Interpretation of thoracoabdominal movements during breathing.

Movements of the thorax and abdomen during respiration are of interest from two points of view. First, such movements can be measured and provide a quantitative assessment of pulmonary ventilation. Secondly, thoracic and abdominal motions offer insight into the actions of the respiratory muscles. Mead and co-workers 11-31 demonstrated a practical means of recording and calibrating thoracic and abdominal movements in normal subjects, using magnetometers to measure their anteroposterior diameter changes. More recently detailed analysis has been made [41 of lateral diameter changes of the thorax and abdomen as well. When these diameter changes are combined with measurements of intragastric and intraoesophageal pressure changes during breathing, activity and co-ordination of the different respiratory muscles can be inferred [SI. Even without pressure measurements, however, considerable use may be made of careful assessment of thoracoabdominal diameter changes in patients with chronic respiratory l6,71 and neuromuscular disease [81. The following examples illustrate the normal motions of the rib cage and abdomen and some of the common clinical conditions in which altered thoracoabdominal movements are prominent features.