Anaes SAQs · Measurement & monitoring physics
Pressure and temperature measurement
Primary — strain-gauge transducer (diaphragm + resistance change + Wheatstone bridge); zeroing to atmosphere and levelling to mid-axillary line (1 mmHg per cm hydrostatic error, systematic bias); damping (under-damped overshoot, over-damped lag, fast-flush test); oscillometric NIBP (max oscillation = MAP); thermistor (resistance falls with temperature, negative temp coefficient); thermocouple (Seebeck effect, two dissimilar metals); core sites: oesophageal, nasopharyngeal, PA, bladder; skin lags; perioperative hypothermia consequences.
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Describe how an invasive arterial blood pressure is measured, including the transducer, zeroing and levelling, and damping. Outline the principles of thermistor and thermocouple temperature measurement and give the core-temperature monitoring sites.
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- [1]Bersten AD, Soni N (eds) Oh's Intensive Care Manual. 8th edition, Elsevier, 2018.