Different effects of lung volume reduction surgery and lobectomy on pulmonary circulation

To clarify the effects of lung volume reduction surgery (LVRS) on cardiopulmonary circulation during exercise in comparison with pulmonary lobectomy for lung cancer.

LVRS improves pulmonary function and dyspnea symptoms acutely in selected patients with heterogeneous emphysema. However, there are few data concerning the effects of LVRS on the cardiopulmonary circulation, especially during exercise.

Pulmonary function tests and pulmonary hemodynamic study at rest and during exercise were performed before and 6 months after LVRS (seven patients) or pulmonary lobectomy (eight patients). In the workload test, an electrically braked bicycle ergometer (25 w) was used in the supine position for at least 2 minutes or until exhaustion or breathlessness developed.

After lung lobectomy, the values of vital capacity, percentage of predicted vital capacity, forced expiratory volume in 1 second, percentage of predicted forced expiratory volume in 1 second, residual volume/total lung capacity, and maximal voluntary ventilation deteriorated significantly. Six months after LVRS, however, vital capacity, percentage vital capacity showed no significant change, and forced expiratory volume in 1 second, percentage of forced expiratory volume in 1 second, diffusing capacity for carbon monoxide, and maximal voluntary ventilation showed marked improvement. Cardiac index was changed neither at rest nor during exercise in either group by the operation. Although postoperative pulmonary arterial pressure in the lobectomy group was significantly increased by the exercise, LVRS did not affect postoperative pulmonary arterial pressure at rest or during exercise. Pulmonary capillary wedge pressure in the lobectomy group showed no significant change after the operation, whereas LVRS ameliorated the marked elevation of pulmonary capillary wedge pressure observed during exercise. After lobectomy, significant increases in the pulmonary vascular resistance index were observed at rest and during exercise. LVRS markedly increased the pulmonary vascular resistance index at rest but not during exercise. In the lobectomy group, the postoperative flow-pressure curve moved upward, and its gradient became steeper than the preoperative one. In the LVRS group, the curve moved upward in a parallel fashion. These results show that much more right-sided heart work is needed to achieve the same cardiac output against higher pulmonary arterial pressure, not only after lobectomy but also LVRS.

The current study demonstrated that the effects of LVRS on the cardiopulmonary circulation were not negligible, especially during exercise, and successful LVRS may depend on improved respiratory function and also preserved cardiac function that can tolerate the damage to the pulmonary vascular bed induced by this operation.