Measurement of maximum inspiratory pressure during routine spirometry.

Abstract

Maximum inspiratory airway pressure (PI max) was measured as part of routine spirometry in a series of 236 subjects. With men and women considered separately, PI max was tested for correlation with age and height, FEV1, FIV1 and vital capacity. The best linear correlation was with FIV1. Prediction formulas for the lower limit are as follows. For men: PI max (cm H2O) = −10 + .021 FIV1 (ml). For women: PI max = − 6 + .019 FIV1. Appropriate formulas are also presented using FEV1 and vital capacity. Values for PI max below these predicted values can be considered reduced out of proportion to the ventilatory defect with approximately 95% confidence. Measurement of PI max may add useful information to the spirogram, but low values are not specific and must be interpreted in the clinical context.