Effect of nasal noninvasive respiratory support methods on pharyngeal provocation-induced aerodigestive reflexes in infants

Abstract

The pharynx is a locus of provocation among infants with aerodigestive morbidities manifesting as dysphagia, life-threatening events, aspiration-pneumonia, atelectasis, and reflux, and such infants often receive nasal respiratory support. We determined the impact of different oxygen delivery methods on pharyngeal stimulation-induced aerodigestive reflexes [room air (RA), nasal cannula (NC), and nasal continuous positive airway pressure (nCPAP)] while hypothesizing that the sensory motor characteristics of putative reflexes are distinct. Thirty eight infants (28.0 ± 0.7 wk gestation) underwent pharyngoesophageal manometry and respiratory inductance plethysmography to determine the effects of graded pharyngeal stimuli (n = 271) on upper and lower esophageal sphincters (UES, LES), swallowing, and deglutition-apnea. Comparisons were made between NC (n = 19), nCPAP (n = 9), and RA (n = 10) groups. Importantly, NC or nCPAP (vs. RA) had: 1) delayed feeding milestones (P < 0.05), 2) increased pharyngeal waveform recruitment and duration, greater UES nadir pressure, decreased esophageal contraction duration, decreased distal esophageal contraction amplitude, and decreased completely propagated esophageal peristalsis (all P < 0.05), and 3) similarly developed UES contractile and LES relaxation reflexes (P > 0.05). We conclude that aerodigestive reflexes were similarly developed in infants using noninvasive respiratory support with adequate upper and lower aerodigestive protection. Increased concern for GERD is unfounded in this population. These infants may benefit from targeted oromotor feeding therapies and safe pharyngeal bolus transit to accelerate feeding milestones.

Keywords: bronchopulmonary dysplasia, neonate.

Fig. 1.

Aerodigestive reflexes evoked upon pharyngeal stimulation. Broken lines represent onset of pharyngeal stimulus. At lower volumes typical primary responses include the following solitary responses pharyngo-upper esophageal sphincter contractile reflex (PUCR) is characterized by upper esophageal sphincter (UES) contraction (A) or pharyngeal reflexive swallowing (PRS) is characterized by pharyngeal contraction, UES relaxation, esophageal body propagation, lower esophageal sphincter (LES) relaxation, and associated deglutition apnea (B). C: as the volume increases multiple PRS reflexes are evident. It is here that we can characterize initial and terminal responses. Note the initial response (light gray box) was defined as the first response to pharyngeal stimulation until a pause in pharyngeal signaling and/or esophageal body propagation. The terminal response (dark gray) is any pharyngeal contractile activity until a terminal swallow (esophageal body propagation) restores respiratory and digestive normalcy.

Fig. 2.

Effect of respiratory support on aerodigestive reflexes in response to 0.3 ml sterile water pharyngeal stimulation. Notice the adequate LES relaxation and duration when relaxation occurs in the nasal cannula (NC) and nCPAP groups. Also, note the respiration scales (abdominal respiration, thoracic respiration, tidal ventilation) are different from Fig. 1 to better accentuate the respiratory rhythm disturbances (shaded gray boxes).

Fig. 3.

Effect of respiratory support on initial pharyngeal provocation-induced responses. A: primary response type: although P is not significant (NS), PUCR is more frequent with increased degree of respiratory support. B: primary reflexive swallow latency: latencies were similar. C: pharyngeal recruitment: recruitment increased with respiratory support. D: pharyngeal response duration: response duration increased during NC but was similar during nCPAP. E: deglutition apnea prevalence: prevalence was not affected with any modes of respiration. F: phase of deglutition apnea: nCPAP has more deglutition apnea during inspiration. *P < 0.05 vs. NC. †P < 0.05 vs. nCPAP.

Fig. 4.

Effect of respiratory support on terminal pharyngeal-induced provocation responses. A: pharyngeal recruitment is not affected. B: total response duration is not affected. C: distal esophagus area under the curve is lower in NC. D: esophageal response duration is lower in NC. E: UES nadir pressure: respiratory support may interfere with complete UES relaxation. F: esophageal propagation: infants with respiratory support may have less complete propagation sequences. *P < 0.05 vs. NC. †P < 0.05 vs. nCPAP.