Oxygen and respiratory failure Flashcards
What is shown in the oxygen cascase?
How oxygen declines from atmosphere to the mitochondria
How do you calculate p02 of inspired dry air at sea level
Concentration of oxygen in air* barometric pressure
What value is normal for p02 of dry air at sea level?
21.2pka
Define tracheal gas
P02 after humidification
What is Fi02
Fractional concentration of oxygen in dry phase
What is PB
Barometric pressure
What is SVP
Saturated vapour pressure
What is dry barometric pressure
Barometric pressure* saturated vapour pressure
What is the value for p02 in air at 37 degrees
19.9kPA
Define saturated vapour pressure
Max amount of water gas will hold
What order does oxygen cascade go in
Dry air Air at 37 degrees End expiratory gas Ideal alveolar gas Arterial blood Mean capillary blood Cytoplasm Mitochrondria
What affects alveolar p02
Affected by hypoventilation and oxygen consumptions
Two equations for PA02 (ideal alveolar pressure)
dry barometric pressure* (Fi02-VO2/VA)
= Pi02-(Paco2/R)
What is Pi02
pp of inspired oxygen
When is arterial P02 measured
During arterial blood gas
Define shunt
Area of the lung that is perfused but not ventilated
What determines alveolar to arterial PO2 difference?
Shunting
What is the usual difference from p02 in alveolar to arterial
2kPa
Equation for normal Pa02
=13.6-(0..044*age in years)
What units are used to measure oxygen delivery?
l/min
Equation for oxygen delivery
[Hb]* oxgen sat 13.410*CO of Hb
5 physiological changes that happen in resp failure
CO2 retention Increased sympathetic tone End organ hypoxia Haemoglobin desaturated Resp. concentration
Signs of CO2 retention
Bounding pulse
CO2 retention flap
Signs of increased sympathetic tone
Tachycardia
Sweating
Hypertension
Signs o haemoglobin desaturation
Cyanosis
Signs of end organ hypoxia
Altered mental state
Bradycardia
Hypotension
Signs of resp concentration changes
Intercostal/ suprasternal recession
Tachypnoea
Nasal flaring
Use of accesory muscle
What is type 1 respiratory failure
- Only hypoxaemia
- Pa02<8kPa
Overall reason that type 1 respiratory failure happens
Damage of the lungs which prevents adequete oxygenation of blood
9 causes of type 1 resp failure
- Pneumothorax
- Collapse
- Obesity
- Pneumonia
- Pulmonary oedema
- Atelectasis
- Asthma
- PE
- COPD
What is type 2 respiratory failure
Hypooxaemia and hypercapnia
Pa02<8kPa
PaCO2> 6.5kPa
Main cause of type 2 resp failure
Hypoventilation
First line treatment for respiratory failure
Oxygen
When are nasal cannulae used
In patients with normal vital signs
When are face masks with resevoir bag used
Higher 02 concentration is needed
When are venturi masks used
Controlled treatment in long term in resp failure
What is the critical threshold for pulse oximetry and what happens beneath this
94%
Below this a small fall in Pa02 leads to a sharp fall in Sp02
What % of COPD patients retain CO2
10
How should you treat a COPD patient if you are certain he retains CO2
- Controlled mask
- Titrate
- Aim for sats 90-92%
- Measure ABGs
How should you treat COPD patient if youre unsure if he retains COPD
Starts high flow oxygen
Monitor
Check ABGs after 30 mins
Is ventilation used for hypercapnea or hypoxia
Hypoxia
