Non-invasive measurement of abnormal ventilatory mechanics in Amyotrophic Lateral Sclerosis.

Introduction: In this study we investigated non-invasive, effort-independent measurement of ventilatory mechanics in patients with amyotrophic lateral sclerosis (ALS). Methods: Ventilatory mechanics were measured by optoelectronic plethysmography (OEP) in ALS patients and matched controls. Analysis determined whether OEP measurements correlated with standard clinical measures. Results: ALS patients (N = 18) had lower forced vital capacity percent predicted (55.2 +/- 22.0 L) compared with controls (N = 15; 104.7 +/- 16.2 L) and higher ventilatory inefficiency (49.2 +/- 9.0 vs. 40.0 +/- 3.5, respectively; P < 0.001 for both measures). Lower tidal volumes within the diaphragm area correlated with the dyspnea subscore calculated from the ALS Functional Rating Scale-revised (P = 0.031), and paradoxical movement of the ribcage compared with the abdominal compartment was seen in the most severe cases. Conclusions: Evaluation of ventilatory mechanics in mild to severe ALS reveals dysfunction that is not readily detected by standard testing and ALS functional severity assessment measures.