oxygen delivery devices

Question 1

nasal cannulae - uses, flow rate, how to use, issues

Answer 1

• used for mild hypoxia (non-acute)
• 24-30% O2 (maximum flow rate of 4L/min)
• the NC tubing is placed around a patient’s face with the prongs positioned at the nostrils. The NC tubing can be secured behind the patient’s head or around their ears
• issues:
  a. high flows will dry and irritate nasal passages
  b. no not allow close control of FiO2

Question 2

simple face mask (Hudson mask) - uses, flow rate, how to use, issues

Answer 2

• mild to moderate hypoxia
• 30-40% O2 (flow rate 5-10L/min)
• the mask is positioned over the patient’s nose and mouth with the elastic strap behind their head
• issues:
  a. they do not allow close control of FiO2
  b. there is a risk of aspiration if the patient vomits whilst wearing the mask

Question 3

non-rebreather mask (reservoir mask) - uses, flow rate, how to use, issues

Answer 3

• moderate to severe hypoxia
• high FiO2 concentrations; 70% O2 when used with a 15L oxygen flow rate
• the mask fits over the patient’s nose and mouth and can be secured to the face using elastic straps
• ensure the reservoir bag fills by temporarily obstructing the valve before positioning the non-rebreather mask on the patient
• issues:
  a. for the mask to work effectively, the reservoir bag needs to be filled before the mask is fitted to the patient. to fill the reservoir bag, obstruct the valve with your finger until the bag is filled with oxygen
  b. reservoir masks don’t have a true seal, so some entraining of the surrounding air is unavoidable. a reservoir mask is therefore not a fixed performance device

Question 4

venturi mask - uses, flow rate, how to use, issues

Answer 4

• used in COPD due to the risk of T2RF
• constant FiO2; fixed-performance device
• the venturi mask fits over the patient’s nose and mouth like other face masks

blue: 24% FiO2, 2-4L/min
white: 28% FiO2, 4-6L/min
yellow: 35% FiO2, 8-10L/min
red: 40% FiO2, 10-12L/min
green: 60% FiO2, 12-15L/min

issues:
- if the flow rate of the oxygen is lower than the recommended amount for a specific Venturi mask, the mask won’t deliver the stated FiO2
- if you increase the oxygen flow rate beyond the rate recommended for the mask, it will not continue to increase FiO2

Question 5

humidified oxygen

Answer 5

• standard oxygen gases have a drying effect on the mucous membranes -> airway damage, heat & fluid loss
• breaks down patient’s respiratory secretions, making them easier to clear
• humidified oxygen is most effective when the gas reaching the alveoli is at body temperature (37) with a relative humidity of 100%
• oxygen is passed through a humidifying device producing sterile vapour before travelling in elephant tubing to a face mask covering the patient’s nose and mouth

issues:
- water can pool in the oxygen tubing and obstruct the flow of oxygen if not drained regularly