The investigators will determine if administration of HMB (hydroxymethylbutyrate) or EPA
(eicosapentaenoic acid) will increase diaphragm and limb muscle strength for patients on
breathing machines in an intensive care unit. The investigators will first measure the
strength of the diaphragm and a limb muscle (the quadriceps)using magnetic stimulators to
activate these muscles. Muscle size will be measured by using an ultrasound to measure
diaphragm thickness and quadriceps thickness. The investigators will also perform a vastus
lateralis muscle biopsy. Patients will then be randomized to receive either placebo (saline
30 ml every 12 hours via the GI tract, EPA (1000 mg given every 12 hours via the GI tract),
HMB (1500 mg given every 12 hours via the GI tract), or the combination of EPA (1000 mg given
every 12 hours via the GI tract) and HMB (1500 mg given every 12 hours via the GI tract).
Drugs will be given for 10 days; at the end of this time (on day 11), strength measurements,
ultrasound muscle size measurements, and the vastus lateralis biopsy will be repeated. On day
21 an additional followup set of diaphragm and quadriceps strength and size measurements will
be made (the biopsy will not be repeated for this last set of measurements). Patients will be
followed clinically and patient outcomes (mortality, duration of mechanical ventilation after
study entry) will be recorded.