This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breathing Systems, Subject name: Anaesthesia
[{'content': 'Tracheostomy reduces dead space by - \nSelect and explain. \nA. By-passing upper airway, B. Increasing V/Q ratio, C. Raising airflow resistance, D. By all of the above mechanisms', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., By-passing upper airway o Important effects of tracheostomy on respiratory physiologya) Tracheostomy decreases dead space as upper air ways and nasal cavity are bypassed.b) Tracheostomy decreases ventilation/perfusion (V/Q) ratio. Increased dead space increases ventilation/perfusion ratio as the dead space (containing air) is ventilated but not perfused for gaseous exchange. Tracheostomy decreases the dead space, therefore it will decrease the V/Q ratio.c) Tracheostomy reduces the airflow resistance", 'role': 'assistant'}]