(please forgive me if this is a stupid question, as I have very little medical knowledge)
I've been found to have an unusally low vital capacity (about 65% of the predicted value) so I'm up for a series of tests. Naturally I'm worried.
However, it would seem that most methods for calculating the predicted VC take into account the age, gender and height, but not weight. Given that I have a very tall and slim build, it seems natural that I would have a lower VC if weight is not factored in.
What I mean is that most men that are as tall as me also have a wider ribcage. Many weigh as much as 20 kg more than me without being overweight (and that means they also need more oxygen).
So, is chest width meaningfully related to vital capacity? And if so, why isn't it taken into consideration when calculating predicted VC?