Oxygen Therapy

Question 1

How is the percentage increase of FiO2 per litre of oxygen?

Answer 1

2%
1 litre= approx 24
2 litre= 26
3 litre= 28 
4 litre= 30

Question 2

What does FiO2 mean?

Answer 2

Fraction of inspired oxygen is concentration of oxygen in gas mixture

Question 3

Nasal cannulas can be used for oxygen therapy. What is the oxygen flow rate, approximate FiO2 and indications for this therapy?

Answer 3

Oxygen flow rates= 1-4L/min 
Approximate FiO2
-1= 24%
-2= 28%
-4= 36%

Indications:

• post-op
• when patient is in stable state but destaturated without additional oxygen support

Question 4

Hudson mask can be used for oxygen therapy. What is the oxygen flow rate, approximate FiO2 and indications for this therapy?

Answer 4

Flow rate= 5-8L

FiO2= 40%-60%

Indications: peri-operative for short-term use when higher flow oxygen that nasal cannula required

Question 5

A non-rebreath mask can be used for oxygen therapy. What is the oxygen flow rate, approximate FiO2 and indications for this therapy?

Answer 5

Flow rate= 8-15L

FiO2= 80-95%

Indications:

• shock
• v ill patient + insure of cause

I.e. 15L high flow oxygen via non-rebreath mask used in EMERGENCY SETTING

Question 6

When are Venturi mask indicated?

Answer 6

Used when specific amount of oxygen needing to be given to patient
I.e. COPD patients= don’t want to over oxygenate due to being at risk of retaining CO2 if FiO2 too high

Question 7

What is the principle of positive end-expiratory pressure therapy? How does it improve ventilation?

Answer 7

Adding positive pressure to end-expiratory pressure (pressure remaining in airways after exhalation) helps to:

• keep airways open to prevent collapse
• prevent atelectasis
• more area for gas exchange i.e. expanded alveolar maximise their exchange potential
• decreased effort for breathing

Question 8

What types of therapy is classed as PEEP?

Answer 8

High-flow nasal cannula
Non-invasive ventilation
Mechanical ventilation

Question 9

How does a high-flow nasal cannula differ from a normal nasal cannula?

Answer 9

The air in high-flow nasal cannula is humidified and warmed which enables it to be run at higher flow rates without causing nasal ulcers

Question 10

Why does high flow oxygen increase concentration of oxygen inhaled?

Answer 10

• Reduced amount of room air patient inhales with each breath
• provides dead space washout where dead space replaced with oxygen to improve oxygenation

Question 11

What equipment is used as part of non-invasive ventilation?

Answer 11

Full face mask or hood or tight-fitting nasal mask

Question 12

What are the two type of NIV used? What is the difference between them?

Answer 12

CPAP (continuous positive airway pressure)
-constant pressure to lungs to keep airways open

BiPAP (bilevel positive airway pressure)
-cycle of high and low pressure corresponding with patient inspiration + expiration

Question 13

When is mechanical ventilation indicated? How is it different from NIV?

Answer 13

When other forms of respiratory support are inadequate or contraindicated

Patient requires sedation
Patient needs endotracheal tube or tracheostomy to connect to ventilator
Moves air into AND out of lungs

Question 14

How can you test whether patient reliant on O2 therapy?

Answer 14

Take off O2 therapy for 10 mins and then do ABG to see if adequate sats without oxygen

Question 15

What is the difference between CPAP and BiPAP and when is each indicated?

Answer 15

CPAP involves positive pressure to splint the upper airways during expiration so prevent their collapse
-only one pressure so no variation regardless of whether in expiration or inspiration
-used in T1RF
=EXPIRATORY SUPPORT

BiPAP involves 2 different pressures depending on whether inspiration or expiration so that airways are splinted open more during inspiration to maximise the tidal volume and the removal of CO2
-used in T2RF
=VENTILATION SUPPORT (T2RF involves hypoventilation of the alveolar)