Normal ventilation is accomplished by the respiratory muscles overcoming forces that oppose volume movement: lung and chest wall compliance, and airway resistance. In general, venilatory muscle dysfunction is a result of an imbalance between energy demands and energy availability. Energy demands are defined by the interrelationship among ventilatory muscle strength, work of breathing, and ventilatory muscle efficiency. Energy availability is determined by the relationship between energy supply and the bodys' energy stores. In mechanically ventilated patients, dyssynchrony between the patient and ventilator is commonly considered a result of the patients' inbility to work with the mechanical ventilator. However, dysynchrony can be a result of problems with the artificial airay, the mechanical ventilator, or the patient. The cause of dyssynchrony is frequently not a result of a change in the paients' clinical status.
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