Oxygen Delivery Systems and Respiratory Failure Flashcards
What are the types of oxygen delivery systems? (8)
Nasal cannula
Hudson facemask
Resevoir bag mask (non rebreather mask)
Venturis
High flow nasal oxygen
CPAP
Intubation/Invasive Ventilation
Non-Invasive Vantilation/ BIPAP
Which ODS treat T1RF (hypoxia only)?
Nasal cannula
Hudson facemask
Resevoir bag mask (non-rebreather mask)
Venturis
High flow nasal oxygen
CPAP
Which ODS treat T2RF (hypoxia and hypercapnia)?
Intubation/Invasive ventilation
NIV
What is type 1 respiratory failure?
Hypoxia only
PO2 <8 kPa
(or PO2 10kPa or more below the inspired oxygen percentage - so if breathing 21% ( = 2kPa air) have a PO2 of 13kPa if healthy
if breathing 30% would expect PO2 of about 20)
(Expect 10 less than percentage breathing)
What is type 2 respiratory failure?
Hypoxia + Hypercapnia
PO2 <8kPa
PCO2 >6 kPa
What are some of the causes of T1RF (Oxygenation failure)?
Hypoxia e.g altitude
Impaired diffusion across membrane - e.g. COPD, pneumonia, ARDS (covid), pulmonary oedema.
Perfusion problems - e.g PE (blood supply)
Right to left shunt - eg. wrong blood, congenital cardiac disorders.
What are some of the causes of T2RF (Ventilatory Failure)?
Failure in control of ventilation
CNS - e.g. Brainstem lesions, MND
PNS - e.g. Guillain-Barre
MSK - e.g. Chest wall deformity, Kyphosis
Lung - e.g. COPD
What is the difference between T1RF and T2RF?
What can cause both?
T1 - Oxygenation Failure
T2 - Ventilation (Control) Failure
Some can cause either e.g. COPD
Type 1 - Pink puffer
Type 2 - Blue bloater
What is the function of a nasal cannula?
What are the risks?
Very simple oxygenation system (T1RF)
Flow 0.5-4 L/min O2
(Less effective in ‘mouth breathers’ and small increased risk of epistaxis)
What is the function of the hudson face mask?
What are the downsides?
Simple oxygenation devise T1RF
Flow rates 0.5-15L/min O2
Uncontrolled due to variable peak inspiratory flow (PIF) rates (60+L/min O2 - more coming from room air - Only avarage of 25% from mask)
What is the function of a Resevoir/Non-Rebreather mask?
Flow rate of 15L/min O2
Oxygen supply fills reservoir, connected via one-way valve, no peak insipriatory flow (PIF) rate issue like with Hudson mask.
As long as patient minute volume <15L/min, patient breathes pure oxygen (uncommon).
Not perfect so FiO2 is 60-80% in reality (gaps in fitting)
What is the minute volume in an avarage person?
Normal minute volume is 6 min/L.
What is the functiion of the Venturi mask?
Controlled O2, delivers a set FiO2.
Uses air entrainment (mixing principle) - set formula percentage.
e.g. white venturi 10:1 entrainment ratio.
4L O2 entrains 40L of air (avarage 28%)
On PIF issue, as long as is less than both then it is fine (add both L) - at low ratios (high FiO2) the PIF may be greated than the capacity of the device - green 15L ONLY as 30L/min supply
In what circumstances are Venturi masks useful?
Blue to Red Levels
Can titrate oxygen accurately to prevent over oxygenation
When is high flow nasal oxygen used?
Heated humidified high flow nasal oxygen
Heated to 37c, saving body energy being wasted heating air and reducing airway driving, reducing inflammation.
Flow rate of up to 100L/min of 100% oxygen - Flow rate exceeds PIF rate = controlled oxygen supply
