<prompt> Answer this question truthfullyWhat happens to the VQ ratio if there is a blood flow obstruction?  <response>: <reason> If there is a blood flow obstruction, the VQ ratio becomes infinite dead space. The VQ ratio is the ratio of alveolar ventilation V to pulmonary blood flow Q and is used to assess gas exchange in the lungs. In cases of blood flow obstruction, such as a pulmonary embolism, there is a decrease in blood flow to the affected area of the lung. This causes the VQ ratio to become imbalanced, with ventilation continuing in the affected area but blood flow being reduced or absent. As a result, the VQ ratio becomes infinite or approaches infinity in the affected area, leading to dead space ventilation. This can lead to hypoxemia and other respiratory complications. 