Scopes Rigid and Flexible

Since the early 1990s there has been a rapid advance in the use of minimally invasive surgery in most hospitals. This means devices for which biomeds have no training are now part of their inventory. In this article we will review some of these devices.

Two types of scopes are commonly used in hospitals: rigid and flexible. Rigid scopes—arthroscopes for joint surgery and laparoscopes for surgery in the peritoneal cavity—are the most widely used. There may be some older rigid bronchoscopes and cystoscopes in use, but mostly these have been replaced with flexible versions. All scopes, rigid or flexible, have a minimum of two internal channels, one for light transmission and the other for viewing. Some heat, which can cause minor problems to the surrounding tissue, is passed from the light source through the fiber-optic cable and the fibers in the scope. Tissue is viewed through the eyepiece on the end of the scope or with a video camera, (usually a CCD, which produces a digital signal).

Additional channels are added to the scope for infusing flush solutions, for suction, and for inserting surgical instruments, such as scissors, tissue grabbers, and laser or electrosurgical probes. Laparoscopes have an additional channel that allows for the infusion of a compressed gas, which moves organs to create a better field of view.

To keep the size of the incision to a minimum with arthroscopic and laparoscopic procedures, it is common to create additional entry sites through which instruments are brought to the desired location via triangulation. This ensures uninterrupted viewing as instruments are brought into the area, to cut, to coagulate, or to remove tissue. Both laparoscopic and arthroscopic procedures require that the skin be punctured with a trocar. This is a spring-loaded device that punctures the skin and provides a sleeve through which the scope or instruments are passed.

Most rigid-scope repairs cannot be made in the field. The most common repairs involve blockages in the instrument or suction/irrigation channels. These blockages must be cleared with compressed air after the scope is removed from the patient.

Flexible scopes—endo, gastro, procto, duodeno, broncho, and cysto—are basically the same except for differences in their diameter and length. They enter the body via a natural orifice—mouth, nose, rectum, or urethra—instead of through a puncture in the skin. The scopes contain one or more instrument/suction channels; a channel for air or water to wash the viewing lens, tissue, or to move tissue out of the viewing field, two light channels, and a view channel. The viewing channel is generally a CCD video system. The end of the scope can be bent up, down, right, and left by moving one of two control knobs on the junction block. One knob is for up-and-down movement, and one knob is for right-and-left movement. This movement should be smooth and easy, but thin wires that connect the control knobs to the distal end of the scope can break or stretch or be too tight and affect the movement.

Users should leak test the scopes before reprocessing. If any of the channels are leaking fluids, the reprocessing can damage the camera or other internal parts.

Fibers in both the viewing light and viewing channels will break. When they do, the breaks are seen as dots on the field. These breaks are not repairable in the field and the device must be sent to a refurbisher or to the manufacturer for repairs.

The light sources used for flexible scopes can be similar to those used for headlamps or higher power units using xenon bulbs. The xenon lamps have a useful life of approximately 500 hours. There is usually a timer that tracks how long the bulb is illuminated. When the timer has reached its limit, the bulb is replaced. The light source may have a built-in air compressor and a pump for washing fluids. Some will also have a cooling fan.

The video control unit, recorder, and printer are also part of the system and are in the same instrument rack. It is a good idea to mark all the interconnecting cables so when an equipment change is made, the cables are reconnected correctly.

Scope Disinfecting and Sterilizing Units
Flexible scopes cannot withstand steam sterilization without deterioration, and it takes 36 hours to sterilize a scope with ethylene oxide and 10 hours to sterilize with glutaraldehyde (Cidex). Since scopes are often used many times during the course of a day, many backup scopes would be needed if these methods were used. Most hospitals choose to use a high-level disinfectant, such as an activated 2% glutaraldehyde, 6% hydrogen peroxide, or 35% peracetic acid in an automatic reprocessor to reduce sterilization time and cost. Generally a chemical monitor is used during each processing cycle to detect the presence and proper concentration of the sterilant.

The operator uses adapters to connect the reprocessor to the open channels of the scope. The disinfectant is pumped through the channels and over the outside of the scope but not the junction block or electrical connections. The units are then flushed, air dried, and ready for use in approximately 30 minutes. The reprocessor documents the process via a printout indicating time and parameters and if the cycle was aborted. Most processors should have a diagnostic cycle run every day to ensure proper operation.

The filters on the water inlet for the rinse cycle need to be changed on a regular basis, but this may not be biomed’s responsibility. Most filters last only 30 to 45 days, and the need for a filter change will be indicated by pressure readings. Sticking valves cannot be repaired. They must be replaced. Some hospitals replace all the valves every year during preventive maintenance of the processor.

Insufflator
An insufflator is a pressure-limited gas-flow regulator used during laparoscopic or endoscopic procedures of the abdomen to create a gas-filled space (pneumoperitoneum), or to move tissue so the physician has a better field of vision and room for instruments. A needle is inserted into the abdomen and gas, usually carbon dioxide, is injected. Once pneumoperitoneum is reached, a trocar is used to enlarge the needle hole, allowing the laparoscope to be inserted. The trocar has an attachment that allows the insufflator to be connected to maintain the pressure as gas escapes from the laparoscope or other incisions. The pressure is maintained at between 10 mm Hg and 50 mm Hg and flows 1 L to 15 L per minute depending on the procedure.

The control units are either pneumatic or electric, with the lower flows and pressures usually controlled pneumatically.

These are simple units with regulator and needle valves to control the flow rates and readouts to show the pressure of the pneumoperitoneum.

If nitrous oxide is used as the inflating gas, a scavenger system must be used to collect the leaking gas from the abdomen so it does not affect the staff. Nitrous oxide should not be used if electrosurgical or laser energy will be introduced to the site.

Very little goes wrong with insufflators except user abuse. Broken gages, loose fittings, and bent cases are common problems. Connectors for the gas, both into and out of the machine, need to have regular checks to ensure safety.

Review Questions

1) How is an arthroscope introduced into the body?
     a. via an existing orifice
     b. after the skin is opened using electrosurgery
     c. via a trocar
     d. only used externally

2) Both rigid and flexible scopes have a minimum of _______________ channels.
     a. 2
     b. 3
     c. 5
     d. 7

3) Broken fibers in a scope show up as _____________________.
     a. bright spots on the viewing image
     b. dark spots on the viewing image
     c. not visible
     d. reversed viewing image

Answers: 1-c; 2-a; 3-b

David Harrington, PhD, is director of staff development and training at Technology in Medicine, in Holliston, Mass.

Contributing to this article is Freeman "Skip" Sands a TiM account manager assigned to North Adams Regional Hospital in North Adams, Mass.


Correction
The correct title for February’s ICC Prep (p 26) should have been “ECG Amplifiers.”