ABGs Flashcards
Respiratory acidosis causes?
Examples?
Respiratory acidosis is caused by inadequate alveolar ventilation leading to CO2 retention.
Low pH and high CO2
-respiratory depression- opiates
-Guillian-Barre- paralysis
-asthma
-COPD
-iatrogenic (incorrect mechanical ventilation settings)
What is classed as type 1 respiratory failure?
Explain why?
Examples of VQ mismatch?
Low O2 and normal CO2
Hypoxaemia and normocapnia
Caused by V/Q mismatched where the volume of oxygen flowing in/ out of the lungs does not match the flow of blood to the lungs.
Reduced ventilation and normal perfusion (e.g. pulmonary oedema, bronchoconstriction)
Reduced perfusion with normal ventilation (e.g. pulmonary embolism)
What is type 2 respiratory failure?
Explain why?
Causes of type 2 respiratory failure?
Low O2 and high CO2
Hypoxaemia and hypercapnia
Caused by alveolar hypoventilation which prevents adequate oxygenation and CO2 elimination from the blood.
-Increased resistance due to airway obstruction- COPD
-Reduced compliance of lung tissue/ chest wall- pneumonia, obesity, rib fractures
-Reduced respiratory muscle strength- MND
-Drugs acting on respiratory centre- opiates
How is respiratory acidosis/ alkalosis compensated?
Increasing or decreasing levels of HCO3- to bring the pH closer to a normal range
How is metabolic acidosis/ alkalosis compensated?
via the respiratory system retaining or blowing off CO2 to bring the pH close to the normal range
Respiratory alkalosis causes?
Examples?
Caused by excessive alveolar ventilation (hyperventilation) resulting in more CO2 than normal being exhaled. As a result, PaCO2 is reduced and pH increases causing alkalosis.
High pH and low CO2
-anxiety/ panic attack
-pain (increased RR)
-hypoxia
-PE
-pneumothorax
Metabolic acidosis causes?
Examples?
- Increased acid production or acid ingestion
- Decreased acid excretion/ increased rate of gastro or renal HCO3- loss
Low pH, low HCO3- and low BE
Causes of a high-anion gap metabolic acidosis?
Causes of a high anion gap metabolic acidosis (typically relate to increased production/ingestion or reduced excretion of H+ by the kidneys):
-Diabetic ketoacidosis
-Lactic acidosis
-Toxins (e.g. aspirin, methanol and ethylene glycol)
-Renal failure
Causes of a normal anion-gap metabolic acidosis?
Causes of a normal anion gap metabolic acidosis
(typically due to loss of bicarbonate which is subsequently replaced by chloride in the plasma, resulting in a stable overall anion concentration):
-Gastrointestinal loss of HCO3– (e.g. diarrhoea, ileostomy, proximal colostomy)
-Renal tubular disease
-Addison’s disease
Metabolic alkalosis causes?
Examples?
Caused by decreased hydrogen ion concentration, leading to increased bicarbonate
High pH, high HCO3- and high BE
-GI loss of H+ ions (V+D)
-Renal loss (diuretics, HF, cirrhosis)
What would a mixed respiratory and metabolic acidosis show on ABG?
Causes?
low pH
high CO2
low HCO3-
MI
Multi-organ failure
What would a mixed respiratory and metabolic alkalosis show on an ABG?
Causes?
high pH
low CO2
high HCO3-
Liver cirrhosis
Hyperemersis gravidarum
Excessive ventilation in COPD
