🫀🫁Cardio & Resp🫀🫁 - Arterial Blood Gases & Acid-Base Regulation Flashcards
Why is pH used as a measurement for [H+]?
Tiny numbers for [H+] are inconvenient
How is pH calculated?
-log10[H+]
How is [H+] calculated from pH?
10^(-pH)
What is an acid?
An acid is any molecule that has a loosely bound H+ ion that it can donate
H+ ions are also called protons
What is the pH paradox?
A greater concentration of H+ ions refers to a lower pH
What is a base?
A base is an anionic (negatively charged ion) molecule capable of reversibly binding protons (to reduce the amount that are ‘free’)
What is the bodies main source of acids?
What can changes in ventilation do?
Change the amount of CO2 in the blood - the pCO2
What is the result of hyperventilation?
Gets rid of CO2 from the blood
Shifts equilibrium towards a (respiratory) alkalosis
Results in respiratory alkalosis, if not compensated
What is the result of hypoventilation?
Lower amount of CO2 removed from blood
Respiratory acidosis
In what situations could there be respiratory alkalosis, AND hypoxaemia?
Classic scenarios:
High altitude
Pulmonary disease
Mechanical ventilation (if a patient has ARDS)
If the cause of hyperventilation is low oxygen, they can co-exist
In what situation can there be respiratory acidosis?
Hypoventilation - COPD etc…
What is the body’s rapid compensatory response to pH changes
Changes in ventilation
What is the body’s slow compensatory response to pH changes?
Changes in HCO3 and H+ retention/secretion in the kidneys
What is the ideal pH for blood?
7.35-7.45
What are the potential pH states for blood?
Acidosis(/acidaemia)
Alkalosis
Normal
What are the aetiologies of pH imbalances?
Respiratory (acidosis or alkalosis)
Metabolic (acidosis or alkalosis)
Mixed (respiratory and metabolic)
Normal
What are the options for compensatory status of the body?
Uncompensated
Partially compensated
Fully compensated
What are the potential oxygenation states for the body?
Hypoxaemia
Normoxaemia
Hyperoxaemia
What is BE?
Base excess
Shows shift of levels of base in the blood from normal levels
Values of -2 - 2 are seen as normal
<-2 suggests compensation to make the blood more acidic
>2 suggests compensation to make the blood more alkaline
What ABG is shown here?
Uncompensated respiratory alkalosis with moderate hypoxaemia
Give the ABG readings for these patients
A - Normal with mild hypoxaemia
B - Uncompensated respiratory acidosis with very mild hypoxaemia
C - Uncompensated respiratory alkalosis with severe hypoxaemia
