Diffusion Capacity

[dl587]

I dont understand the rational. My pulmonologist has put me on Symbicort and Spiriva, I thought these meds was for helping to open the airways when diagnosed with a obstructive defect.
I had a pft done in December and the report states are as follows:

The flow volume relationships are qualitatively and quantitatively acceptable. The diffusing capacity when adjusted for alveolar ventilation is only 43% of predicted. The alveolar arterial gradient as calculated by the room air arterial blood gas is 50 mmHg. The total lung capacity of 6.36 is 85% of
predicted with a slightly elevated residual volume. This resulted in reduced forced vital capacity of 2.71. The FEV1, FEV1/FVC, and maximum end-expiratory flow are normal. The maximum voluntary
ventilation is normal. No evidence of a restrictive ventilatory defect. There is mild fixed obstruction with abnormal diffusing capacity. I have tried several inhalors and none apears to be doing any good.
The Pulmonologist did say he wants me to be evaluated for a transplant. Is this the only option for my desat problems? I was hospitalized in Sep/Oct for 5 weeks at time of admission it took 15 ltr of O2 to get my sats to 88%.
Thanks
Dave