The Estimation of Normal Vital Capacity

For controlling a contemplated experimental research on orthopnea we found it necessary to establish some standards for normal vital capacity in healthy persons in both the sitting and the lying position. In the literature many observations were found on the vital capacity under almost every other conceivable experimental condition, but although the statment is frequently made that a normal person can breathe more when sitting erect than when recumbent, we discovered no attempt to estimate the percental differences due to posture. Experimental investigation doubtless began with the work of John Hutchinson, 1 who gives data to show that the vital capacity is smaller in the supine position than in the erect. A few observations were made by us on individuals about the laboratory, and the results were found to vary considerably; that is, some could after a maximum inspiration expire as much lying as sitting, a few could expire more, and