1 (C) Oxygen Therapy and Humidification

Question 1

Methods to improve Pa02

Answer 1

Medical
• Increased diffusion
– Oxygen therapy
•IncreasedFIO2
• Increased PatmosO2
• Increased surface area (FRC)
– PEEP
– CPAP

Question 2

• What gas %s make up room air?

Answer 2

21%

Question 3

What is the barometric pressure at sea level?

Answer 3

760

Question 4

• What is your PaO2?

Answer 4

100

Question 5

• The partial pressure of a gas

Answer 5

Pgas = % x PB (760 mmHg)

Question 6

– PO2 upper airway =

Answer 6

– PO2 upper airway = 20.93% x (760 – 47)

= 149 mmHg

Question 7

Pa02 =

Answer 7

Fi02 x 5

Question 8

General use of Oxygen

Answer 8

• O2 therapy used in acute & chronic hypoxaemic
respiratory failure
– PaO2 < 60 mmHg
• Also used for some cardiac conditions
• Medically prescribed drug
– Titrated to meet a target SpO2 or PaO2 (which will depend
on patient’s age, clinical condition or any risk factors for
receiving supplemental oxygen)

Question 9

hOW TO CHANGE 02

Answer 9

Change the FIO2 by mixing O2 with room air
– Cylinders & wall gas
– Cold and dry
• O2 concentrator

Question 10

Uncontrolled oxygen therapy

Answer 10

• Uncontrolled ‐ variable performance
– nasal catheter/prongs/spectacles
– (non venturi) masks

Question 11

Controlled oxygen therapy

Answer 11

Controlled – fixed performance
– Venturi devices (mask, aquapak)
– Tents/head box/incubator
– Mechanical ventilator

Question 12

What are nasal prongs

Answer 12

Variable performance
• Nasal prongs
– Commonly used
– Comfortable and non‐invasive oxygen
delivery system
– Open system, oxygen is diluted by room air
breathed in through the patient’s nose and
mouth (variable)
– Low flow device

Question 13

Advantages nasal prongs

Answer 13

Advantages
• Patients can eat, drink and communicate easily
• Suitable for long term use
• Natural humidification can occur via nose

Question 14

Disadvantages nasal prongs

Answer 14

– Disadvantages
• Only for delivering low flows (< 5 L/min)
• Unable to reliably record an accurate FIO2, but often estimated as:
– 1 L/min  FIO2 0.24
– 2 L/min  FIO2 0.28
– 3 L/min  FIO2 0.32
– 4 L/min  FIO2 0.36
• Can dry nasal mucosa and lead to nose bleeds

Question 15

What is a simple face mask

Answer 15

• Simple face mask
– These mix air and oxygen
– For short term use eg. post operative
patients
– Difficult to estimate the concentration of
oxygen received
– Must maintain a minimal flow rate of 5
L/min to ensure adequate CO2 removal
– Mask acts as a reservoir
– More suited to mouth breathers
– Short term use

Question 16

Reservoir Mask

Answer 16

Reservoir Masks
– These deliver high concentrations of oxygen to
spontaneously breathing patients
– For short term use
– The reservoir bag stores oxygen allowing a patient
to receive high concentrations of O2, even when
breathing rapidly
– Small amounts of room air entrained
– High oxygen flow rates 10‐15 L/min, FiO2 0.6 ‐ 0.9
– Either partial re‐breathing valve in mask (PRB), or
non re‐breather valve (NRB)
– Disadvantages ‐ very drying to mucosa – ideally
should change to a humidified system if required
long term

Question 17

What is fixed performance O2 therapy

Answer 17

Flow rate to give a percentage of oxygen

Question 18

Dangers of oxygen therapy

Answer 18

• COPD patients with hypoxaemic drive
• Toxicity
– Adults
• Acute tracheobronchitis
• Diffuse alveolar damage
• Reduced cilial activity
– Neonates
• Bronchopulmonary dysplasia
• Retrolental dysplasia

Reduced matching of gas and blood
movement via hyperoxia induced
vasodilation
• Absorption atelectasis
• Fire

Question 19

Complications 02 therapy

Answer 19

Related to both the FIO2 and length of
exposure
• The higher the FIO2 the shorter the time &
vice versa
• Clinically for adults keep FIO2 < 0.6

Question 20

Domiciliary O2 therapy

Answer 20

• Home O2 shown to reduce mortality
in severe COPD
• Nocturnal O2

Question 21

Humidity and oxygen therapy

Answer 21

• Humidity is the amount of water vapour in a gas

* Heating a gas can increase its capacity to hold water

Question 22

Indications for humidification

Answer 22

– Administration of therapeutic medical gases at a flow rate
greater than 4 L/min
– Use of an artificial airway for ventilation i.e. bypassing
upper airways
– To reduce airway resistance in asthma and croup
– In the presence of thick tenacious sputum

Question 23

• Benefits humidification

Answer 23

– Reduce irritation of the nasal and oropharyngeal surfaces
– Maintains airway hydration
– Prevents crusting around, and blockage of artificial airways
– Facilitates the removal of secretions

Question 24

• Disadvantages humidification

Answer 24

– Over humidification/saturation
– Colonisation of bacteria
– Cost (water bath)
– Can over‐heat the airways (water bath)
– Some patients find it uncomfortable

Question 25

Types of Humidifiers

Answer 25

• Bubble
• Water bath
• Nebuliser (Jet, Aquapak or Ultrasonic)
• Heat and moisture exchanger (HME)
• Combined (Aquapak, Hi flow)

Question 26

When is water bath humidifier used?

Answer 26

• Water bath humidifier
– Mechanical ventilation
– Clients requiring supplemental oxygen
therapy and who have copious amounts of
pulmonary secretions
– Costly (therefore not always available for
ward use)

Question 27

What is • Heat & moisture exchanger (HME)

Answer 27

– Replace the function of the upper respiratory tract
• Swedish nose (trache)
• Short term mechanical ventilation (< 24hr)

Question 28

Nebulisation to facilitate airwayclearance - what can be used?

Answer 28

Normal saline (0.9%)
Hypertonic Saline (3-9%)

Question 29

Normal saline nebulisation

Answer 29

• Normal saline (0.9%)
– Often used to facilitate the removal of secretions
– Useful adjunct to other techniques

Question 30

Hypertonic saline neubulisation

Answer 30

• Hypertonic saline (3‐9%)
– For patients with very viscous secretions eg. Cystic fibrosis
– Osmotic agent: draws water into mucus thereby making it
easier to clear

Question 31

Benefits Combined O2 therapy and humidification

Answer 31

– Deliver higher concentrations of oxygen
– 3 cm H2O PEEP
– Improved airway clearance (humidification)
– Well tolerated and comfortable for the patient