Handling the Endoscope

The control head of the endoscope is held in the left hand. The index and middle fingers activate the suction and air/water valves. Many examiners operate the angulation control wheels with the right hand, but an endoscopist with large hands can also manage these controls with the left hand. This leaves the right hand free to manipulate the insertion tube, which is advantageous in some situations. The control head is used to control the four functional systems listed in Table 1.8.

Optics

In a conventional endoscope, the control head has an eyepiece that allows for individual focusing. A video endoscope dispenses with this function, transmitting the image electronically from a distal chip to a video monitor.

The endoscopist should rehearse instrument manipulations to get a feel for how the image is transmitted from object to eyepiece. When the endoscope shaft is in a straightened position, it gives an upright view of the object with the right and left sides correctly displayed. Bending the shaft in the 12/6-o'clock plane correctly displays the right and left sides but inverts the image by 180°. Bending in the 3/9-o'clock plane results in an upright image with the left and right sides reversed.

Table 1.7 Five-step program for endoscopy training

1. Bench practice with the endoscope.

2. The instructor controls the endoscope while the trainee pushes the shaft and watches the procedure using a teaching attachment or video monitor.

3. The instructor advances the instrument, the trainee withdraws it.

4. The trainee advances and withdraws the instrument under supervision.

5. Solo endoscopy by the trainee.

Table 1.8 Control head functions

► Eyepiece or video output

► Tip angulation controls

► Air insufflation/irrigation

► Suction/instrumentation

- Fig. 1.6 Effect of straightening the endoscope

- Fig. 1.6 Effect of straightening the endoscope

Duodenum Straightening

a Pushing the instrument forward initially causes it to advance. On reaching the antrum, the endoscope tends to slacken and form a large loop in the stomach b The angled endoscope tip is in the duodenum. Pulling back on the shaft will straighten the loop in the stomach, causing the tip to advance down the duodenum

c When the loop has been completely straightened, further pulling will effect a withdrawal of the endoscope tip a Pushing the instrument forward initially causes it to advance. On reaching the antrum, the endoscope tends to slacken and form a large loop in the stomach b The angled endoscope tip is in the duodenum. Pulling back on the shaft will straighten the loop in the stomach, causing the tip to advance down the duodenum c When the loop has been completely straightened, further pulling will effect a withdrawal of the endoscope tip

Fig. 1.7 Rotation. Effect of a rotating movement on a bowed endoscope

Table 1.9 The elements of endoscope movements

Fig. 1.7 Rotation. Effect of a rotating movement on a bowed endoscope

a When the bow is defined by the shape of the lumen b When the endoscope is free to move a When the bow is defined by the shape of the lumen b When the endoscope is free to move

Table 1.9 The elements of endoscope movements

Moreover, when the endoscope is bowed into a large loop, pulling back on the instrument will straighten the shaft, initially causing the endoscope tip to advance by several centimeters. This phenomenon occurs routinely in the proximal duodenum (Fig. 1.6).

Rotation

Rotation of the endoscope about its long axis is transmitted to the tip of the torque-stable shaft, virtually without spiral twisting. Thus, when the instrument tip is in a raised position, the shaft can be rotated as an alternative to using the right/left control wheel.

Mechanics of Endoscope Movements

The individual components of endoscope movements are listed in Table 1.9.

Angulation

The bending section of the endoscope is controlled with two angulation wheels, which deflect the tip by means of pull wires. The large inner wheel moves the endoscope tip up and down, and the smaller outer wheel deflects it to the left and right (in the 3/9-o'clock plane).

Pushing and Pulling The fact that the endoscope can be advanced and withdrawn is self-evident. It should be noted, however, that when the instrument tip is retroflexed into a "J" shape, pulling back on the endoscope will advance the tip toward the object being viewed.

Bowing/Looping

Passive bowing or looping of the endoscope is determined by the anatomical shape of the lumen that surrounds the shaft. Though not actively controlled by the endoscopist, it is always an element of instrument control. This is because the actual effect of a rotating maneuver depends on the overall bend of the endoscope, on the freedom of movement of the endoscope within the organ and of the organ itself, and on the position of the bending section (Fig. 1.7).

Overall Control

The application of these control maneuvers cannot be learned theoretically. Endoscopic control is a very complex process whose separate elements are not always precisely known. The overall effect of combined control maneuvers can be learned only through practice.

Air Insufflation and Irrigation

The light source is combined with a compressed air pump that can deliver either compressed air or pressurized water through the umbilical cord to the endoscope, as desired. This function is controlled by the air/water valve. This valve has three positions (Fig. 1.8):

► Neutral position: no air insufflation, no water jet

► Air insufflation

- Fig. 1.8 Air insufflation and irrigation

Air ^ vent

Air ^ vent

Water

a Air/watervalve in the neutral position. The air/watervalve permits airto exit through a vent hole. Thevented aircan be felt by holding a finger over the hole. When thisvalve is not activated, it automatically assumes a position that blocks the water channelwhile allowing airto escape through the vent hole

Water jet

Water jet

Air/water valve

Water

Air/water valve

Water b Air insufflation.

Placing the finger lightly on the vent hole keeps the air from escaping and redirects it to the distal end of the endoscope. This does not involve activating the valve c Irrigation.

Pressing the valve button down closes off the air channel and redirects air pressure into the water bottle, causing water to be pumped from the bottle into the endoscope. The air and water channels converge atthe distal end ofthescope and open at the air/water nozzle

Suction and Instrumentation

The suction channel and instrument channel converge at the distal end of the control head to a common channel that passes down the shaft to the suction/instrument channel opening at the distal bending section. The tapered connector for the suction pump tube is located on the side of the supply plug. Suction is controlled by the suction valve on the control head, which has two positions (Fig. 1.9):

► Neutral position

► Suction position

- Fig. 1.9 Suction and instrumentation

Instrument channel

Instrument channel

Suction valve a Suction valve in the neutral position. When the suction valve is not activated, it automatically assumes the neutral position and blocks suction

Instrument channel

Instrument channel

Suctionvalve b Suction position.

Pushing thevalve button opens the suction channel, creating a negative pressure that draws airorfluid into the opening ofthe suction/instrument channel at the distal end ofthescope. Becausethe proximal opening ofthe instrument channel communicates with the suction channel, this opening must be occluded with a valve

Instrument channel

Instrument channel

Suction valve c Instrumentation.

Instruments (injection needles, biopsy forceps, catheters) can be introduced through the instrument channel and passed down the endoscope. The instrument channel can be used to flush the suction channel if the latter becomes clogged, and it can be used for introducing large amounts offluid (e.g., to irrigate a bleeding lesion)

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