Background: Establishment of baseline values for forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), or total lung capacity (TLC) is required when diagnosing and phenotyping chronic lung allograft dysfunction after lung transplant. It is generally accepted that the baseline (peak) values of these parameters occur simultaneously, but this assumption has not been substantiated for TLC.
Methods: All lung function measurements in all double lung transplant recipients from a single center in the period from 1992-2014 were included. Time to baseline FEV1 was assessed according to standards from the International Society for Heart and Lung Transplantation, and time to peak FVC, TLC, and diffusion capacity for carbon monoxide were evaluated.
Results: A total of 288 double lung transplants surviving more than 3 months after transplant were included. Baseline FEV1 occurred at a median of 0.77 years post transplant and was statistically different from median times to the peak FVC (1.02 years), to peak TLC (1.37 years), and to peak diffusion capacity for carbon monoxide 1.04 years post transplant (all log-rank P < .001). At the time of baseline FEV1, FVC, and TLC were at a mean of 96% and 95% of their peak values, respectively.
Conclusion: The peak lung function is reached at different time points for different parameters post transplant with FEV1 baseline occurring first. For most patients values of FVC and TLC obtained at time for baseline FEV1 is a good estimate of peak values, but in a small percentage of patients this procedure may jeopardize phenotyping of chronic lung allograft dysfunction based solely on lung function parameters.
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