Gastro-oesophageal reflux in mechanically ventilated preterm infants.

Long duration oesophageal pH recordings were performed on 42 mechanically ventilated and parenterally fed preterm infants for a mean (SD) of 94 (28) hours. Their mean (SD) gestational age was 31.5 (2.6) weeks and birth weight 1514 (448) g. Their mean postnatal age was 19 (10) hours at the onset of pH recording, which was performed with the babies supine. The mean hourly values for the total number of episodes of gastro-oesophageal reflux (GOR) was 2.3 (2.7), for acid GOR 1.2 (1.4), and for acid GOR longer than 5 minutes 0.08 (0.09). The time the pH was greater than 4 (the reflux index) was 3.5 (3.3)% and the mean airway pressure was 6.6 (5.1) cm H2O. Fifteen infants had a reflux index above 5%. GOR patterns were not significantly correlated to birth weight, gestational age, postconceptional age, ventilatory patterns, and duration of mechanical ventilation. We concluded that the reproducibility of the reflux index was low because the median of the absolute differences was 1% when two consecutive 12 hour periods were compared and reached 2.5% when the two periods were separated by 96 hours. A second 24 hour pH recording was performed in 30 of the 42 patients after weaning from the ventilator and at a time when patients were asymptomatic and enterally fed. Compared with the late postprandial period of the second pH recording, the first recording showed an increase in the number of episodes of GOR and a decrease in reflux index, without any difference in the number of episodes of acid GOR.