CP Exam 3: Arterial Blood Gasses Flashcards
What does an ABG measure?
partial pressure of gases and pH of arterial blood
this includes: info on respiratory gases, level of alveolar ventilation and metabolic state of patients
When performing ABG calculations what number is used for pH?
7.4
What are normal values of PaCo2?
35-45 mmHG
use 40 for calculations
Why could PaCO2 increased?
- respiratory acidosis- hypoventilation due to decreases minute ventilation (OLungD, MS impairments)
- hypoventilation as compensation for a metabolic alkalosis (high HCO3 levels will cause to return to homeostasis)
What are reasons PaCO2 may be decreased?
- respiratory alkalosis: hyperventilation due to increased minute ventilation (fear/ anxiety, acute resp. conditions)
- hyperventilation due to compensation for metabolic acidosis (low HCO3)
What is PaCO2 affect on pH?
inverse, as PaCO2 increases, pH will drop and become more acidic
What are number rules for PaCO2?
for every 10 point change in pac02 there will be an opposite change in pH of 0.08
What is bicarbonate?
level of base within the body, bicarbonate buffers the acidity of the blood to maintain homestasis it comes from the kidneys
How long until compensation of acidosis occurs from kidneys?
24-48 hours
What are normal HCO3 levels?
22-26 mEq/L
24 for calculations
Why would bicarbonate be increased?
- metabolic acidosis- vomiting, certain diuretics
2. compensation for resp acidosis- increase HCO3 to offset high co2 levels
Why would bicarbonate be decreased?
- metabolic acidosis- DKA (takes HCO3 out), renal dz, lactic acidosis
- compensation from resp. alkalosis- kidneys decrease production due to low CO2
What effect does HCO3 have on pH?
direct, as bicarbonate increases pH increases
every 10 point change equals .15 change in pH
What order is most ABG written in?
pH/ PaCO2/ PaO2/ HCO3
When does respiratory alkalosis/acidosis said to be compensated?
HCO3 is rising or falling to compensate for falling/rising CO2
