Type 1 & Type 2 Respiratory Failure

Question 1

For type I respiratory failure, state:

• What it is (include pO2 and pCO2)
• Mechanism/generic casue of hypoxia
• Example conditions which can lead to type I respiratory failure

Answer 1

• pO2 <8kPa but normal paCO2 (<6kPa)
• Ventilation perfusion mismatch
• Example conditions:
  
  • Pneumonia
  • Pulmonary oedema
  • PE
  • Asthma
  • Emphysema
  • Pulmonary fibrosis
  • ARDs

Question 2

For type II respiratory failure, state:

• What it is (include pO2 and pCO2)
• Mechanism/generic casue of hypoxia
• Example conditions which can lead to type I respiratory failure

Answer 2

• paO2 <8kPa with paCO2 >6kPa
• Hypoventilation
• Example conditions:
  
  • Pulmonary diseases: asthma attack as they get tired, COPD, obstructive sleep apnoea, pneumonia, end stage pulmonary fibrosis
  • Reduced respiratory drive: sedative drugs, CNS tumour or trauma
  • Neuromuscular diseases: cervical cord lesion, Guilain-B**arre syndrome, myasthenia gravis
  • Thoracic wall disease: kyphoscoliosis

Question 3

State some symptoms and signs of hypoxia

Answer 3

• Dyspnoea
• Restlessness
• Agitation
• Confusion
• Cyanosis

Question 4

State some symptoms and signs of hypercapnia

Answer 4

• Headache
• Tachycardia
• Peripheral vasodilation
• Bounding pulse
• Tremor/flap
• Confusion
• Drowsiness
• Coma
• Papilloedema

Question 5

State 3 potential complications of long term hypoxia

Answer 5

• Polycythaemia vera
• Pulmonary hypertension
• Cor pulmonale

Question 6

If you suspect type I or II respiratory failure, the investigations you do will be primarily aimed at identifying the underlying cause. State some of the investigations you would do, include:

• Bedside
• Bloods
• Imaging

Answer 6

Bedside

• Sputum culture: infection?
• Spirometry: pattern of obstructive or restrictive
• ABG: figure out if pt in CO2 retention

Bloods

• FBCs
• U&Es
• CRP: infection/inflammation
• Blood culture: infection, sepsis?

Imaging

• CXR

Question 7

Discuss the management of type I respiratory failure

Answer 7

• Treat underlying cause
• Oxygen
• Assisted ventilation (if 60% O2 and paO2 <8kPa)

Question 8

Discuss the management of type II respiratory failure

Answer 8

• Treat underlying cause
• CONTROLLED oxygen therapy- start at 24%
• Recheck ABG after 20-30 mins:
  
  • If paCO2 is steady or lower and pt still hypoxic increase oxygen
  • If paCO2 has risen (>1.5kPa) and pt is still hypoxic consider non-invasive ventilation. If non-invasive ventilation fails consider intubation and ventilation

Question 9

Remind yourself of what the pH, PaCO2 and HCO3- should be in each of the following:

• Respiratory acidosis
• Metabolic acidosis
• Respiratory alkalosis
• Metabolic alkalosis

Answer 9

Question 10

Discuss the different methods of oxygen delivery. For each try to include:

• The amount of oxygen the device delivers
• When it should be used/when it shouldn’t be used

Answer 10

• Nasal cannulae
  
  • 1-4L/min
  • Roughly 24-40% O2 concentration
  • May be used if pt only need low dose of oxygen or to maintain saturations when nebulisers need to be run on air e.g. in COPD
• Simple face mask
  
  • 4-8L/min
  • Difficult to know how much O2 pt getting
  • Don’t use if need to monitor exaclty how much O2 pt getting e.g. in COPD
• Venturi face mask
  
  • Provides precise fraction of oxygen at high flow rates
    
    • Blue= 24%
    • White= 28%
    • Yellow= 35%
    • Red= 40%
    • Green= 60%
• Non-rebreathe mask
  
  • 10-15L/min oxygen (60-90%)
  • Used in emergencies

Question 11

What is base excess on ABG or VBG result?

Answer 11

Base excess tells you whether the amount of HCO3- in blood is high or low:

• Base excess >+2mmol/L: higher than normal amount of HCO3- in blood (could be due to metabolic alkalosis or a compensated respiratory acidosis)
• Base excess (could be due to metabolic acidosis or a compensated respiratory alkalosis)

Question 12

Discuss management of chronic respiratory failure

Answer 12

• Treat underlying condition
• Controlled oxygen
• Assisted ventilation (pts may have this whilst sleeping)

Question 13

What is the A-a gradient?

Why is it useful?

How do you calcuate A-a gradient?

Answer 13

• Alveolar arterial gradient: measurement of difference between alveolar concentration of oxygen and arterial concentration of oxygen
• Useful as it can help you distinguish whether hypoxia is due to problem with lungs or hypoventilation e.g. if pt is hypoxic and don’t know why

*NOTE: WE USE kPa NOT ATM. SO JUST CHANGE UNITS. pH2O in atm is ~ 6.28kPa at 37 degrees

Question 14

What should the A-a gradient be in young healthy people?

What should the A-a gradient be in elderly people?

Answer 14

• Young, healthy= less than 2kPa
• Elderly= less than 4kPa

Question 15

A-a gradient greater than what implies lung pathology?

Answer 15

A-a gradient >4kPa

Question 16

See worked example

Answer 16

Question 17

State 4 causes of hypoxia

Answer 17

• Hypoventilation
• Diffusion impairment
• Shunt
• V/Q mismatch

Question 18

Once you have worked out that you have a metabolic acidosis, you can calculate the anion gap to see if its high, normal or raised. This can help you think of possible causes for metabolic acidosis.

Explain how you calculate anion gap

Answer 18

**NOTE: sometimes see formula without potassium and if that is case normal anion gap is between 16-20mmol/L

Question 19

State some causes of metabolic acidosis with a raised anion gap

*HINT: MUDPILES CAT

Answer 19

• Methanol
• Uraemia
• DKA
• Paraldehyde
• Isoniazid
• Lactic acidosis
• Ethanol/ethylene glycol
• Salicyclates
• Carbon monoxide
• Aminoglycosides
• Theophylline