Improving Muscle Function in Nutritionally at Risk, Elderly Patients

The investigators propose to conduct a randomized, control trial of β-hydroxy-β-methylbutyrate (HMB) supplementation in elderly patients (≥65 years of age) with acute respiratory failure, who are identified at high risk for malnutrition by ICU-specific nutritional risk scores. Patients will receive either 3g of HMB daily, or control, daily until day 28 following randomization (even if discharged).The investigators will measure functional outcomes using standard, validated measures prior and after discharge.