A Simple Method for the Determination of Vital Capacity—Time Relationships

¹ Clinical Professor of Medicine, Tufts College Medical School, and Director, Department of Inhalational Therapy, Boston City Hospital.
² The Department of Inhalational Therapy, Boston City Hospital, and the Department of Medicine, Tufts College Medical School.
³ Research Fellow in Medicine, Tufts College Medical School, The Department of Inhalational Therapy, Boston City Hospital.

A simple ruler-graph device has been described for use with single determinations of the vital capacity on a recording drum apparatus. This permits the rapid determination of the volume of air ejected during each second of the vital capacity tracing on a graphic record. The same record also affords an opportunity for analyzing the contour of the graph for evidence of trapping or change in mid-position.

These time relationships enhance the value of the simple vital capacity determination. The relative efficacies of bronchodilator preparations in relieving the bronchospasm of the patient with bronchial asthma or pulmonary emphysema can be determined readily with this technique.

This method was compared with the vitalometer. Both methods yield comparable values. The ruler-graph method, however, affords additional significant data, easily obtained by employing the apparatus which is generally in use in laboratories studying pulmonary function.