The positional change in vital capacity as a tool to identify diaphragm dysfunction: A qualitative systematic review.

Background: Sitting to supine fall in vital capacity (∆VC) is commonly used to screen for diaphragmatic dysfunction (DD), but the predictive threshold value varies. This systematic review aimed to compare the position-dependent change in vital capacity (VC) in patients with objectively confirmed DD.

Research Question: What is the optimal predictive value of ∆VC to diagnose DD.