Plethysmographic measurements in the clinical assessment of infants with bronchopulmonary disease.

Whole-body plethysmography makes it possible, to measure, during the same test sequence, the end-expiratory resting level (thoracic gas volume (TGV)), and, hence, an estimate of lung volume, and its close inter-relationship to airway function (airway resistance (Raw), or its reciprocal value airway conductance (Gaw). An overview is given of the physiological background and some equipment required for this technique. Furthermore, the attractive usefulness of whole-body plethysmography in clinical routine is discussed. Based on plethysmographic data obtained in 118 infant survivors of respiratory distress syndrome (RDS), in wheezy infants and infants with cystic fibrosis (CF), the important inter-relationship between changes in end-expiratory resting level (TGV) and the deficit in airway mechanics (Gaw) is shown, and special emphasis is given to the absolute need to obtain these measurements simultaneously. It can be shown that this recommendation is of even greater clinical importance in view of the fact that the younger the child the more frequent and severe the pulmonary hyperinflation present. Finally, this inter-relationship has to be borne in mind when reversibility of functional abnormalities on adrenoceptor agonists is assessed by lung function measurements.