Changes in lung function and respiratory muscle strength after sternotomy vs. laparotomy in patients without ventilatory limitation

A relevant ventilatory defect occurs after sternotomy, a very common thoracic surgical opening. The mechanism of the ventilatory impairment is unclear. Moreover, until now, the effect of sternotomy on pulmonary gas exchange has scarcely been investigated. We evaluated the time-course up to recovery and changes in spirometry, maximum static inspiratory (PI(max)) and expiratory (PE(max)) mouth pressures and pulmonary gas exchange in 6 patients after sternotomy and in 8 patients after laparotomy. All patients were free of cardiopulmonary diseases and had normal preoperative lung function. Sternotomy and laparotomy decreased forced vital capacity (FVC) by 67 and 49%, respectively. Moreover, the percent decreases in PI(max), PE(max) and PaO(2) after sternotomy vs. laparotomy were respectively 54 vs. 57%, 54 vs. 60%, and 22.6 vs. 7.5% (p < 0.05). Following sternotomy, the percent decreases in FVC correlated with the percent decreases in PI(max) (p < 0.05) and PE(max) (p < 0.01). The return to baseline values occurred after approximately 2 weeks. The present study shows that sternotomy can induce greater respiratory effects than laparotomy and suggests a relevant involvement of respiratory muscle weakness after surgical opening of the thorax. The study also supports the view that the evaluation of patient's lung function before sternotomy can be clinically relevant.