好几个地方没看明白

Effect of Reduced Ventilation/Perfusion Ratio

Absorption collapse may still occur in the absence of total airway obstruction, provided the ventilation/perfusion (V . /Q . ) ratio is sufficiently low. Older subjects, as well as those with a pathological increase in scatter of V . /Q . ratios, may have substantial perfusion of areas of lung, with V . /Q .ratios in the range of 0.01 to 0.1. This shows as a characteristic ‘shelf ’ in the plot of perfusion against V . /Q . (Fig. 30.2).These grossly hypoventilated areas are liable to collapse if the patient breathes oxygen (Fig. 30.2, B). If the V . /Q . ratio is less than 0.05, ventilation even with 100% oxygen can­ not supply the oxygen that is removed (assuming the nor­ mal arterial/mixed venous oxygen content difference of 5 mL.dL21). As the V . /Q . ratio decreases below 0.05, so the critical inspired oxygen concentration necessary for collapse also decreases (Fig. 30.2, C). The flat part of the curve be­ tween V . /Q . ratios of 0.001 and 0.004 means that small differences in inspired oxygen concentration in the range of 20% to 30% may be very important in determining whether collapse occurs or not. In lung regions with these very low V . /Q . ratios collapse is therefore likely to occur, but still not inevitable—a modelling study suggests that lung recoil is crucial for maintaining airway patency even with apnoeic ventilation of the alveoli.

即使呼吸道不完全阻塞时，只要通气/血流（V/Q）比足够低，仍可发生吸收后肺萎陷。年龄较大的受试者，以及病理性V/Q比失调（译者注：即V/Q比为0~1）的受试者，有大量区域的肺泡V/Q比为0.01~0.1，这在血流为纵坐标、V/Q比为横坐标的图中曲线中显示为一个典型的“shelf”（图30.2）。如果患者吸氧，这些严重通气不足的区域很容易萎陷（图30.2，B）。如果比V/Q＜0.05，即使吸入纯氧也不能补偿被吸收的氧气（假设正常的动脉/混合静脉血含氧量相差5mL·dL-1)。随着V/Q比＜0.05，肺萎陷所需的临界吸入氧浓度也随之降低（图30.2，C）。V/Q比0.001~0.004曲线的平坦部分意味着吸入氧浓度在20%~30%的微小差异对是否会肺萎陷十分重要。因此，在比非常低的肺组织，肺萎陷更易发生，但这种情况也不是不可避免——一项模型研究表明，即使肺泡窒息通气，肺弹性对维持气道开放也是至关重要的。

1.shelf该怎么翻译？

2.为啥说“肺弹性对维持气道开放也是至关重要的”

Inspiration of 100% oxygen causes collapse of alveoli with very low ventilation/perfusion (v Q ) ratios. (A) The minor change in the distribution of blood flow (in relation to v /Q ) when a young subject breathes oxygen. Collapse is minimal, and a shunt of 1 % develops. (B) The changes in an older subject with a ‘shelf of blood flow distributed to alveoli with very low v /Q ratios. Breathing oxygen causes collapse ofthesealveoli, and this is manifested by disappearance of the shelf and development of an intrapulmonary shunt of 10.7%. (C) The inspired oxygen concentration relative to the inspired v /Q ratio that is critical for absorption collapse.

英文注释：Blood flow 血流；1% shunt breathing O2 吸氧时1%的分流；Breathing air呼吸空气；Breathing 100% O2 吸纯氧；Age 22 22岁；10.7% shunt breathing O2 吸氧时10.7%分流；Age 44 44岁；Ventilation/perfusion ratio 通气/血流比 ；Inspired oxygen concentration (%) 吸入氧浓度(%)；Inspired ventilation/perfusion ratio吸氧后的通气/灌注比；Stable 稳固的；Unstable Liable to collapse 不稳固容易萎陷

图30.2 吸入100%纯氧可导致V/Q比过低的肺泡塌陷示意图。（A）当年轻受试者吸入氧气时，在以V/Q比为横坐标的曲线上，血流分布的改变微小。肺萎陷程度最低，出现1%的分流。（B）老年具有“shelf”状血流的患者，吸入氧后，血流分布至V/Q比非常低的肺泡。吸入氧会导致肺泡塌陷，其表现为“shelf ”消失及10.7%的肺内分流。（C）吸入氧浓度为纵坐标、横坐标为对吸氧造成吸收塌陷至关重要的V/Q比

3.B和C的解释，翻译的对吗？

4.“shelf”是不是就是椭圆形的红圈表示的

5.不是太明白，吸氧之后不是“红色的断点线”了吗？不就是V/Q优化了吗，00.1-0.1的部分都消失了，不是改善了V/Q吗?为啥还会吸入氧导致肺泡塌陷及10.7%的肺内分流