Breathing Systems
The APL valve must always be opened or closed? and what's a result if not done, correct?
Open, leaving it closed is FATAL!
Main CO2 removal method?
Chemical reaction with soda lime
CO2 prevention method?
High O2 flow rate (100-350 mL/kg/min)
Formula?
Time constant = Volume of circuit/Fresh gas flow rate
Purpose of scavenging?
Remove waste gases, protect personnel.
Function of the breathing system?
To provide fresh gas, remove CO2 and allow for manual ventilation.
Minimum bag size recommendation?
3-5x tidal volume (50 mL/kg)
Typical use case?
Small patients <2-3kgs
How many T for 95% change?
3T (time constants)
Passive vs. active difference?
Active uses suction and passive vents naturally.
What is the CO2 removal type for each system?
Chemical absorbent (rebreather) and high O2 flow rate (non-rebreather)
Indicator soda lime needs changing?
Color change, >30 days, increased inspired CO2
Key advantages?
Light weight, low resistance, less dead space, expired gases completely removed
You are adjusting your inhalant % on a circle system how long will it take to for it to be 95% equilibrated with the new setting, Circuit 5L, flow 1 L/min = T?
T= 5L divided by 1 L/min = 5 minutes * 3T = 15 minutes
So, at 1 L/min flow rate, your 5 L circle system will take about 15 minutes to be 95% equilibrated with the new vapor setting.
Which gases do charcoal canisters NOT absorb?
Nitrous oxide
What happens if the one-way valve is stuck open?
Circuit becomes total dead space and CO2 rebreathing occurs
Average flow for maintenance?
5 mL/kg/min
Costly, wasteful gas use
Increasing flow rate does what to the time constant?
Decreases (faster equilibrium)
When do you replace f/air canister?
when it weighs 50g
What is the role of the reservoir bag and is it an area of compliance?
Gas reserve for patient and yes, it's the only area of compliance in the system
Benefit vs disadvantage?
Economical but more dead space
Flow relation to minute volume?
2-3x MV
What analogy is often used with how fresh gas flow rates affects the inhaled anesthetic concentration?
Bathtube analogy
OSHA's concern with chronic exposure to gases?
Reproductive & fatal risk.