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: Physiology
All the following are false regarding physiological dead space except 
Select and explain. 
A. In healthy adults, 20-50ml more than anatomical dead space, B. Detected by Bohr's method, C. 10-15% of tidal volume, D. Increased by endotracheal intubation
B: Detected by Bohr's method
Answer: B: Detected by Bohr's method 
Explanation: Ans: b {Detected by Bohr's method) Ref.Gonong 22ndPhysiological dead space is calculated by Bohr's method.In normal healthy adult, physiological dead space = anatomical dead space.Anatomical dead space in a healthy 70kg adult is 150 ml, which is 30% of tidal volume.Total dead space/ physiological dead space = Anatomical dead space + alveolar dead space.Anatomical dead space = The part of the respiratory system that is not available for gas exchange with pulmonary capillary blood. It is 150 ml.Alveolar dead space = Those alveoli that are non functioning and not receiving adequate blood flow.The total dead space can be calculated from the PCO2 of expired air, the PCO2 of arterial blood, and the tidal volume. The tidal volume (VT) times the PCO2 of the expired gas (PECO2) equals the arterial PCO2 (PaCO2) times the difference between the tidal volume and the dead space (VD) plus the PCO2 of inspired air (PICO2) times VD (Bohr's equation):PFCO2 x VT = PaCO2 x (VT - VD) + PICO2 x VDThe term PICO2 x VD is so small that it can be ignored and the equation solved for VD.