All the following are false regarding physiological dead space except
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.
In healthy adults, 20-50ml more than anatomical dead space
Detected by Bohr's method
10-15% of tidal volume
Increased by endotracheal intubation
Respiratory System