Postbypass pulmonary artery pressure influences respiratory system compliance after ventricular septal defect closure

It is reported that surgical correction of left-to-right shunt improves res piratory function in paediatric cardiac patients. However, such correction sometimes does not result in an improvement of respiratory compliance. The purpose of this study was to look for factors determining changes in respir atory system compliance (Crs) in patients who underwent closure of ventricu lar septal defect (VSD closure). In a prospective study, 17 children (< 10 kg) who underwent VSD closure were enrolled. They were divided into two gro ups, according to postbypass mean pulmonary artery pressure (mPAP). The pat ients were allocated to Group C if mPAP was less than or equal to 18 mmHg ( n=12) and to Group PH if > 18 mmHg (n=5). We compared the ratio of postoper ative Crs to preoperative Crs (C-post/C-pre) between the groups. A multiple occlusion technique was used to measure Crs. The C-post/C-pre in group C w as larger than that in group PH (1.11 +/- 0.17 vs. 0.81 +/- 0.12, P < 0.01) . There was a correlation between postbypass mPAP and C-post/C-pre (r(s)=0. 49, P < 0.05), but no correlation was noted between preoperative mPAP, Qp/Q s or Rp/Rs and C-post/C-pre. We concluded that high postbypass mPAP was ass ociated with a perioperative decrease in Crs after VSD closure.