Is lung capacity at 53% dangerous?

Need to find out why: During a pulmonary function test, there are typically three measurements taken. First, how well the air "moves" in and out of the lungs. Copd, asthma, bronchitis, etc are things that would cause it to drop. Second, the efficiency of oxygen transfer is measured, the diffusion. Last, the lung sizes are measured. Again, which value is down and why its down is the most important thing to find.