such指代什么？

The increased cardiac output (see later discussion) will cause a small reduction in pulmonary capillary transit time, which, together with the reduced mass of haemoglobin in the pulmonary capillaries, causes a modest decrease in diffusing capacity (page 119). However, such is the reserve in the capacity of pulmonary capillary blood to reach equilibrium with the alveolar gas (see Fig. 8.2) that it is highly unlikely that this would have any measurable effect on the alveolar/end-pulmonary capillary Po2 gradient, which in the normal subject is believed to be negligible. Thus pulmonary end-capillary Po2 should also be normal in anaemia.

心排血量增加（见下文讨论）将导致肺血流通过肺毛细血管时间略微缩短，再加上肺毛细血管中血红蛋白的总量减少，使得肺弥散能力轻度降低（第 119 页）。然而，弥散能力只是肺毛细血管血液与肺泡气体达到平衡能力的储备（见图 8.2），其轻度降低不会产生肺泡/肺毛细血管氧分压差的任何可测量的影响，可忽略不计。因此，贫血时肺毛细血管末梢血氧分压也应正常。

such 指diffusing capacity吗？