ANALYSIS OF THE VENTILATORY DEFECT BY TIMED CAPACITY MEASUREMENTS

Abstract

A simplified inexpensive instrument was devised to record both the vital capacity and the max. breathing capacity. The instrument consists briefly of a spirometer on a fast-moving drum and an electronic timer which can be pre-set and which is initiated by the patients'' own breathing efforts. The timer is set as 1 mm., 2 min. and 3 min., since these times show the greatest variation between normal people and patients. The instrument records the total volume of air expired as well as the percentage of this volume expelled in the 1st sec., the 1st 2 sec. and the 1st 3 sec. Expiratory patterns varied very little on repeated occasions. The 35 normal volunteers, as well as having the expected normal vital capacity, were able to expel 83% of this total vital capacity in the 1st sec. of effort, 94% in the 1st 2 sec. and 97% in the 1st 3 sec. The 282 patients selected fell into 2 groups: (I) Those having the restrictive type of pulmonary insuffiency such as seen in pulmonary fibrosis, following thoracoplasty or pneumonectomy. In this group, the total vital capacity was severely reduced, whereas the timed percentages remained essentially normal. (II) Those exhibiting the obstructive type of pulmonary insufficiency such as seen in bronchial asthma, bronchial stenosis, pulmonary emphysema. In these the total vital capacity was not greatly reduced, but the timed percentages were sharply reduced. In 28 patients with bronchial asthma, these percentages were 43, 49, 71, in the 1st, 1st 2, and 1st 3 sec. The same percentages in 40 patients with pulmonary emphysema were 42, 57, 68.