O2 Therapy

Question 1

O2 therapy is:

Answer 1

the administration of oxygen at concentrations greater than those found in ambient air in order to treat or prevent hypoxaemia. When used as a medical treatment, oxygen is regarded as a drug and must be prescribed according to a target saturation range

Question 2

The patient is monitored to:

Answer 2

ensure that the oxygen therapy administered keeps them within the target saturation range. For most patients, a target of 94-98% is appropriate. For those at risk of carbon dioxide retention (hypercapnia), a target of 88-92% ensures safe levels of oxygenation and minimises risk of respiratory acidosis

Question 3

O2 therapy will improve:

Answer 3

oxygenation but it does not treat the underlying cause of hypoxaemia which must be diagnosed and treated as a matter of urgency

Question 4

Indications for O2 Therapy:

Answer 4

• Documented hypoxemia as evidenced by: 1) PaO2 < 8Kpa or SaO2 < 90-92% on room air 2) PaO2 or SaO2 below desirable range for a specific clinical situation
• Acute care situations in which hypoxaemia is suspected
• Severe trauma
• Acute myocardial infarction
• Short term therapy (Post anaesthesia recovery)
• Decrease the symptoms associated with chronic hypoxaemia in pts who are not CO2 retainers
• Decrease the workload hypoxaemia imposes on the cardiopulmonary system, i.e. increased CO and redistribution to vital organs

Question 5

Strong indicator for oxygen therapy is:

Answer 5

PaO2 < 9 kPa is a strong indicator for oxygen therapy

Question 6

Early signs of hypoxemia include:

Answer 6

PaO2 8-10 kPa: Cold, clammy extremities/restless

Question 7

Late signs of hypoxemia include:

Answer 7

Symptoms if PaO2 <8 kPa: Cyanosis (peripheral and central), tachycardia (increased HR), dyspnoea (SOB)

Symptoms of PaO2 <6kPa: Mental deficiency, memory loss, arrhythmia, confusion, loss of co-ordination (ataxic)

Symptoms of PaO2 <4kPa: Bradycardia (reduced HR), cardiac arrest, hypotension

Question 8

Complications of O2 therapy are:

Answer 8

• Oxygen toxicity: increased free radicals results in fibrotic changes. Occurs from prolonged exposure. Seen as tremors, twitching, convulsions
• Depression of ventilation: Those with hypoxic drive are at risk of slowing RR leading to cardiac arrest. Require Non-Invasive Ventilator (NIV) to blow off CO2
• Retinopathy of Prematurity: premature babies ocular system affected results in visual changes
• Absorption atelectasis: increased O2 concentration levels at detriment of normal N2 levels in lungs that maintain alveoli to stay open thus alveoli will begin to collapse
• Fire hazard: smoking

Question 9

Guidelines procedure in starting and monitoring O2 therapy include:

Answer 9

Oxygen should be prescribed prior to administration (except in an emergency)
Oxygen therapy is started using an appropriate delivery system and flow rate
Oxygen saturations should be observed for first 5 mins after a change to oxygen therapy
Oxygen therapy is titrated to maintain target saturation
Patients requiring >28% oxygen for more than 24 hours can have oxygen delivered via a humidification system for comfort and to avoid the drying of secretions
Oxygen saturation is documented with the oxygen device, FiO2 (concentration) and flow rate

Question 10

Signs of Respiratory Deterioration:

Answer 10

Increased RR (especially if >30)
Decreased SpO2
Increase in O2 dose needed to keep SpO2 in target range
Increase in NEWS score
Patients require prompt medical review and further assessment including monitoring of arterial blood gas

Question 11

Signs of CO2 retention:

Answer 11

Drowsiness, headache, flushed face, flapping tremor

Question 12

Those at risk of hypercapnia are:

Answer 12

Chronic obstructive pulmonary disease (emphysema); Neuromuscular and chest wall disorders; Cystic fibrosis; Morbid obesity.

Question 13

Assessment techniques for suitability of O2 therapy include:

Answer 13

Pulse Oximetry: 1st port of call, Non-invasive, Measures SpO2 and HR only (no information on pH, PaCO2, haemoglobin levels)
Arterial Blood Gases: ‘Gold Standard Test’ for assessing respiratory failure, Measures PaO2, pH, PaCO2, HCO3, SaO2, Invasive

Question 14

Oxygen Delivery Methods include:

Answer 14

Variable-Performance Devices (estimated oxygen delivery): Nasal Cannula (Reservoir Cannula), Simple Face Mask, Reservoir Mask (Partial re-breath mask, Non-rebreathe)
Fixed-Performance Devices: Venturi Mask (fixed FiO2 model, variable FiO2 model)
Other: Nasal Catheter, Transtracheal Catheter, Oxygen tent, Hyperbaric chamber

Question 15

Indications for nasal cannula

Answer 15

Low to mod O2 requirement: 2-4 l min-1 (28-36%); < 2 L/min(child)
No or mild respiratory distress: Mild hypoxaemia on air (9-10 Kpa)
Long term O2 therapy

Question 16

Indications for simple face mask

Answer 16

· mod O2 requirement: 5-8 litres /min (30-60%), > 5L/min to prevent CO2 rebreathing
· mild to mod respiratory distress: Mild hypoxaemia on air (9-10 Kpa), Moderate hypoxaemia <8Kpa (type I failure)
· Increased O2 delivery for short period (<12h)

Question 17

Indications for non-rebreath mask

Answer 17

· High O2 requirement and/or emergency care: 8-15l min-1 (60-80%), Flow > 8L/min: The bag should remain inflated to ensure the highest FiO2 and to prevent CO2 rebreathing
Moderate hypoxaemia <8Kpa (type I failure)

Question 18

Indications for Venturi system

Answer 18

· Desire to delivery exact FiO2: in monitoring those at risk hypercapnia

Question 19

Contraindications/precautions for nasal cannula

Answer 19

· Poor respiratory efforts, apnoea, severe hypoxia

· Mouth breathing

Question 20

Contraindications/ Precautions for simple face mask

Answer 20

· Poor respiratory efforts, apnoea, severe hypoxia

Question 21

Contraindications/ Precautions for non-rebreath mask

Answer 21

· Poor respiratory efforts, apnoea, severe hypoxia
· O2 flow into mask must be sufficient to prevent collapse of reservoir (12l/min)
· To ensure highest O2 concentration given, reservoir needs inflating before placing on patient

Question 22

Contraindications/ precautions for Venturi system

Answer 22

· Poor respiratory efforts, apnoea, severe hypoxia

· FiO2 depends on flow rate so must be set at correct level

Question 23

Advantages of nasal cannula

Answer 23

Less expensive
Comfortable, well tolerated
Able to eat, drink and talk

Question 24

Advantages of simple face mask

Answer 24

Less expensive

Can be a mouth breather

Question 25

Advantages of non-rebreath mask

Answer 25

Highest possible O2 without being intubated
Suitable for severely hypoxic patients who are still spontaneously breathing
A one-way valve prevents exhaled air entering the bag

Question 26

Advantages of Venturi system

Answer 26

Fine precise control of FiO2 at fixed flow ensuring an accurate concentration of oxygen delivery regardless of inspiratory volumes and rate
High flow comes from air, reducing O2 cost
Can be used for low and mod FiO2
Helps in deciding if O2 requirement is changing

Question 27

Disadvantages of nasal cannula

Answer 27

· Doesn’t deliver high FiO2: Flow rates > 4 l/min can cause considerable drying of nasal mucosa and are more difficult to tolerate
· Irritation to nasal cavity (nose bleeds)
· Less FiO2 with nasal obstruction
· FiO2varies with inspiratory effort

Question 28

Disadvantages of simple face mask

Answer 28

· Requires tight seal, Uncomfortable, Difficult to keep in position for long, Can cause skin breakdown
· Doesn’t deliver high FiO2
· FiO2varies with inspiratory effort
· Interfere with eating, drinking and communication
· CO2 Rebreathing (if input flow is less than 5 L/min)

Question 29

Disadvantages of non-rebreath mask

Answer 29

· Expensive
· Increases WOB
· Require tight seal so uncomfortable
· Interfere with eating, drinking and communication
· Not suitable for long term use
· Malfunction or incorrect use can cause CO2 build up, suffocation

Question 30

Disadvantages of Venturi system

Answer 30

· Uncomfortable
· Expensive
· Can’t deliver high FiO2
· Interferes with eating, drinking and communication

Question 31

What is the difference between a non rebreather and partial rebreather mask?

Answer 31

Non Rebreather: one way valve

Partial Rebreather: not one way valve

Question 32

An alternative to nasal cannula is:

Answer 32

Reservoir cannula - nasal or pendant reservoir

Question 33

Advantages of reservoir cannula:

Answer 33

Lower O2 use and cost
Increased mobility
Less discomfort because of lower flow

Question 34

Disadvantages of reservoir cannula:

Answer 34

Poor compliance due to unattractive
Must be regularly replaced (3 weekly)
Breathing pattern affects performance (must exhale through nose to reopen reservoir membrane)

Question 35

In variable-performance devices the amount of oxygen delivered is dependent on:

Answer 35

Oxygen flow rate, Patient’s inspiratory volume, Respiratory rate

Question 36

What are the alternative delivery methods if there is facial devices are inappropriate:

Answer 36

Nasal Catheter
Transtracheal Catheter: Fixed-performance device between cartilage in throat via fine needle surgery. For those that have facial trauma but do not need tracheostomy. Increased risk of infection.
Oxygen tent
Hyperbaric chamber (less common; expensive): above atmospheric pressure of O2 (21%) therefore O2 more readily absorbed.