Measurement validity of an electronic inspiratory loading device during a loaded breathing task in patients with COPD.

We studied the validity of a recently introduced, handheld, electronic loading device in providing automatically processed information on external inspiratory work, power and breathing pattern during loaded breathing tasks in patients with COPD. Thirty-five patients with moderate to severe COPD performed an endurance breathing task against a fixed resistive inspiratory load that corresponded to 55 ± 13% of their maximal inspiratory pressure. Flow and pressure signals during this task were sampled and processed at 500 Hz by the handheld loading device and at 100 Hz with an external, laboratory system that provided the "gold standard" reference data. Intra Class Correlations between methods were 0.97 for average mean inspiratory power, 0.98 for average mean pressure, 0.98 for average duty cycle, and 0.99 for total work (all p < 0.0001). We conclude that the handheld device provides automatically processed and valid estimates of physical units of energy during loaded breathing tasks. This enables health care providers to quantify the load on inspiratory muscles during these tests in daily clinical practice.