Читать книгу Small Animal Laparoscopy and Thoracoscopy - Группа авторов - Страница 103

A seal is located at the top of the cannula, which allows instruments to pass through the cannula while preventing carbon dioxide (CO₂) from escaping from the abdominal cavity. A gas‐tight valve is located at the top of the cannula to allow instruments to be inserted and removed during a procedure without permitting the insufflated carbon dioxide escape. Various types of valves are available (spring loaded, magnetic trap door, trumpet, silicone, and so on), offering different characteristics in terms of leakage, mode of operation, and location on the cannula. More recently, a valveless cannula has been designed that makes use of a pressurized curtain of gas at the top of the instrument, eliminating the need for a valve altogether. This approach has the dual benefit of significantly reducing carbon dioxide leakage and smudging of the laparoscope lens, which is problem commonly associated with traditional valve types [2].