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Principles I Test 2
Breathing Systems
Question | Answer |
---|---|
What is the purpose of an anesthesia breathing system? | links the patient to the anesthesia machine by delivering O2 and anesthetic gases and eliminating CO2 |
What are 6 types of breathing systems (circuits)? | insufflation, open-drop, draw-over, maplesons, circles, resuscitation |
Which types of breathing circuits are open? | insufflation and open-drop |
What types of breathing circuits are semi-open? | draw-over and maplesons |
Which type of breathing circuit is semi-closed or closed? | circle systems |
How can you decrease resistance in a circuit? | decrease circuit length, increase circuit diameter, avoid sharp bends, maintain laminar flow, eliminate valves (NOT possible) |
Which breathing system that is no longer used today used chloroform or ether dripped onto gauze over mask? | open-drop anesthesia |
Which breathing system's vaporizer is dependent on flow and on temperature? | draw over anesthesia |
Describe draw over anesthesia | ambient air is inhaled (drawn over) liquid anesthesia agent; most of these systems do not have a ventilator |
What are the advantages of draw over anesthesia? | simple, portable, can be used without compressed gas or ventilators (war zones) |
What is insufflation? | blowing gas across the face; it is more a technique than a circuit |
When is insufflation used? | inhalation induction (peds), under drapes during sedation (not safe = flammable & trapped CO2), apneic techniques (oxygenation without ventilation to keep survivable O2 sat during airway surgery) |
What components were added to a breathing circuit to make it a mapleson? | breathing tube, fresh gas inlet, APL valve, reservoir bag |
Absolute and total non rebreathing occurs with which type of breathing circuit? | maplesons |
Maplesons are expensive and require a special adapter on the machine. Are they associated with high flows or low flows? Why does this matter? | high flows; high flows are associated with gas wasting, contamination of OR, losing moisture, losing heat |
What determines the classification of mapleson? | location of components |
What makes a breathing circuit a mapleson? | the components |
Why does a mapleson not have a CO2 absorber as one of its components? | exhaled gases go straight to scavenging (absolute non rebreathing), so it is not needed |
With spontaneous ventilation in a mapleson system, fresh gas flow must equal what? | minute ventilation |
With controlled positive pressure ventilation in a mapleson system, ____ the minute ventilation is required | 3 times |
What is a bain circuit? | the "tube in a tube" version of the Mapleson D; they require an adaptor |
Bain circuits help conserve what? | expired heat and moisture |
What are the components of a circle system? | CO2 absorber & absorbent, fresh gas inlet, unidirectional valves, y piece, APL valve, reservoir bag, breathing tubes |
Why are breathing tubes large (22 inches in diameter)? | larger diameter means decreased resistance |
The longer the breathing tube, the greater the __________ | resistance |
As the volume of the reservoir bag increases, so does the __________. This is a safety feature that prevents excess pressure from going to patient & causing ____________ | compliance; barotrauma |
Why are rebreathing systems beneficial? | they conserve heat, humidity, and costly medical gases |
The cycle system allows for rebreathing of _______ ________ without rebreathing of _______ | medical gases, CO2 |
Unlike anesthesia machine reservoir bags, AMBU bags are ______-________ | self-refilling |
Unlike anesthesia machine reservoir bags, AMBU bags need ______ flows for high FiO2's | high |
With anesthesia machine reservoir bags, you must have a _____ _____ in order for the bag to fill | good seal |
What is the definition of dead space? | tidal volume that does not move into alveoli |
Where does dead space end? | where inspiratory and expiratory flows divide |
Because of the valves, dead space is distal to the __-_______ in a circle system | Y-piece |
True or False: breathing system tube length does not affect dead space | True |
In what 3 situations are high gas flows beneficial? | induction, emergencies, and compensating for leaks |
In a circle system, heat and humidity of inspired gas depends on what? | proportion of rebreathed gas vs. fresh gas |
What two things does the CO2 absorbent add to the system? | heat and humidity |
What are the 4 disadvantages of circle systems? | less portability, greater risk of malfunction, complications related to absorbent, less predictability of inspired gas concentrations at low flows |
What 3 things does rebreathing conserve? | heat, humidity, and volatile agent |
Soda lime (CO2 absorbents) neutralizes carbonic acid (H2CO3) into what two products? | water and heat (energy) |
What are the ingredients of soda lime? | Ca(OH)2, NaOH, H2O |
Why is silica added to soda lime? | to decrease dust and resistance |
How much CO2 is soda lime capable of absorbing? | up to 23 L of CO2 per 100 grams of absorbent |
Why is barium lime no longer used? | it is a fire hazard |
pH indicator turns white absorbent one of two colors, what are these colors? | purple or pink |
At what percentage of color change should the CO2 absorbent be replaced? | 50 - 70% |
True or False: absorbent can revert back to original color with rest | true; however, this does NOT mean that absorbency is restored |
The higher the flows, the _____ the patient rebreathes | less |
Fresh gas flows of 0.3 - 0.5 L/min means what in terms of rebreathing and CO2 absorbent? | almost total rebreathing and fully reliant on absorbent to eliminate CO2 |
Fresh gas flows of 5 - 8 L/min means what in terms of rebreathing and CO2 absorbent? | little rebreathing with almost all CO2 being eliminated via scavenging |
What is exhaustion? | occurs when absorbent has absorbed all the CO2 of which it is capable of |
What is mesh? | the number of holes per linear inch of a screen; most absorbents are 4 - 8 mesh |
What is desiccation? | when absorbent becomes dry |
What does desiccation lead to? | higher volatile gas degradation |
What is degradation? | it occurs when volatile agents are broken down by absorbent |
The degradation of desflurane produces what? | carbon monoxide |
The degradation of sevoflurane produces what? | Compound A |
What is Amsorb? | a newer CO2 absorbent with less degradation; allows you to run Sevoflurane at lower flows and not risk Compound A development |
Without Amsorb, if you are running sevoflurane how many liters of flow do you have to have to prevent a Compound A problem? | 2L |
What 3 things contribute to Compound A formation? | high concentration of sevoflurane, long anesthesia time (>2 MAC hours), low flow technique (< 2 L/min) |
What is channeling? | absorbent exhaustion in areas where gas enters the absorber; baffle system in absorber directs gas flow thru center to minimize channeling |
How can you detect rebreathing of CO2 through monitoring? | CO2 > 3 mmHg noted on the capnograph during inspiratory phase |
What are 3 possible causes of increased inspired CO2 (> 3 mmHg)? | exhausted absorbent, patient stacking breaths, unidirectional valve incompetency |