Obesity apnoea — FRCA Primary MCQ

Correct answer: B — High oxygen consumption and low FRC shorten safe apnoea time

Obesity reduces FRC and increases oxygen consumption. Hypothermia shifts the oxyhaemoglobin curve left is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Closing capacity exceeding FRC causes airway closure is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Reduced baroreceptor firing increases sympathetic outflow is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Left ventricular coronary perfusion occurs mainly in diastole is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physiology, the correct answer is usually the variable that best explains the observed change in the anaesthetised patient.

Reference: West's Respiratory Physiology; Ganong Review of Medical Physiology; Primary FRCA textbooks