Blood gases, pH and buffer systems Flashcards
Proton donator
Acid
Proton acceptor
Base
When you dissolve acid in water, it will yield?
Hydrogen ions or H+
When you dissolve base in water, it will yield?
Hydroxyl ions or OH-
ratio of dissociated ions to the original acid
Dissociation constant or K value
Relative strengths of acids/bases - ability to dissociate in water
Dissociation constant or K value
pH at which the protonated, known as? and unprotonated, known as? forms are present in equal conc.
A. Base
B. Acid
pKa
Pk value of strong acid
Less than 3.0 or <3.0
Pk value of strong base
Greater than 9.0 or >9.0
Increase pH above pk - yields H+
Strong acid
Decrease pH below pk - yields OH-
Strong base
- Paglagay sa water nag separate ang acid from its proton (H+)
- kapag nag dissociate, it will dissociate completely
Strong Acid/Strong Base
Paglagay sa water, may iba nag dissociate, may iba na wala
Weak acid/base
Combination of weak acid/base and it’s salt
Buffer
Resist changes in pH [not all the substances we intake/ingest are neutral] - maong acidic/basic
Buffer
Pressure/exerted by CO2 has dissolved in blood
Index of efficiency of gas exchange (lungs)
Not measure of CO2 conc. in blood
Partial pressure of CO2 or pCO2
Value of pCO2
35-45 mm Hg
Ionized: HCO3-, CO3-, carbamino compound
Unionized: H2CO3, dissolved CO2
Total carbon dioxide conc. or tCO2
Value of tCO2
23-27 mmol/L
Equilibrated with CO2 at 40 mm Hg @ 37°C
Bicarbonate Ion conc.
Value of Bicarbonate Ion conc.
22-26 mmol/L
Exerted by O2 dissolved in arterial blood
Partial pressure of O2 or pO2
Value of pO2
80-110 mm Hg
Index of the acidity/alkalinity of blood
Inversely proportional to H+ conc.
pH
the more you have H+ conc. in blood, the lesser the blood pH
Results:
A. <7.35?
B. >7.45?
A. Acidosis/Acidemia
B. Alkalosis/alkalemia
Suffix
Process in body (conditions of pH in the blood)
-osis
Suffix
State in blood
-emia
The lesser the bicarbonate in blood, the lesser the blood pH
HCO3- directly proportional to blood pH
Bicarbonate-carbonic acid system
Maintenance of H+
Normal? pH?
36-44 nmol/L
pH 7.34-7.44
Maintenance of H+
A. Metabolism produces?
B. Controls/Excretes H+ maintain?
A. Greater quantities of H+
B. pH homeostasis
Formula of Henderson-Hasselbalch Equation
pH = pK’ + log [A-] / [HA]
Ref ranges : Arterial Blood Gas
A. pH
B. pCO2 (mm Hg)
C. HCO3- (mmol/L)
D. Total CO2 content (mmol/L)
E. pO2
F. SO2 (%)
G. O2 Hb (%)
A. 7.35-7.45
B. 35-45 mm Hg
C. 22-26 mmol/L
D. 23-27 mmol/L
E. 80-110
F. >95
G. >95
Acid-Base Disorders (2)
Acidemia (reflects excess acid)
Alkalemia (reflects excess base)
pH of Acidemia
<7.35-7.45
pH of Alkalemia
> 7.35-7.45
Remember:
If it is DOWN the pH scale, it is ACID
Acidosis
Normal ratio of Bicarbonate-carbonic acid seen in Henderson-Hasselbalch Equation
20:1
Disorders (2)
Primary Respiratory Disorder
Metabolic (non-respiratory) Disorder
Caused by ventilatory dysfunction (change in pCO2)
Primary Respiratory Disorder
Change in HCO3 ion level
Metabolic (non-respiratory) Disorder
Compensation
A. Restore acid-base homeostasis whenever?
B. Body accomplishes by?
C. If the imbalance is of metabolic origin, the body compensates by?
A. Imbalance occurs
B. Altering the factor
C. Altering the ventilation
Lungs
A. Disturbances of respiratory component, kidneys compensate by selectively?
B. Can compensate?
C. Response?
A. Excreting/Reabsorbing anions and cations
B. Immediately
C. Short term and often incomplete
Kidneys
A. Respond?
B. Can compensate?
A. Long term and potentially complete
B. Slow (2-4 days)
pH has returned to the normal range (20:1 restored)
Fully compensated
pH is approaching normal
Partially Compensated
(4) Main Acid-Base Disorders
Primary Metabolic acidosis
Primary Respiratory acidosis
Primary Metabolic alkalosis
Primary Respiratory alkalosis
Bicarbonate: decrease
pH: decrease
pCO2: normal
compensation?
Primary Metabolic Acidosis
through hyperventilation
Alveolar ventilation(hypo): decrease
bicarbonate to carbonic acid ratio: decrease
pCO2: increase
compensation?
Primary Respiratory Acidosis
through non-respiratory processes
pH: increase
non-respiratory component: increase
compensation?
Primary Metabolic Alkalosis
hypoventilation (increases retention of CO2)
Alveolar ventilation: increase
compensation?
Primary Respiratory Alkalosis
hyperventilation
Specimen collection for ABG
A. Prevent O2 consumption?
B. Not be in excess; limit: 0.05 mL of heparin per mL of blood
A. Arterial blood (chilled)
B. Heparin
Sources of error
Specimen exposed to air:
A. pCO2
B. pH
C. pO2
A. Decrease
B. Increase
C. Increase
Specimen at room temp. (30mins)
A. pCO2
B. pH
C. pO2
A. Increase
B. Decrease
C. Decrease
Bacterial contamination
pO2
False decrease
Fever
@38°C
A. pO2
B. pH
C. pCO2
@39°C? Multiply by 2
A. Decrease by 7%
B. Decrease by 0.015
C. Increase by 3%
