Critical Care and ABG Interpretation Flashcards

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:

Answer: Tension pneumothorax

Tension pneumothorax causes tracheal deviation away from the affected side, hypotension, absent breath sounds, and severe hypoxia — a life-threatening emergency.

Systemic inflammatory response syndrome (SIRS) criteria include all of the following EXCEPT:

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.

Prone positioning in ARDS improves oxygenation primarily by:

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.

A pulmonary artery catheter (Swan-Ganz) wedge pressure (PAWP) of 25 mmHg suggests:

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.

Septic shock is defined as sepsis PLUS:

Answer: MAP 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.

Which condition is characterized by a normal PAWP with elevated pulmonary artery pressure and high pulmonary vascular resistance?

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.