CSE Questions, Clinical Scenarios, ABG Interpretation,
Mechanical Ventilation & Comprehensive Study Guide|
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Question 1
A respiratory therapist is evaluating a patient admitted with septic shock.
During the past 8 hours, the patient's urine output has averaged 18 mL/hr. Which
interpretation is MOST appropriate?
A. The patient's kidneys are functioning normally.
B. The urine output indicates inadequate renal perfusion and should be reported
immediately.
C. This urine output is expected in healthy adults.
D. The patient is experiencing osmotic diuresis.
Correct Answer:
B. The urine output indicates inadequate renal perfusion and should be reported
immediately.
Comprehensive Rationale:
Urine output is one of the most important indicators of tissue perfusion and
renal function in critically ill patients. Normal adult urine output is approximately
40 mL/hr, or about 0.5 mL/kg/hr. An output of 18 mL/hr is significantly below
normal and suggests that the kidneys are not receiving adequate blood flow. In
a patient with septic shock, this may indicate worsening hypoperfusion, acute
kidney injury, or inadequate fluid resuscitation.
,As a respiratory therapist working in the ICU, recognizing poor urine output is
important because it often reflects overall cardiovascular status. Decreased
renal perfusion frequently accompanies shock and can signal multiple-organ
dysfunction if not corrected.
Why the Other Answers Are Incorrect
A. The patient's kidneys are functioning normally.
Incorrect. Normal urine output is approximately 40 mL/hr. An output of 18 mL/hr
is concerning.
C. This urine output is expected in healthy adults.
Incorrect. Healthy adults generally produce around 1 liter or more of urine per
day, averaging about 40 mL/hr.
D. The patient is experiencing osmotic diuresis.
Incorrect. Osmotic diuresis causes increased, not decreased, urine production.
NBRC Clinical Pearl
Low urine output is often one of the earliest indicators of poor organ perfusion.
TMC Exam Tip
On the NBRC exam, decreasing urine output almost always suggests worsening
circulation or renal perfusion until proven otherwise.
Question 2
A patient has received several liters of intravenous fluids during treatment for
trauma. The respiratory therapist notices worsening oxygenation and increasing
crackles throughout both lung fields.
Which assessment finding would MOST likely support fluid overload?
A. Decreased body weight
B. Decreased central venous pressure
,C. Weight gain and elevated central venous pressure
D. Dry mucous membranes
Correct Answer:
C. Weight gain and elevated central venous pressure
Comprehensive Rationale
Excess fluid administration can result in hypervolemia, causing fluid
accumulation within the vascular system and eventually the lungs. Clinical signs
include:
• Weight gain
• Elevated CVP
• Pulmonary crackles
• Pulmonary edema
• Increased hemodynamic pressures
• Decreased lung compliance
• Increased work of breathing
An elevated CVP reflects increased right-sided filling pressures and is
commonly seen with fluid overload.
Why the Other Answers Are Incorrect
A. Decreased body weight
Incorrect. Fluid overload causes weight gain.
B. Decreased central venous pressure
Incorrect. A decreased CVP suggests hypovolemia.
D. Dry mucous membranes
Incorrect. Dry mucous membranes are associated with dehydration rather than
excess fluid.
NBRC Clinical Pearl
When intake greatly exceeds output, expect:
• Pulmonary edema
, • Increased CVP
• Increased blood pressure
• Weight gain
• Reduced lung compliance
TMC Exam Tip
Weight changes are one of the best bedside indicators of fluid balance.
Question 3
A mechanically ventilated patient has a CVP of 2 mmHg.
Which interpretation is MOST appropriate?
A. Fluid overload
B. Normal to low intravascular volume
C. Left ventricular failure
D. Pulmonary hypertension
Correct Answer:
B. Normal to low intravascular volume
Comprehensive Rationale
Normal CVP ranges from 2–6 mmHg (or 4–12 cmH₂O). A CVP at the lower end of
normal—or below normal—may indicate reduced venous return or hypovolemia,
particularly when accompanied by hypotension or tachycardia.
Patients with low CVP often benefit from evaluation for fluid replacement if
clinically indicated.
Why the Other Answers Are Incorrect
A. Fluid overload
Fluid overload generally causes an elevated CVP.
C. Left ventricular failure
Although heart failure can influence filling pressures, isolated low CVP does not
support this diagnosis.