NBRC Critical Care and ABG Interpretation 2 — Questions and Answers
Question 1: A patient on mechanical ventilation has a sudden decrease in SpO2 and a shift of the trachea to the unaffected side. The most likely diagnosis is:
- Mucus plug causing atelectasis
- Tension pneumothorax (Correct answer)
- Pulmonary embolism
- Right mainstem intubation
Correct answer: Tension pneumothorax
Tension pneumothorax causes tracheal deviation away from the affected side, hypotension, absent breath sounds, and severe hypoxia — a life-threatening emergency.
Question 2: Systemic inflammatory response syndrome (SIRS) criteria include all of the following EXCEPT:
- Temperature >38°C or <36°C
- Heart rate >90 bpm
- Respiratory rate >20 breaths/min or PaCO2 <32 mmHg
- SpO2 <88% on room air (Correct answer)
Correct answer: SpO2 <88% on room air
SIRS criteria include temperature, heart rate, respiratory rate/PaCO2, and WBC count abnormalities; SpO2 below 88% is not a SIRS criterion.
Question 3: Prone positioning in ARDS improves oxygenation primarily by:
- Increasing FiO2 delivery
- Redistributing blood flow to better-ventilated dorsal lung regions and recruiting dependent lung (Correct answer)
- Reducing lung compliance
- Decreasing cardiac output
Correct answer: Redistributing blood flow to better-ventilated dorsal lung regions and recruiting dependent lung
Prone positioning recruits previously collapsed dorsal (posterior) alveoli and redistributes perfusion to better-ventilated regions, improving V/Q matching and oxygenation.
Question 4: A pulmonary artery catheter (Swan-Ganz) wedge pressure (PAWP) of 25 mmHg suggests:
- Right heart failure
- Left ventricular failure and pulmonary venous hypertension (Correct answer)
- Normal hemodynamics
- Pulmonary arterial hypertension
Correct answer: Left ventricular failure and pulmonary venous hypertension
Elevated PAWP (>18 mmHg) reflects high left atrial filling pressure from left ventricular failure, indicating cardiogenic pulmonary edema.
Question 5: Septic shock is defined as sepsis PLUS:
- Temperature above 39°C
- MAP <65 mmHg despite adequate fluid resuscitation requiring vasopressors, with lactate >2 mmol/L (Correct answer)
- WBC count above 20,000
- PaO2/FiO2 ratio below 300
Correct answer: MAP <65 mmHg despite adequate fluid resuscitation requiring vasopressors, with lactate >2 mmol/L
Septic shock (Sepsis-3 definition) requires vasopressor use to maintain MAP ≥65 mmHg and serum lactate >2 mmol/L despite adequate fluid resuscitation.
Question 6: Which condition is characterized by a normal PAWP with elevated pulmonary artery pressure and high pulmonary vascular resistance?
- Cardiogenic pulmonary edema
- Pulmonary arterial hypertension (Correct answer)
- Left ventricular failure
- Fluid overload
Correct answer: Pulmonary arterial hypertension
Pulmonary arterial hypertension involves elevated pulmonary artery pressure due to increased pulmonary vascular resistance with a normal PAWP, distinguishing it from cardiac causes.
NBRC Critical Care and ABG Interpretation 2
A patient on mechanical ventilation has a sudden decrease in SpO2 and a shift of the trachea to the unaffected side.
The most likely diagnosis is: