Electromyography for Diaphragm Effort

Overview

Mechanical ventilation may be necessary to save the life of a patient due to an accident, pneumonia or surgery. The ventilator then temporarily takes over the function of the respiratory muscles. During treatment in the Intensive Care, the amount of support provided by the ventilator is usually lowered gradually, until the point that the patient can breathe unassisted once again. However, in a large fraction of patients (up to 40%) it takes days to weeks before the patient is able to breathe unassisted, even after the initial disease has been treated. This is called prolonged weaning. A possible cause of prolonged weaning is weakness of the respiratory muscles. The diaphragm, the largest respiratory muscle, can become weakened if it is used too little, much like all other muscles in the body. Additionally, damage and weakness of the diaphragm can occur when the diaphragm has to work excessively. Therefore, it is important that the diaphragm works enough; not so little that it becomes weakened, but not too much either. Measurements of pressure generated by the diaphragm are needed to determine the current level of diaphragm activity in a patient on mechanical ventilation. However, these measurements are rarely performed, because they are time-consuming and require placement of two additional nasogastric catheters. This is a shame, as adequate loading of the diaphragm might prevent development of weakness, leading to shorter duration of mechanical ventilation. Finding alternative measurements of diaphragm effort might be a solution to this problem. It has been hypothesized that the electrical activity of the diaphragm provides a reliable indication of diaphragm effort. This study aims to determine whether there is a correlation between pressure generation by the diaphragm and electrical activity of the diaphragm over a wide range of respiratory activity, from low effort to extreme effort, in healthy volunteers.