Endoscopy: troubleshooting equipment (Proceedings)

The Veterinary technician wears many professional hats in the average veterinary hospital, ranging from receptionist, primary care nurse, nurse anesthetist, surgical nurse, nutrition consultant, to equipment maintenance specialist. The technician should understand the operation of the equipment that is encountered in daily practice so that the tasks of maintaining and troubleshooting the equipment are not major obstacles. Endoscopy units are growing in numbers in veterinary facilities, along with their equipment complexity and technological advances. A valuable endoscopy nurse has the ability to maintain and care for the equipment, and to systematically troubleshoot the equipment. Possessing these skills will thereby save practice time and repair costs, plus reduce equipment downtime.

Power supply

It begins here: the power supply to the endoscopy equipment. If endoscopy equipment is not functioning, the very first troubleshooting step should begin at the power source. Many endoscopy units are arranged on a wheeled cart or tower specifically designed to stack a light source, video processor and/or camera, monitor, and image capture devices on several shelves. Some of the carts possess an attached electrical plug strip to accommodate each component on the cart. The electrical strip should include a good internal electrical surge protector. Some electrical strips have an "on" and "off" switch, another item to look at when troubleshooting the power supply. The main power supply from the plug strip is the only plug necessary to plug into an external electrical outlet. Large oversized plugs can crowd an average linear-designed power strip, taking the space of a couple of electrical outlets and preventing adjacent plugs from being well seated into the their outlets. There are power strips on the market that have outlets designed for over-sized plugs, and are an ideal design for endoscopy units. As a general rule, power to all components should be off when attaching or unattaching an endoscope.

Monitors

Monitors for viewing endoscopic images sent via video processor or digital camera vary greatly in quality and resolution. Medical grade monitors typically are of high resolution and range from 600 to 1280 lines of resolution. They offer RGB, S-video and composite inputs. The technician must be familiar with the operation of the monitor settings, including changing input sources from both the front control panel and the back input/output terminals of the rear panel. If a permanent mount is considered for an endoscopy monitor, select a site away from windows to minimize glare, and preferably in a minimally lit room.

Light sources

Endoscopic light sources have evolved from simple 150-Watt halogen bulb units to sophisticated 300-Watt xenon bulbs with automatic and manual settings, automatic gain controls, and a variety of light delivery systems within a single unit that can be adjusted to various endoscope designs and models. In the case of bulb failure, it is always wise to have extra halogen bulbs on hand. A 150-watt halogen bulb is under $30. Xenon bulbs range from $550-$800 and have a shelf life. The xenon gas-filled bulbs become inert if not used regularly. It is more economical to purchase replacement xenon bulbs when needed, and have them shipped overnight. Most xenon light sources possess an internal backup halogen light bulb in the event of xenon bulb failure.

Metallic contacts where the endoscope attaches to the light source should be dry, clean, and free of oxidation. A simple arrowhead-style pencil erasure can help in cleaning residue and oxidation off these contacts. Some light sources have options of manual or automatic light levels or intensities. The technician should be aware of these adjustment settings and functions.

Air pumps are often included in the housing of the light source. Settings are seen on the front display panel of the light source and include: on, off, low, medium, and high. A water bottle, typically hanging from the left side of the light source, is attached to the water bottle port of the terminal end of the endoscope. If air is not being delivered into an attached endoscope, check the pump settings, make certain that the endoscope is properly secured within the light source, and the water bottle is properly attached to the endoscope. Fill the water bottle ¾-full. Overfilling will result with decreased air and water production through the endoscope. Check for a tight seal of the water bottle lid and hose. O-ring failure or absence of an o-ring is a common troubleshooting finding.

Video processors

A video processor is the "computer "of an endoscope that possesses a video chip in its distal tip. The processor is electronically linked via a pigtail adapter to a video endoscope. The video chip in the distal end of the endoscope sends signal back to the video processor, and the unit then processes an image that is sent out to a monitor. The electronic prongs and pins that unite the scope and the processor are evaluated for damage and should be kept dry at all times. The video processor can communicate to the light source via the endoscope for light intensity changes. Automatic gain control and peak iris settings are examples of controls found on the front control panel. The video processor also has controls for color saturation and hues. Once set, these color controls rarely need adjustments. White balancing is a function that should be practiced at the beginning of every endoscopic procedure. Once the endoscope is attached to the light source and video processor, power to both units are turned on. The bulb of the light source is then ignited. The distal tip of the endoscope is placed in close proximity of a pure white object. There are white tubes designed for this purpose or alternatively, white gauze pads can be used. With the white object in full view, the operator must depress the white balance button on the front panel of the video processor. The white balance button may illuminate or the processor might beep indicating the white balance is set. If the white object seen by the endoscope has a blue hue to it, white balancing was not successful and must be repeated.

The video processor's computer has the capability of storing patient information and other data. Information is entered via a keyboard. If the processor fails to store or recall patient information, an internal memory battery may need replacement. Refer to the processor's manual. Memory batteries found in processors can be simple flat disk-style batteries that slide in and out of a receptacle and are easily replaced.

Camera attachments for fiberoptic endoscopes

Pure fiberoptic endoscopes can adapt to a monitor system via a camera designed to fit on the endoscope. The unit consists of a camera control box and a long cord that leads to the camera head which attaches to the endoscope's ocular head. Metallic contacts of both the camera and ocular head of the endoscope should be dry, clean, and free of oxidation. The camera head should fit securely onto the endoscope ocular piece. Light leaks around the camera will result in decreased image quality. The camera control box has similar control functions of a video processor, such as automatic gain control, color saturation and hue, and white balancing.

Inspect the camera cord for kinks and injury. Crimping of the camera cord is common at the head of the camera where the endoscopist may rest the camera against their shoulder. Camera cords may crush by walking on them, rolling anesthesia machines over them, etc. Likewise, storage of the camera and cord should be done in such a fashion that the cord is not severely kinked or twisted. Depending on the manufacturer and model, waterproof caps are provided for the protection of the camera and cord during cleaning and disinfection.

Fiber optic light cables

Fiberoptic light cables are used commonly with rigid endoscopes, video otoscopes, and some ultra-thin flexible endoscopes. Inspect cables for punctures or pinpoint holes. If the integrity of the cord is compromised, immersing the cable for cleaning and disinfection is not advised. Fluid will ruin the fiber optic cables within the cord. If decreased light transmission is experienced from the fiber optic cord with full illumination from the light source, broken fiber optic bundles is a probability.

Endoscope function

Flexible endoscopes possess internal channels: suction/biopsy channels, air and water channels. Occluded channels can occur and result in a frustrated endoscopist! The veterinary technician can systematically troubleshoot the operation and patency of these channels. An outline for troubleshooting is as follows:

Suction

Check suction source. Is the external suction source plugged into an electrical outlet and is it on? Is suction heard at the valve? Check suction valve – depress valve; is debris plugging hole? O-ring(s) intact? Is the valve secured? There are two types of valve designs – snap and threaded into place. Aspirated large particles through biopsy/suction channel? If so, remove scope from patient. Turn off light source, camera or video processor, and remove endoscope. Implement all channel irrigation or 3-way brush endoscope.

Air and water

Check light source or pump. Is the pump on? Check water bottle level (empty or too full?) Check valve. Inappropriate water dispensed? Valve o-rings worn or missing? Clean, dry, lubricate valve and replace into valve housing. No air? Air felt at open hole on top of valve? This confirms air from pump to valve, and suggests that problem is distal, probably at nozzle. Depress valve. No water? Check water bottle level. Check valve. Air/water nozzle at distal tip of scope plugged? Soak distal tip in enzymatic cleaner. Syringe fitting adapter to air/water source away from components and patient. Reverse flush. Stuck valve? Remove, clean and dry valve and apply silicone oil.

Caution

Never attach an all-channel irrigator to an endoscope when the scope is attached to a light source. Never attach an air/water cleaning adapter valve while scope is in a patient.

Image

The endoscope is attached to the light source and to the video processor or camera. All components are wired to one another. The image seen on the monitor is not of good quality. To follow are examples of problems associated with image problems:

Light guide fracture

The long metallic rod located at the terminal end of a flexible endoscope that inserts into the light source is called the light guide. This light guide contains a glass rod. Dropping or banging the light guide against a solid object will fracture the glass rod. The illuminating light from the light source will then be fracture and dispersed unevenly though the fractured glass rod and there will be a notable decreased light transmission through the endoscope. Inspect the light guide for fractures or cracks.

Broken fiberoptic bundles

There are two types of fiberoptic bundles: coherent bundles and non-coherent bundles. Coherent bundles are in flexible fiberoptic endoscopes and transmit the image from the distal tip of the endoscope back to the ocular piece. The bundles are perfectly arranged. That is, bundles arranged at the 12 o'clock position at the distal tip of the endoscope, are also arranged at 12 o'clock at the ocular piece. If these bundles are altered and not arranged perfectly, the image will become distorted. An example of this type of trauma is with exterior crushing of the endoscope caused by animal bites. If the coherent bundles break, a black area is seen in the image, representing loss of image transmission from that bundle. If fluid invades the interior of the endoscope, a wavy distorted image is seen. Fluids will eventually damage the fiber optic bundles and they will become brittle and begin to break. A large number of broken coherent fiber bundles will reduce image detail. Non-coherent bundles are arranged at random and their purpose is to transmit light from the light source to the distal tip of the endoscope. They transmit light for both fiber- optic and video endoscopes. Broken or damaged non-coherent fiberoptic bundles will result in decreased light transmission despite maximum light settings on the light source. All fiberoptic bundles can be damaged or broken when excessive twisting or torque is applied to the endoscope.

Endoscope lenses

Endoscopes possess lenses at their distal tips. Lens caps are placed over a video chip or coherent fiber bundles that transmit the image. Lens caps are also placed at the end of the non-coherent bundles that transmit the light to the distal tip of the endoscope. Lenses can be damaged or cracked if the distal tip is allowed to slap against an exam table, counter, floor or wall. The image transmitted back to the monitor is often distorted or fragmented. The image can also mimic the appearance of a water bubble under a microscope, displaying a prominent black outline. Lens caps should be evaluated each time the endoscope is used. Cracked or lost lens caps can lead to fluid invasion within the scope and subsequent damage.

Image capture units

VHS video tape recorders, digital tape recorders, digital still capture units, printers, and computer software for video and still capture programs are becoming commonplace in the endoscopy suite. Also emerging are computerized programs that integrate medical records including endoscopy reports with images of patient procedures. Quality of captured images is vastly improving. The new generation of video processors and cameras for endoscopes have digital outputs, such as USB ports or fire wires, which transfer directly into digital capturing devices or computers with higher resolution. However, most of the endoscopy equipment found in veterinary hospitals have analog outputs, thereby transferring images from analog to digital. Common output/input connection-types encountered are S-video, composite video (BNC), and RCA fittings. It is ideal to wire your capturing devices directly from the image source, from the outputs of the video processor or camera. Troubleshooting capturing devices can be challenging. The technician must understand the configuration and wiring of each component. If multiple image sources, such as a video processor and a camera are feeding into the same image capture devices, it is important to toggle or program the source of capture for each image source. Likewise, viewing the captured images on a monitor may require changing the monitor's source selection if multiple inputs are used from the image sources.

Repair

Despite all your best efforts, your endoscope or its accessories need to be sent out for repair. When shipping your endoscope, always attach the ETO cap to the leak test port. Many endoscope manufacturing companies have authorized repair centers that may be less expensive, be closer to your clinic, and have faster repair times.

Summary

The veterinary technician is a vital part of a prosperous endoscopy practice. Having a firm understanding of the equipment is essential in order to take on the responsibility of caring and maintaining the unit. Possessing the ability to troubleshoot all the components of the endoscopy unit is a valued asset to any veterinary facility and increases the technician's role value in the endoscopy team effort.