Anaes SAQs · Measurement & monitoring physics
Oxygen measurement — pulse oximetry, the Clark electrode and the oxyhaemoglobin curve
Primary physics — the Beer-Lambert law at 660 nm and 940 nm with the AC/DC pulsatile separation; the dyshaemoglobin (carboxy- and methaemoglobin), dye and poor-perfusion errors; the Clark electrode (membrane, platinum cathode, current proportional to PO2, oxygen-consuming); and the sigmoid oxyhaemoglobin curve with its P50 of 3.5 kPa (26.8 mmHg) and its left and right shifts.
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Prompt
Outline the principles of oxygen measurement in anaesthesia. Describe how a pulse oximeter works (the Beer-Lambert law, the two wavelengths and the pulsatile-flow detection), the principal sources of error, the Clark polarographic electrode for PaO2, and the oxyhaemoglobin dissociation curve including the P50.
Question
Outline the principles of oxygen measurement in anaesthesia. Describe how a pulse oximeter works (the Beer-Lambert law, the two wavelengths and the pulsatile-flow detection), the principal sources of error, the Clark polarographic electrode for PaO2, and the oxyhaemoglobin dissociation curve including the P50.
References4ShowHide
- [1]Moon K, et al. Pulse oximetry: a perioperative perspective. Diagnostics (Basel), 2026.PMID 42351472
- [3]Atuar B, et al. Reduce hypoxemia overestimation in pulse oximetry based on iso-pathlength: a Monte Carlo study. Opt Lett, 2026.PMID 42066129
- [5]Severinghaus JW. Simple, accurate equations for human blood O2 dissociation computations. J Appl Physiol Respir Environ Exerc Physiol, 1979.PMID 35496
- [7]Shi Y, et al. Diffusion correction of Beer-Lambert law in visible light optical coherence tomography for retinal vessels. Med Biol Eng Comput, 2026.PMID 42008039