Predicted versus observed FEV1 in the immediate postoperative period after pulmonary lobectomy

Abstract

OBJECTIVE: Scanty information can be found regarding ppoFEV1% correlation with true FEV1% in the immediate days after surgery, when most cardio-respiratory complications are developed. This prospective multicentric investigation aims to describe the evolution of FEV1 in a series of uneventful lobectomy cases before hospital discharge, and to identify factors associated with the variation of postoperative residual FEV1, with the ratio between the actual and the predicted postoperative FEV1 measured during the first 6 postoperative days. METHODS: One hundred and sixty-one patients submitted to lobectomy were prospectively enrolled in the study. Patients with chest wall resections and postoperative complications were excluded. Data from a total of 125 patients were thus used for the analysis. The following clinical variables were recorded: age, preoperative FEV1, ppoFEV1, presence of chronic obstructive pulmonary disease (COPD), surgical approach (VATS or muscle-sparing thoracotomy), side (right or left) and site (upper or lower) of resection, type of analgesia (epidural or intravenous), and daily visual analogue pain score (VAS). FEV1 was measured in every patient at hospital admission and daily until discharge or up to postoperative day 6. Random effects time-series cross-sectional regression analyses were performed to identify factors associated with variation of postoperative residual function (100-(preoperative FEV1-postoperative FEV1/preoperative FEV1 x 100)), and of FEV1 ratio ((actual postoperative FEV1 x 100)/ppoFEV1). For these analyses, the dependent variables (postoperative residual function and FEV1 ratio) and the pain score were analysed as panel longitudinal data. The regression analyses were subsequently validated by bootstrap procedure. RESULTS: FEV1% was lower at first postoperative day and increased gradually up to day 6 but mean values never reached ppoFEV1%. Pain scores decreased from day 1 to day 6. Preoperative FEV1 (p<0.0001) and postoperative pain score (p<0.0001) resulted independently and reliably inversely associated with postoperative residual FEV1 (model R2, 0.16). Preoperative FEV1 (p=0.001), postoperative pain score (p<0.0001), and epidural analgesia (p=0.04) resulted independently and reliably associated with postoperative FEV1 ratio (model R2, 0.13). CONCLUSION: Current methods of prediction of postoperative FEV1 greatly underestimated the real functional loss in the immediate postoperative period. Therefore, for the purpose of a more accurate risk stratification we need to correct the traditional prediction of postoperative FEV1.