Sildenafil: a definitive NO in COPD.

Several studies have shown that chronic obstructive pulmonary disease (COPD) patients have a low stroke volume at rest and an impaired stroke volume response during exercise [1, 2]. As a consequence, oxygen delivery to the tissues is impaired. Since oxygen delivery is critical for maintenance and growth of muscles, the systemic effects of COPD might, in part, be attributed to the lowered stroke volume. Therefore, restoring the stroke volume response would not only improve oxygen delivery capacity, but may also have beneficial effects at the muscle level. Improving muscle strength may, in turn, enhance exercise tolerance by reducing negative feedback from lower limb sensory muscle afferents and by reducing ventilatory responses and dyspnoea during exercise [3].