NU 606 Advanced Pathophysiology Exam 3 Questions and
Answers | Verified Answers with Detailed Rationales (2026/2027
Edition)
Advanced Pathophysiology Examination
Regis College
NU 606 – Exam 3
2026/2027 Edition
SECTION 1: Acid-Base Balance and Regulation
(8 Questions)
Question 1
A client with chronic obstructive pulmonary disease (COPD) presents with an arterial
blood gas (ABG) showing pH 7.32, PaCO2 58 mmHg, and HCO3- 30 mEq/L. The APRN
recognizes that the primary pathophysiological disturbance involves which mechanism?
A. Excessive renal excretion of bicarbonate
B. Inadequate alveolar ventilation leading to carbon dioxide retention
C. Excessive lactic acid production from tissue hypoxia
D. Inappropriate hyperventilation causing hypocapnia
Correct Answer: B
Rationale: The ABG demonstrates respiratory acidosis (pH < 7.35, PaCO2 > 45 mmHg)
with metabolic compensation (elevated HCO3-). The primary disturbance in COPD is
inadequate alveolar ventilation due to airway obstruction and loss of elastic recoil,
causing carbon dioxide retention and subsequent carbonic acid accumulation. Option A
is incorrect because renal excretion of bicarbonate would cause metabolic acidosis, not
compensation for respiratory acidosis. Option C describes metabolic acidosis from
lactic acid, which would present with decreased HCO3- and typically a normal or
decreased PaCO2. Option D describes respiratory alkalosis (hypocapnia with elevated
pH), which is the opposite of this client's presentation.
,Question 2
Which statement accurately describes the relationship between arterial carbon dioxide
(PaCO2) and blood pH in primary respiratory disorders?
A. As PaCO2 increases, pH increases in a directly proportional manner
B. As PaCO2 increases, pH decreases in an inversely proportional relationship
C. PaCO2 and pH are unrelated in primary respiratory pathophysiology
D. As PaCO2 decreases, pH decreases in a directly proportional manner
Correct Answer: B
Rationale: In primary respiratory disorders, PaCO2 and pH have an inverse relationship:
as PaCO2 increases (hypercapnia), pH decreases (acidosis), and as PaCO2 decreases
(hypocapnia), pH increases (alkalosis). This reflects the hydration reaction of CO2 to
form carbonic acid (H2CO3), which dissociates to release hydrogen ions. Option A is
incorrect because the relationship is inverse, not direct. Option C is incorrect because
PaCO2 is the primary determinant of respiratory acid-base status. Option D is incorrect
because decreased PaCO2 causes respiratory alkalosis with increased pH.
Question 3
A client with diabetic ketoacidosis (DKA) presents with pH 7.25, PaCO2 22 mmHg, and
HCO3- 12 mEq/L. Which pathophysiological process best explains the low bicarbonate
level?
A. Excessive renal reabsorption of bicarbonate in response to hypoxia
B. Accumulation of ketoacids that consume bicarbonate during buffering
C. Hyperventilation causing renal excretion of bicarbonate
D. Increased aldosterone secretion stimulating bicarbonate generation
Correct Answer: B
Rationale: In DKA, insulin deficiency promotes lipolysis and hepatic ketogenesis,
producing acetoacetic acid and beta-hydroxybutyric acid. These ketoacids dissociate
and release hydrogen ions, which are buffered by bicarbonate, resulting in decreased
serum HCO3- and metabolic acidosis. Option A is incorrect because renal reabsorption
,of bicarbonate would elevate, not decrease, HCO3-. Option C confuses cause and effect;
hyperventilation is a compensatory respiratory response to metabolic acidosis, not the
cause of low bicarbonate. Option D is incorrect because aldosterone primarily regulates
sodium and potassium, not bicarbonate generation in this context.
Question 4
A client has been vomiting profusely for 48 hours due to gastric outlet obstruction. The
APRN anticipates which acid-base disturbance based on the pathophysiology of
hydrogen ion loss?
A. Metabolic acidosis with decreased bicarbonate
B. Metabolic alkalosis with increased bicarbonate
C. Respiratory acidosis with increased PaCO2
D. Respiratory alkalosis with decreased PaCO2
Correct Answer: B
Rationale: Profuse vomiting of gastric contents results in loss of hydrochloric acid (H+
and Cl-), leading to metabolic alkalosis. The loss of hydrogen ions causes a relative
excess of bicarbonate. Additionally, volume contraction activates the
renin-angiotensin-aldosterone system, further promoting bicarbonate reabsorption and
hypokalemia, which sustains the alkalosis. Option A is incorrect because hydrogen ion
loss causes alkalosis, not acidosis. Options C and D are incorrect because the primary
disturbance is metabolic, not respiratory, in origin.
Question 5
Which organ system provides the most rapid compensatory response to metabolic
acidosis, and what is the mechanism?
A. Kidneys; increased generation and reabsorption of bicarbonate over hours to days
B. Lungs; hyperventilation to eliminate carbon dioxide within minutes
C. Liver; increased urea synthesis to buffer excess hydrogen ions
D. Bone; release of calcium carbonate to neutralize acid over weeks
, Correct Answer: B
Rationale: The respiratory system provides the most rapid compensation for metabolic
acidosis through hyperventilation (Kussmaul respirations), which decreases PaCO2 and
raises pH within minutes. Chemoreceptors in the medulla and carotid bodies detect
decreased pH and stimulate increased ventilatory drive. Option A describes the renal
compensatory mechanism, which is the most powerful but slowest, requiring hours to
days. Option C is incorrect because the liver does not participate in acute acid-base
buffering through urea synthesis. Option D describes a chronic buffering mechanism
but is not the most rapid response.
Question 6
A pregnant client in her third trimester presents with pH 7.48, PaCO2 28 mmHg, and
HCO3- 22 mEq/L. Which pathophysiological mechanism explains this acid-base
disturbance?
A. Increased minute ventilation due to elevated progesterone stimulating the respiratory
center
B. Decreased alveolar ventilation from uterine compression of the diaphragm
C. Excessive renal excretion of bicarbonate triggered by human chorionic gonadotropin
D. Accumulation of lactic acid from increased metabolic demands of pregnancy
Correct Answer: A
Rationale: Physiologic respiratory alkalosis of pregnancy results from
progesterone-mediated stimulation of the respiratory center, causing increased minute
ventilation and decreased PaCO2. This facilitates fetal CO2 transfer across the
placenta. Option B is incorrect because uterine compression does not cause
hypoventilation in pregnancy; tidal volume actually increases. Option C is incorrect
because hCG does not stimulate bicarbonate excretion. Option D would produce
metabolic acidosis, not the respiratory alkalosis pattern observed.
Question 7
Answers | Verified Answers with Detailed Rationales (2026/2027
Edition)
Advanced Pathophysiology Examination
Regis College
NU 606 – Exam 3
2026/2027 Edition
SECTION 1: Acid-Base Balance and Regulation
(8 Questions)
Question 1
A client with chronic obstructive pulmonary disease (COPD) presents with an arterial
blood gas (ABG) showing pH 7.32, PaCO2 58 mmHg, and HCO3- 30 mEq/L. The APRN
recognizes that the primary pathophysiological disturbance involves which mechanism?
A. Excessive renal excretion of bicarbonate
B. Inadequate alveolar ventilation leading to carbon dioxide retention
C. Excessive lactic acid production from tissue hypoxia
D. Inappropriate hyperventilation causing hypocapnia
Correct Answer: B
Rationale: The ABG demonstrates respiratory acidosis (pH < 7.35, PaCO2 > 45 mmHg)
with metabolic compensation (elevated HCO3-). The primary disturbance in COPD is
inadequate alveolar ventilation due to airway obstruction and loss of elastic recoil,
causing carbon dioxide retention and subsequent carbonic acid accumulation. Option A
is incorrect because renal excretion of bicarbonate would cause metabolic acidosis, not
compensation for respiratory acidosis. Option C describes metabolic acidosis from
lactic acid, which would present with decreased HCO3- and typically a normal or
decreased PaCO2. Option D describes respiratory alkalosis (hypocapnia with elevated
pH), which is the opposite of this client's presentation.
,Question 2
Which statement accurately describes the relationship between arterial carbon dioxide
(PaCO2) and blood pH in primary respiratory disorders?
A. As PaCO2 increases, pH increases in a directly proportional manner
B. As PaCO2 increases, pH decreases in an inversely proportional relationship
C. PaCO2 and pH are unrelated in primary respiratory pathophysiology
D. As PaCO2 decreases, pH decreases in a directly proportional manner
Correct Answer: B
Rationale: In primary respiratory disorders, PaCO2 and pH have an inverse relationship:
as PaCO2 increases (hypercapnia), pH decreases (acidosis), and as PaCO2 decreases
(hypocapnia), pH increases (alkalosis). This reflects the hydration reaction of CO2 to
form carbonic acid (H2CO3), which dissociates to release hydrogen ions. Option A is
incorrect because the relationship is inverse, not direct. Option C is incorrect because
PaCO2 is the primary determinant of respiratory acid-base status. Option D is incorrect
because decreased PaCO2 causes respiratory alkalosis with increased pH.
Question 3
A client with diabetic ketoacidosis (DKA) presents with pH 7.25, PaCO2 22 mmHg, and
HCO3- 12 mEq/L. Which pathophysiological process best explains the low bicarbonate
level?
A. Excessive renal reabsorption of bicarbonate in response to hypoxia
B. Accumulation of ketoacids that consume bicarbonate during buffering
C. Hyperventilation causing renal excretion of bicarbonate
D. Increased aldosterone secretion stimulating bicarbonate generation
Correct Answer: B
Rationale: In DKA, insulin deficiency promotes lipolysis and hepatic ketogenesis,
producing acetoacetic acid and beta-hydroxybutyric acid. These ketoacids dissociate
and release hydrogen ions, which are buffered by bicarbonate, resulting in decreased
serum HCO3- and metabolic acidosis. Option A is incorrect because renal reabsorption
,of bicarbonate would elevate, not decrease, HCO3-. Option C confuses cause and effect;
hyperventilation is a compensatory respiratory response to metabolic acidosis, not the
cause of low bicarbonate. Option D is incorrect because aldosterone primarily regulates
sodium and potassium, not bicarbonate generation in this context.
Question 4
A client has been vomiting profusely for 48 hours due to gastric outlet obstruction. The
APRN anticipates which acid-base disturbance based on the pathophysiology of
hydrogen ion loss?
A. Metabolic acidosis with decreased bicarbonate
B. Metabolic alkalosis with increased bicarbonate
C. Respiratory acidosis with increased PaCO2
D. Respiratory alkalosis with decreased PaCO2
Correct Answer: B
Rationale: Profuse vomiting of gastric contents results in loss of hydrochloric acid (H+
and Cl-), leading to metabolic alkalosis. The loss of hydrogen ions causes a relative
excess of bicarbonate. Additionally, volume contraction activates the
renin-angiotensin-aldosterone system, further promoting bicarbonate reabsorption and
hypokalemia, which sustains the alkalosis. Option A is incorrect because hydrogen ion
loss causes alkalosis, not acidosis. Options C and D are incorrect because the primary
disturbance is metabolic, not respiratory, in origin.
Question 5
Which organ system provides the most rapid compensatory response to metabolic
acidosis, and what is the mechanism?
A. Kidneys; increased generation and reabsorption of bicarbonate over hours to days
B. Lungs; hyperventilation to eliminate carbon dioxide within minutes
C. Liver; increased urea synthesis to buffer excess hydrogen ions
D. Bone; release of calcium carbonate to neutralize acid over weeks
, Correct Answer: B
Rationale: The respiratory system provides the most rapid compensation for metabolic
acidosis through hyperventilation (Kussmaul respirations), which decreases PaCO2 and
raises pH within minutes. Chemoreceptors in the medulla and carotid bodies detect
decreased pH and stimulate increased ventilatory drive. Option A describes the renal
compensatory mechanism, which is the most powerful but slowest, requiring hours to
days. Option C is incorrect because the liver does not participate in acute acid-base
buffering through urea synthesis. Option D describes a chronic buffering mechanism
but is not the most rapid response.
Question 6
A pregnant client in her third trimester presents with pH 7.48, PaCO2 28 mmHg, and
HCO3- 22 mEq/L. Which pathophysiological mechanism explains this acid-base
disturbance?
A. Increased minute ventilation due to elevated progesterone stimulating the respiratory
center
B. Decreased alveolar ventilation from uterine compression of the diaphragm
C. Excessive renal excretion of bicarbonate triggered by human chorionic gonadotropin
D. Accumulation of lactic acid from increased metabolic demands of pregnancy
Correct Answer: A
Rationale: Physiologic respiratory alkalosis of pregnancy results from
progesterone-mediated stimulation of the respiratory center, causing increased minute
ventilation and decreased PaCO2. This facilitates fetal CO2 transfer across the
placenta. Option B is incorrect because uterine compression does not cause
hypoventilation in pregnancy; tidal volume actually increases. Option C is incorrect
because hCG does not stimulate bicarbonate excretion. Option D would produce
metabolic acidosis, not the respiratory alkalosis pattern observed.
Question 7
