Predictive equations over-estimate the resting energy expenditure in amyotrophic lateral sclerosis patients who are dependent on invasive ventilation support

Abstract

Background: Amyotrophic lateral sclerosis (ALS) is a form of degenerative motor neuron disease. At the end stage of the disease artificial feeding is often required. Nevertheless, very little is known about the energy demand of those ALS patients who are chronically dependent on tracheostomy intermittent positive pressure ventilation. The objective of our study was to clarify the resting energy expenditure (REE) in mechanically ventilated ALS patients.

Methods: We measured the REE of five ALS patients (four men, one female) twice during a 12 month-period using indirect calorimetry with two sampling flow settings (40 L/min and 80 L/min). The measured REEs (mREE) were compared with values calculated using five different predictive equations.

Results: The mean (± SD) of all mREEs was 1130 ± 170 kcal/d. The measurements with different flow settings and at different time instances provided similar results. The mean of mREEs was 33.6% lower, as compared to the mean calculated with five different predictive equations REE (p < 0.001). Each of the predictive equations over-estimated the REE.

Conclusions: The mREE values were significantly lower for every patient than all the predicted ones. Determination of daily nutrition with predictive equations may therefore lead in mis-estimation of energy requirements. Because ALS patients may live years with artificial ventilation their nutritional support should be based on individual measurements. However, further study is needed due to the small number of subjects.

Figure 1

Drawing of the measurement setup. The head of the subject is covered with a transparent plastic half ellipsoidal canopy. A tight flexible plastic sleeve of the canopy is wrapped carefully under the pillow and around the inspiration tubing to minimize any leakages in the measurement circuit. The patient is ventilated with ambient air via the tracheostomy. Expiratory gases exit inside the canopy from the valve next to the tracheostomy.