Oxygen Therapy and Oxygen Delivery Devices

Question 1

What should be indicated on the drug chart when prescribing oxygen?

Answer 1

• concetration or flow rate
• method of delivery
• duration of therapy
• monitoring of treatment
• target oxygen saturation

Question 2

What are the indications for acute oxygen treatment?

Answer 2

• cardiac and respiratory arrest
• Hypoxaemia (paO₂ <7.8kPa, SaO₂ < 90%)
• Hypotension (systolic BP < 100mmHg)
• Low CO and metabolic acidosis (bicarbonate <18mmol/L)
• Respiratory distress ( RR > 24)

Question 3

What are the major risks of oxygen therapy?

Answer 3

• respiratory depression in patients with type II respiratory failure
• ARDS - damage to alveolar membrane if recieveing high conc. of O₂ for more than 48hrs
• Absoprtion atelectasis
• Retrolenthal fibroplasia in neonates (causing blindness)
• Fire - smoking and oxygen

Question 4

Normal SpO₂ for a health person?

Answer 4

97-99%

Question 5

When is pulse oximetry not accurate?

Answer 5

• hypovolemic
• following CPR

Question 6

What are the two main types of oxygen delivery system?

Answer 6

• fixed performance (high flow)
• variable performance (low flow)

Question 7

What is the FiO₂ of normal air and oxygen?

Answer 7

Normal air = 0.2

Oxygen = 1.0 (100%)

Question 8

What are the characteristics of low flow devices and give the main examples

Answer 8

not sealed to the patients face so there is a variable mix of room air and oxygen is inspied with each breath

Deliver flow at a rate of 8L/min or less

• nasal cannula
• simple face (oxygen) mask
• Non-0rebreather Face mask with resovoir

Question 9

What is the usual indication of a nasal cannula and what are its pros and cons?

Answer 9

Stable patients and can provide oxygen concentrations of 24-44% for a flow rate from 1-4L/min

• Pros
  
  • more comfortable and easily tolerated
  • patient can talk, sleep, eat, drink
• Cons
  
  • Not suitable for emergencies
  • can dry the nasal mucosa causing epitaxis in some cases

Question 10

What is the usual indication of a simple face mask and what are its pros and cons?

Answer 10

Can deliver oxygen concentrations of 35-50% for flow rates of 5-10L/min

• Pros
  
  • useful for pateints unable to tolerate nasal cannula
  • mouth breathers
• Cons
  
  • Not suitable for emergencies
  • uncomfortable and claustrophic
  • difficult to talk, sleep, eat, drink

Question 11

What is the usual indication of a non-rebreather face mask with resovoir and what are its pros and cons?

Answer 11

Has one way vales and can provide high inspired oxygen concentrations of 60-80% for flow rates of 6-10L/min

• Pros
  
  • suitabel for emergencies - provides high concentrations of oxygen
• Cons
  
  • Mask must be tightly sealed into the face
  • uncomfortable

Question 12

What are the characteristics if high flow oxygen devices?

Answer 12

deliver oxygen at about 40L/min of gas and control the mixture of room air with the delivered oxygen to provide a consistent inspired concentration

Used when there is concern about CO₂ retention

Question 13

What is the usual indication of a venturi mask?

Answer 13

Oxygen mask and a set of interhcangeable colour-coded valves

Concentration levels vary from 24-60% (typical = 24, 28, 30, 35, 40)

Question 14

How does the ventuir mask work?

Answer 14

when oxygen follows through the narrow tube its velocity increases and pressure decreases which allows room air to be drawn in through the base of the valve

port size of the venturi value and appropraite oxygen floe rate ensures that the correct proprtion if oxygen and entrained room air are mixed producing a fixed concetration