There are different types of anesthesia. Nerve blocks stop the transmission of nerve signals from the body to the spinal cord. Axial blocks stop the flow of transmission from nerves in the spinal cord. General anesthesia affects the brain, causing unconsciousness. It is used on many people during surgery and for certain procedures that they would not be able to tolerate while awake. The anesthesia machine is designed to safely deliver anesthetics.
Gas Delivery System
The gas delivery system is designed to deliver gases to the patient. The gas delivery system typically is able to deliver air, pure oxygen and nitrous from two sources, according to "Clinical Anesthesiology" by G. Edward Morgan, et al. Gas is delivered through the the hospital's supply lines. Gas may also be delivered from tanks on the machine in the event the hospital's supply lines stop working. In addition, volatile anesthetics, such as sevoflurane, desflurane and isoflurane, are added to the gas during general anesthesia. Since the pressure from the hospital lines and the tanks is much higher than pressures delivered to the patient, pressure regulators are added to the system to bring the pressure down. Pressure gauges and flow meters measure gas delivery. In addition, there is a high-flow oxygen flush valve that can rapidly deliver oxygen to the patient.
Ventilator
According to "Miller's Anesthesia," during general anesthesia the patient's breathing is controlled by the ventilator. A reservoir of gas is delivered by a pressure system to the patient. Gas delivery can be controlled by such parameters as the volume of gas delivered per breath, or the pressure achieved per breath. Other settings, such as the respiratory rate, can also be controlled.
Patient Breathing System
The patient breathing system includes the tubing that transmits the gases to and from the patient from the ventilator. The tubing delivers gas to and from the airway through a small tube inserted into the windpipe, or trachea. Alternatively, a soft rubber device called a laryngeal mask airway, or LMA, can fit over the airway in the back of the throat, or a face mask can be used. A circular series of tubing is used to deliver and remove gases.
Scavenging System and Suction
A scavenging system on the anesthetic machine removes anesthetic gases after they have been delivered to the patient. In addition, suction tubing attached to a suction canister is available to remove excess secretions from the mouth, airway or gastrointestinal tract.
Monitors
Monitors on the anesthesia machine monitor parameters of the machine, such as gas delivery and pressures, as well as parameters of the patient. The monitors can display such variables as the number breaths per minute, the heart rate, the electrical activity of the heart, the blood pressure, the pressure in heart itself, the amount of oxygen in the blood, temperature, the exhaled carbon dioxide and inhaled and exhaled gases.
References
- "Clinical Anesthesiology"; G. Morgan, Maged Mikhail, and Michael Murray; 2005
- "Miller's Anesthesia"; Ronald D. Miller, M.D., Lars I. Eriksson, Lee A. Fleisher M.D. and Jeanine P. Wiener-Kronish; 2009
