THE EFFECT OF INSPIRATORY MANEUVERS ON EXPIRATORY FLOW-RATES IN HEALTH AND ASTHMA - INFLUENCE OF LUNG ELASTIC RECOIL

We studied the effect of breath holding and inspiratory speed on airfl ow during the FVC maneuver in seven healthy subjects and eight patient s with asthma. The purpose of the study was to determine whether the e ffects of inspiratory speed and breath holding on expiratory flow were greater in patients with asthma than in healthy individuals; whether these effects were lessened by inhalation of aerosolized bronchodilato r in the patients with asthma; and whether there was a relationship be tween the lung elastic recoil pressure and the expiratory flow achieve d during four different maneuvers. We found that peak expiratory flow rate (PEFR) was significantly lower after both a slow inspiration and a breath hold than after a fast inspiration without a breath hold. In addition, a breath hold was associated with a significantly lower FEV( 1). The effects of inspiratory speed and breath holding in the patient s with asthma were not significantly different from those observed in the healthy subjects. There was a significant relationship between lun g elastic recoil pressure at the point of onset of the FVC maneuvers ( Pel Blow) and expiratory flow in both healthy and asthmatic subjects. Also, the decrease in Pel Blow with equivalent breath-hold time was gr eater in asthmatic subjects, which is consistent with an increase in v iscoelastic elements in the lung. These findings corroborate previous suggestions that inspiratory speed and the duration of breath holding have significant implications in the performance of spirometry and pea k flow measurements, and indicate the importance of standardization of the preceding inspiration when determining FEV(1) and PEFR.