The effect of matching donor and lung transplant (LTx) recipient lung volumes on LTx outcomes is unknown. The Forced Oscillation Technique (FOT) is a simple measure of the mechanical properties of the respiratory system. We have recently developed novel measures of airway closure using FOT. This study aims to assess the effect of matching donor and recipient lung volumes on respiratory system mechanics using FOT.
A multi-centre (Alfred Hospital, Melbourne and St Vincent's Hospital, Sydney) prospective study of (n=19) subjects (63% male, age 56 ±13yrs) at one time point 3-6 months post bilateral LTx were divided into two groups: G1 - Recipient measured pre-LTx total lung capacity (rTLC) < predicted donor TLC (dTLC) n=9; G2 - rTLC > predicted dTLC, n=10. All subjects underwent pulmonary function testing including, spirometry, plethysmography and FOT (Tremoflo 2000, Thorasys, Canada).
In G1, respiratory system elastance (stiffness=AX5) positively correlated with difference between dTLC and rTLC (p<0.01, r2=0.45) in non-obstructed subjects (Figure 1A); i.e. implanting oversized lungs increases respiratory system stiffness. In G2, airway closure occurred at a higher lung volume as size mismatching increased (p<0.01, r2=0.37); i.e. implanting undersized lungs can increase airway closure (Figure 1B).
Novel measurements of respiratory mechanics from FOT demonstrate both oversizing and under-sizing donor TLC can alter recipient respiratory mechanics post-LTx. Longitudinal studies are underway to correlate these effects with the incidence and extent of baseline or chronic lung allograft dysfunction (BLAD & CLAD).