ASSESSMENT OF FORCED EXPIRATORY VOLUME IN 1 2ND-FRACTION OF THE ENGRAFTED LUNG WITH 133-XE RADIOSPIROMETRY IMPROVES THE DIAGNOSIS OF BRONCHIOLITIS OBLITERANS SYNDROME IN SINGLE-LUNG TRANSPLANT RECIPIENTS

Background: Staging of bronchiolitis obliterans syndrome is based on t he decline of forced expiratory volume in 1 second, a measure of overa ll ventilatory capacity. A single staging system is applied to all lun g recipients, regardless of the bias which can be caused by the native lung after single lung transplantation. Methods: We determined the de cline of graft function in single lung recipients by a combination of two methods: 133-Xe radiospirometry and dynamic spirometry. The forced expiratory volume in 1 second fraction of the transplant (FEV(1tx)) w as calculated from the proportion of ventilation of the transplant (V( tx)) and forced expiratory volume in 1 second. Eight single lung recip ients were followed up for a median observation period of 17 months; b ronchiolitis obliterans syndrome developed in four of them. Results: T he fractional decline of forced expiratory volume in 1 second of the t ransplant was significantly greater than the decline of forced expirat ory volume in 1 second (p = 0.016) in all patients during the follow-u p. In the patients with bronchiolitis obliterans syndrome, the mean de cline in forced expiratory volume in 1 second was 1.1 L (39.5%), and i n forced expiratory volume in 1 second of the transplant it was 0.9 L (55.8%). The measurement of forced expiratory volume in 1 second of th e transplant suggested stage 2a and 3a dysfunction in two grafts in wh ich the assessment of forced expiratory volume in 1 second indicated s tage 1a bronchiolitis obliterans syndrome. In one patient, decrease of forced expiratory volume in 1 second of the transplant was suggestive of chronic dysfunction 4 months before it was diagnosed by biopsy and declined lung function. Conclusions: The assessment of forced expirat ory volume in 1 second seems to underestimate the severity of chronic dysfunction in single lung grafts. Instead, the determination of force d expiratory volume in 1 second of the transplant with radioactive tra cers provides selective information of the graft function, which could be used for clinical evaluation of bronchiolitis obliterans syndrome in single lung recipients.