much pressure allows fluid to bypass the O-rings and enter the interior of the endoscope. Some duodenoscopes (currently only the Pentax brand) have a different design where the elevator wire is sealed at the tip with an O-ring that prevents debris from refluxing up the elevator wire channel.
The elevator wire channel must be reprocessed in the same way as all other channels after each procedure.
| On an ERCP endoscope locate the elevator control knob and the elevator riser. Turn the knob and watch the riser move and have a look at the space behind it. |
The suction/biopsy channel is basically a length of tubing running from one end of the endoscope to the other with an on/off valve in the middle and attachments to stainless steel connectors at the ends. This tubing is required to be extremely flexible and pliable as well as stiff and strong.
The first potential problem area is the light guide plug. Cotton applicators should not be used to probe this or any channel port during cleaning. The applicator may wedge itself between opposing interior walls, catch on the milling marks and eventually break off inside as the user attempts to work it free.
Another area of concern is the bend in the channel where the umbilical cable meets the body. Aggressive cleaning with a coil spring cleaning brush or damaged brush can gradually wear through the channel.
There is a short length of tubing between the suction valve and Y pipe at the biopsy port that is often missed when brushing gross debris from the endoscope. It is only short (less than 20cm) and cleaning it requires inserting the brush at an acute angle into the valve unit. Damage will occur to the suction cylinder or the valve port if a metal coil brush is repeatedly inserted into the cylinder and passes all the way through the distal tip. Brush the short length through the suction valve and the insertion tube channel through the biopsy port.
Prompt cleaning of the endoscope after procedures and cautious insertion of anything into the suction/biopsy channels is the best way to ensure proper suction system operation. Avoid over-flexing the umbilical cable and insertion tubes to prevent kinking or collapsing of the channel.
Damage to the channel may result in the channel being unable to be properly cleaned and disinfected. It may also eventually lead to a puncture that increases the risk of fluid invading the other internal elements of the endoscope.
| If possible watch someone brushing the suction biiopsy channels after a procedure. |
The air from the pump flows into the endoscope through a seal either at the air inlet pipe on the light guide plug or at the water bottle. From here it flows to the body of the endoscope and out the air/water valve. To inflate the organ being examined the air/water valve is covered, which diverts air down the insertion tube and out the distal tip.
When the air/water valve is depressed air entering the endoscope is split with some of it diverted into the water bottle which forces water into another channel in the umbilical cable. The water travels through the channel in the umbilical cable, through the air/water valve and down the insertion tube to the distal tip.
Some water bottles are pressurised directly from the air pump. Some endoscopes have an auxiliary water port that connects directly into the water channel so the water flows through the auxiliary water port prior to flowing down the insertion tube. Other endoscopes have an entirely separate auxiliary water channel.
The air/water nozzle is the point of smallest inner diameter and can become obstructed with debris or crushed from an impact. Air infused into an organ during endoscopy may produce a luminal pressure high enough to force debris to back up several centimetres into the nozzle and the air and water channels. Irrigation of the channels immediately after each procedure will prevent clogging of the nozzles or channels. Some models of endoscopes have separate air and water outlets, whilst in others the channels are joined in the distal tip and emerge through a common outlet.
Never probe the opening of the nozzle with a sharp object as it may damage or loosen the nozzle and could inadvertently scratch the image lens. A soft bristle brush should be used to clean the nozzle. Avoid using cotton tipped applicators to clean any port or component of the air/water system as fibres from the applicator may clog the channels or nozzle.
When blowing air through any of the channels, do not exceed 20 PSI of pressure. The auxiliary water port or channel should be cleaned and reprocessed in the same manner as any other channel in the endoscope.
| Look at the nozzle of an endoscope. Ask someone if they can help you to identify the different channels and nozzles. |
The image system is made up of a variety of components including fibreoptics, electronics and the lens system. The internal structure of a video endoscope is virtually the same as a non-video endoscope except for the optical system.
Fibreoptic bundles composed of thousands of individual fibres are used to transmit light from the light guide plug to the distal tip of the insertion tube. An optical fibre is composed of two layers of glass of different reflective values that trap the light inside the length of the fibre. The flexibility of the fibres enables the light to be bent around corners and curves.
Non-video endoscopes also use a fibre bundle to transmit the image from the objective lens at the distal tip of the endoscope through the eyepiece to the user's eye. The image guide bundles are set up such that each fibre carries a portion of the image and is in the same place at both ends of the bundle. The final image is made up of the many small pieces of the whole image.
A broken fibre will result in a black or grey dot in the image. The fibres can be broken by trauma such as crushing of the insertion tube, severe impact or excessive bending of the insertion tube. Moisture around the fibres can cause them to become brittle which results in breakage.
In a video endoscope the image bundle is replaced with a video camera unit consisting of a lens assembly and an electronic chip attached to about 16 small wires. Many individual sensors (pixels) make up the image by detecting light levels and colours. An external video processor then assembles the image that is transmitted along the wires to a video monitor.
All endoscopes have lenses in both the lighting and image systems. A non-video endoscope has a lens system in the eyepiece that focuses on the end of the fibre bundle and magnifies the image.
All flexible endoscopes use an objective lens system at the distal tip. This reduces and focuses the image onto the surface of the image guide fibre bundle or the electronic chip.
Another lens system at the distal tip focuses light onto the area being examined to provide evenly distributed lighting.
It is important to protect these lenses from scratching or other trauma.
Over the years the basic electrical systems which existed in pre-video endoscopes have become very sophisticated.
There are several wires that travel from electrical contact pins on the light guide plug to contact pins on the eyepiece. These wires supply power to a camera attachment and communicate information from the camera to the light source to control automatic exposure systems within the light source.
There are electrical contact pins in various locations on the light guide connector. These control auto brightness and special features on certain models such as the colour wheel on black and white chip endoscopes. There are also pins located inside the electrical connector which transfer signals from the remote switches near the top of the control body to the documentation system.
Most endoscopes have an S-cord connector or grounding port on the light guide connector or elsewhere on the endoscope, usually the control body. All metal endoscope components are connected to this port to conduct any leakage current to ground on an electro surgical unit.
This controls the light level on all video endoscopes and some non-video endoscopes. Illumination decreases as you get closer to the object and increases as you get further away. The brightness intensity is also affected by how reflective the image is (ie. forceps vs. mucosa), the colour of the image and how much of the image is on the same plane. The auto brightness compensates for these differences to provide an appropriate illumination level.
Video endoscope systems have the ability to capture information in several different media including videotapes, computer files and prints. The switches on top of the control body are used to control the various recording devices or change settings on the video processor. The switch assembly consists of several components:
Tears in the rubber switch covers can allow fluid into the endoscope, and will interrupt the electrical signals. The switches should be examined closely every time a leakage test is performed.
| Ask someone to help you identify all the knobs and switches on the control body of an endoscope. |
If using an automated reprocessor there are specific connection systems available for each type of flexible endoscope from the different endoscope manufacturers. These connectors enable the endoscope to be connected to the ports of the automated reprocessor. They are available from the manufacturer of the reprocessor and must be used to adequately process the endoscopes.
Cleaning attachments or accessories are specific for the particular brand of endoscope. Some types of endoscopes have extra channels and will require extra accessories. These are available from the endoscope manufacturer and are essential for the proper cleaning and reprocessing of the endoscope. They include, brushes, cleaning adaptors and soaking caps.
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