I want someone to inform me about transpulmonary pressure, and significance of it.

I really don't understand it.

can't anyone inform me about my question,please?

When you googled "transpulmonary pressure" and read the first few search results, what did you gather from them, and what left you confused?

what is confusing me is :

how compliance of the lung is measured as

unit change in lung volume per unit change in transpulmonary pressure.

and so , why we didn't use intrapleural pressure or the change in pulmonary pressure

I don't know, but have you read about pulmonary compliance in Wikipedia.