Week 1 (A) Flashcards
What is a normal pH?
7.38-7.42
What is a normal PaCO2?
35-45
What is a normal Pa02?
80-100
What is a normal BE?
+/- 3
What is homeostasis?
Body always trying to correct itself
What is a high pH?
alkolaemia
What is a low pH?
acidaemia
If someone has high pH and low PaC02
Respiratory Alkalosis (uncompensated)
If someone has high pH and high HC03
Metabolic alkalosis (uncompensated)
If someone has low pH and high PaC02
Respiratory acidosis (uncompensated)
If someone has low pH and low HC03
Metabolic acidosis (uncompensated)
What is respiratory acidosis?
PaCO2 > 42
- Decreased gas movement overall
- Low tidal volume without increased RR
- Low RR without increased tidal volume
What are the signs and symptoms of respiratory acidosis?
Cerebral vasodilation and increased ICP
Drowsiness/confusion
Headache
Unsteady/falls
What is a condition that may present with respiratory acidosis?
COPD > gas trapping. Someone who has low tidal volume
What is a metabolic acidosis and how may get it
HC03 <22
Diabetoc ketoacidosis Methanol poisoning Lactic acidosis (eg post marathon) Starvation Renal failure Severe diarrhoea
What are the signs and symptoms of metabolic acidosis?
Cardiac arrythmias, decreased contractility
Hyperventilation
Confusion, drowsiness
decreased renal blood flow
What is respiratory alkalosis?
PaC02 < 38 Hyperventilation (blowing off too much C02) - Anxiety - Pain - Acute (severe) hypoxaemia - sepsis
What are the signs and symptoms of respiratory alkalosis
Tingling lips, fingers
Cerebral vasoconstriction - dizziness, fainting
Arrhythmias
What is a metabolic alkalosis
HC03 > 26 Acid loss ( or bicarbonate gain)
GI: vomiting, nasogastric suction
Renal: metabolic syndromes, drugs ( invluding over diuresis) NOT renal failure
Signs and symptoms of metabolic alkalosis
Muscle cramps, weakness
decreased minute ventilation (decreased RR +/- tidal volume)
Arrythmias
What is complete compensation?
When the system is able to offset the change in the other and pH is restored to within normal limits
Why does compensation occur?
The body tries to restore pH equilibrium as it is essential for healthy function
How does metabolic compensation occur?
The metabolic system (renal) compensates by excreting or reabsorbing more bicarbonate HC03- to buffer H + ions… this response takes 3-5 days to occur
How does respiratory compensation occur?
The respiratory system compensates by altering rate and depth of breathing (hypervetiation or hypoventilation) it can do this quickly - within minutes or hours?
What if the PaC02 and HCO3- are outside the normal range?
When one system has begun to offset the change in the other system but it is not sufficient enough to return the pH to within normal limits = uncompensated
What is the Pa02?
Arterial partial pressure of oxygen
What is Sa02?
arterial haemoglobin saturation of oxygen
What is Sp02
haemoglobin saturation of oxygen measured with pulse oximetry (surrogate for Sa02?)
What is the oxygenation index?
P/F ratio
Pa02/F102
What is the A-a gradient
alveolar-arterial gradient
Measure of the difference between the alveloar concentration of oxygen and the arterial concentration of oxygen
allows you to see where the problem is (ventilation or perfusion) and compare Pa02 values where F102 differs
What are some factors that affect oxygenation?
02 cncentration Barometric pressure (Usuall Patmos) Age (take off 1 mmHg per year >60) PaC02 Pathogies
General rule for expected Pa02
[02]% X 5
21X 5 =105
What is the normal oxygenation index
> 400
What is the oxygenation index for acute lung injury?
<300
What is oxygenation for acute respiratory distress syndrome?
< 200
What does an oxygenation index of < 200 indicate
acute respiratory distress syndrome
What does an oxygenation index of <300 indicate?
acute lung injury
What does an oxygenation index of >400
normal
What us the normal value for Aa gradient
Normal values vary with age but usual normal range 5-15
