P2-52. Respiratory impairment with preserved diaphragmatic function in ALS

Diaphragmatic compound muscle action potential (DCMAP) has been reported to be a potential indicator of respiratory impairment in amyotrophic lateral sclerosis (ALS). However, we occasionally encounter ALS patients lacking a correlation between DCMAPs and the other biomarkers of respiratory function such as forced vital capacity (%FVC) and sniff nasal-inspiratory pressure (SNIP). We longitudinally studied ALS patients to elucidate a relationship between respiratory biomarkers including DCMAPs and clinical characteristics. We enrolled 42 ALS patients from October 2006 to December 2011. The patients were classified into three groups according to the timing of initiation of respiratory support such as non-invasive ventilation or tracheostomy. In eleven patients (group A), the respiratory support was initiated when DCMAP amplitude remained more than 0.2 mV. The other 11 patients (group B) received the respiratory support when DCMAP amplitude was lower than 0.2 mV. The other 20 patients (group C) received no respiratory support during the observation periods. There were no significant differences of the onset age, disease duration, ALSFRS, %FVC and SNIP between the groups A and B. Our findings indicate that DCMAP may not accurately indicate hypoventilation in some ALS cases. We should note the respiratory impairment with preserved diaphragmatic functions in ALS.