Week 2- Hazards of ANE Delivery System Flashcards
PaO2 less than 60 mmHg, may be caused by problems with anesthesia delivery system. What problems would this cause with the patient?
Hypoxemia
If the patient is adequately ventilated and the alveolar oxygen concentration is as expected, then the cause of hypoxemia is a:
Problem with the patient
Pulmonary conditions that cause shunting, venous mixture, ventilation-perfusion mismatch, or diffusion defect can cause
Hypoxemia
Examples of pulmonary conditions that can cause hypoxemia:
- pneumonia
- atelectasis
- pulmonary edema
- penumothorax
- hemothorax
- P.E
- Bronchospasm
-proteinosis
*** anemia and shock may also contribute
Causes of inadequate Arterial Oxygenation:
- Failure to deliver adequate oxygen to the alveoli
- Inadequate alveolar ventilation
- Low FIO2
- Intrapulmonary pathology
- Shunt
- Ventilation/ Perfusion mismatch
- Diffusion defects
Causes of Failure to Deliver Oxygen to the Alveoli
(UPSTREAM of the WORKSTATION):
- Liquid oxygen reservoir empty or filled with hypoxic gas (ex. Nitrogen)
- Crossed hospital pipelines
- Crossed hoses or adapter in the OR
- Closed pipeline valves
- Disconnected oxygen hose
- Failure of back-up hospital oxygen reserve
Causes of Failure to Deliver Oxygen to the Alveoli
(WITHIN the machine or circuit)
- Cylinder filled with hypoxic gas
- Empty cylinder
- Incorrect cylinder on oxygen yoke
- Crossed pipes within machine
- Closed oxygen cylinder valve
- Oxygen Flowmeter off
- Failure of proportioning system
- Oxygen leak within the machine or Flowmeter
- Incompetent or absent circuit unidirectional valves
- Breathing circuit leak
- Closed system anesthesia with inadequate fresh oxygen supply.
- Inadequate ventilation
The anesthesia delivery system may cause hypoxemia by delivering insufficient oxygen to the lungs and thereby reducing the :
Alveolar oxygen concentration
Inadequate ventilation, cause by either _______ or ____________, is a well -described cause of alveolar hypoxia
Apnea or low-minute ventilation
This feature allows time for airway management with near-zero pollution of the OR by unscavenged anesthetic. It also prevents the potential liability of forgetting to turn the vaporizer back on (is turned off during intubation).
Pause fresh gas flow (FGF)
Insufficient or low inspired O2 concentrations can be detected via the use of
Oxygen analyzer
The pulse oximeter, while valuable tool, does not replace the:
O2 analyzer
An O2 analyzer by the _________ unidirectional valve may indicate a normal oxygen concentration, but if there is a disconnection between that point and the patient, the patient will not receive the gas.
Inspiratory
In the event of a pipeline crossover, the hypoxic gas would also be delivered from the
Auxiliary O2 Flowmeter
Turning os the oxygen flow control valve may result in no oxygen gas flow due to:
- Shutdown central supply
- O2 hose became disconnected
- Back up cylinder is empty
- O2 piping in machine is obstructed
- O2 flow control valve is obstructed
O2 delivery at the Flowmeter could potentially be compromised if the flow tubes become filled with:
Water
** the source of water is the air pipeline. If the dehumidifying process fail, the air pipeline may deliver air and water, or extreme cases just water.
The “fail-safe” system is sensitive to ________ of oxygen rather than the ______ of O2.
Pressure; flow
*on old machines the N2O flow could be turned on without the O2 Flowmeter also being turned on.
Limitations of all oxygen/nitrous oxide proportioning systems are that they DO NOT _________ the gas that is flowing through the O2 Flowmeter, nor do they prevent administration of a ______________ if the machine has flowmeters for a third or fourth gas that is hypoxic.
Analyze; hypoxic mixture
In the Mapleson circuits, loss of the __________ supply from the machine leads to severe _________ of a hypoxic mixture as the patient uses up the oxygen and replaces it with carbon dioxide.
Fresh gas ; Rebreathing
A leak in the ventilator bellow might allow the drive gas in the ventilator bellow housing to enter the
Patient-circuit
Sources of leaks can include
- valve housings
- circuit hoses
- pressure monitoring
- gas sampling lines
- connection sites
- pressure relief valves
- carbon dioxide absorbents
Proportioning systems ONLY function between ______ and _______ flows.
N2O ; O2
_________ or ________ anesthesia can lead to delivery of a hypoxic mixture
Closed-system or Low-flow
** if O2 content of the circuit gases is not carefully monitored, the uptake of N2O may be low and of oxygen may be high. The resultant mixture could become hypoxic.
Administration of a mixture that contains more oxygen than required results in
Hyperoxia
Flowmeter leaks and inaccurate flowmeters may cause gases to be lost, with resultant high _______________ concentrations.
Oxygen
When carbon dioxide production exceeds elimination, the arterial carbon dioxide increases until equilibrium is achieved.
Hypercarbia