PERCEPTION OF LUNG VOLUME IN NORMAL HUMAN SUBJECTS.

Abstract

Ability to duplicate an inspired volume level was studied in five healthy males using the psychophysical method of reproduction. Three conditions were evaluated in order to investigate the perceptual cues used for obtaining a specific inspired volume. Conditions were designed to progressively remove cues that might affect the subject's ability to duplicate an inspired lung volume. In each, the subject performed a standard inspiration, spanning from end expiratory position to 35% of inspiratory capacity. Conditions were varied as follows: (1) subjects were instructed to perform both the standard and test (reproduction) inspirations at the same flow rate and beginning at the same lung volume, (2) subjects were instructed to make the flow rate of the test inspiration faster or slower from standard inspiration, and (3) subjects were instructed to begin the test inspiration at a different lung volume than the standard inspirations. The group mean error for all conditions combined for the first day on which each condition was performed was 173 ml, compared to a mean error of 133 ml. Reduction in errors for all conditions from the first to the second day of performance indicates a practice effect. There was no significant difference in errors between conditions. These results indicate the final lung volume, which remained constant for all three conditions, is important for accurate duplication of inspired volume. This finding for learned respiratory movements is comparable to that found by other researchers for skilled limb movements.