Assisted vital capacity to assess recruitment level in neuromuscular diseases

Respiratory muscle weakness and chest wall abnormalities in neuromuscular diseases (NMD) may lead to decreased pulmonary volumes. We assessed the reversibility of vital capacity (VC) reduction with mechanical In-Exsufflation (MI-E). We evaluated the effects of positive inspiratory and negative expiratory pressures on spirometric variables under passive (without patients' participation) and active (with active participation) application in 47 NMD patients. VC, inspiratory capacity (IC), expiratory reserve volume (ERV) were measured during maneuvers without and with MI-E assistance, delivering inspiratory assistance (+40cmH2O), expiratory assistance (-40cmH2O) and both (±40cmH2O). Passive and active assistance improved significantly VC and IC compared to baseline (P<0.0001 for both). ERV improved only with active assistance which normalized VC in 10, IC in 18 and ERV in 6 patients, mainly in patients with late-onset NMD. MI-E assistance produced greater increases in IC than in ERV, resulting in a VC increase enhanced by patients' active participation. This type of evaluation may help to evaluate the potential reversibility of restrictive ventilatory pattern in NMDs.