Mechanical Ventilation and Critical Care Monitoring — WACS Viva & Clinical Scenarios (Acute Medical Care and Intensive Care Medicine)

Exam-style mechanical ventilation and critical care monitoring viva scenarios with examiner probes and model answers for Internal Medicine candidates.

Scenarios covered

• SCENARIO 1: A 42-year-old male with severe community-acquired pneumonia develops worsening tachypnoea and hypoxaemia despite high-flow oxygen. Arterial blood gas shows a PaO2/FiO2 ratio of 120 mmHg, and chest radiography demonstrates bilateral diffuse alveolar infiltrates without cardiomegaly. He is intubated. Describe the initial mechanical ventilator settings following lung-protective principles, specifying target tidal volume calculation, plateau pressure limits, driving pressure thresholds, and indications for rescue prone positioning.
• SCENARIO 2: A 58-year-old mechanically ventilated female with severe chronic obstructive pulmonary disease suddenly triggers the ventilator high peak airway pressure alarm, with peak inspiratory pressure rising from 28 cmH2O to 46 cmH2O. Outline the immediate bedside diagnostic algorithm to differentiate increased airway resistance from decreased thoracic compliance, the critical maneuver using inspiratory hold to assess plateau pressure, and the emergency management of suspected breath stacking with intrinsic PEEP.
• SCENARIO 3: A 67-year-old patient presents to the emergency high-dependency unit in acute respiratory distress secondary to an exacerbation of COPD with an initial ABG demonstrating pH 7.24, PaCO2 68 mmHg, and PaO2 54 mmHg on room air. Outline the physiological rationale, interface selection, initial ventilator parameter titration, and definitive failure criteria for non-invasive positive pressure ventilation (NIV) before converting to invasive mechanical ventilation.
• SCENARIO 4: A 50-year-old male recovering from severe pancreatitis on mechanical ventilation for 5 days undergoes evaluation for liberation from the ventilator. Detail the physiological readiness criteria for initiating a spontaneous breathing trial (SBT), the calculation and clinical threshold of the Rapid Shallow Breathing Index (RSBI), the interpretation of the cuff leak test, and the monitoring parameters that indicate extubation failure.
• SCENARIO 5: In a patient with septic shock and multiorgan dysfunction in the intensive care unit, evaluate the role of multi-parameter hemodynamic and gas exchange monitoring. Detail the systematic appraisal of arterial line waveforms (including resonance, damping, and respiratory pulse pressure variation), capnography waveform patterns (identifying bronchospasm and rebreathing), and bedside point-of-care ultrasound of the inferior vena cava for fluid responsiveness.