Pulmonary Diffusing Capacity in Normal Children, Ages 4 to 13

CARBON MONOXIDE absorption, the pulmonary diffusing capacity (Dl), and the pulmonary capillary blood volume (Vc) are less in normal adults in the upright than in the supine position.¹,²The ventilation-perfusion relationship of the normal adult lung is different in the upright and the supine position, and the upper regions of the lung are poorly perfused in the upright position. These differences have been related to the existence in the upright position of a pressure gradient and a capillary bedfilling gradient which are dependent upon gravity.³Exercise in the adult results in increases in Dland Vcwhich are greater in magnitude than those found in changing from the upright to the supine position.⁴Very few Dland Vcmeasurements have been reported in children under the age of 13,⁵and the physiological relationships of Dland Vcto