A physiological approach to hemidiaphragm paralysis.

The occurrence of unilateral phrenic nerve injury with the resultant hemidiaphragm paralysis or paresis can cause significant respiratory distress or respiratory failure in infants and children. An early bedside diagnosis of this problem will allow appropriate therapy and prevent needless diagnostic procedures. With the patient in the lateral decubitus position and the paralyzed side up, accentuated paradoxical inspiratory inward epigastric motion ipsilateral to the paralyzed hemidiaphragm can be seen. With the paralyzed hemidiaphragm down, abdominal motion appears to be normal as if the paralyzed hemidiaphragm were plicated. Thus, ventilation may be improved by changing body position as well as instituting ventilatory support while the potential for phrenic nerve recovery is evaluated.