This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': 'Dead space is reduced in tracheostomy by \nSelect and explain. \nA. 5-10%, B. 15-20%, C. 20-30%, D. 30 - 50%', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Airflow resistance of the normal upper airway is substantial, constituting up to 80% of total airway resistance during nose breathing and 50% during mouth breathing.Theoretically, tracheostomy tubes should decrease airflow resistance, but in fact, this does not occur because of the smaller radius (inner diameter 7-8 mm) of the tubes. Tracheostomy tubes may reduce dead space by up to 100 mL -150 mL, 30-50% when compared to spontaneous breathing. This occurs because the tubes are small and bypass the glottic and supraglottic spaces.', 'role': 'assistant'}]