22 Questions
What is the primary function of the anesthesia workstation?
To administer anesthesia to patients
Which of the following is NOT a component of the anesthesia workstation?
Electrocardiogram (ECG) monitor
What is the main purpose of the anesthetic gas scavenging system?
To remove excess anesthetic gases
What is the purpose of the adjustable pressure-limiting valve in an anesthesia workstation?
To remove excess gas from the breathing system
What component of an anesthesia workstation delivers the fresh gas mixture to the patient breathing system?
Common gas outlet
What happens to the excess gas in the breathing system during mechanical ventilation?
It is vented out of the system via the ventilator pressure relief valve
What is the purpose of the fresh gas flowmeters in an anesthesia workstation?
To regulate the flow rate of fresh gas
What is the primary function of the vaporizer in an anesthesia workstation?
To vaporize anesthetic agents
What is the primary purpose of describing the flow of compressed gases in an anesthesia machine?
To understand the function of each component
What is the significance of voluntary consensus standards in anesthesia machine manufacturing?
They are highly unlikely to be ignored by manufacturers
What has driven changes in the design of anesthesia workstations?
Advances in technology
What is a valuable resource for understanding specific anesthesia machine models?
Manufacturer's operator and service manuals
What is the minimum percentage of oxygen flow that can be set in some anesthesia machines?
25%
What is the purpose of the controlling computer in anesthesia machines with electronically-controlled flow controllers?
To adjust the flow controllers to achieve the set flows
What type of device controls the flow of gases in some anesthesia machines?
Needle valve
What is the result of an oxygen leak downstream of the flowmeter in an anesthesia machine?
A hypoxic mixture is possible
What is the function of the device that measures the flow of gases in anesthesia machines with electronically-controlled flow controllers?
To measure the flow of gases
What is the direction of rotation to loosen a mechanical flow-control valve in an anesthesia machine?
Counterclockwise
What determines the resultant flow in a mechanical flow-control valve in an anesthesia machine?
The size of the orifice and the pressure
What is the purpose of the electronic flow controllers in anesthesia machines?
To prevent hypoxic gas mixtures
What is the effect of adding high concentrations of a potent volatile inhaled anesthetic downstream of the proportioning system in an anesthesia machine?
A hypoxic mixture is possible
What is the function of the fresh gas proportioning system in an anesthesia machine?
To prevent hypoxic gas mixtures at the level of the user interface
Study Notes
Anesthesia Workstation Standards
- 80601-2-13 is the standard for the basic safety and essential performance of an anesthesia workstation, first published in 2011 and confirmed up-to-date in 2017.
- It superseded the ASTM standard F1850-00, which introduced the term "workstation" in distinction to "anesthesia (or gas) machine."
History of Anesthesia Machine Standards
- ASTM standard F1850-00 was first published in 2000.
- ASTM standard F1161-88 was first published in 1989 and was superseded by the 80601-2-13 standard.
- The original anesthesia machine standard was American National Standards Institute (ANSI) Z79.8, first published in 1979.
Anesthesia Workstation Components
- An anesthesia workstation consists of the gas delivery system, breathing system, anesthetic gas scavenging system, anesthetic vapor delivery system, anesthesia ventilator, and associated monitoring and protection devices.
Contemporary U.S. Anesthesia Workstations
- Dräger Medical Inc. and GE Healthcare manufacture most of the anesthesia workstations sold in the United States.
- Examples of contemporary U.S. anesthesia workstations include Fabius, Apollo, Perseus A500, Aestiva MRI, Carestation 600 Series, and Avance CS2.
Gas Flow in Anesthesia Workstations
- Compressed gases flow from the point of entry into the machine, through the components, and to the exit at the common gas outlet (CGO).
- The resulting gas mixture of oxygen with other compressed gases and vaporized anesthetics is delivered to the patient breathing system, typically a circle breathing system.
- Excess gas leaves the breathing system via the adjustable pressure-limiting (APL) valve or ventilator pressure relief valve.
Anesthesia Machine and Workstation
- The anesthesia machine is a component of an anesthesia workstation.
- The anesthesia gas delivery system consists of the anesthesia machine, anesthesia workstation, and scavenging system.
Anesthesia Gas Delivery System
- The system has three components:
- High-pressure system (45-2200 psig)
- Intermediate-pressure system (16-55 psig)
- Low-pressure system (slightly above atmospheric pressure)
Components of the Anesthesia Machine
- Vaporizers
- Common gas outlet
- Reservoir bag
- Patient's lungs
- Breathing system
- Ventilator
- Adjustable Pressure Limiting Valve (APL)
- Scavenging system
Gas Flow Control
- Controlling flow of gases from high-pressure sources to exit the Common Gas Outlet (CGO) at atmospheric pressure requires changes in pressure and/or resistance.
Pressure Gauges and Sensors
- Pipeline and cylinder supply pressure gauges are of the Bourdon tube design.
- Electronic flow controllers and flowmeters are used in modern anesthesia machines.
Fresh Gas Controllers and Flowmeters
- Electronically-controlled flow controllers and electronic flowmeters prevent hypoxic gas mixtures at the user interface level.
- The computer continuously adjusts the flow controllers to achieve set flows, rapidly responding to changes in supply pressures.
Mechanical Flow-Control Valves
- Mechanical flow-control valves are used to adjust total gas flow delivered to the CGO and proportions of oxygen, nitrous oxide, air, and other medical gases.
This quiz covers the safety and performance requirements of an anesthesia workstation, including the components and functions of a traditional anesthesia machine. It also touches on the pre-use checks and automation features of modern workstations.
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