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CO2 Absorbents
Kevin's CO2 Absorbents Lecture (SIUE Nurse Anesthesia)
Question | Answer |
---|---|
What is the purpose of the breathing circuit? | Delivery of anesthesia gases and elimination of CO2. |
What are the two main ways to rid the anesthesia system of CO2. | 1. increased FGF 2. CO2 scrubber |
Do breathing circuits increase or decrease dead space? | Increase |
Where does the dead space end? | At the Y piece where the inspiratory and expiratory limbs are. |
What adjustment to ventilator must be made to account for the increased dead space of the breathing circuit? | TV on vent must be set higher than that which the patient's body would naturally desire. |
What is the most common anesthesia breathing circuit? What is its main advantage? | Circle system Prevents rebreathing of CO2 while allowing rebreathing of all other gases. |
What is the advantage of the Bain circuit? What problems are associated with the Bain circuit? | It heats inspired air with expired air. Problem with bain circuit is that you would not know if there was a leak, due to continous FGF. (the expiratory valve closes during inhalation) |
What type of respiratory device is similar to a Mapelson E circuit? | a t-piece |
What type of respiratory device is similar to a Mapelson F circuit? What is another name for this circuit? | Ambu bag Jackson-Reese circuit |
Name 3 advantages to rebreathing. | 1. cost reduction (less IA used). 2. increased warmth and humidification of inspired air. 3. decreased occupational exposure. |
What is the path which gas follows through the circle system? | fresh gas delivery hose --> common gas outlet --> runs through system --> gas exits circe system via APL or ventilatory relief valve --> scavenger |
Name and discuss the 4 types of breathing circuits. | Open 0 rebreathing (NC, face tent) Semi-open 0 rebreath, has res. (circle sys. at high FGG) Semi-closed Partial rebreath, has res. (circle sys. at FGF less than MV) Closed Complete rebreath, has res. (circle sys with low FGF and APL closed) |
Open | No mask on face Anesthetic to patient by insufflation Room air inhaled and anesthetic diluted Not used much today No rebreathing or reservoir bag No valves Pollution Can’t positive pressure ventilate! |
Semi-open | Mask on face/ETT Reservoir bag; no rebreathing Room pollution High gas flow Unidirectional valve (can increase resistance) |
Semi-closed | Mask on face/ETT No room air inspired Expired gas exits through scavenging system, CO2 absorber Partial rebreathing Very common Unidirectional valves and reservoir bag Conserves moisture and heat FGF can be less than patients minute volume |
Closed | Anesthetics are in system and not vented Keep heat and humidity Complete rebreathing of gases (pop-off closed) Less pollution CO2 scrubber Unidirect. valve and reservoir Flow of 150-500ml/min for phys. require! (150-250ml/min under GA) Low FGF |
Name 4 rules for managing a CO2 scrubber. | 1. Make sure to take out of plastic wraper before placing in assembly. 2. Change 1 at a time 3. Top one turns first 4. Move old one to top, new one on bottom |
What happens if the plastic wrapper is not taken off CO2 absorbent canister before it is placed in CO2 scrubber and why? | Due to unidirectional valves in circle system, if you do not take wrapper off canister, will not get any ventilation. |
What are the products of the 1st neutralization reaction between CO2 and adsorbents? | sodium carbonate, water, and heat |
What are the products of the 2nd neutralization reaction? | sodium hydroxide |
What are the 3 reactions for the reaction between CO2 and soda lime? | CO2 + H2O = H2CO3 2NaOH + H2CO3 = Na2CO3 + 2H2O + heat Na2CO3 + Ca(OH)2 = 2NaOH + CaCO3 |
How much energy is produced during the absorbtion of 1 mole of CO2? | 13,000 kcals |
What type of reaction causes ethyl violet to turn absorbent? | alcohol dehydration |
Is the color change of soda lime a reliable indicator for exhausted canister? | No |
What is the chemical makeup of soda lime | Calcium hydroxide – Ca(OH)2 = About 80% Water - H2O = About 15% Sodium hydroxide – NaOH = About 4% Potassium hydroxide - KOH = About 1% Small amounts of Silica |
Name 3 problems with CO2 absorbents. | 1. Sevoflurane is unstable in CO2 absorbents 2. Production of CO. 3. Sevoflurane has been reported to interact with desiccated Baralyme, resulting in fires within the breathing system |
What are the primary constituents of Amsorb? | calcium hydroxide and calcium chloride |
Which HA produces the most CO? Which HA produces the least CO? | Desflurane = most Halothane and Sevoflurane = least |
How can production of compound A be avoided? | 1. Avoid low FGF (less reliance on CO2 scrubber)(try to run at least 1.5 L FGF) 2. Lower sevo concentrations (less conversion by CO2 scrubber) |
How can production of CO be avoided? | 1. Turn O2 off at end of case 2. Change canisters if O2 left on overnight 3. Consider changing canisters weekly 4. Use relatively low FGF for majority of procedures 5. Decrease flow ASAP in any given case 6. Use of calcium hydroxide lime |