Combined diffusing capacity for nitric oxide and carbon monoxide as predictor of bronchiolitis obliterans syndrome following lung transplantation

Acute Rejection and Chronic Lung Allograft Dysfunction: Obstructive and Restrictive Allograft Dysfunction

Lung transplantation is an established treatment of well-selected patients with end-stage respiratory diseases. However, lung transplant recipients have the highest rates of acute and chronic rejection among transplanted solid organs. Owing to ongoing alloimmune recognition and associated immune-driven airway/vascular remodeling, precipitated by multifactorial, endogenous or exogenous, post-transplant injuries to the bronchovascular axis of the secondary pulmonary lobule, most lung transplant recipients will suffer from a pathophysiological decline of their allograft, either functionally and/or structurally. This review discusses current knowledge, barriers, and gaps in acute cellular rejection and chronic lung allograft dysfunction-the greatest impediment to long-term post-transplant survival.

Diffusing Capacity for Carbon Monoxide (DLCO): Association with long-term outcomes after Lung Transplantation in a 20-year longitudinal study

RATIONALE

The diffusing capacity for carbon monoxide corrected for haemoglobin (DLCO_cor), measures gas movement across the alveolar-capillary interface. We hypothesised that DLCO_cor is a sensitive measure of injurious allograft processes disrupting this interface.

OBJECTIVES

To determine the prognostic significance of the DLCO_cor trajectory on chronic lung allograft dysfunction (CLAD) and survival.

METHODS

A retrospective analysis was conducted of all bilateral lung transplant recipients at a single centre, between Jan-1998 and Jan-2018, with ≥1 DLCO_cor measurements. Low baseline DLCO_cor was defined as the failure to achieve a DLCO_cor >75% predicted. Drops in DLCO_cor were defined as >15% below recent baseline.

RESULTS

1259/1492 lung transplant recipients were included. The median time to peak DLCO_cor was 354 (range 181-737) days and the mean %-predicted DLCO_cor was 80.2% (sd 21.2). Multivariable analysis demonstrated that low baseline DLCO_cor was significantly associated with death (HR 1.68, 95% CI 1.27-2.20, p<0.001). Low baseline DLCO_cor was not independently associated with CLAD after adjustment for low baseline FEV₁ or FVC. Any DLCO_cor declines ≥15% were significantly associated with death, independent of concurrent spirometric decline. Lower %-predicted DLCO_cor values at CLAD onset were associated with shorter post-CLAD survival (HR 0.75 per 10%-unit change, p<0.01).

CONCLUSION

Low baseline DLCO_cor and post-transplant declines in DLCO_cor were significantly associated with survival, independent of spirometric measurements. We propose that DLCO_cor testing may allow identification of a sub-phenotype of baseline and chronic allograft dysfunction not captured by spirometry. There may be benefit in routine monitoring of DLCO_cor after lung transplantation to identify patients at risk of poor outcomes.