Transfer factor of the lung for carbon monoxide (TLCO) in morbid obese subjects

Rationale and objectives: The impact of severe obesity on transfer factor of the lung for carbon monoxide (TLCO) remains uncertain. We hypothesized that, in addition to the potential intrinsic effects of obesity on lung function, morbidly obese subjects may require specific TLCO reference values. To this end, TLCO was measured in obese subjects before and after bariatric surgery (BS) and adjustment of the data to reported TLCO reference values was assessed.

Methods: We explored 220 morbidly obese subjects (BMI ≥40 kg/m2) before BS and 129 of them were studied one year after BS. The Lin's concordance coefficient (LCC) (1) was used to assess adjustment between TLCO measurements and the corresponding predicted values derived from different sets of reference equations.

Results: TLCO measurements significantly increased after BS (p
Conclusions: The results indicate that obesity has a significant negative impact on TLCO. Moreover, current reference equations are not adequate for lung function assessment of these subjects. The new TLCO reference equations herein developed may contribute to enhance evaluation of morbidly obese subjects.