What are the normal values for ABG?
- pH: 7.35-7.45
- pCO2: 4.5-6.0kPa
- pO2: 11-13kPa
- HCO3: 22-26mmol/l
- BE: -2 to+2
- SaO2: >95%
- PaO2 should be equiv to FiO2%-10%
- Alveolar arterial gradient: <10 (inc in emphysema, fibrosing alveolitis, age)
- Lactate <2
Causes of type 1 respiratory failure?
Type 1 = 1 gas abnormal = Low 02, normal CO2:
- Low V/Q: areas of lung are perfused with deoxygenated blood but not ventilated with oxygen (ie airway obstruction)
- Causes: mucus plug in asthma/COPD, airway collapse in emphysema
- High V/Q: areas of lung are ventilated with oxygen but not perfused with deoxygenated blood (ie block in blood flow)
- Causes: PE
Why is CO2 normal in type 1 respiratory failure?
- Because areas of the lung which are perfused and ventilated can blow off xs CO2 by increasing ventilation
- Making CO2 low in this area and high where V/Q mismatch, which makes it normal all over
- However extra oxygen cannot be absobed because the max amount of O2 diffuses across the alveolar membrane in normal circumstances anyway
What are the cause of type 2 respiratory failure?
Type 2 = 2 gasses abnormal = low O2/High CO2:
- Caused: by alveolar hypoventilation, O2 cannot get into alveoli and CO2 cannot get out
- Causes: Obstructive lung disease (COPD), Restrictive lung disease, decreased respiratory drive, neuromuscular disease, thoracic wall disease
What is Lactic Acidosis?
Lactic acid is a product of anaerobic metabolism
What are the types of Lactic Acidosis?
Types of Lactic Acidosis?
TYPE 1 (Hypoxic)
- produce too much lactic acid
- DKA, starvation, CV/Resp depression
TYPE 2 (non Hypoxic)
- cannot breakdown lactic acid
- secondary to metformin or poisening
- an enzyme involved in anaerobic metabolism pathway
- inc in tissue breakdown etc, muscle trauma, MI, stroke, haemolysis, cancer, acute pancreatitis, HIV, meningitis/encephalitis