Dr. Levine’s study shows that the combination of mechanical ventilation and diaphragm inactivity elicits marked atrophy of diaphragm muscle fibers. These prominent decreases in diaphragm muscle fiber size would be expected to decrease the pressure generating capacity of the diaphragm by approximately 50%. Therefore, it may explain the difficulty in breathing experienced by patients who have undergone prolonged mechanical ventilation and have difficulty breathing following removal from the ventilator.