Optical measurement of the change in trunk volume with breathing.

Optical mapping provides three-dimensional information about the size and shape of the trunk. We have used the technique to measure and partition the volume change of the trunk with breathing in upright subjects. In 13 subjects, 12 of whom were normal and one scoliotic, respired volume could be measured with an average error (+/- SEM) of 170 +/- 20 ml. In one of the normal subjects, 24 measurements of respired volume were in error by, on average, 120 +/- 20 ml. In a further eight normal subjects, partitioning of ventilation showed that the anterior trunk contributed 91 +/- 12%, the back 9 +/- 12%, the upper trunk 43 +/- 4%, the lower trunk 57 +/- 4% and the right and left sides 50 +/- 2% each, to a vital capacity expiration. The measurements of respired volume suggest that the technique is sufficiently accurate for clinical purposes, but it offers the added advantage that the information generated can be used to determine the spatial distribution of each breath.