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What are the 4 causes of hypoxia?
1) Hypoxic inspired gas mixture (malfunction of oxygen ratio device)
2) Problems with flow control valve or flowmeters (accidental turning of knob)
3) oxygen leak to atmosphere
4) air entrainment (if breathing system pressure < atm, air will enter and dilute FiO2)
5) Incorrect gas supplied (usually during construction or maintenance of machine)
What should you do if you suspect pipeline O2 system is delivering less than 100% oxygen?
Open cylinder and disconnect pipeline
What is the minimum FiO2 delivery with N2O due to the proportioning system (oxygen ratio device)?
What things can cause a flowmeter to be inaccurate?
- 1) dirt, oil, grease on tube or indicator
- 2) indicator stuck or damaged
- 3) tube misaligned
- 4) static electricity
- 5) improper calibration
- 6) wrong gas/flowmeter combination
What are the causes of hypoventilation? (4)
- 1) Low inflow
- 2) excessive outflow
- 3) Blocked inspiratory and/or expiratory pathway
- 4) ventilator problems
What are the causes of low inflow?
1) Pipeline Problems, cylinder problems, machine problems preventing delivery of gas (Leaks, obstruction)
2) Gas Supply switched OFF
3) Fresh Gas Supply Problems
What are the causes of excessive outflow?
- 1) Losing gas from the system
- 2) Leaks (commonly absorber)
- 3) Disconnections
- 4) Negative pressure to breathing system (inlet valve of closed scavenging system, NGT to suction in trachea)
- 5) Improper APL valve adjustment (open too much during manual or assisted ventilation)
What should you do if you suspect a leak?
Put alcohol on hands and begin searching
What are the causes of Inpiration/Expiration pathways blocked?
something blocking in the system - can be plastic, manufacturing defects, blood/secretions in system etc
How is a blockage in the Inspiratory/expiratory pathway typically detected before a case?
by blowing into the system - should see good capnography waveform and reservoir bag movement
What are 5 ways to detect hypoventilation?
- 1) airway pressures
- 2) tidal volume
- 3) ETCO2
- 4) O2 analyzer
- 5) Low temp alarm on heated humidifier
What should you do in response to hypoventilation?
switch to manual ventilation - if obstruction continues disconnect and manually bag - if obstruction continues, it is in the airway.
What are the causes of hypercapnea?
- 1) hypoventilation
- 2) rebreathing without CO2 removal
How do you know your hypercapnea is the result of hypoventilation?
inpspired CO2 will be zero
What would cause the patient to rebreathe CO2?
- 1) exhausted absorbent
- 2) bypassed absorbent (attached incorrectly)
- 3) excessive dead space
What are the causes of excessive airway pressure?
- 1) High inflow
- 2) Low gas outflow
What is the cause of high gas inflow?
typically O2 flush valve
What are the causes of low gas outflow?
- 1) expiratory limb obstruction
- 2) obstruction at ventilation
- 3) scavenging system obstruction