Effect of EPA and HMB on Diaphragm and Limb Muscle Strength in Mechanically Ventilated Patients

Objectives. There is a single objective for this study, namely, to determine if early administration of either EPA or HMB can prevent or reverse the development of respiratory muscle weakness in critically ill, mechanically ventilated patients. The investigators plan to randomize patients accepted into this protocol to administration of either a control (saline enteral control solution), EPA administration (enteral EPA), HMB (enteral HMB), or a combination of EPA and HMB. Drugs will be administered for 10 days and measurements of diaphragm and quadriceps strength and size will be performed immediately before (day 0) and immediately after (day 11) the period of drug administration. A third set of measurements (diaphragm and quadriceps strength and size) will be performed on day 21. Vastus lateralis muscle biopsies will also be taken on days 0 and 11; no biopsy will be performed for day 21 assessments. The investigators will also perform a chart review and assess ventilator mechanics (respiratory system static compliance and inspiratory airway resistance) at the time of the initial strength assessment. Patient outcomes (time on mechanical ventilation and mortality) will also be recorded. The investigators would expect that mean diaphragm strength and limb muscle strength measurements will be similar for four groups immediately before initiation of drug administration. The hypothesis will be supported if, post drug administration, diaphragm and limb muscle strength are higher for patients receiving EPA and/or HMB than the control group receiving no active drug.

Study Design.

The basic study design is to:

1. measure magnetic stimulated Pdi twitch and quadriceps strength and size, obtain a muscle biopsy from the vastus lateralis of the quadriceps, determine respiratory system compliance, determine airway resistance, and perform a chart review,
2. randomize patients to treatment with either: control solutions (30 ml of enteral saline solution every 12 hours), EPA (30 ml of enteral solution containing 1000 mg of EPA every 12 hours), HMB (30 ml of enteral solution containing 1500 mg HMB every 12 hours) or both EPA (30 ml of enteral solution containing 1000 mg of EPA every 12 hours) and HMB (30 ml of enteral solution containing 1500 mg HMB every 12 hours).
3. continue drugs for 10 days then
4. on day 11 remeasure magnetic stimulated Pdi twitch and quadriceps strength, repeat measurements of diaphragm and quadriceps size (i.e. thickness), repeat the vastus lateralis muscle biopsy, determine respiratory system compliance, determine airway resistance, and perform a chart review.
5. on day 21 remeasure magnetic stimulated Pdi twitch and quadriceps strength, and repeat measurements of diaphragm and quadriceps size (i.e. thickness), and perform another chart review.

For each chart review the investigators will obtain the following information: age, sex, diagnoses, reason for institution of mechanical ventilation, vital signs, bedside parameters of mechanical ventilation use (including mode of ventilation, duration of ventilation, level of oxygen, breath volume and rate, % triggered breaths), most recent arterial blood gas values, chest radiograph readings, recorded assessments of limb muscle strength and mental status.