BLOOD GASES PH Flashcards
• A substance that can donate hydrogen ions (H+ ) when dissolved in water.
Acid
Bronsted-Lowry Acid (Proton Donor )
A species that donates protons
Acid
A substance that can yield hydroxyl ions (OH-) when dissolved in water
Base
Bronsted-Lowry Base (Proton Acceptor)
• A species that accept protons
Base
• The relative strengths of acids and bases, their ability to dissociate in water.
Dissociation Constant (Ka).
The ratio of dissociated ion to the original acid
Dissociation Constant (Ka).
pH at which protonated and unprotonated species are present in equal concentrations.
pKa
defined as the negative log of the dissociation constant.
pKa
• Have pK values of less than 3.0
Strong Acids
• Raising the pH above the pK will cause it to dissociate and yield a H+
• Complete dissociates in a solution
Strong Acids
• Have pK values greater than 9.0
Strong Bases
• Lowering the pH below the pK will cause it to release OH
• Completely dissociates in a solution
Strong Bases
• Are species that partially/ incompletely dissociate in a solution
Weak Acids/ Bases
• consists of a weak acid and a salt of its conjugate base
Buffer
it resists the change in pH upon adding acid or base.
Buffer
• Pressure or tension exerted by CO2 gas dissolved in blood.
• An index of efficiency of gas exchange in the lungs
• Not a measure of CO2 concentration in the blood
Partial Pressure of CO2 (pCO2)
Partial Pressure of CO2 (pCO2)
Reference Range:
35-45 mm Hg
When we say______ that is the pressure exerted by the gas in the blood and does not mean the concentration of the gas in the blood
partial pressure
• Total CO2 Content (tCO2)
• Refers to the total concentration of CO2 in the blood
Total Carbon Dioxide Concentration
• Consisting of lonized (HCO3-, CO3-, Carbamino compound) and unionized fraction (H2CO3)
• 23 - 27 mmol/L
Total Carbon Dioxide Concentration
• The bicarbonate ion concentration in the blood has been equilibrated with CO2 at 40 mm Hg at 37 degree Celsius
Bicarbonate lon Concentration
Main samples used in blood gas is arterial blood
Reference Range:_____ mmol/L
It can be calculated through
_________
22-26mmol/ L
Henderson Hasselbalch equation
• The pressure or tension exerted by oxygen gas dissolved in arterial blood which reflects the availability of the gas in blood but not its content
• 80 - 110 mm Hg
Partial Pressure of Oxygen (pO2)
• A collection of chemical compounds and reactions in the body that help maintain the pH level of the blood and other bodily fluids within a narrow and optimal range.
The pH level is a measure of the acidity or basicity of a solution, and maintaining the proper pH is essential for many biological processes to function properly.
BUFFER SYSTEMS
The____ together with the____ provide the first line of defense to change the acid-base status.
lungs
buffer systems
So for the extracellular fluid the main buffer system is the carbonic acid- bicarbonate buffer system
Remember when cells metabolize they release______ as a waste product
Now this carbon dioxide will combine with water to form______
carbon dioxide
carbonic acid
Since carbonic acid is an unstable molecule so it immediately dissociates into hydrogen and bicarbonate ions which is accelerated by the enzyme
_________
Carbonic Anhydrase
_______ ions accumulate in the blood, to avoid a pH change, so chloride ions will go inside the cell to maintain electroneutrality.
Bicarbonate
• Why does chloride need to go inside the cell? Remember bicarbonate and chloride ions bear a net negative charge. So if both anions are accumulating in the blood there will be an electrolyte imbalance. To fix this chloride ions will enter the cell in an even known as_______
Chloride Shift
pH
↑ H+ — ↓ Blood pH
Acidic
pH
↓ H+ — ↑ Blood pH
Alkaline
• <7.35 =
• >7.45 =
acidosis
alkalosis
•_____ – process in the body
-osis
– state in blood
-emia
Bicarbonate-Carbonic Acid System
↓ HCO3-
↓ Blood pH
(Directly proportional)
Acidic
Bicarbonate-Carbonic Acid System
↑ HCO3-
↑ Blood pH
Alkaline
Buffer sustems occur in
Intracellular fluid
Extracellular fluid
Buffer system
Intracellular fluid
Phosphate buffer system
Protein buffer systems
Buffer system
Extracellular fluid
Protein buffer systems
Carbonic acid-bicarbonate buffer system
Protein buffer systems
Hemoglobin buffer system
Amino acid buffer system
Plasma protein buffers
The main site for retaining bicarbonate is in the
Proximal Convoluted Tubule
Respiratory component
CO2 - lungs
Metabolic component
Kidneys - bicarbonate
Bicarbonate-Carbonic Acid System
↓ HCO3-
↓ Blood pH
Acidic
Bicarbonate-Carbonic Acid System
↑ HCO3-
↑ Blood pH
Alkaline
Maintenance of H+
• Normal:
36 – 44 nmol/L (pH 7.34 – 7.44)
Maintenance of H+
• Through metabolism, the body produces much greater quantities of_____
• The body controls and excretes H+ in order to maintain______ (lungs and kidneys)
H+
pH homeostasis
Maintenance of H+
• Increase ____ will cause alterations in the rates of chemical reactions within the cell and affect the many metabolic processes of the body
• Can lead to alterations in consciousness, neuromuscular irritability, tetany, coma, and death
H+
Henderson-Hasselbalch Equation
• [A-] =
• [HA] =
• pK’ =
proton acceptor (HCO3 - )
proton donor or weak acid (H2 CO3 )
pH at which there is an equal concentration of protonated and unprotonated species
= pK’ of HCO3-
6.1
= the value for the combination of the solubility constant for pCO 2 and the factor to convert mm Hg to mmol/L
0.0307 mmol/L/mm Hg
= equilibrium between H2 CO 3 and CO 2 in plasma
1:800
= proportional to the pCO2
cH2CO 3
are measured in blood gas analysis
pH and pCO 2
