Low Flow Anesthesia

Appendix of low flow anesthesia related terminology

Article also available in PDF: 51 KB

Definitions are in accordance with either the European (CEN) Standard or International (ISO) Standard. Please note that the name of the respective standard is indicated at the end of the definition.

Absorbent
Substance, usually soda lime, used to absorb carbon dioxide in a breathing system.
Airway Pressure (Paw)
Pressure at a specified point in the patient’s airway. (ISO)

Anesthetic Gas Scavenging System (AGS-System)
A system, which is connected to the exhaust port(s) of an anesthetic workstation, for the purpose of conveying expired and/or excess anesthetic gases to an appropriate place of discharge. (CEN)

Anesthesia Machine
Integrated anesthesia delivery system, including gas supply and control system, a breathing and ventilation system, and a scavenging system for dispensing and delivering anesthetic gases and vapors into a breathing system.

Anesthesia System
Any of a variety of assemblies designed to administer an anesthetic.

Anesthetic Agent
A drug used, usually in vaporized form, to reduce or abolish sensation of pain, consciousness or muscle activity. Examples of anesthetic agents are halothane, enflurane, isoflurane, sevoflurane and desflurane.

Anesthetic Agent Vapor
The gaseous phase of an anesthetic agent that is a liquid at room temperature and atmospheric pressure (desflurane is an exception as it has a boiling point of 23.5 °C).

Anesthetic Agent Concentration
The percentage of anesthetic agent present in the total anesthetic gas mixture.

Anesthetic Gas
Any gas and/or vapor of volatile agent used in anesthesia. (CEN)

Anesthetic Vaporizer
A device designed to facilitate the change of an anesthetic agent from a liquid to a vapor. (ISO)

Anesthetic Work Station
A system for the administration of inhalation anesthesia, which includes one or more actuator modules, monitoring, and their particular alarm modules, and essential hazard protection modules. (CEN)

APL Valve (=Adjustable Pressure Limiting Valve)
Pressure limiting valve, also called a "POP-OFF valve ", which releases gas over an adjustable range of pressures on purpose to control system pressure and thus intrapulmonary pressure, or to release excess anesthetic gases and vapors.

Auxiliary Mains Socket Outlet
Electrical outlets built into the ventilator for connecting other electrical equipment.

Bellows
An active part of a ventilator system acting as a reservoir for the gases. It separates gas breathed by the patient from the ventilator driving the gas.

Ascending (standing)
The bellows move downwards during inspiration.

Descending (hanging)
The bellows move upwards during expiration.

Berner Valve
A valve specially designed for manually assisted ventilation with options for spontaneous breathing, as well as for volume-and pressure-controlled assistance of ventilation. The Berner valve got its name after its inventor, Dr. Berner from Denmark.

Breathing System
Gas pathway in direct connection with the patient, through which intermittent or reciprocating gas flow occurs, and into which a mixture of a controlled composition of anesthetic gas mixture may be dispensed. (ISO)

Carbon Dioxide (CO2)
CO2 is an end product of metabolism and is eliminated from the body by exhalation through the lungs. CO2 acts as a breathing center stimulator. In some countries (like in the U.K.) it has been customary to administer CO2 to the patient at the end of anesthesia to activate spontaneous breathing.

CO2 Absorber
An absorbent, (usually soda lime) in a container, is used to remove CO2 from the gas exhaled by the patient.

Circle System
Anesthetic breathing system where the gas flows through separate inspiratory and expiratory pathways, which are connected together to form a circle. Unidirectional valves usually determine direction of flow in that circle. (CEN)

Circle Absorption System
Circle system incorporating a carbon dioxide absorber. (ISO / CEN)

Common Gas Outlet
The port through which the dispensed mixtures from the anesthetic gas supply module is delivered to the breathing system. (See also Fresh Gas Inlet). (ISO)

NOTE -The above definition is related to function. In structural terms, any gas outlet port will be known by the component of which it is a port; for example vaporizer outlet, machine outlet, cabin outlet. (A note from the ISO standard.)

"Complete" Rebreathing System; Closed System
System from which no expired mixture is discharged. In anesthetic practice, carbon dioxide is removed from the mixture within the system, completely, partially or not at all. (ISO)

Continuous Flow Apparatus
Device delivering continuous flow of anesthetic gases and/or vapors at the ambient pressure, to meet the patient’s respiratory requirements. (ISO)

Cylinder (for Medical Gas)
Color-coded cylindrical-shaped tanks containing specified medical gases like oxygen, air, nitrous oxide, CO2 etc.

Cylinder Pressure Gauge
A gauge used to monitor the pressure of gas within the cylinder.

Dead Space
Area in the patient’s respiratory tract, or portion of a breathing system, which does not take part in gas exchange. Dead space can be classified according to the following subdivision:

• Anatomical dead space
• Physiological dead space
• Mechanical dead space

DISS
Diameter Index Safety System: a safety gas supply system to the anesthesia machine, incorporating a specifically indexed pipeline gas inlet. Inlets between gases supplied to the anesthesia machine are non-interchangeable.

Exhaustion Time
Length of time an absorbent may be used before it fails to keep CO2 concentration at an acceptable level.

Expiration (or exhalation)
The act of breathing out.

Expiratory Valve
Valve that (when open) allows gas to pass through from the patient, and only during the expiratory phase. (ISO)

Flow Control Valve
Device that controls the rate of flow of a gas or a mixture of gases. (ISO)

Flow Direction Sensitive Component
Component through which the gas must flow in one specific direction only, to ensure proper function of the component and/or patient safety. (ISO)

Flowmeter
Any device that measures the flow of a specific gas or gas mixture passing through. (CEN)

Fresh Gas
Mixture of "fresh " gases (O2, N2O, air, CO2, anesthetic agent) administered from flow meters and vaporizer to the patient breathing system for administration of anesthesia.

Fresh Gas Inlet
The port on a breathing attachment, through which the dispensed mixtures from the anesthetic gas delivery module, is delivered into the anesthetic breathing system. (See also Common Gas Outlet). (CEN)

Gas Power Outlet
An accessory outlet of an anesthesia machine that supplies driving gas (air or oxygen) for auxiliary equipment, e.g. suction.

Inhalation Anesthesia Apparatus
Equipment intended for dispensing and delivering anesthetic gases and vapors into a breathing system for delivery to the patient. (ISO)

Inspiration (or inhalation)
The intake of air (or other substances) into the lungs.

NOTE: In mechanical ventilation air is pushed into the lungs.

Inspiratory Pause Time
Interval from the end of inspiratory flow to the start of expiratory flow. (ISO)
Inspiratory-Expiratory Phase Time Ratio (I:E Ratio)
Ratio of the inspiratory phase time to the expiratory phase time. (ISO)

The usual I:E ratio in controlled mechanical ventilation is 1:2, which means that the expiratory phase is twice as long in duration as the inspiratory phase.

Inspiratory Valve
Valve that (when open) allows gas to pass through to the patient, and only during the inspiratory phase. (ISO)

Medical Air
Clean compressed air that can be used for patient ventilation. (Complies with ANSI Standard Z86.1 Grade F Specification).

Medical Gas
Any gaseous substance that meets medical purity standards and has application in a medical environment, e.g. oxygen, nitrous oxide and air.

Minute Volume (MV)
Volume of gas, expressed in liters per minute, entering or leaving the patient or lung model. The physical conditions under which measuring was made should be given. (ISO)

mmHg
Millimeter of mercury (a unit of pressure).

Non-rebreathing system
System from where all the expired mixtures of gases are directly discharged. (ISO)

Oxygen Flush Valve
Manually operated valve for delivery of a relatively large flow of oxygen (35-70 l/min). That delivery takes place close to the common gas outlet, and it should not pass through the flowmeter and/or vaporizer. Therefore, this so called "emergency oxygen flow", is straightly directed into the breathing system. (ISO)

Oxygen Supply Failure Alarm
An audible alarm that has to last at least seven (7) seconds (=ISO standard) to give a warning about insufficient oxygen pressure supply to the anesthesia machine.

Partial Rebreathing System
System where a portion of the expired mixture is retained within the system. Carbon dioxide may be totally or partially eliminated.

Patient Connection Port
The opening at the patient end of an expiratory valve unit: an Y-piece fitting or a unidirectional valve, to which either a tracheal tube adapter or a face mask angle piece may be connected. (ISO)

PISS
Pin Index Safety System: safety pin indexed coding system of the cylinder yokes and cylinders.

Pipeline Gas
Medical gas delivered by permanently piped, hospital distribution system, usually O2, N2O and air.

Pneumatic
Relating to, or using, gas under pressure.

Pediatrics
Specialty of medicine dealing with development, care and diseases of children (usually from premature or newborn to adolescents of 15 years of age).

Pressure Gauge
Any device used to measure pressure within a specified pressurized system, most often it is the metric system, and the device is then calibrated in kiloPascals (kPa).

Pressure Relief Valve
Pressure limiting valve, its prime function is to serve as a safety device, for example the APL-valve. (ISO)

Pressure Units

• kPa =kiloPascal ERS
• cmH2O = Centimeters of water
• bar =1 atmosphere
• mmHg =millimeters of mercury
• PSI (G)=pounds per square inch (gauge)
• Torr =Torr, unit of pressure, named after the Italian physicist
• Torelli =mmHg
• 1 kPa =approximately 10 cmH2O =7. 5 mmHg
• 100 kPa =1 bar =approximately 1 atm =750 mHg
• 100 kPa =approximately 15 psi
  

Proportional Regulator
Regulator controlling the proportion of oxygen in the O2 /N2O gas mixture (e. g. minimum of 25 % of O2). If the O2 setting is reduced, the N2O supply will automatically be reduced, too, to maintain the minimum O2 percentage at the specified level.

Rebreathing
Inhalation of previously breathed mixture of gases from where carbon dioxide (CO2) may or may not have been removed. (ISO)

Respiration
Exchange of gases (O2 and CO2) between atmosphere (alveoli) and blood (body cells).

Respiration Rate
Respiratory rate is the number of breaths (inspirations and expirations) in one minute.

Scavenging System
An assembly of specific components that collect excessive exhaled gases and exhausts them out of the operating room.

Last updated: 1 January 2001Created
Legal notice	© GE Healthcare 2008 ISSN 1795-6269 (Web) ISSN 1795-6277 (CD)	Webmaster