The effect of obesity on respiratory mechanics and physiology is well recognized. However, the accurate assessment of diffusion across the membrane is a debated issue in overweight adults. Studies have shown conflicting data whether to use DLCO or DLCO/VA for an accurate measure in order to assess the gas transfer in such patient population. We have conducted a retrospective analysis on overweight adults to correlate Body Mass Index (BMI) with the Diffusion Capacity (DLCO) and Diffusion Capacity adjusted for lung volume (DLCO/VA).
In our study we retrospectively reviewed the pulmonary function test data of overweight adults who had a BMI of > 25. Data on FEV1/FVC, TLC, DLCO and DLCO/VA were collected and analyzed by using the SPSS 15.0 software.
A total of 447 patients met the inclusion criteria and the PFT data were analyzed. 77% patients had FEV1/FVC < 80% of predicted and 48% patients had Total Lung Capacity (TLC) of < 80% of predicted. There was no correlation between BMI and DLCO by using Pearson Correlation (correlation coefficient 0.071 with p value 0.66). DLCO/VA correlated poorly with BMI (correlation coefficient 0.243 with p value 0.0). The FEV1/FVC and TLC data did not have any effect in the model.
In our study DLCO did not correlate with BMI in overweight adults. DLCO/VA positively correlated with BMI although the correlation was poor. Further studies need to be conducted in this aspect before reaching a common consensus to consider DLCO/VA to be used for an accurate assessment of diffusion capacity in overweight adults.
DLCO/ VA may be more accurate than DLCO in assessment of gas transfer in overweight adults but further studies need to be conducted to support this statement.
Mehjabin Zahir, No Financial Disclosure Information; No Product/Research Disclosure Information