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 airflow during the FVC maneuver in seven healthy subjects and eight patients with asthma. The purpose of the study was to determine whether the effects 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 bronchodilator in the patients with asthma; and whether were was a relationship between the lung elastic recoil pressure and the expiratory flow achieved 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 FEV1. The effects of inspiratory speed and breath holding in the patients with asthma were not significantly different from those observed in the healthy subjects. There was a significant relationship between lung 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 greater in asthmatic subjects, which is consistent with an increase in viscoelastic 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 peak flow measurements, and indicate the importance of standardization of the preceding inspiration when determining FEV1 and PEFR.