Lecture 6 9/5/24 Flashcards
What are the general functions of an anesthesia machine?
-deliver anesthetic gas with precision
-provide O2
-support ventilation
-evacuate anesthetic gases safely and properly
What are the characteristics of an ideal anesthesia machine?
-offers minimal resp. resistance to breathing
-maintains resp. airway pressure close to 0
-contains minimal dead space
-eliminates CO2 and prevents its re-inspiration
-has a high compliance
What are the basic components of the anesthesia machine?
-gas supply
-pressure gauges
-pressure regulators/reducing valve
-safety systems
-flowmeter
-O2 flush valve
-vaporizers
-common gas outlets
What are the potential forms of oxygen supply?
-liquid oxygen
-O2 concentrator
-O2 cylinders
What are the characteristics of an oxygen concentrator?
-extracts oxygen from air we breathe
-air passes through filters that extract O2
-allows a concentration of approximately 95% O2
What are the characteristics of an H cylinder?
-used as main oxygen source
-brass valve with specific outlet to attach to pipeline/hose
What are the characteristics of an E cylinder?
-reserve/mobile source
-valve body attaches directly to anesthesia machine at the hanger yokes
Why is it important that the pressure of the O2 gas can is proportional to the gas left in the tank?
it allows for the remaining gas to calculated based on the pressure reading
What are the colors associated with the different gases?
oxygen: green
nitrous oxide: blue
medical air: yellow
How is pressurized gas safely manipulated?
-transported in carts
-stored in dry, separate, well-ventilated rooms
-E tanks stored horizontal in storage cart
-H tanks chained to wall
-valve protected from dust, oil, inflammable substances, and falls
-close flowmeter prior to opening tank
-close tank when not in use
-open slowly
What are the characteristics of pressure gauges?
-measure pressure in the pipeline/cylinders in PSI
-color coded, labelled, and calibrated for each gas
-pressure measurement is proportional to tank content for O2
When should a new tank be switched to?
when the pressure reading is 500 PSI or less
What is the pressure in the high pressure system component of the anesthesia machine?
1900-2200 PSI
What is the pressure in the intermediate pressure system component of the anesthesia machine?
50-60 PSI
What is the pressure in the low pressure system component of the anesthesia machine?
12-16 PSI
What is the main component of the high pressure system?
O2 cylinder supply
What is the main component of the intermediate pressure system?
oxygen flush valve
What are the main components of the low pressure system?
-flowmeters
-calibrated vaporizers
-machine outlet/common gas outlet
What is the function of the regulator/pressure-reducing valve?
-reduces the high/variable storage pressure to a lower/more constant pressure appropriate for the machine
-maintains a constant pressure of 50-60 psi to ensure constant flow to flowmeter even when the cylinder gas content is depleted
-avoids rupture of hoses and barotrauma to patient
What happens if the regulator fails?
downstream pressure relief valves open at a pressure of 80-100 psi to allow gas escape
What are the safety systems on the different cylinders?
E tank: PIN index safety system
H tank/pipelines: diameter index safety system
What is the function of the tank safety system?
prevent accidental connection of another gas to the oxygen port and vice versa
What are the characteristics of the PIN safety system?
-holes with specific configuration on the cylinder valve
-matching pins protruding from anesthesia machine hanger-yoke
-configuration specific for each medical gas to prevent fitting of the wrong cylinder
What are the characteristics of the diameter safety system?
-flexible hoses that are labeled and color coded terminate in color coded, self-sealing sockets
-unique, non-interchangeable threaded fittings match each gas-specific coded connector
What are the characteristics of the flowmeter?
-transparent glass/plastic tubes containing lightweight ball/bobbin that floats when the gas is on
-individually calibrated for each gas
-graduations vary between adult and pediatric flowmeters
What is the purpose of the flowmeter?
controls flow rate at which a specific gas passes through it
What is the purpose of the needle valve?
-controls the gas flow through the flowmeter
-final stage of pressure reduction
How does gas flow reading differ between a ball and a bobbin?
ball: read at center
bobbin: read at top
What are the issues associated with flowmeters?
-must be vertical
-affected by dirt, static electricity, magnetic field, humidity, and mechanical impact
What is the vaporizer?
device that converts liquid to vapor
What are the characteristics of the vaporizer?
-anesthetic gas quantity is expressed in % related to total quantity of gas passing through
-color coded specific to each anesthetic gas
-must be calibrated to be precise
-area of high resistance to breathing
Why does anesthetic gas delivery remain stable over a wide range of temperatures and flowrates?
the vaporizer compensates for changes in external temperature and oxygen flow
What is a variable bypass vaporizer?
vaporizer with two chambers that allows for O2 to follow two different paths; bypass chamber carries only O2 to patient, while vaporization chamber carries O2 mixed with anesthetic to patient
How does oxygen move through the bypass vaporizer based on desired anesthetic depth?
reduced depth: less O2 goes through vaporization chamber, more O2 goes through bypass chamber
increased depth: more O2 goes through vaporization chamber, less O2 goes through bypass chamber
What are the consequences of tilting the vaporizer?
-liquid anesthetic enters bypass chamber
-quantity of anesthetic delivered to patient increases
What is the solution to a tilted vaporizer?
-maintain high flow rate for 20 minutes
-monitor inspired gas concentration
-possibly perform maintenance
How does anesthetic potency affect inhalant concentration reaching the patient?
the more potent the anesthetic, the higher the concentration and efficacy
What is the solution to putting the wrong anesthetic in the vaporizer?
-empty the vaporizer and use a high flow rate for 45 minutes with a low gas setting on the dial
-wait two hours before adding correct gas
-possibly perform maintenance
What are the characteristics of the O2 flush valve?
-direct communication between high pressure circuit and low pressure circuit
-supplies O2 to the breathing circuit without anesthetic gas
-should not be activated while patient is connected to circuit
-correct set up involves flush valve bypassing vaporizer
What are the functions of the O2 flush valve?
-flush anesthetic gas out of breathing circuit
-pressurize circuit to perform leak test
What are the characteristics of the common gas outlet?
-attaches to breathing system
-last step for the gas in the anesthesia machine before entering breathing circuit
