Carbon monoxide
diffusion capacity (DLCO) increased with increasing obesity
and reversed with weight loss due to an increase in pulmonary
blood volume. Also, DLCO is directly related to the lung volume
at which it is measured and any tendency toward reduced
lung volumes with obesity will decrease DLCO. A low to normal
DLCO in obesity may represent a loss of pulmonary capillary
bed (as seen with atelectasis), especially at high BMIs
[20].