[The influence of the supine and prone positions in the esophageal pH monitoring in very low birth weight infants].

Background: Scarce information is available on the effects of body's positioning in the number and the duration of gastroesophageal reflux episodes in very low birth weight infants.

Aim: To evaluate the influence of prone compared to supine positions on the frequency and duration of acid gastroesophageal reflux episodes in very low birth weight infants and study the role of body position in the occurrence of exams with reflux index > or = 5% and > or = 10%.

Methods: Sixty one prolonged esophageal pH monitoring exams were retrospectively analyzed. The difference between the prone and supine position exam duration was not longer than 3 hours. The reflux index was evaluated for the total period of the exam (reflux index total) and for each period in the two positions. The total number of reflux episodes, the number of reflux episodes > 5 minutes and the longest reflux episode were evaluated for each period in the two positions. These parameters were compared in accordance with body positioning, for each one of the three reflux index total categories: reflux index total < 5%, > or = 5% and > or = 10%. The frequencies of exams with reflux index total > or = 5% and reflux index total > or = 10% were compared for both positions.

Results: The number of hours in prone (11.2 +/- 1.0) and in supine (11.2 +/- 1.1) position were not different. All the prone positions monitoring parameters were significantly lower than the supine ones, in the three reflux index total categories. In the supine position, 32.7% (20/61) and 27.8% (17/61) of the exams, which were normal in prone, became abnormal, taking into account reflux index > or = 5% and > or = 10%, respectively, obtained for each position.

Conclusions: In prone position, there is a significant decrease in number and duration of acid reflux episodes in very low birth weight infants. Supine position promotes a significant increase in the number of esophageal pH monitoring exams with reflux index > or = 5% and > or = 10%, making easier the diagnose of the gastroesophageal reflux disease.