This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Complications of anaesthesia, Subject name: Anaesthesia
[{'content': 'The physiological dead space is decreased by \nSelect and explain. \nA. Upright position, B. positive pressure ventilation, C. Neck flexion, D. Emphysema', 'role': 'user'}, {'content': "Answer: C \nExplanation: Dead space is defined as the volume of the airway that doesnot paicipate in gas exchange (It is nothing but ventilation occurs but perfusion doesnot occur) Anatomical Dead Space : from nasopharynx to respiratory bronchioles.average adult,normally 150ml Alveolar dead space : Alveoli that are ventilated but not perfused.usually it is absent Physiological or total dead space : Anatomical + Alveolar dead space Factors that increase dead space : upright position neck extension advanced age positive pressure ventilation decreased pulmonary perfusion (pulmonary emboli or pulmonary hypeension) lung diseases (emphysema or cystic fibrosis ) FACTORS THAT DECREASE DEAD SPACE : supine position , neck flexion , intubation Anatomical dead space is measured by single breath nitrogen test , physiological dead space is measured by modified bohr's equation.", 'role': 'assistant'}]