Validation of respiratory inductive plethysmography (LifeShirt) in obesity hypoventilation syndrome

Validation of respiratory inductive plethysmography (LifeShirt system) (RIP _LS) for tidal volume (V _T), minute ventilation (VE), and respiratory frequency (f _B) was performed among people with untreated obesity hypoventilation syndrome (OHS) and controls. Measures were obtained simultaneously from RIP _LS and a spirometer during two tests, and compared using Bland Altman analysis. Among 13 OHS participants (162 paired measures), RIP _LS-spirometer agreement was unacceptable for V _T: mean difference (MD) 3mL (1%); limits of agreement (LOA) -216 to 220mL (±36%); VE MD 0.1Lmin ^-1 (2%); LOA -4.1 to 4.3Lmin ^-1 (±36%); and f _B: MD 0.2brmin ^-1 (2%); LOA -4.6 to 5.0brmin ^-1 (±27%). Among 13 controls (197 paired measures), RIP _LS-spirometer agreement was acceptable for f _B: MD -0.1brmin ^-1 (-1%); LOA -1.2 to 1.1brmin ^-1 (±12%), but unacceptable for V _T: MD 5mL (1%); LOA -160 to 169mL (±20%) and VE: MD 0.1Lmin ^-1 (1%); LOA -1.4 to 1.5Lmin ^-1 (±20%). RIP _LS produces valid measures of f _B among controls but not OHS patients, and is not valid for quantifying respiratory volumes among either group.