GasGasGas - The FRCA Primary Exam Podcast VivaCast 006 - Physiology Station - Oxygen - Sensing - Valsalva
Feb 4, 2025
Discover the fascinating journey of oxygen from the alveoli to the mitochondria, unraveling key concepts like the shunt and hypoxic pulmonary vasoconstriction. Explore the complexities of the Valsalva manoeuvre as it challenges the body's responses. Dive into the physiological details of alveolar gas equations and how various factors affect oxygen levels. Learn about carotid body sensing and the implications of autonomic neuropathy on reflex responses. It's a captivating blend of physiology and practical exam techniques!
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What Determines Alveolar Oxygen
- Alveolar oxygen depends on inspired fraction, humidification, and mixing with exhaled gas in the airways.
- The alveolar gas equation unifies these factors to calculate PAO2 from FiO2 and PaCO2.
Write The Alveolar Gas Equation Fast
- Memorise and write the alveolar gas equation quickly in vivas to save time and avoid verbal errors.
- Use writing as a visual shortcut so the examiner can rapidly confirm your answer.
Mitochondrial Oxygen Is Much Lower
- PaO2 approximates alveolar O2 but mitochondrial PO2 is far lower due to diffusion across tissues.
- Tom cited mitochondrial PO2 ~1.4 kPa versus ~21 kPa in air as an order-of-magnitude difference.