EVOLUTION OF LUNG-FUNCTION TESTS IN INFAN TS WITH BRONCHOPULMONARY DYSPLASIA

Background - Reports of short- and medium-term evolution of Lung Funct ion rests (LFT) in infants with bronchopulmonary dysplasia (BPD) are s till scarce. Population and methods. - The results of the first (befor e 3 months of corrected age) and the second (between 3 and 9 months of corrected age) LFT in 22 premature infants with BPD (gestational age: 31 +/- 2.5 weeks; birth weight: 1570 +/- 440 g; duration of mechanica l ventilation: 46 +/- 24 days; total duration of oxygen therapy: 88 +/ - 47 days) were compared to those obtained in 27 normal infants for th e first LFT and 10 normal infants for the second LFT, similar to the p atients for birth weight and corporeal index (CI). Results. - In the f irst LFT, major abnormalities were on increased thoracic gaz volume (T GV) (165 +/- 42 vs 122 +/- 24 mL; P < 0.001) and TGV CI ratio (1.25 +/ - 0.31 vs 0.89 +/- 0.17 mL/kg/m(2); P < 0.0001) a decreased pulmonary compliance (2.49 +/- 1.46 vs 11.60 +/- 4.50 mL/cmH(2)O; P < 0.0001) an d specific pulmonary compliance (0015 +/- 0.10 vs 0.100 +/- 0.042 mL/c mH(2)O/mL, de TGV; P < 0.0001), an increased total pulmonary resistanc e (20.4 +/- 12.1 vs 10.5 +/- 5.3 cmH(2)O/L/s; P < 0.001). In the secon d LFT, an increased TGV (235 +/- 62 vs 166 +/- 28 mL P < 0.01) and TGV CI ratio (1.64 +/- 0.65 vs 0.98 +/- 0.11 mL/kg/m(2); P < 0.05), a dec reased pulmonary compliance (2.68 +/- 2.0 vs 15.2 +/- 5.7 mL/cmH(2)O; P < 0.0001) and specific pulmonary compliance (0.013 +/- 0.010 vs 0.10 6 +/- 0.050 mL/cmH(2)O/mL de TGV; P < 0.0001), an increased total pulm onary resistance (17.1 +/- 9.6 vs 8.6 +/- 4.9 cmH(2)O/L/s; P < 0.05) w ere noted when compared with the control group results. Major abnormal ities of the blood gases were hypoxemia (63 +/- 10 vs 85 +/- 20 mmHg; P < 0.05), hypercapnia (38.5 vs 31 +/- 4 mmHg; P < 0.0001) during the first LFT. Hypoxemia (77 +/- 14 vs 90 +/- 14 mmHg) and hgpercapnia (37 +/- 4 vs 29 +/- 5 mmHg) continued in the second LFT. Thoracic distent ion and total pulmonary resistances in infants with BPD did not improv e but their pulmonary compliance (P < 0.0001) and PaO2 (P < 0.01) betw een the first and second LFT did it. Infants who had been ventilated f or a hyaline membrane disease (HMD) were more hypoxic on the second LF T (P < 0.05) than those who had been ventilated for other causes. Stat istically significant relationships were found between thoracic disten tion and duration of positive inspiratory pressure (P < 0.05; r = 0.43 ), duration of positive expiratory pressure (P < 0.05; r = 0.45), tota l oxygen therapy duration; between total pulmonary resistance and dura tion of mechanical ventilation with high frequency (P < 0.05; r = 0.52 ); between hypoxemi0a and duration of oxygen therapy with FiO(2) great er than or equal to 60% (P < 0.05; r = 0.54). Conclusions. - This stud y shows prolonged clinical and functional abnormalities of the respira tory functions requiring longer follow-up.