Pharyngeal swallowing: defining pharyngeal and upper esophageal sphincter relationships in human neonates

Abstract

Objective: To test the hypothesis that the sensorimotor characteristics of the reflexes evoked on stimulation with air and water infusions differ by studying the effect of pharyngeal stimulation on pharyngeal-upper esophageal sphincter (UES) interactions in healthy neonates.

Study design: Pharyngo-UES-esophageal manometry was recorded in 10 neonates at 39 +/- 4 weeks postmenstrual age. Pharyngeal infusions (n = 155) of air (0.1 to 2.0 mL) and sterile water (0.1 to 0.5 mL) were given. Two types of reflexes were recognized: pharyngeal reflexive swallowing (PRS) and pharyngo-UES-contractile reflex (PUCR). Frequency occurrence, distribution of reflexes, threshold volume, response time, and stimulus-response relationship were evaluated.

Results: The reflex response rates were 30% for air and 76% for water (P < .001). PRS was more frequent than PUCR with air and water (P < .05), even though the stimulation thresholds and response latencies were similar. Graded volumes of water but not air resulted in an increased frequency of PRS (P < .01).

Conclusions: PRS is more frequent than PUCR, and the 2 reflexes have distinctive characteristics in air and water stimuli. Both PRS and PUCR have implications for the evaluation of swallowing in infants.

Figures

Figure 1

Examples of pharyngeal reflexive swallowing (PRS) and pharyngo-UES-contractile reflex (PUCR) evoked upon pharyngeal air (Figure 1A) and water (Figure 1B) infusions are shown in a representative neonate. PRS is characterized by the occurrence of pharyngeal waveform, submental EMG signal, and UES relaxation. PUCR is characterized by an increase in UES pressure after the infusion.

Figure 2

Frequency and distribution of PRS and PUCR with air and water infusions. Between air and water, the frequency of PRS was greater (P

Figure 3

Examples of A) spontaneous swallow, B) solitary PRS, and C and D) multiple swallow sequences. Each swallow is associated with submental EMG signal and UES relaxation. Recordings from P-Eso, M-Eso and D-Eso represent proximal-, middle-, and distal esophageal motility respectively. In figures A and B, note the propagation of peristaltic waveforms with solitary swallows. In figures C and D, multiple succeeding swallows inhibit the propagation of previous swallow. Only the terminal pharyngeal swallow resulted in a fully propagated sequence.

Figure 4

Stimulus Volume-PRS response relationship with air and water infusions. Note progressive increase in swallow frequency with graded volume increments of water, but not with air (P = 0.045).