RESPIRATORY MECHANICS IN INFANTS AND YOUNG-CHILDREN BEFORE AND AFTER REPAIR OF LEFT-TO-RIGHT SHUNTS

In an attempt to investigate the relationship between respiratory mech anics and pulmonary hemodynamics, we evaluated pulmonary function in 3 1 infants with left-to-right shunts and subsequent high pulmonary bloo d flow, undergoing cardiac surgery. Measurements were performed 1 d be fore and repeated 10 d and 4-5 wk after correction. The age of the pat ients ranged from 4 d to 24 mo, body weight from 2.7 to 11.8 kg. Pulmo nary artery pressure, assessed by Doppler echocardiography, was pre-op eratively elevated in 23 patients (group 1), whereas it was within nor mal values in eight infants (group 2). Respiratory mechanics were meas ured using the single-breath occlusion technique in sedated infants. T o evaluate specific compliance, functional residual capacity was deter mined by using an open circuit nitrogen washout technique. A reduced p reoperative compliance value (mean with 95% confidence interval) was f ound in group 1: 34.8 (26.5-43.1) mL.kPa-1. After hemodynamic correcti on, a progressive significant (p < 0.01) improvement was demonstrated at 10 d and 1 mo with values of 47.5 (39.2-55.8) mL . kPa-1 and 56.5 ( 45.6-67.4) mL-kPa-1, respectively. A similar trend was noted evaluatin g specific compliance with values of 0.27 (0.24-0.30) kPa-1 and 0.44 ( 0.42-0.46) kPa-1, respectively before and after surgery. Preoperative functional residual capacity value was 130 (100-160) mL. In group 2, n ormal preoperative compliance values were obtained, without significan t changes after surgery. In both groups, resistance was within the nor mal range both before and after surgical correction, and functional re sidual capacity did not change either. No correlations were found betw een compliance and pulmonary artery pressure and pulmonary blood flow values. In conclusion, these results show that infants with left-to-ri ght shunts and pulmonary hypertension present with reduced compliance of the respiratory system that rapidly improves after cardiac surgery.