The doc recommended going no higher than 60% of the maximum volume.

医生建议声音最高不要超过人体可接受声级的60%。

What is the maximum volume on this device?

此设备的最大音量是多少？

Conversely, for air going in, the TLC, or total lung capacity, which is the maximum volume of air that can be taken in or inspired into the lungs, is actually often often higher because of the air trapping.

相反的，吸气时，TLC，也就是肺总量，即吸气时可以被吸入肺中的所有气体量，由于气体残留就会升高。