Changes in breathing and ventilatory muscle recruitment patterns induced by lung volume reduction surgery

Patients with chronic obstructive pulmonary disease have abnormal breathing and ventilatory muscle recruitment patterns at rest and during exercise, and these alterations may contribute to the limited exercise capacity seen in this disease. Lung volume reduction surgery (LVRS), a recently described treatment for emphysema, is reported to improve exercise performance. We studied the breathing and ventilatory muscle recruitment (VMR) patterns in eight patients with severe chronic obstructive lung disease (median FEV1 = 0.79 L, range 0.46 to 1.13 L) by measuring esophageal and gastric pressure measurements as well as tidal volumes (VT), respiratory rates (f), inspiratory (TI) and expiratory (TE) times, and watts at rest and during maximal exercise, before and 3 mo after lung volume reduction surgery. Maximal exercise capacity increased a median of 49% (median increase 17 watts, range 6 to 44 watts, p < 0.05) and maximal minute ventilation (VEmax) increased by a median of 22% (median increase 6.5 L/min, range 3 to 25 L/min, p < 0.05). At isowatt exercise after surgery, VT increased 0.31 L (range 0.07 to 0.69 L) and f decreased four breaths/min (range +0.5 to -15 breaths/min). Dyspnea scores as measured by a visual analog scale (VAS) decreased significantly at rest and at peak exercise after surgery. End-expiratory esophageal (Pes) and gastric (Pga) pressures at rest and at isowatt exercise decreased. A rightward shift in the slope of the Pes versus Pga plot was also observed suggesting increased use of the diaphragm after surgery. Our data indicate that LVRS improves the mechanics of breathing both at rest and during exercise.