Understanding Pulmonary Function Test (PFT) Results: Restricted Lung Function

Question
Hello. I recently had a pft done to determine if my respiratory system is affected by a neuromuscular disease that I have. I'm wondering if you can tell me what the results might mean.

The report states:
"Spirometry shows a normal forced vital capacity and a normal timed vital capacity. The total ventilation is reduced to 61% of predicted. The inspiratory flow volume loop is somewhat distorted. Consistent with restricted ventilatory impairment with reduction of total ventilation to 61% of predicted. The distorted inspiratory flow volume loop suggests an upper airway obstruction. The results should be interpreted in light of the clinical findings. The requesting diagnosis of mitochondrial myopathy is consistent with ventilatory derangement."

I really have no idea what restricted ventilatory impairment or ventilatory derangement means. I'm hoping you can better explain this to me.

Thanks in advance.

Answer
Hi Hanna,
What this is saying is that the lungs are restricted by your disease allowing only 60% of air exchange from the norm expected. It would be consistent with the neuromuscular disease that doesn't allow the lungs to expand to the normal amount---- that is called a restriction (in movement of the chest cage). You have normal lung capacity but aren't using all of it.