Gas exchange and pulmonary hemodynamics during lung resection in patients at increased risk - Relationship with preoperative exercise testing

Study objectives: To evaluate the intraoperative evolution of patients with COPD dining lung resection and to test whether exercise testing could be h elpful in the prediction of the intraoperative course. Design: Prospective study. Setting: University teaching hospital. Patients: Forty patients (mean [+/- SD] age, 65 +/- 9 years) with COPD (ie, FEV1, 55 +/- 11% of predicted) and resectable lung neoplasms. Interventions: Preoperatively, pulmonary function testing, quantitative lun g perfusion scanning, and exercise performance testing were administered. I ntraoperatively, pulmonary, hemodymamic, and blood gas measurements were pe rformed at five stages, including periods of two-lung ventilation (TLV) and periods of one-lung ventilation (OLV). Results: During OLV, compared with TLV, the PaO2/fraction of inspired oxyge n (FIO2) ratio decreased from 458 +/- 120 to 248 +/- 131 mm Hg (p < 0.05), whereas pulmonary artery pressure (PAP) increased from 18 +/- 5 to 23 +/- 5 mm Hg (p < 0.05). Cardiac output ((Q) over dott) also increased from 4.0 /- 1.2 to 5.1 +/- 1.9 L/min (p < 0.05), yielding to a higher mixed venous P O2. Both PaO2 and (Q) over dott during OLV were significantly lower in pati ents who had undergone right thoracotomies compared with those who had unde rgone left thoracotomies. The PaO2/FIO2 ratio dining OLV correlated with di e PaO2 during exercise (r = 0.39; p = 0.01) and with the perfusion of the n on-neoplastic lung (r = 0.44; p = 0.005). Conclusions: In COPD patients, OLV leads to a significant derangement of ga s exchange, which is more pronounced in right thoracotomies. Preoperative m easurement of PaO2 during exercise and the distribution of perfusion by lun g scan might be useful to identify those patients who are at the greatest r isk of abnormal gas exchange during lung resections.