This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'All of the following features are characteristic of ARDS except \nSelect and explain. \nA. Hypercapnia, B. Right to left shunt, C. Stiff lungs, D. Lack of response to conventional oxygen therapy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ARDS is a clinical syndrome characterised by severe dyspnea of rapid onset, hypoxemia and diffuse pulmonary infiltrates leading to respiratory failure. It is characterised by type 1 respiratory failure with hypoxemia but normocapnia. Patients meeting clinical criteria for ARDS frequently become fatigue from increased work of breathing and progressive hypoxia requiring mechanical ventilation for suppo. The ideal tidal volume for mechanical ventilation in ARDS patient is 4-6ml/ kg body weight. The impact of hypercapnia in ARDS. The impact of hypercapnia has not been clearly elucidated and is still controversial given its disparate effects (7,8). Neveheless, it has come to be seen as a major factor in ARDS . source :ref Davidson edition23rd pg 199-200', 'role': 'assistant'}]