6.2: Blood Gases, pH, and Electrolytes Flashcards
Which of the following represents the Henderson-Hasselbalch equation as applied to blood pH?
A. pH = 6.1 + log HCO3-/PCO2
B. pH = 6.1 + log HCO3/(0.03×PCO2)
C. pH = 6.1 + log dCO2/HCO3-
D. pH = 6.1 + log (0.03×PCO2)/HCO3-
B. pH = 6.1 + log HCO3/(0.03×PCO2)
What is the PO2 of calibration gas containing 20.0% O2, when the barometric pressure is 30 in?
A. 60mm Hg
B. 86mm Hg
C. 143mm Hg
D. 152mm Hg
C. 143mm Hg
Convert the bariatric pressure from inches to mm:
25.4mm/in x 30 in= 762mmHg
762mmHg - 47mmHg (water vapor pressure)= 715mmHg (dry gas pressure)
0.20 x 715mmHg= 143mmHg
What is the blood pH when the partial pressure of carbon dioxide (PCO2) is 60mmHg and the
bicarbonate concentration is 18 mmol/L?
A. 6.89
B. 7.00
C. 7.10
D. 7.30
C. 7.10
Henderson-Hasselbalch equation to solve
pH = 6.1 + log HCO3/(0.03×PCO2)
pH= 6.1 + log (18/(0.03 x 60))
pH= 6.1 + log (18/1.8)
pH= 6.1 + log (10)
pH= 7.1
Which of the following best represents the reference (normal) range for arterial pH?
A. 7.35-7.45
B. 7.42-7.52
C. 7.38-7.68
D. 6.85-7.56
A. 7.35-7.45
What is the normal ratio of bicarbonate to dissolved carbon dioxide (HCO3-:dCO2) in arterial blood?
A. 1:10
B. 10:1
C. 20:1
D. 30:1
C. 20:1
What is the PCO2 if the DCO2 is 1.8 mmol/L?
A. 24 mm Hg
B. 35 mm Hg
C. 60 mm Hg
D. 72 mm Hg
C. 60 mm Hg
DCO2= PCO2 x 0.03
PCO2= DCO2 / 0.03
PCO2= 1.8 / 0.03
PCO2= 60mmHg
In the Henderson-Hasselbalch expression pH = 6.1 + log HCO3-/dCO2, the
6.1 represents:
A. The combined hydration and dissociation
constants for CO2 in blood at 37°C
B. The solubility constant for CO2 gas
C. The dissociation constant of H2O
D. The ionization constant of NaHCO3
A. The combined hydration and dissociation
constants for CO2 in blood at 37°C
Which of the following contributes the most to the serum total CO2 (TCO2)?
A. PCO2
B. DCO2
C. HCO3-
D. Carbonium ion
C. HCO3-
Total CO2 is the sum of DCO2, H2CO3, and Bicarb
When serum is measured, DCO2 doesn’t matter bc it went into the air
In addition to NaHCO3, what other substance contributes most to the amount of base in the blood?
A. Hemoglobin concentration
B. Dissolved O2 concentration
C. Inorganic phosphorus
D. Organic phosphate
A. Hemoglobin concentration
Primary blood buffer bases preventing acidosis are bicarb, deoxyhgb, albumin, and mono hydrogen phosphate
Which of the following effects results from exposure of a normal arterial blood sample to room air?
A. PO2 increased;PCO2 decreased; pH increased
B. PO2 decreased;PCO2 increased; pH decreased
C. PO2 increased; PCO2 decreased; pH decreased
D. PO2 decreased; PCO2 decreased; pH decreased
A. PO2 increased;PCO2 decreased; pH increased
Blood releases CO2 gas and gains O2 when exposed to air, the loss of CO2 shifts the bicarb buffer system to the R, losing Hs so blood becomes more alkaline
Which of the following formulas for O2 content is correct?
A. O2 content = %O2 saturation/100 × Hgb g/dL × 1.39 mL/g + (0.0031 × PO2)
B. O2 content = PO2 × 0.0306 mmol/L/mm
C. O2 content = O2 saturation × Hgb g/dL × 0.003 mL/g
D. O2 content = O2 capacity × 0.003 mL/g
A. O2 content = %O2 saturation/100 × Hgb g/dL × 1.39 mL/g + (0.0031 × PO2)
Oxygen content is the sum of O2 bound to Hgb and O2 dissolved in the plasma
The normal difference between alveolar and arterial PO2 (PAO2-PaO2 difference) is:
A. 3 mm Hg
B. 10 mm Hg
C. 40 mm Hg
D. 50 mm Hg
B. 10 mm Hg
A decreased PAO2-PaO2 difference is found in:
A. A/V (arteriovenous) shunting
B. V/Q (ventilation/perfusion) inequality
C. Ventilation defects
D. All of these options
C. Ventilation defects
pts with A/V shunts, V/Q inequalities, and cardiac failure will have an increased difference
The determination of the oxygen saturation of hemoglobin is best accomplished by:
A. Polychromatic absorbance measurements of a
whole-blood hemolysate
B. Near infrared transcutaneous absorbance
measurement
C. Treatment of whole blood with alkaline dithionite prior to measuring absorbance
D. Calculation using PO2 and total hemoglobin
by direct spectrophotometry
A. Polychromatic absorbance measurements of a
whole-blood hemolysate
Correction of pH for a patient with a body temperature of 38°C would require:
A. Subtraction of 0.015
B. Subtraction of 0.01%
C. Addition of 0.020
D. Subtraction of 0.020
A. Subtraction of 0.015
pH decreases by 0.015 for each degree C above 37C
Select the anticoagulant of choice for blood gas studies.
A. Sodium citrate 3.2%
B. Lithium heparin 100 units/mL blood
C. Sodium citrate 3.8%
D. Ammonium oxalate 5.0%
B. Lithium heparin 100 units/mL blood
What is the maximum recommended storage time and temperature for an arterial blood gas sample drawn in a plastic syringe?
Storage Time; Temperature
A. 10 min; 2°C-8°C
B. 20 min; 2°C-8°C
C. 30 min; 2°C-8°C
D. 30 min; 22°C
D. 30 min; 22°C
A patient’s blood gas results are as follows:
pH= 7.26
DCO2= 2.0 mmol/L
HCO3-= 29 mmol/L
These results would be classified as:
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis
C. Respiratory acidosis
idk why it just is
A patient’s blood gas results are:
pH = 7.50
PCO2 = 55 mm Hg
HCO3- = 40 mmol/L
These results indicate:
A. Respiratory acidosis
B. Metabolic alkalosis
C. Respiratory alkalosis
D. Metabolic acidosis
B. Metabolic alkalosis
I still don’t know why
Which set of results is consistent with uncompensated respiratory alkalosis?
A. pH 7.70; HCO3 30 mmol/L; PCO2 25 mm Hg
B. pH 7.66; HCO3 22 mmol/L; PCO2 20 mm Hg
C. pH 7.46; HCO3 38 mmol/L; PCO2 55 mm Hg
D. pH 7.36; HCO3 22 mmol/L; PCO2 38 mm Hg
B. pH 7.66; HCO3 22 mmol/L; PCO2 20 mm Hg
Which of the following will shift the O2 dissociation curve to the left?
A. Anemia
B. Hyperthermia
C. Hypercapnia
D. Alkalosis
D. Alkalosis
Acidosis will shift it to the right
In which circumstance will the reporting of calculated oxygen saturation of hemoglobin based on PO2, PCO2, pH, temperature, and hemoglobin be in error?
A. Carbon monoxide (CO) poisoning
B. Diabetic ketoacidosis
C. Oxygen therapy
D. Assisted ventilation for respiratory failure
A. Carbon monoxide (CO) poisoning
Which would be consistent with partially compensated respiratory acidosis?
A. pH increased; PCO2 increased; Bicarbonate increased
B. pH increased; PCO2 decreased; Bicarbonate decreased
C. pH decreased; PCO2 decreased; Bicarbonate decreased
D. pH decreased; PCO2 increased; Bicarbonate increased
D. pH decreased; PCO2 increased; Bicarbonate increased
Which condition results in metabolic acidosis with severe hypokalemia and chronic alkaline urine?
A. Diabetic ketoacidosis
B. Phenformin-induced acidosis
C. Renal tubular acidosis
D. Acidosis caused by starvation
C. Renal tubular acidosis
Which of the following mechanisms is responsible for metabolic acidosis?
A. Bicarbonate deficiency
B. Excessive retention of dissolved CO2
C. Accumulation of volatile acids
D. Hyperaldosteronism
A. Bicarbonate deficiency
Which of the following disorders is associated with lactate acidosis?
A. Diarrhea
B. Renal tubular acidosis
C. Hypoaldosteronism
D. Alcoholism
D. Alcoholism
Which of the following is the primary mechanism of compensation for metabolic acidosis?
A. Hyperventilation
B. Release of epinephrine
C. Aldosterone release
D. Bicarbonate excretion
A. Hyperventilation
The following conditions are all causes of alkalosis. Which condition is associated with respiratory (rather than metabolic) alkalosis?
A. Anxiety
B. Hypovolemia
C. Hyperaldosteronism
D. Hypoparathyroidism
A. Anxiety
Which of the following conditions is associated with both metabolic and respiratory alkalosis?
A. Hyperchloremia
B. Hypernatremia
C. Hyperphosphatemia
D. Hypokalemia
D. Hypokalemia
In uncompensated metabolic acidosis, which of the following will be normal?
A. Plasma bicarbonate
B. PCO2
C. p50
D. Total CO2
B. PCO2
Which of the following conditions is classified as normochloremic acidosis?
A. Diabetic ketoacidosis
B. Chronic pulmonary obstruction
C. Uremic acidosis
D. Diarrhea
A. Diabetic ketoacidosis
Which PCO2 value would be seen in maximally compensated metabolic acidosis?
A. 15 mm Hg
B. 30 mm Hg
C. 40 mm Hg
D. 60 mm Hg
A. 15 mm Hg
A patient has the following arterial blood gas results:
pH = 7.56
PO2 = 100 mm Hg
PCO2 = 25 mm Hg
HCO3 = 22 mmol/L
These results are most likely the result of which condition?
A. Improper specimen collection
B. Prolonged storage
C. Hyperventilation
D. Hypokalemia
C. Hyperventilation
