Spirometry after transplantation: how much better are two lungs than one?

BACKGROUND: The purpose of this study was to determine how much double lung transplantation improves lung function over single lung transplantation and to identify predictors of lung function after transplantation.
METHODS: From February 1990 to November 2005, 463 adults underwent lung transplantation. Among 379 of these patients (82%), 6372 evaluations of postoperative normalized forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC) were analyzed using longitudinal temporal decomposition methods for repeated continuous measurements. We characterized the time course of postoperative spirometry, compared it between double and single lung transplantation, and identified its modulators.
RESULTS: FEV(1) (% of predicted) was only somewhat better after double than single lung transplantation (65%, 58%, and 59% vs 51%, 43%, and 40% at 1, 3, and 5 years, p = 0.03), as was FVC (% of predicted) (67%, 68%, and 66% vs 62%, 56%, and 51%, p < 0.0001). Both FEV1% and FVC% increased sharply to 1 year. For double lung transplantation, these values persisted, with minimal decline to 5 years; but for single lung transplantation, they continuously declined to 5 years. Values for double lung transplantation remained higher than for single lung transplantation at all time points but never approached twice the value. Patients undergoing double lung transplantation for emphysema had the highest postoperative FEV1% and FVC%, but also the lowest values for single lung transplantation; the benefit of double lung transplantation was between these values for other diagnoses.
CONCLUSIONS: Spirometry weakly favors double lung over single lung transplantation. The advantage of spirometry values alone may not justify double lung transplantation.