Lecture 1 - Oxygen Flashcards
What is hypoxia?
Reduced oxygen levels at the tissue level measured in SpO2
What are the causes of hypoxia?
Reduced cardiac output
Hypoxaemia
Reduced oxygen carrying capacity of the blood
Reduced ability of tissues to extract oxygen
Reduced or disrupted blood flow
What is hypoxaemia?
Reduced oxygen in the blood measured in PaO2
What are the causes of hypoxaemia?
Wasted perfusion
Wasted ventilation
Hypoventilation
Diffusion problem
Lack of available O2
What is scale 1’s target sats?
94-98%
What are some conditions that someone on type 1 might have?
Post surgical
Bronchiectasis
Asthma
Pneumonia
What are the target sats for someone on scale 2?
88-92%
Why would a patient be on scale 2?
Patient at risk of CO2 retention due to chronic hypercapnia, this causes their respiratory drive to switch to a hypoxic drive and then if they are over saturated with oxygen then their respiratory drive may fail
What are some conditions that someone might have if they are scale 2?
Chronic asthma
Chronic bronchiectasis
COPD
Cystic fibrosis
Kyphoscoliosis
Neuromuscular diseases
What is considered a critically unwell emergency regarding oxygen sats?
If a patient’s oxygen falls below 85%
Describe some risks of over oxygen-saturation?
Absorption atelectasis
Impairs respiratory drive of hypercapnic patients
Oxygen toxicity
Cardiovascular changes such as reduced stroke volume and therefore cardiac output
What is absorption atelectasis?
Absorption atelectasis is when oxygen becomes the primary gas in the air inhaled instead of nitrogen which is what usually props open the alveoli. The body doesn’t absorb nitrogen but does absorb the oxygen which can lead to collapse.
What is oxygen toxicity
Oxygen in the body leads to production of reductive oxygen species which are balanced by anti-oxidants in order to not be harmful. Too much oxygen can lead to this balance being disrupted.
What is the difference between variable and fixed devices for administering oxygen?
Variable devices allow you to increase the flowrate by increasing % of oxygen whereas fixed devices require a specific flow rate which you can’t change unless you change the device
How do you set up nasal cannulae?
Attach nasal cannulae tubing directly to the oxygen flow and set the flow rate for desired FiO2
What are some pros of nasal cannulae?
It’s easy to speak, eat and drink
It’s more comfortable for the patient than a mask
No rebreathing of expired air
What are some cons of nasal cannulae?
Can dry out nasal mucosa
If patients are mouth breathing it becomes ineffective
How do you set up a venturi mask?
Attach the desired valve to the simple face mask
Attach oxygen tubing to the bottom of the valve
Attach the other end to the oxygen flow meter
Set the correct flow rate at the oxygen flow meter as it says on the valve
Apply the mask to the patient
What are the pros of a venturi mask?
Delivers accurate oxygen concentrations - good for patients on scale 2
What are the cons of a venturi mask?
Drying
Difficult to eat, drink and communicate
Can be uncomfortable
How do you set up a non-rebreathe/reservoir mask?
Connect oxygen tubing to the mask
Connect other end of tube to the oxygen flow meter
Set flow to 15L/min
Occlude the valve at the base of the mask to allow the reservoir bag to inflate
Put the mask on the patient when the bag is fully inflated
Why does the bag need to be inflated to use a non-rebreathe mask?
The bag needs to be inflated so that there is a reservoir for gas to be drawn from if respiratory demand exceeds the gas flow being delivered
What should you do if a patient’s oxygen sats fall below 85?
Use a non-rebreathe/reservoir mask to bring their oxygen sats above 85
Once above 85, titrate down to achieve target sats
What are the pros of a non-rebreathe mask?
One way valve systems in the mask prevents room air being included in the system dilating the oxygen and prevents retention of exhaled gases during exhalation
Delivers high concentrations of oxygen so is good for emergency treatments
