The video camera is usually attached to the eyepiece of the endoscope where it captures the image and transmits it to the body of the camera located outside the operative field, where it is processed and sent to a monitor and, if desired, a recording device (Fig. 23.11). Laparoscopes without an optical path were introduced, with the sensor located on the distal tip of the endoscope, a design that requires a remote camera location. The resolution capability of the monitor should be at least equal to that provided by the camera. Most monitors have the potential to display about 800 horizontal lines of resolution while high definition (HD) systems generally possess 1,080 lines. The more light transmitted through the endoscope, the better the video visualization. The best
Figure 23.11 Laparoscopic tower. This tower comprises a monitor (A), a camera body or base unit (B) attached to a camera sensor; a light source (C) attached to a cable, which in turn will be connected with the endoscope; a still-image printer (D), and an insufﬂation machine (E). A video recorder is shown in (F).
available output is achieved from 250 to 300 watts, usually using xenon or metal halide bulbs. Most camera systems are integrated with the light source to vary light output automatically, depending on the amount of exposure required. Light guides or cables transmit light from the source to the endoscope via a bundle of densely packed optical fibers (fiberoptic). Fiberoptic cables lose function over time, generally secondary to breakage of the fiber bundles, especially if they are mishandled.
Creation of a Working Space
The peritoneal cavity is only a potential space, so it is necessary to fill it with a gas, typically CO2, to create a working environment. Other approaches are being explored that use mechanical lifting systems that allow room air into the peritoneal cavity.
Carbon dioxide is injected into the peritoneal cavity under pressure by a machine called an insufﬂator. The insufﬂator delivers the CO2 from a gas cylinder to the patient through tubing connected to a Luer adaptor on one of the laparoscopic cannulas. Most insufﬂators can be set to maintain a predetermined intra-abdominal pressure. High ﬂow rates (9 to 20 L per minute) are especially useful for maintaining exposure when suction of smoke or ﬂuid depletes the volume of intraperitoneal gas.
Intraperitoneal retractors attached to a pneumatic or mechanical lifting system can be used to create an intraperitoneal space much like a tent (93). This gasless or isobaric technique may have some advantages over pneumoperitoneum, particularly in patients with cardiopulmonary disease. Airtight cannulas are not necessary, and instruments do not need to have a uniform, narrow, cylindrical shape. Consequently, some conventional instruments may be used directly through the incisions.
Manipulation of Tissue and Fluid Fluid Management
Fluid may be disseminated into the peritoneal cavity through wide-caliber arthroscopy or cystoscopy tubing using gravity pressure and an infusion cuff or a high-pressure mechanical pump. The pumps deliver ﬂuid faster than the other techniques, and the highly pressurized stream of ﬂuid may facilitate blunt dissection (hydro-or aqua dissection). Small volumes of ﬂuid can be removed with a syringe attached to a cannula; for large volumes, it is necessary to use suction generated by a machine or a wall source.
The type of cannulas used for suction and irrigation depends on the irrigation ﬂuid used and the ﬂuid being removed. For ruptured ectopic gestations or other procedures in which there is a large amount of blood and clots, large-diameter cannulas (7 to 10 mm) are preferred. Cannulas with narrow tips are more effective in generating the high pressure needed for hydrodissection.