 clinically stable preterm infants with birth weight less than 1.5 kilograms and gestational age less than 32 weeks admitted to the neonatal intensive care unit at Sunnybrook Health Sciences centre on nasal continuos positive airway pressureCPAP of 5-6 cmH2O support for at least 48 hours, treated with Methylxanthines for apnea of prematurity and in less than 35 oxygen. 