【.】評論

(A)正確，Both ventilation and blood flow per unit volume decrease from the bottom to the top of the upright lung. However, the changes for blood flow are more marked than those for ventilation. As a consequence, the ventilation-perfusion ratio increases from low values at the base to high values at the apex of the normal upright lung在肺部的頂部區域（肺尖部），通氣/血流比（V/Q）通常是最高的。這是因為在肺尖部，血流量相對較低，而通氣量則相對較高。在這些區域，氧氣的分佈和氧氣與血液的接觸面積較小，因此在肺尖部的V/Q值較高。這種現象也被稱為重力引起的V/Q不匹配。(B) 錯誤？The normal value for physiologic shunt as a ratio of total blood flow is less than 0.05.這個選項可能需要進一步的解釋和澄清。生理性分流（physiologic shunt）通常用百分比表示。在正常情況下，生理性分流的值約為2-5%，這意味著大約有2-5%的血流沒有經過有效的氣體交換就回到了心臟。所以，正常的生理性分流應該是小於5%，而不是0.5。選項(B)可能想表達的是小於5%而非0.5。(C) 正確，In a person with emphysema-type COPD, the ventilation distribution is bimodal, with large amounts of ventilation to lung units with extremely high ventilation-perfusion ratios (alveolar dead space). (Figure 10.21)REF: Murray, 7th edition, Ch 10 Ventilation, Blood Flow, and Gas Exchange, p.135-139(D) 錯誤，Beta-2 agonist can produce mild hypoxemia by causing V/Q mismatch. The worsening V/Q ratio is due to increase perfusion of poorly ventilated areas due to salbutamol-induced release of hypoxic pulmonary vasoconstriction. Moreover, diversion of perfusion from adjacent well-ventilated areas creates new areas with low V/Q ratio.Sarkar M et al. Mechanisms of hypoxemia. Lung India. 2017 Jan-Feb;34(1):47-60.Ballester E et al. Ventilation-perfusion mismatching in acute severe asthma: Effects of salbutamol and 100% oxygen. Thorax. 1989;44:258–67.這個選項是錯誤的。在哮喘患者中，使用β受体激动剂（例如舒喘通气剂）後，其通常會導致支氣管平滑肌的緩解和擴張，從而增加氣道通氣。因此，V/Q（通氣/血流比例）在治療後的五分鐘內應該是先低後高，而不是先高後低。