Describe the physiological consequences of breathing 100% oxygen at sea level.
The question related to physiological changes occurring when FiO2=1 Many
candidates focused on the toxic effects of oxygen, which were often incorrect (CNS
symptoms will not occur at one atmosphere). Candidates simply lacked knowledge,
those that did have some understanding failed to provide adequate detail (ie. it was
occasionally mentioned oxygen stores are increased but not the mechanism by
which or extent to which stores are increased).
In addition it was expected that candidates would outline and describe the
mechanism behind the changes in PaO2 in arterial and mixed venous blood, shift in
CO2 ventilation, hypoxic pulmonary vasoconstriction as well as pulmonary toxic
Syllabus: B2a, c
Recommended sources: Applied Respiratory Physiology, Nunn, Pages 265 to 268,
288 and 491 to 508