Single lung transplantation for emphysema: predictors for native lung hyperinflation

Single lung transplantation is an established procedure for the treatment of respiratory failure resulting from emphysema. Initial concerns suggested that ventilation/perfusion mismatch may result in an unsatisfactory outcome, but good clinical results proved those concerns to be unfounded. However, a proportion of patients have had development of native lung hyperinflation (NLH), with increased morbidity and mortality rates. This study was undertaken to evaluate the factors that might predict those patients with emphysema who are at greatest risk for development of NLH.

We retrospectively analyzed data from 27 patients who underwent 31 single lung transplantations for emphysema. The patients were divided into two groups: group A, 12 patients with development of acute or chronic NLH, and group B, 15 patients without development of hyperinflation. NLH was defined as radiologic mediastinal shift with flattening of the ipsilateral diaphragm associated with respiratory dysfunction or hemodynamic instability. All preoperative and postoperative data from recipients and data from donors were analyzed.

There were no differences between the two groups regarding age, preoperative partial pressure of oxygen, partial pressure of carbon dioxide, acid-base status, donor lung size and physiological structure, side of transplantation, primary pathologic condition, rejection score, infection episodes and obliterative bronchiolitis in the transplanted lung after operation. Patients with NLH had a significantly higher preoperative mean pulmonary artery pressure of 31.6 mm Hg (confidence interval [CI] 26.7 to 35.7), transpulmonary gradient of 20.5 mm Hg (CI 17.4 to 23.5), a lower mean forced expiratory volume in 1 second of 427 ml (CI 352 to 502), and higher mean residual volume of 4450 ml (CI 3769 to 5132). The duration of ventilation, 168 hours (CI 45 to 290), and the postoperative mean pulmonary artery pressure of 26 mm Hg (CI 23 to 28.7) are significantly higher in the hyperinflation group. Early death in group A (n = 5) was higher than in group B (no deaths) (p = 0.02). Six patients in group A required surgical treatment (two early native lung volume reductions, two early ipsilateral retransplantations, and two late contralateral transplantations). Group A patients tended to have poorer long-term lung function after transplantation, with reduced forced expiratory volume in 1 second, forced vital capacity, and higher residual volume (p = NS).

Patients with end-stage emphysema and relative pulmonary hypertension, severe airway obstruction, and air trapping are at greatest risk for development of early and late NLH. In this subgroup of patients, an alternative treatment strategy may be considered.