Lung size mismatch and primary graft dysfunction after bilateral lung transplantation

Abstract

Background: Donor-to-recipient lung size matching at lung transplantation (LTx) can be estimated by the predicted total lung capacity (pTLC) ratio (donor pTLC/recipient pTLC). We aimed to determine whether the pTLC ratio is associated with the risk of primary graft dysfunction (PGD) after bilateral LTx (BLT).

Methods: We calculated the pTLC ratio for 812 adult BLTs from the Lung Transplant Outcomes Group between March 2002 to December 2010. Patients were stratified by pTLC ratio >1.0 ("oversized") and pTLC ratio ≤1.0 ("undersized"). PGD was defined as any ISHLT Grade 3 PGD (PGD3) within 72 hours of reperfusion. We analyzed the association between risk factors and PGD using multivariable conditional logistic regression. As transplant diagnoses can influence the size-matching decisions and also modulate the risk for PGD, we performed pre-specified analyses by assessing the impact of lung size mismatch within diagnostic categories.

Results: In univariate analyses oversizing was associated with a 39% lower odds of PGD3 (OR 0.61, 95% CI, 0.45-0.85, p = 0.003). In a multivariate model accounting for center-effects and known PGD risks, oversizing remained independently associated with a decreased odds of PGD3 (OR 0.58, 95% CI 0.38 to 0.88, p = 0.01). The risk-adjusted point estimate was similar for the non-COPD diagnosis groups (OR 0.52, 95% CI 0.32 to 0.86, p = 0.01); however, there was no detected association within the COPD group (OR 0.72, 95% CI 0.29 to 1.78, p = 0.5).

Conclusion: Oversized allografts are associated with a decreased risk of PGD3 after BLT; this effect appears most apparent in non-COPD patients.

Keywords: lung size mismatch; lung transplantation; mechanical ventilation; primary graft dysfunction; tidal volume.

Figure 1

Lung size mismatch (pTLCratio) is associated with the probability of PGD3. The relationship of pTLCratio (pTLCdonor / pTLCrecipeint) and predicted probability of any grade PGD3 within 72 hours is shown using a fractional polynomial fit with 95% CIs (gray area). A) Unadjusted analysis. The dashed line represents the occurrence of PGD3 in all bilateral lung transplant patients (31%). B) Multivariate adjusted analysis (as described in table 2 as multivariate model 1)

Figure 2

Lung size mismatch (pTLCratio) is associated with the probability of PGD3 in Non-COPD subjects, but not COPD. Unadjusted relationship via fractional polynomial regression (95% confidence intervals [CI] as gray area) of the pTLC-ratio (pTLCdonor / pTLCrecipeint) and the predicted probability of any grade PGD3 within 72 hours analyzed within individual diagnoses. A) Subjects with Non- Chronic obstructive pulmonary disease (COPD), B) Subjects with COPD.

Figure 3

Lung size mismatch (pTLCratio) is associated with the mechanical ventilation tidal volumes (TV) at reperfusion, when the TV is related to the size of the allograft. Fractional polynomial regression of the TV in ml/kg donor-predicted body weight (PBW) plotted against the pTLCratio (pTLCdonor / pTLCrecipeint). The solid vertical bars represent the mean values of the TV in ml/kg donor-PBW according to pTLCratio-quintiles.