The calcium sensitizer levosimendan improves human diaphragm function

Rationale: Acquired diaphragm muscle weakness is a key feature in several chronic conditions, including chronic obstructive pulmonary disease, congestive heart failure, and difficult weaning frommechanical ventilation. No drugs are available to improve respiratorymuscle function in these patients. Recently, we have shown that the calcium sensitizer levosimendan enhances the force-generating capacity of isolated diaphragmfibers. Objectives: To investigate the effects of the calcium sensitizer levosimendan on in vivo human diaphragm function. Methods: In a double-blind, randomized, crossover design, 30 healthy subjects performed two identical inspiratory loading tasks. After the first loading task, subjects received levosimendan (40 μg/kg bolus followed by 0.1/0.2μg/kg/mincontinuous infusion) or placebo.Transdiaphragmatic pressure, diaphragm electrical activity, and their relationship (neuromechanical efficiency) were measured during loading. Magnetic phrenic nerve stimulation was performed before the first loading task and after bolus administration to assess twitch contractility. Center frequency of diaphragmelectrical activitywas evaluated to study the effects of levosimendan onmuscle fiber conduction velocity. Measurements and Main Results: The placebo group showed a 9%(P=0.01) loss of twitch contractility after loaded breathing, whereas no loss in contractility was observed in the levosimendan group. Neuromechanical efficiency of the diaphragm during loading improved by 21% (P < 0.05) in the levosimendan group. Baseline center frequency of diaphragmelectrical activity was reduced after levosimendan administration (P < 0.05). Conclusions: The calcium sensitizer levosimendan improves neuromechanical efficiency and contractile function of the human diaphragm. Our findings suggest a new therapeutic approachto improve respiratory muscle function in patients with respiratory failure