Gastroesophageal Reflux and Body Movement in Infants: Investigations with Combined Impedance-pH and Synchronized Video Recording

The aim of this paper was to investigate the temporal association of gastroesophageal reflux (GER) and body movement in infants. GER were registered by combined impedance-pH, documentation of body movement was done by video. Videorecording time (Vt) was divided into “resting time” and “movement time” and analyzed for occurrence of GER. Association was defined as movement 1 minute before/after the beginning of a GER. Statistical evaluation was by Fisher's exact test. In 15 infants, 341 GER were documented during Vt (86 hours). 336 GER (99%) were associated with movement, only 5 episodes (1%) occured during resting time. Movement was significantly associated with the occurrence of GER (P < .0001). There is a strong temporal association between GER and body movement in infants. However, a clear distinction between cause and effect could not be made with the chosen study design. Combined impedance-pH has proven to be the ideal technique for this approach.


Introduction
The role of gastroesophageal reflux (GER) and its association with various extraesophageal symptoms have been studied previously in children [1]. The combined measurement of multiple intraluminal impedance and pH (MII-pH) is increasingly accepted as the primary diagnostic tool in this situation [2]. Irritability and dystonic body movements in infants with regurgitation are a common clinical observation [3][4][5]. The aim of this study was to investigate the temporal association of body movement and GER in infants, by combining MII-pH [6,7] with continuous, synchronized video recording.

Patients and Methods
Fifteen infants (mean age at study 97 ± 52 days; 8 female, 7 male) with recurrent regurgitation were examined over approximately 6 hours each. None received medication to control GER. They were fed their regular milk formula and kept supine after feeding.
The combined technique of MII-pH has been described in detail previously [6,8]. In this study, a standard flexible catheter (outer diameter 1.5 mm) with a pH-sensitive antimony electrode and six impedance channels (Helmholtz Institut, Aachen, Germany) was placed in the esophagus under fluoroscopy. Distance between impedance channels was 1.5 cm, over a total measuring length of 9 cm. Measuring segments were positioned from just above the cardia (channel 6) to the hypopharynx (channel 1), with the pH sensor situated at the level of channel 5, that is, approximately 3 cm above the gastroesophageal junction. The acquisition rate of pH and impedance signals was 50 Hz per channel. For analysis, MII-pH data was stored on a standard recording device with implemented custom software (MOT 2.01, Helmholtz Institut, Aachen, Germany) [9].
For movement documentation, video recording was performed with a standard video camera (PC224, Panasonic, Hamburg, Germany) positioned at the left side of the bed.
The video signal was recorded simultaneously and picturein-picture together with the MII-pH signal with a recording system at the bedside.
MII-pH data were visually analyzed for the typical impedance pattern of GER, indicated by a retrograde esophageal volume flow [6]. In this study, GER was diagnosed only if this typical pattern was noted in the esophageal impedance. Documentation during each GER included the minimal pH value, the maximal height reached by the refluxate, and the GER duration, defined as time needed to reach 50% of the initial impedance value in the most distal impedance channel [9].
The total analyzable time with video and MII-pH recording in all patients was defined as "video time" (Vt). GER episodes that occured during Vt were further analysed.
All video recordings were analysed, and all body movements during Vt were documented. Per definition, phases with visible movement of the infant during Vt were called "movement time" (MT), phases without visible movement during Vt were called "resting time" (RT). To discriminate between RT and MT during prolonged periods of movement, the duration of a resting episode had, by arbitrary definition, to be ≥10 sec to be registered as such, that is, episodes of movement that were interrupted by a resting phase <10 sec were considered as one movement episode. For further consistent statistical analysis, MT and RT were divided into intervals of 120-second duration.
The occurrence of a body movement episode during 60 secs preceding or following the beginning of a GER (GER window time, GWT) was defined as temporal association. Accordingly, the remaining Vt was dvided into 120-second intervals (non-GER window time, nGWT) [10].
Statistical analysis was performed using Fisher's exact test. Significance was established by a P value <.05.
The study protocol was approved by the Ethics Committee of the Medical Faculty, RWTH Aachen, Germany. Before commencing any evaluation of an infant, informed consent was obtained from the parents.

Results
During a total measurement time of 115 h 37 min, 462 episodes of GER were registered in the 15 infants. 341 of these GER occured during Vt (86 h 46 min) and formed the database for the following analysis.
When compared to GER-free measuring time, movement time was significantly associated with the occurrence of GER (P < .0001).

Discussion
An association with GER is presumed for various extraesophageal symptoms [1]. The results described here demonstrate an association of movement episodes and gastroesophageal reflux in infants. During 336 of 341 (98.5%) two-minute intervals surrounding a GER episode, a body movement of the infant was documented, only 5 of 341 (1.5%) two-minute intervals surrounding a GER episode were without movement. This result was highly significant when compared to the GER-free measurement phases, where body movement of the infants was documented in less than 20% of the measurement time.
Gastroesophageal reflux is frequent in infants and may constitute a physiological phenomenon that triggers various extraesophageal reactions [3,4]. The clinical observation, that body movements in infants occur more frequently in the phases around GER events [11], could be confirmed with this study. Whether these movements are a sign of arousal prior to a GER episode or means of, for example, facilitating GER clearance by altering the position and slope of the esophagus for protection against potentially damaging GER content, could not be clarified with the chosen study design.
In line with the current guideline, the exclusive use of pH 3 monitoring is not suitable for the detection of symptomassociated GER in infancy [2,12], the combined multiple esophageal impedance-pH recording, which has now finally made its way from bench to bedside in all age groups, is clearly superior [2,10]. Further studies are needed to investigate the relation of cause and effect.

Conflict of Interests
T. G. Wenzl received research support from AstraZeneca, he received research support and served as a consultant for Sandhill Scientific and received research support and served as a speaker for Tecnomatix Germany; he also served as a speaker for Reckitt Benckiser and received research support from Johnson & Johnson. The other authors declare no conflict of interest. No honorarium, grant, or other form of payment was received for producing the paper.