Hi there,
This is Kitt and I am sorry your having respiratory problems.........I am sure this is affecting your anxiety level.
FVC - Forced Vital Capacity - after you have has taken in the deepest possible breath, this is the volume of air which can be forcibly and maximally exhaled out of the lungs until no more can be expired. FVC is usually expressed in units called liters. This PFT value is critically important in the diagnosis of obstructive and restrictive diseases.
If the patient has an obstructive disease, the amount of air in the lungs will not be readily exhaled because of physical obstruction and airway collapse during exhalation (loss of elastic recoil of the lungs). FVC is, therefore, an important PFT value to look at when evaluating the presence of obstructive pathology. In obstructive diseases, the lung's air volume will be more slowly expelled and will be a smaller volume over the time course of the FVC test than would be expected in a normal, healthy individual.
With restrictive lung disease, the FVC will be smaller because the amount of air that can be forcefully inhaled or exhaled from the lungs is smaller to start with because of disease. This may be due to the fact that thoracic cage does not have the ability to expand very much. FVC will therefore be smaller due to mechanical limitations. However, since FVC will be smaller in obstructive disorders and in restrictive disorders FVC alone cannot be used to diagnose obstructive and restrictive disorders all by itself. Reference: Pulmonary Function Testing; Medical Surgical Nursing; Williams and Hopper 2nd Edition
Hope this gives you a bit of info on FVC. Keep working with your physician on determining the cause. Keep posting as we are here to support you.