Respiratory function in children with neuromuscular disease.

Respiratory failure is the most common cause of death in children with neuromuscular disease (NMD). This article provides a conceptual framework for understanding failure of the respiratory pump in these children. Pump failure can be attributed to faulty control of respiration, to mechanical defects, and to respiratory muscle fatigue. In most patients with NMD, respiratory drive is intact. Mechanical defects can be due to either an abnormal pump or an excessive respiratory load on which the pump must operate. In patients with NMD, the weak respiratory muscles cannot generate normal respiratory pressures. Furthermore, inefficient chest wall motion leads to increased work for the respiratory system. Abnormalities of lung and chest wall compliance increase respiratory load. The combination of a weak, inefficient respiratory pump and an abnormally high elastic load can predispose these patients to respiratory muscle fatigue. Respiratory muscle rest with nocturnal assisted ventilation, therefore, provides a rational approach to the treatment of chronic respiratory failure in patients with NMD. Areas of future research that may prove useful in the care of children with respiratory failure due to NMD include: the development of better ways of assessing respiratory muscle fatigue; studies to increase understanding of the role of mechanical ventilation in improving chest wall and respiratory pump function; and studies delineating the role of respiratory muscle training in these patients.