Compartmental nutritional status and respiratory muscle function assessment in subjects with neuromuscular diseases

There are few data devoted to the combined assessment of the nutritional and respiratory status of subjects with neuromuscular diseases. The objective was to establish correlations between compartmental nutritional variables and respiratory variables to identify respiratory muscle weakness determinants of patients with amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD). Cross-sectional study with ALS and DMD patients included in an Institutional Registry of Neuromuscular diseases. Nutritional status was assessed through body mass index (BMI), expected weight for zero muscle mass (ZMM%) and creatinine-height index (CHI%). Respiratory indices evaluated were spirometry, maximal static inspiratory and expiratory pressures at the mouth (MIP and MEP), and peak cough flow (PCF). A total of 36 ALS and 34 DMD patients were included. Both groups showed a decrease in the body muscle mass and an excess in body fat (p < 0.001). Only in the ALS group was there a weak uphill relationship between body mass index (BMI) and the respiratory variables. In both groups, the ZMM% index did not correlate with any respiratory variable. The CHI% showed the strongest (r > 0.700) positive linear relationship with FVC%, MIP%, MEP%, and PCF% in both ALS and DMD patients (p < 0.001).In this study our patients, BMI did not accurately reflect body composition and underestimated excess fat. This study puts into perspective the relevance of compartmental evaluation to assess respiratory muscle function and establishes that body muscle mass is the most relevant nutritional parameter in relation to respiratory muscle strength.