Anaes Vivas · Applied cardiovascular & respiratory physiology
Data viva — the oxygen cascade
A Primary data viva — read each step of the oxygen cascade; explain the humidification fall and the alveolar gas equation; state the two levers (FiO2, alveolar ventilation) that raise PAO2.
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Prompt
A staircase diagram shows the partial pressure of oxygen falling from dry inspired air through the trachea, alveolus, arterial blood, capillaries to the mitochondria, with the alveolar gas equation alongside. Give the approximate PO2 at each step, explain why humidification lowers inspired PO2, and state how the anaesthetist raises PAO2.
Stimulus
A staircase diagram shows the partial pressure of oxygen falling from dry inspired air through the trachea, alveolus, arterial blood, capillaries to the mitochondria, with the alveolar gas equation alongside. Give the approximate PO2 at each step, explain why humidification lowers inspired PO2, and state how the anaesthetist raises PAO2.
References3ShowHide
- [1]Heymer J. Alveolar gas equation: a metabolic perspective. Intensive Care Med, 2026.PMID 41661294
- [5]Jung C, et al. Respiratory rate and ventilatory efficiency. Ann Intensive Care, 2026.PMID 42306311
- [42306312]Bersten AD, Soni N (eds) Oh's Intensive Care Manual. 8th edition, Elsevier, 2018.