In contrast, FRC and RV were less than normal levels
and after weight reduction, there was a significant increase of
FRC but insignificant as regards RV [13]. 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.