oxygen therapy Flashcards
What is the goal of oxygen therapy
Maintain adequate tissue oxygenation
Decrease cardiopulmonary work
Define hypoxia
Abnormal condition in which the oxygen available to the body cells is inadequate to meet metabolic needs
An abnormal condition in which the oxygen available to the body in cells is inadequate to meet metabolic needs
Hypoxia
Define hypoxemia
Abnormal deficiency of oxygen in arterial blood
An abnormal deficiency of oxygen in the arterial blood is called
Hypoxemia
What are the signs of hypoxia/hypoxemia?
Tachypnea
Tachycardia
Headache
SOB
Coughing
Wheezing
Confusion
Cyanosis
What signs would you see in the early stages of severe hypoxia/hypoxemia?
Changes in the color of skin ranging from blue to cherry red
Confusion ‘
Cough
Tachycardia
Tachypnia
What signs would you see in the later stage of severe hypoxia/hypoxemia?
sweating/diaphoresis
Severe shortness of breath
Bradypnea
Bradycardia
Lethargy
Define cyanosis
abnormal bluish discoloration of the skin or mucus membranes
An abnormal bluish discoloration of the skin or mucus membranes
Cyanosis
Arterial desaturation and discoloration of the skin, mucous membranes, lips younger and nail beds is associated with what?
Central cyanosis
When does peripheral cyanosis occur?
Occurs when there is increased oxygen uptake in peripheral tissues and is not associated with arterial desaturation
What a chronic response to hypoxia?
Pulmonary vasoconstriction
Pulmonary hypertension
Pulmonary hypertension increases the workload on which side of the heart?
The right side/right ventricle
What is jugular vein distortion indicative if?
Right ventricular failure
Pulmonary hypertension
Pulmonary vasoconstriction
When would a nasal catheter be used?
Generally limited to short term oxygen administration during specialized procedures
Bronchoscopy
Surgery
What flow rate should you set a nasal catheter to?
¼ to 6 L/m
What is the FiO2 delivered by a nasal catheter?
.22-.45
How often should a nasal catheter be replaced and what should you be sure to do?
Replace every 8 hours
Place in opposite naris
What should the flow rate be set to for a low flow nasal cannula?
⅛-6 L/minute
When should a bubble bottle or humidifier be attached to a nasal cannula?
When flow is at 4 L/m or above
What FiO2 can a nasal cannula deliver?
24-40%
What is the rule of thumb for how flow correlates to FiO2?
Every increase of 1 liter of flow raises the FiO2 by 4%
What should the flow rate be set to for a salter high flow nasal cannula?
1-15 L/m
Describe trans tracheal oxygen therapy
A method of delivering oxygen directly into the lungs by a small flexible catheter which passes from the lower neck via stoma into the trachea or windpipe
Why would you use a salter high flow nasal cannula instead of a low flow nasal cannula?
When the situation requires flow rates greater than 6 L/m
What are the flow rates used with a transtracheal catheter?
¼-4 L/m
Why use a transtrachial catheter over a nasal cannula?
Uses 40%-60% less oxygen to achieve the same oxygenation via nasal cannula
What are the disadvantages and risks of a transtracheal catheter?
Requires careful maintenance and cleaning
Complications such as infections are possible
Tracheal irritation
Mucus accumulation
Requires mandatory outpatient surgical procedure
What are the advantages of a transtracheal catheter?
Reduces oxygen requirement to achieve desirable oxyhemoglobin saturation
Improves activity and mobility
Improves physical social and psychological function
Improves compliance (daily duration of oxygen use)
Which patient will receive a greater FiO2, a patient with small tidal volumes or a patient with large tidal volumes? Why? Note, both patients are on the same liter flow
Patients that take small tidal volumes will receive proportionally more FiO2 than patients with large tidal volumes
A patient with a larger tidal volume will have a greater minute ventilation than a patient with a smaller tidal volume. This results in the amount of inspired oxygen from the nasal cannula being proportionally smaller than the patient with a lower minute ventilation
How does respiratory rate impact the amount of FiO2 delivered?
High rates dilute the amount of FiO2 received
Low rates increase the amount of FiO2 received
Why do patients with a lower respiratory rate receive proportionally more 100% oxygen from an oxygen delivery device than patients with a higher respiratory rate? Assume same tidal volume
A higher respiratory rate will result in a greater minute ventilation. This will result in the amount of inspired 100% oxygen being proportionally smaller when compared to a patient with the same tidal volume but a lower respiratory rate
Humidification is …..
The act of adding water vapor to an anhydrous gas (a dry gas)
Define absolute humidity
Absolute humidity is the density of water in the air
It is usually measured in grams of water vapor per cubic meter of water
Define relative humidity
The absolute humidity in a volume of gas expressed as a PERCENTAGE of the water vapor capacity of the gas
During exhalation, the heat and humidity that our body has added to the inspired gas is deposited where?
The upper airways
The nasal mucosa
At what point should inspired gases be warmed to body temperature and fully saturated? Where is this located
Isothermic saturation boundary
Just below the carina
What are the characteristics of gas at the ISB?
100% relative humidity
97 degrees C
What is the absolute humidity of the inspired gas after it passes the isothermic saturation boundary?
44 mg per L
How does the ISB react to inhalation of dry gas
The ISB moves deeper into the respiratory tract
The effects of inadequate humidification include…
Increased risk of damage to the epithelial lining of the airways due to increased susceptibility to infection and inflamation
Disruption of the mucociliary escalator
Increase in mucus production
Thickening of secretions
Increased airway irritability
Structural damage to the lung
Cold dry air has what effect on secretions?
Increase in mucus production
Increase in secretion viscousity
T/F Decreases in air humidity will have minimal effect on the mucociliary escalator
False. The decrease in humidity will cause secretions to thicken resulting in decreased effectiveness of the mucociliary escalator
T/F Decreases in humidity will not cause structural damage to the lungs, although it may increase airway irritability.
False. A decrease in humidity can cause structural damage to the lungs as well as increase airway irritability
What effect does increased humidity have on secretions
Increased humidity can potentially decrease secretion viscosity and make them easier to expectorate
Intubated patients rely on us to humidify and warm the air that they are receiving. Why?
By intubating patients, we are bypassing the natural physiological processes that humidify and warm the air such as the nasal concha
What 3 factors affect the humidity output of a humidification device?
Temperature - warmer air can hold more water vapor
Surface area - by increasing the surface area, we can increase the amount of gas that is exposed to water and allow more water to be picked up
Exposure time - the longer amount of time that gas is exposed to water, the more water it can pick up
You have a patient on a 2 L low flow nasal canula. They are complaining of a dry nose. What can you do to make them more comfortable?
Attach a bubble passover humidifier to the oxygen output to humidify the air
You have a patient on 8 L of oxygen on a high flow nasal cannula. They need the air to be humidified. What device would you use for this?
High flow bubble bottle
Why should bubble bottles not be used with flow rates greater than 10 L a minute?
At flow rates over 10 L/min the bubble bottle can produce an aerosol which can overhydrate the patient or carry bacteria
How does a high flow bubble bottle work?
Conducts gas down a small tube submerged in water
Gas passes through a diffuser which breaks the gas down into smaller bubbles increasing the surface area
The bubbles float to the surface allowing the gas to be humidified and sent to the patient
What can happen to a bubble bottle with prolonged use?
The pressure relief valve may become dysfunctional and not alert staff when the flow has been blocked
If flow is blocked with a bubble humidifier bottle (the disposable kind) what can happen?
They can explode
How does a reservoir device work?
Incorporate a method for gathering and storing oxygen between patient breaths
Patient draws on the reservoir whenever inspiratory flow exceeds the oxygen flow into the device
Why are reservoir devices superior to standard oxygen delivery devices?
They are capable of delivering a higher FiO2 than low flow devices at the same flow rate
Nasal reservoirs and pendant reservoirs are found on what type of oxygen delivery devices?
Nasal cannulas
Nasal reservoirs and pendant reservoirs can reduce oxygen use by how much?
50-75%
Is humidification needed when used a nasal cannula with a reservoir?
No
How do reservoir cannula devices increase FiO2?
They store a small amount of oxygen in a small membrane reservoir during exhalation so when the patient inhales they receive an additional burst of oxygen
How much can a reservoir cannula reduce flow requirements by?
Low flow reservoir cannulas can reduce flow requirements by up to 50%
What are the types of reservoir mask?
Simple mask
Partial rebreathing mask
Non-rebreathing mask
What must a patient do when using a reservoir cannula?
Exhale through the nose ‘
What is the flow range for the simple mask?
The flow range for an adult simple mask is 5-10 L/m
What will happen if the flow rate on a simple mask is set to less than 5 liters a minute?
At flows less than 5 liters per minute the mask volume acts as dead space and causes carbon dioxide rebreathing
What is the FiO2 range for the simple mask?
0.35-.050
What can cause variable FiO2 delivery when using a simple mask?
Air dilution via the mask ports and leaks around where the mask makes contact with the face
FiO2 varies depending on the oxygen input flow, the mask volume, the extent of air leakage and the patients breathing pattern
Long term use of the simple mask can result in what?
Skin irritation and break down
What is the FiO2 range on a partial rebreather mask?
.40-.70
What is the minimum flow required when using a partial rebreather mask?
10 liters per minute
You walk into a patients room after a nurse has called because of a patients low oxygen saturation. The patient is on a partial rebreather mask and the bag is deflating completely every time the patient breaths. What is wrong?
The flow is too low
Why does a partial rebreather mask deliver a higher FiO2 than a reservoir nasal cannula or a simple mask?
The bag increases the reservoir volume which allows for a higher FiO2
How is a partial rebreather different from a non rebreather?
A non rebreather has a one way valve that closes off the reservoir during exhalation and prevents the patient from exhaling into the bag. When they inhale, the valve opens and they receive the pure oxygen from the reservoir. A partial rebreather does not have this valve and the patient will end up inhaling more carbon dioxide than with a non-rebreather.
What is the FiO2 range on a non-rebreathing mask?
The FiO2 range on a non rebreathing mask is .60-.80
What is the minimum flow required for a non rebreathing mask?
10 liters per minute
What are the advantages of a nasal cannula?
Can be used on adults, children and infants
Easy to apply
Cheap and disposable
Generally well tolerated at flows less than or equal to 6 L
What are the disadvantages of a nasal cannula?
Unstable, easily dislodged
FiO2 varies with rate, depth of breathing and inspiratory flow
Flows greater than 6 L per minute can be uncomfortable
Can cause dryness/bleeding
Polyps or deviated septum may block flow
What is the best use scenario for nasal cannulas?
Stable patient needing low FiO2
Home care patients requiring long term oxygen therapy
What are the advantages of the simple mask?
Can be used on adults, children and infants
Quick and easy to apply
Disposable
Low cost
What are the disadvantages of a simple mask?
Uncomfortable, some may find them claustrophobic
Must be removed for eating or taking oral meds
Prevents radiant heat loss
Blocks vomitus in unconscious patients
What is the best use scenario for the simple mask?
Emergencies
Short term therapy requiring moderate FiO2
What are the advantages of a partial rebreathing mask?
Can be used on adults, children, infants
Quick and easy to apply
Disposable
Low cost
Moderate to high FiO2
What are the disadvantages of the partial rebreathing mask?
Same as simple mask
Potential suffocation hazard
What is the best use scenario for partial rebreather masks?
Emergencies
Short term therapy requiring moderate to high FiO2
What are the advantages of a nonrebreathing mask?
Same as simple mask
High FiO2
What is the best use scenario for a non rebreather mask?
Emergencies
Short term therapy requiring high FiO2
Heliox therapy
A trach collar is what kind of oxygen therapy device?
Entrainement device
Entrainment devices can use what kind of interfaces?
Mask (venti mask)
Face tent
Trach collar
T-piece
How does an entrainment device work?
Utilizes the bernoulli principle by directing 100% oxygen through a flow restrictor adjacent to an entrainment port
Concentration of oxygen delivered is depended upon resistor size, not flow
Describe how the amount of air is related to the flow rate of the oxygen
The amount of air entrained at the ports varies directly with the size of the port and the velocity of oxygen at the jet
What does the fraction of inspired oxygen depend on?
The air to oxygen ratio
The amount of flow resistance downstream from the mixing site
The advantage of entrainment devices over low flow devices is
That we can set a fixed FiO2
T/F: Bigger ports and smaller jets cause less air dilution, low oxygen percentage and higher total flows
False. Bigger ports and smaller jets cause more air dilution, lower oxygen percentage and higher total flows
T/F: Smaller ports and smaller jets cause less air dilution and higher oxygen percentage but lower total flows
False. Smaller ports and bigger jets cause less air dilution, higher oxygen percentages but lower total flows
T/F: The higher the oxygen percentage from the entrainment device, the higher its total flow output
False. The higher the delivered oxygen percentage from an entrainment device, the lower its total output flow
T/F: Entrainment devices are incapable of delivering 100% oxygen
True. entrainment devices utilized the bernoulli principle to dilute oxygen with air to get a specific oxygen percentage delivered. They are incapable of delivering 100% oxygen
When setting up an entrainment device, we must ensure that the patient is receiving the proper amount of oxygen and we must also ensure that we are meeting the patients _________ requirement
Peak flow requirement
A jet for a venti mask gives what important information to the therapist?
Amount of oxygen delivered
Minimum flow requirement
If a patient is desatting and on a venti mask, what should the therapist do?
Change the venti port to increase the oxygen percentage delivered
How is an aerosol generated with cool large volume nebulizers?
Gas is passed through a small jet orifice
The resulting low pressure at the jet draws fluid up the reservoir to the top of the siphon tube where it is sheared off and shattered into liquid particles
Large unstable particles fall out of suspension
Remaining particles leave through the outlet port and are carried away in the gas stream
When using a cool large volume nebulizer, what must a therapist confirm before attaching the tubing to the patient interface?
That mist is coming out of the tubing near the patients airway
If you, a therapist (i know, unlikely, right?) do not see mist coming out of the tubing on a cool large volume jet neb, what does this indicate?
It indicates air dilution which means that there is not enough flow
In this situation, this high flow system becomes a low flow system delivering variable oxygen