Basic Anesthesia Machine Concepts Flashcards
ASA 4 monitoring standards
1.) oxygenation (pulse ox)
2.) ventilation (etCO2)
3.) circulation (blood pressure and ECG)
4.) temperature
Why is BP measurement important
It is how we know the patients is being adequately perfused
BP ranges
Normal: 120/80
Hypertension: >140/90
Hypotension: <90/60
Mean Arterial BP
Average pressure during one cardiac cycle. AVG = 70-100mmHg
MAP=[(2xDiastolic BP)+Systolic BP]/3
What is pulse pressure
Systolic minus diastolic
Normal is: 30-40mmHg
End tidal CO2
Amount of carbon dioxide in expired air. Normal range is 35-45mmHg
2 main functions of EtCO2
1.) reveal patients EtCO2
2.) Reveal patients respiratory rate
Normal core body temperature
36-38 degrees celsius
2 main purposes of the anesthesia machine
1.) Allows an anesthetist to deliver anesthetic gas to keep the patient asleep
2.) Allows an anesthetist to ventilate a patient with positive pressure ventilation
Volatile agents
Sevoflurane, Isoflurane, Desflurane
Fresh gas flow gases
Oxygen, air, and Nitrous oxide
Y-piece
Merges the inspiratory and expiratory limbs
Elbow adapter
allows the circuit to more easily connect to the mask or ETT
Humidifier
filters out bacteria and viruses, and humidifies the dry gases that come from the machine
Gas sampling line
Measures the exhaled gases (oxygen, CO2, and volatile agent). Connected to the elbow adapter or the humidifier
What controls the fresh flow gases
Flow control valves or rotameters
Anesthesia flowmeters
Indicate how much each gas is entering the circuit each minute
Using oxygen as fresh flow gas
1.) Higher fiO2 compensates for atelectasis
2.) Some patients (lung disease, COPD) may need higher FiO2 in order to have an adequate oxygen saturation
3.) The higher FiO2 allows the patient to maintain adequate oxygen saturation for longer periods in case of unexpected apnea
Using nitrous oxide as fresh flow gas
1.) Only anesthetic gas that has analgesic properties
2.) allows an anesthetist to use lower concentrations of volatile agent
Using air as fresh flow gas
Benefit is that it allows us to use a lower FiO2 which is good because:
1.) Too much oxygen for too long can be toxic (Free radicals) especially in neonates it can cause “retinopathy of prematurity”
2.) High FiO2 can cause “absorption atelectasis”
3.) An FiO2 above 30% and/or use of nitrous oxide increases the risk of airway fire
Two fresh flow gas supplies
1.) Wall supply (H cylinder)
2.) E cylinder (tank) supply
Green hose
Oxygen
Blue hose
Nitrous oxide
Yellow hose
air
Diameter index safety system (DISS)
Prevents us from connecting the machine to the wrong wall supply hose
Pin index safety system (PISS)
Prevents us from connecting the machine to the wrong gas tank
Flowmeter mechanical proportioning system
Limits the % of nitrous oxide that can be given to a patient. Max nitrous oxide to oxygen ratio allowed is 3:1. Minimum oxygen concentration allowed with nitrous oxide is 25%
Low pressure pathway
1.) Flowmeters
2.) Common manifold
3.) Vaporizers
4.) Fresh (common) gas outlet
5.) Inspiratory tubing of circuit
6.) Patient
7.) Expiratory tubing of circuit
8.) Rebreathing bag or ventilator
9.) CO2 absorber & APL valve
10.) Exhaled gas joins fresh gas outlet
Scavenging system
takes excess gas away from the circuit (purple hose)