Haemodynamic Monitoring, Pressure Transducers, and Cardiovascular Measurement Instrumentation — WACS Viva & Clinical Scenarios (Clinical Measurement and Equipment)

Exam-style haemodynamic monitoring, pressure transducers, and cardiovascular measurement instrumentation viva scenarios with examiner probes and model answers…

Scenarios covered

• SCENARIO 1: A 62-year-old male with end-stage renal disease and severe vascular calcification undergoes emergency Hartmann's procedure for perforated diverticulitis. His non-invasive blood pressure (NIBP) cuff reads 195/105 mmHg, but the radial intra-arterial catheter shows a reading of 125/60 mmHg. You perform a square-wave fast-flush test and count 4 oscillating cycles following the flush before returning to the baseline waveform. Explain the physical principles of oscillometry versus strain-gauge transducer systems, interpret the fast-flush test, and outline your troubleshooting algorithm.
• SCENARIO 2: You are placing a right internal jugular vein central venous line in a 45-year-old patient undergoing liver resection. After connecting the fluid-filled tubing to the pressure transducer, you obtain a CVP reading of 18 mmHg with loss of the 'a' wave and prominent 'cv' fusion waves. Detail the calibration, zeroing, and leveling steps to ensure accurate CVP measurement at the phlebostatic axis, explain the morphological changes seen on the trace, and outline your diagnostic workup.
• SCENARIO 3: A 58-year-old male is admitted to the intensive care unit following coronary artery bypass grafting with a pulmonary artery catheter (PAC) in place. The cardiac output measured by intermittent cold saline bolus thermodilution is reported as 2.4 L/min. Explain the mathematical derivation of cardiac output using the modified Stewart-Hamilton equation, detail the physical sources of measurement error, and outline your clinical management to improve oxygen delivery.
• SCENARIO 4: During a major open abdominal aortic aneurysm repair under general anaesthesia and mechanical ventilation (tidal volume 8 mL/kg, PEEP 5 cmH₂O), the arterial pulse contour analysis monitor indicates a Pulse Pressure Variation (PPV) of 18% and Stroke Volume Variation (SVV) of 16%, while the mean arterial pressure is 55 mmHg. Discuss the physiological and physical prerequisites for valid PPV/SVV monitoring, evaluate these findings, and formulate a targeted haemodynamic management plan.
• SCENARIO 5: A 70-year-old male with a history of anterior wall myocardial infarction is undergoing emergency repair of an incarcerated incisional hernia. The operating room ECG monitor shows intermittent runs of wide-complex tachycardia and ST-segment depression in lead II and V5. Explain the electronic filtering modes of clinical ECG monitors (monitor vs. diagnostic mode), the common-mode rejection ratio (CMRR), and your protocol to verify true myocardial ischaemia versus electrical artifact.