Post-operative epidural analgesia: effects on lung volumes.

A study was undertaken to assess the role of post-operative pain in reducing Functional Residual Capacity (FRC) and Vital Capacity (VC). The efficacy of post-operative epidural analgesia in reversing these changes was measured in eight subjects after upper abdominal operations. With pain, FRC and VC were 78 per cent and 37 per cent of control respectively. Following epidural analgesia, the values were 84 per cent and 55 per cent. These figures indicate the pain component in the post-operative reduction of these two lung capacities. This partial restoration may be of value in the prevention of post-operative pulmonary complications by avoiding closure of small airways during tidal breathing and by increasing the effectiveness of deep breathing and coughing in the removal of secretions and the reversal of atelectasis.