I can't speak to how your dysautonomia affects your lungs, but being significantly overweight can certainly cause similar PFT results with normal dlco and can increase or cause pulmonary vascular engorgement. It can also decrease those numbers when going to a supine position. Best to get it all checked by the pulmo. If weight is the case or partially the case, then ask for a referral to a nutritionist for help with diet rather than trying one of the fads. Especially because of your other disorder. Pulmonary Rehab might also be an option.
Dysautonomia is an unusual condition. It is associated with a change in the functioning of the autonomic nervous system. This can cause a variety of health problems. Please see the responses to your questions below.
1. What do these numbers suggest?
They suggest pure restrictive lung disease. In this instance, this could be on the basis of disease of the nerves that communicate with the lungs. This could also be on the basis of the respiratory muscles responsible for ventilation, also called the "bellows-function of the lungs".
2. If the lungs are "OK". what other specialists should I see to understnad why these values are abnormal?
The evidence of the testing you cite strongly suggests that the lungs are intrinsically normal.
3. Does the fact that my lung volumes are low and yet my diffusing capacity is normal suggest anything?
Yes, it suggests that the lung tissue or parenchyma is normal. With better lung expansion, that is, without the restriction, your diffusing capacity might even be higher on the basis of increased surface area for gas diffusion.
4. Some of the scans noted mild engorgement of the pulmonary vasculature. (Maybe the reason for the normal diffusing.) Does this suggest anything?
The vasculature may be mildly engorged or simply appear to be engorged because of the low lung volumes. If the vasculature is engorged, that might facilitate diffusion. At the same time, the engorged vasculature could be an indicator of reduced autonomic tone of the pulmonary vessels, as a result of the dysautonomia.
I am just curious...this question has been posted for 2 weeks. Others above have been answered. How long does ti take for responses on this site.