Effects of Instructions on Pulmonary Function Values

This study examined the influence of specific components of standard forced expiratory maneuver instructions on spirometric values. Thirty-six subjects received instructions and practice in performing the forced expiratory maneuver prior to experimental manipulation of instructions. Instructions to begin with a maximal inhalation and then to blow into the spirometer as hard, fast, and long as possible were reiterated prior to every maneuver. During the instruction manipulation period, subjects were additionally instructed to blow either harder, faster, or longer. Overall, instructions to blow harder resulted in the most stable pattern of increase in all measures (IC, FVC, FEV1, FEF25-75%, and FEV1/FVC); instructions to blow longer consistently led to decreases in some values.