1 (C) Oxygen Therapy and Humidification Flashcards
Methods to improve Pa02
Medical • Increased diffusion – Oxygen therapy •IncreasedFIO2 • Increased PatmosO2 • Increased surface area (FRC) – PEEP – CPAP
• What gas %s make up room air?
21%
What is the barometric pressure at sea level?
760
• What is your PaO2?
100
• The partial pressure of a gas
Pgas = % x PB (760 mmHg)
– PO2 upper airway =
– PO2 upper airway = 20.93% x (760 – 47)
= 149 mmHg
Pa02 =
Fi02 x 5
General use of Oxygen
• 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)
hOW TO CHANGE 02
Change the FIO2 by mixing O2 with room air
– Cylinders & wall gas
– Cold and dry
• O2 concentrator
Uncontrolled oxygen therapy
• Uncontrolled ‐ variable performance
– nasal catheter/prongs/spectacles
– (non venturi) masks
Controlled oxygen therapy
Controlled – fixed performance
– Venturi devices (mask, aquapak)
– Tents/head box/incubator
– Mechanical ventilator
What are nasal prongs
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
Advantages nasal prongs
Advantages
• Patients can eat, drink and communicate easily
• Suitable for long term use
• Natural humidification can occur via nose
Disadvantages nasal prongs
– 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
What is a simple face mask
• 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
Reservoir Mask
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
What is fixed performance O2 therapy
Flow rate to give a percentage of oxygen
Dangers of oxygen therapy
• 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
Complications 02 therapy
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
Domiciliary O2 therapy
• Home O2 shown to reduce mortality
in severe COPD
• Nocturnal O2
Humidity and oxygen therapy
- Humidity is the amount of water vapour in a gas
* Heating a gas can increase its capacity to hold water
Indications for humidification
– 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
• Benefits humidification
– Reduce irritation of the nasal and oropharyngeal surfaces
– Maintains airway hydration
– Prevents crusting around, and blockage of artificial airways
– Facilitates the removal of secretions
• Disadvantages humidification
– Over humidification/saturation – Colonisation of bacteria – Cost (water bath) – Can over‐heat the airways (water bath) – Some patients find it uncomfortable
Types of Humidifiers
- Bubble
- Water bath
- Nebuliser (Jet, Aquapak or Ultrasonic)
- Heat and moisture exchanger (HME)
- Combined (Aquapak, Hi flow)
When is water bath humidifier used?
• 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)
What is • Heat & moisture exchanger (HME)
– Replace the function of the upper respiratory tract
• Swedish nose (trache)
• Short term mechanical ventilation (< 24hr)
Nebulisation to facilitate airwayclearance - what can be used?
Normal saline (0.9%) Hypertonic Saline (3-9%)
Normal saline nebulisation
• Normal saline (0.9%)
– Often used to facilitate the removal of secretions
– Useful adjunct to other techniques
Hypertonic saline neubulisation
• 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
Benefits Combined O2 therapy and humidification
– Deliver higher concentrations of oxygen
– 3 cm H2O PEEP
– Improved airway clearance (humidification)
– Well tolerated and comfortable for the patient
