Respiratiry Failure Flashcards
What are the 4 stages of the oxygen cascade
Inspired gas - PiO2
Alveolar gas - PAO2
Arterial blood - PaO2
Cell - PO2
What kind of gas exchange occurs in the lungs
Passive diffusion
What factors effect alveolar PO2
Alveolar ventilation
Oxygen consumption
CO2 production
What determines the alveolar to arterial PO2 difference
Shunting
How is normal PaO2 calculated
13.6 - (0.044 x age in yrs) kPa
Shunting
Areas of the lung that are perfused but not ventilated
Factors increasing oxygen transport in blood
Low pH
Incr temp
More 2,3-DPG
incr CO2
What is the difference between type 1 and type 2 respiratory failure
Type 1 just hypoxaemia
Type 2 hypoxaemia and hypercapnic
What O2 and CO2 arterial partial pressures show type 1 respiratory failure
O2 - <8.0kPa
CO2 - normal
What o2 and CO2 arterial partial pressures show type 2 respiratory failure
O2 - <8kPa
CO2 - >6kPa
What type of respiratory failure is caused by lung failure
Type 1
What type of respiratory failure is caused by pump failure
Type 2
5 pathophysiological mechanisms of hypoxaemia
Ventilation perfusion mismatch
Anatomical R-L shunt
Impaired diffusion
Alveolar hypoventilation
Low partial pressure of inspired o2
Reasons for hypoventilation
Increased resistance due to airway obstruction
Reduced compliance of lung tissue or chest wall
Reduced strength of resp muscles
Drugs reducing overall ventilation
Signs of respiratory failure
Tachypnoea
Use of accessory muscles
Nasal flaring
Intercostal recession
Suprasternal recessiom
Tachycardia
Hypertension
Sweating
End organ hypoxia
Cyanosis
Asterixis
Bounding pulse
What causes asterixis and bounding pulse
CO2 retention
How does respiratory failure affect sympathetic tone
Increase
First line respiratory failure investigations
Physical exam
Pulse oximetry
ARterial blood gas
Chest x ray
Can pulse oximetry be used to assess ventilation
No
Sourced of error in pulse oximetry
Poor peripheral perfusion
Dark pigmented skin
False nails/nail varnish
Lipaemia/hyperlipidaemia/protocol infusion
Bright ambient light
Poorly adherent probe
Excessive motion
Do oximeters over or under read on patients with dark pigmented skin
Over read
What is normal blood pH
7.35-7.45
What is acidotic blood pH
<7.35
What is alkalosis blood pH
> 7.45
What 2 mechanisms drive blood pH
Respiratory
Metabolic
How can metabolic acidosis and respiratory acidosis be told apart
Metabolic - low HCO3
Respiratory - high CO2
How can respiratory and metabolic alkalosis be told apart
Metabolic - high HCO3
Respiratory - low CO2
Is HCO3 normal in respiratory or metabolic acidosis/alkalosis
Respiratory
Is PaCO2 normal in respiratory or metabolic alkalosis
Metabolic
Compensation
Body tries to adjust other buffers to keep pH normal
What is normally the SpO2 target for patients receiving supplemental O2
94-98%
What is the first line treatment for respiratory failure
Oxygen
4 oxygen delivery systems
Nasal cannula
Simple face mask
Non rebreather mask
Venturi mask
Which masks could be used for a patient with normal vital signs
Nasal cannula, simple face mask
Which mask could be used when a high O2 concentration is needed
Non rebreather mask
Which face mask could be used for controlled treatment in long term respiratory failure
Venturi mask
What are the different colours of Venturi masks from low to high flow rate + oxygen delivery
Blue
White
Yellow
Red
Green
What needs to be monitored during oxygen therapy
Vital signs
Arterial blood gas
How is hypercapnia treated
Ventilation
What sO2 should be aimed for in CO2 retainers
90-92%
May need 85+
