pH: 7.40

PCO2: 40 mm Hg

PO2: 82 mm Hg

HCO3: 24 mEq/L

Which of the following statements is most accurate?

a) The patient does not have an acid-base disorder.

b) To determine if there is an acid base disorder you need to know the measured serum bicarbonate, since the HCO3 from blood gases is only a calculation.

c) Need to know patient's respiratory rate, as PaCO2 may be inappropriately "normal" and signify a respiratory acidosis.

d) A patient can have normal blood gases if two metabolic acid-base disorders oppose to give normal bicarbonate.

e) The PaO2 is lower than predicted for a patient breathing room air.

9) A patient with respiratory failure has the following room air (FIO2 = .21) arterial blood gases:

pH: 7.20

PCO2: 70 mm Hg

PO2: 60 mm Hg

SaO2: 86%

Which of the following is the least likely cause of these abnormal blood gases?

a) congestive heart failure

b) narcotic overdose

c) myasthenia gravis

d) flail chest

e) Guillain Barre' Syndrome

10) A 42-year-old man is admitted to the hospital with dehydration and hypotension.

Electrolytes show:

Na+	165 mEq/L
K+	4.0 mEq/L
CO2	32 mEq/L
Cl-	112 mEq/L

No arterial blood gas is obtained. Which statement best applies about this patient's acid-base status?

a) Electrolytes indicate the presence of metabolic acidosis.

b) Electrolytes indicate the presence of metabolic alkalosis.

c) Electrolytes indicate the presence of both metabolic acidosis and metabolic alkalosis.

d) Need serum albumin to make any clinically useful assessment of his metabolic acid-base disorders.

e) Need serum lactate to make any clinically useful assessment of his metabolic acid-base disorders.

11) A 30-year-old man, previously healthy, is brought to the ED after suffering smoke inhalation. Measured carboxyhemoglobin is 20% and hemoglobin content = 15 gm%. He has following blood gas values:

PaO2: 80 mm Hg (on room air at sea level)
PaCO2: 32 mm Hg
pH: 7.34
SaO2: 96% (calculated)

Exam shows clear lungs to auscultation and his chest x-ray is normal. From this information alone, you can determine that:

a) His actual SaO2 is much lower than the calculated value.

b) There is no lung abnormality present, though pulmonary disease could develop in the ensuing 24 hours.

c) He has a mild metabolic acidosis associated with an increased anion gap.

d) His arterial oxygen content is in the normal range.

e) None of the above.

12) Below are two sets of blood gases:

Patient A: pH 7.48, PaCO₂ 34 mm Hg, PaO₂ 85 mm Hg, SaO₂ 95%, Hemoglobin 7 gm%

Patient B: pH 7.32, PaCO₂ 74 mm Hg, PaO₂ 55 mm Hg, SaO₂ 85%, Hemoglobin 15 gm%

Which is the most correct statement?

a) B is more hypoxemic because PaO2 is lower than A.

b) B is more hypoxemic because SaO2 is lower than A.

c) A is more hypoxemic because A-a gradient is higher than B.

d) A is more hypoxemic because O2 content is lower than B.

e) The differences balance out and neither A nor B is more hypoxemic than the other.

13) State which one of the following situations would be expectedto lower a patient's arterial PO2.

a) anemia
b) carbon monoxide poisoning
c) an abnormal hemoglobin that holds oxygen with half the affinity of normal hemoglobin
d) an abnormal hemoglobin that holds oxygen with twice the affinity of normal hemoglobin
e) lung disease with more than a normal amount of ventilation-perfusion imbalance

14) A 40 year-old patient is admitted to the ICU with the following lab values:

BLOOD GASES
pH: 7.40
PCO2: 38 mm Hg
HCO3: 24 mEq/L
PO2: 88 mm Hg (on room air)

ELECTROLYTES, BUN & CREATININE
Na: 149 mEq/L
K: 3.8 mEq/L
Cl: 100 mEq/L
CO2: 24 mEq/L
BUN: 110 mg%
Creatinine: 8.7 mg%

Which statement best describes the disorder(s)?

a) Normal electrolytes, normal blood gases

b) Abnormal electrolytes and abnormal blood gases

c) Metabolic acidosis

d) Metabolic alkalosis

e) Metabolic acidosis and metabolic alkalosis

15) All of the following are true about cyanosis except:

a) For cyanosis to manifest there needs to be 5 gm% of deoxygenated hemoglobin in the capillaries.
b) Patients with normal hemoglobin manifest cyanosis at higher SaO2 values than patients with anemia.
c) Cyanosis can be caused by excess methemoglobin, which is HbFe⁺³.
d) For methemoglobin to cause cyanosis, the PaO2 generally has to be <80 mm Hg.
e) Some drugs may cause cyanosis without causing vasoconstriction, or any impairment in PaO2, SaO2, or oxygen content.

16) Since the early 1980s, climbers have summited Mt. Everest without supplemental oxygen. Since the barometric pressure on the summit is only 253 mm Hg, summiting (without extra O2) has only been possible due to prolonged acclimitization at altitude and profound hyperventilation. Indeed, if a a climber maintained PaCO2 of 40 mm Hg and an alveolar-arterial PO2 difference of 5 mm Hg, what would be his/her theoretical PaO2?

a) 25 mm Hg
b) 15 mm Hg
c) 5 mm Hg
d) -5 mm Hg
e) -10 mm Hg

17) All are true about excess carbon monoxide except:

a) shifts the oxygen dissociation curve to the left
b) lowers the PaO2
c) lowers the oxygen saturation
d) lowers the arterial oxygen content
e) is not accounted for when SaO2 is calculated from arterial blood gas measurements

18) A mountain climber ascends from sea level to 18,000 feet over a two day period, without supplemental oxygen. With ascent all of the following factors will decrease except:

a) Fraction of inspired oxygen (FIO2)
b) Barometric pressure
c) PaO2
d) PaCO2
e) Arterial hydrogen ion concentration

19) You are scuba diving to a depth of 99 feet in the ocean, breathing compressed air from a tank. At this depth, compared to the surface, your arterial PO2 will be approximately:

a) the same
b) 2x the surface value
c) 3x the surface value
d) 4x the surface value
e) dependent on amount of air pressure in the tank

20) While all of the following conditions could possibly be managed without measuring arterial blood gases, in which one would blood gases be most helpful?