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Pulmonary artery pressure (PAP) changes in the vary low birthweight (VLBW) infant developing prolonged oxygen dependency (POD)

Elevated PAP is invariably found in infants with chronic lung disease (CLD). Previous studies have focussed on changes in PAP in infants developing CLD but recent research has suggested that POD, defined as a persistent oxygen requirement at 36 weeks post-conceptional age (PCA) is a better predictor than CLD of subsequent morbidity and mortality.We studied, weekly, the changes in PAP in 34 VLBW infants from day 1 to 36 weeks PCA. The time to peak velocity (TPV): right ventricular ejection time (RVET) ratio, measured from the pulmonary artery Doppler, correlated negatively with PAP. 19 infants developed POD, 15 did not and acted as controls.Results: There was a similar rise in TPV:RVET in both groups over the first 2 weeks after birth. By the 3rd week the POD group had a significantly lower TPV:RVET ratio than the controls, p= 0.02. By 36 weeks PCA the ratio in the POD group was similar to the level obtained in the first week (0.28 vs 0.27, p > 0.05). In contrast the control group showed a significant rise over the same period (0.28 vs 0.34, p < 0.05).Conclusion: Elevated PAP was invariably found in the VLBW infants who developed prolonged oxygen dependency. These changes were evident by 3 weeks post-partum suggesting that therapy aimed at preventing such changes would need to be introduced before that time.