Know How To Perform Pulse Oximetry - Prescribing And Administering Oxygen

1.

An 80 year old man comes to the emergency department with severe shortness of breath, he is exhibiting an obvious tremor and appears distressed and unsure of where he is or who he is. His pulse rate is 94bpm. What is his target oxygen saturation?

A.

92-98%
B.

88-92%
C.

Unknown until ABGs taken
D.
E.

Depends on the presence of asterixis

Correct Answer
B. 88-92%

Explanation
This man is exhibiting enough factors to classify him as at risk of type 2 hypercapnic respiratory failure. Remember:
Hypercapnia is indicated by:
-Tremor
-Asterixis
-Confusion
-Drowsiness
-Increased pulse rate
Although asterixis is an indicator for hypercapnia it is not always present
ABGs should be taken as a routine and used to confirm the diagnosis at this point. But for the time being 88-92% is the most appropriate target.

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2.

The same man's ABGs come back. They show that he is severely hypercapnic and acidotic. How would you treat him?

A.

100% administered oxygen via non-rebreather
B.

Treat with the lowest concentration of oxygen required to maintain target saturation
C.

Immediately begin non-invasive ventilation
D.

Use no oxygen at all
E.

Wait for a senior colleague before proceeding

Correct Answer
B. Treat with the lowest concentration of oxygen required to maintain target saturation

Explanation
In cases of hypercapnia oxygen should be limited but titrated so that enough is administered to prevent hypoxia (keep arterial saturation within target range)
Non-invasive ventilation should be considered but only if the patients breathing becomes inadequate (infrequent and shalloe)
A senior colleague should be immediately informed but do not hesitate to provide essential treatment provided you are qualified.

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3.

You are in A&E. A 20 year old woman is brought in from a recent RTA. There is a deep laceration running the length of her left leg. She is fully conscious and in severe pain. What Oxygen treatment is indicated assuming the airway is clear?

A.

None
B.

15L/min non-rebreather
C.

Venturi with 60% filter
D.

4L/min nasal cannulae
E.

Monitor her oxygen saturation with oximetry and titrate if required

Correct Answer
B. 15L/min non-rebreather

Explanation
In an emergency situation the standard response is to provide high flow oxygen with a non-rebreather mask to ensure highest possible oxygen saturation. The exception is the presence of an alert card or clear signs of type 2 hypercapnic respiratory failure.
She can then be assessed once stabilised and her oxygen dose titrated accordingly.

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4.

A 35 year anaemic old woman in hospital with bronchiectasis shows dropping oxygen sats. ABGs come back and her CO₂levels are normal. You’re superior tells you to prescribe oxygen. What do you specify?

A.

24% venturi
B.

28% venturi
C.

40% venturi
D.

Nasal Cannulae 4L/min
E.

Non-rebreather 15L/min

Correct Answer
B. 28% venturi

Explanation
Remember- if hypoxaemia without hypercapnia 40-60% oxygen should be administered-this is most accurately achived with a venturi device.
Non-rebreathers can be used but carry an increased risk of precipitating type 2 respiratory failure and oxygen toxicity.
Nasal cannulae will only provide up to 35%. This may not be adequate to reverse severe hypoxamia. It is indicate in less severe situations.

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5.

When should you use an ear lobe probe?

A.

Cyanide poisoning
B.

Poor peripheral circulation
C.

Carbon monoxide poisoning
D.

Emergency situations
E.

Patients with carbon dioxide retention

Correct Answer
B. Poor peripheral circulation

Explanation
Poor peripheral circulation leads to false reading due to the lack of haemoglobin in the extremities. The earlobe is more central so retains its blood supply.
Cyanide and CO will give false readings from any probe due to thier effect on haemoglobin. CO binds to haemoglobin to form carboxyhaemoglobin which cannot be distinguished from oxyhaemoglobin by oximetry. Oximetry will indicate a higher % arterial saturation of oxygen than is actually present.
Oximetry should be applied as soon as possible in an emergency and regularly monitored to ensure early management of hypoxaemia.

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6.

The following are situations in which you should use a non-rebreather mask:

A.

Cardiac arrest
B.

Facial trauma
C.

COPD patients
D.

Oxygen toxicity
E.

Acute respiratory episode

Correct Answer(s)
A. Cardiac arrest
E. Acute respiratory episode

Explanation
Remember, a non-rebreather is used in cardiac and respiratory arrest.
The mask is contraindicated in facial trauma.
The mask may precipitate type 2 respiratory failure in COPD patients.
Oxygen toxicity occurs when too much oxygen is delivered so using a non-rebreather will just make things worse.

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7.

A patient’s breathing has become noticeably shallow and at a severely reduced rate, his latest ABG results show high arterial CO₂ saturation, acidosis and hypoxaemia. How should he be treated?

A.

Non-rebreather mask 15L/min
B.

Lowest concentration of inspired oxygen to maintain O2 sats with non-invasive ventilation
C.

Lowest concentration of inspired oxygen to maintain O2 sats
D.

Venturi mask with 24% filter
E.

No oxygen administered

Correct Answer
B. Lowest concentration of inspired oxygen to maintain O2 sats with non-invasive ventilation

Explanation
If a patient's breathing becomes inadequate non-invasive ventilation hould be considered
Hypercapnia-lowest concentration required to maintain dose

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8.

The following is a/are danger(s) with Nasal Cannulae:

A.

Mucosal Dermatitis
B.

Ear pressure sores
C.

Carbon Dioxide re-breathing
D.

Non-adherence
E.

Oxygen toxicity

Correct Answer(s)
A. Mucosal Dermatitis
B. Ear pressure sores
D. Non-adherence

Explanation
Foreign objects in the nose coupled with the drying effect on the mucosa from dry oxygen flowing past increases the risk of dermatitis and pressure sores.
Cannulae are not masks so there is no-where for CO2 to be trapped so no chance of rebreathing.
Cannulae can become uncomfortable and many patients will remove them.
The % oxygen administered is only up to 35%. this is too low the cause oxygen toxicity.

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9.

Which of the following is/are not true:

A.

Venturi masks can be used in non-COPD patients to titrate a correct dose
B.

Nasal cannulae are used at flow rates of up to 6L/min
C.

Humidifiers reduce the risk of nasal infection
D.

Pure water should not be used in a humidifier
E.

If a patient is carrying their own oxygen mask the mask should be used

Correct Answer
B. Nasal cannulae are used at flow rates of up to 6L/min

Explanation
Nasal cannulae are only used up to 4L/min (even though they have the capacity to be used up to 6L/min) as they are unreliable at higher flow rates.

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10.

Which of the following is/are true?

A.

Non-rebreather prevents rebreathing using a one way valve
B.

Nasal cannulae prongs curve upwards to the roof of the nasopharynx to slow oxygen before it reaches the trachea and thus prevent mucosal drying
C.

Pure water in a humidifier can precipitate bronchoconstriction
D.

Oxygen should be prescribed in an emergency
E.

Some normal, healthy elderly individuals can have arterial oxygen saturation values of

Correct Answer(s)
A. Non-rebreather prevents rebreathing using a one way valve
C. Pure water in a humidifier can precipitate bronchoconstriction
E. Some normal, healthy elderly individuals can have arterial oxygen saturation values of

Explanation
Nasal cannulae prongs should always face downwards towards the trachea to ensure a direct flow of oxygen into the lungs-even if they are more prone to falling out this way around.
0.9% saline should be used in a humidifier
Never prescribe oxygen in an emergency-you will waste precious time filling out forms. Instead administer it as soon as possible or needed and once the patient is stable document all the care he has recieved including a full account of the oxygen therapy in the patient's notes.
It is true that many elderly patients have normal arterial oxygen saturation scores below the target range for normal patients. I such cases titrate oxygen to maintain the target arterial oxygen concentration and be vigilant for signs of hypercapnia or hypoxia.

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Know How To Perform Pulse Oximetry - Prescribing And Administering Oxygen

An 80 year old man comes to the emergency department with severe shortness of breath, he is exhibiting an obvious tremor and appears distressed and unsure of where he is or who he is. His pulse rate is 94bpm. What is his target oxygen saturation?

The same man's ABGs come back. They show that he is severely hypercapnic and acidotic. How would you treat him?

You are in A&E. A 20 year old woman is brought in from a recent RTA. There is a deep laceration running the length of her left leg. She is fully conscious and in severe pain. What Oxygen treatment is indicated assuming the airway is clear?

A 35 year anaemic old woman in hospital with bronchiectasis shows dropping oxygen sats. ABGs come back and her CO2 levels are normal. You’re superior tells you to prescribe oxygen. What do you specify?

When should you use an ear lobe probe?

The following are situations in which you should use a non-rebreather mask:

A patient’s breathing has become noticeably shallow and at a severely reduced rate, his latest ABG results show high arterial CO2 saturation, acidosis and hypoxaemia. How should he be treated?

The following is a/are danger(s) with Nasal Cannulae:

Which of the following is/are not true:

Which of the following is/are true?

A 35 year anaemic old woman in hospital with bronchiectasis shows dropping oxygen sats. ABGs come back and her CO₂levels are normal. You’re superior tells you to prescribe oxygen. What do you specify?

A patient’s breathing has become noticeably shallow and at a severely reduced rate, his latest ABG results show high arterial CO₂ saturation, acidosis and hypoxaemia. How should he be treated?