ABGS Flashcards
(21 cards)
What is the normal range of paco2?
4.7-6
What is the normal range for PaO2?
11-13
What is the normal range for HCO3-?
22-26
What is FiO2?
Fraction of inhaled O2
What is type 1 and type 2 Resp failure?
Type 1 = hypoxia
Type 2 = hypoxia and hypercapnia
What is the mechanism behind type 1 Resp failure?
Ventilation perfusion mismatch
The volume of air flowing is not matched to flow of blood in lung tissue
What are some examples of type 1 Resp failure? (3)
Pulmonary oedema
Bronchoconstriction
Both reduced ventilation and normal perfusion
PE
Reduced perfusion with normal ventilation
What is the mechanism for type 2 Resp failure?
Alveolar hypoventilation
Prevents adequate oxygenation and can’t eliminate CO2 form blood
What are 4 examples of type 2 Resp failure and how they work?
• Increased resistance due to airway obstruction
• e.g. COPD
• Reduced compliance of lung tissue/chest wall
• e.g. pneumonia, rib fractures, obesity
• Reduced strength of respiratory muscles
• e.g. Guillain-Barre, MND
• Drugs acting to reduce ventilation
• e.g. opiates
How does blood become acidic in resp acidosis?
CO2 binds to H2O and forms H2CO3 (carbonic acid)
What is respiratory compensation?
Occurs quickly
Increasing or decreasing alveolar ventilation to blow off or retain co2
What is metabolic compensation?
Takes a few days to occur
Kidneys either reduce or increase HCO3-
What is the main mechanism that causes Resp acidosis?
Give 5 examples of how this occurs
Inadequate ventilation leads to CO2 retention
Resp depression from opiates
COPD
Asthma
Msk e.g. guillaim barre
Iatrogenic e.g. incorrect ventilation settings
What is the main mechanisms of Resp alkalosis?
Give 6 examples of how this occurs.
Excessive alveolar ventilation (hyperventilation) blows co2 off
Anxiety
Pain increases Resp rate
Hypoxia leads to increased ventilation in order to compensate
PE
Pneumothorax
Iatrogenic (excessive ventilation)
Both anxiety and PE cause Resp alkalosis how would you tell the difference?
Anxiety = raised PaO2
PE = reduced PaO2
What are the 2 main causes of metabolic acidosis?
Give examples that fit into each mechanism
Increased acid production = high anion gap
- DKA
- lactic acidosis
- aspirin overdose
- renal failure
Decreased acid excretion/increased rate of HCO3- loss = normal anion gap
- GI loss of HCO3- e.g. diarrhoea
- renal tubular disease
- Addisons disease
What is the mechanism that causes metabolic acidosis?
Give 3 examples
Decreased H+ concentration causes increase in bicarbonate
- GI loss of H+ = vomiting
- renal loss of H+ e.g.loop and thiazide diuretics, HF, nephrotic syndrome, cirrhosis,conns (these all increase aldosterone activity .: increasing h+ loss)
- iatrogenic
What can cause mixed acidosis? (3)
Cardiac arrest
Multi organ failure
Severe COPD with sepsis
What can cause mixed alkalosis? (3)
Liver cirrhosis in addition to diuretic use
Hyperemesis gravidaeam
Excessive ventilation in COPD
What is the equation of the anion gap?
Cations - anions
(Na+ + K+) - (Cl- + HCO3-)
What is the normal range for anion gap?
4-12
