KEY POINTS

1. In the event of a pipeline crossover, two actions must be taken. The backup oxygen cylinder must be on, and the wall supply sources must be disconnected.
2. Fail-safe valves and proportioning systems help minimize delivery of a hypoxic mixture, but they are not foolproof. Delivery of a hypoxic mixture can result from the wrong supply gas, a defective or broken safety device, leaks downstream from the safety devices, inert gas administration, and dilution of the inspired oxygen concentration by high concentrations of inhaled anesthetics.
3. Because of desflurane's low boiling point and high vapor pressure, controlled vaporization of desflurane requires special, sophisticated vaporizers such as the Datex-Ohmeda Tec 6 and the Aladin Cassette Vaporizer.
4. Misfilling an empty variable-bypass vaporizer with desflurane could be catastrophic, resulting in delivery of a hypoxic mixture and a massive overdose of inhaled desflurane anesthetic.
5. Inhaled anesthetics can interact with carbon dioxide absorbents and produce toxic compounds. During sevoflurane anesthesia, compound A can be formed, particularly at low rates of fresh gas flow, and during desflurane anesthesia, carbon monoxide can be produced, particularly with desiccated absorbents.
6. Anesthesia ventilators with ascending bellows (i.e., bellows that ascend during the expiratory phase) are safer than those with descending bellows because disconnections readily manifest with ascending bellows.
7. When using anesthesia ventilators with ascending bellows, during the inspiratory phase, fresh gas flow and oxygen flushing contribute to the patient's tidal volume because the ventilator's relief valve is closed. Oxygen flushing during the inspiratory phase can cause barotrauma, particularly in pediatric patients. The anesthesiologist must never activate the oxygen flush during the inspiratory phase of mechanical ventilation.
8. New ventilators that use FGD technology virtually eliminate the possibility of barotrauma by oxygen flushing during the inspiratory phase because fresh gas flow and oxygen flush flow are diverted to the reservoir breathing bag. However, if the breathing bag has a leak or is absent, the patient may become aware while under anesthesia, and a lower than expected oxygen concentration may be delivered because of entrainment of room air.
9. With newer Ohmeda anesthetic ventilators such as the 7100 and 7900 SmartVent, the gas from the patient and the drive gas are scavenged, resulting in substantially increased volumes of scavenged gas. The scavenging systems must be set appropriately to accommodate the increased volume, or pollution of the operating room environment can result.
10. The low-pressure circuit is the vulnerable area of the anesthesia machine because it is most subject to breakage and leaks. The low-pressure circuit is located downstream from all anesthesia machine safety features except the oxygen analyzer, and it is the portion of the machine that is missed if an inappropriate leak test for a low-pressure circuit is performed.
11. It is mandatory to check the low-pressure circuit for leaks before an anesthetic is delivered because leaks in the circuit can cause delivery of a hypoxic mixture or cause the patient to become aware during anesthesia, or both.
12. Because most Ohmeda anesthesia machines have a one-way check valve in the low-pressure circuit, a negative-pressure leak test is required to detect leaks. A positive-pressure leak test cannot detect leaks in the low-pressure circuit of most Datex-Ohmeda products.
13. Internal vaporizer leaks can be detected only with the vaporizer turned on.
14. Before an anesthetic is administered, the circle system must be checked for leaks and for flow. To test for leaks, the circle system is pressurized to 30 cm H₂ O, and the circle system's airway pressure gauge is observed (i.e., static test). To check for appropriate flow to rule out obstructions and faulty valves, the ventilator and a test lung (e.g., breathing bag) are used (i.e., dynamic test).
15. Newer anesthesia workstation self-tests do not detect internal vaporizer leaks unless each vaporizer is individually turned on during the self-test.