Oral, pharyngeal, and esophageal transit of an acidic bolus in healthy subjects

The effect of taste on swallowing: A scoping and systematic review

Consuming foods and liquids for nutrition requires the coordination of several muscles. Swallowing is triggered and modified by sensory inputs from the aerodigestive tract. Taste has recently received attention as a potential modulator of swallowing physiology, function, and neural activation; additionally, taste impairment is a sequela of COVID-19. This review presents factors impacting taste and swallowing, systematically summarizes the existing literature, and assesses the quality of included studies. A search was conducted for original research including taste stimulation, deglutition-related measure(s), and human participants. Study design, independent and dependent variables, and participant characteristics were coded; included studies were assessed for quality and risk of bias. Forty-eight articles were included after abstract and full-text review. Synthesis was complicated by variable sensory components of stimuli (taste category and intensity, pure taste vs. flavor, chemesthesis, volume/amount, consistency, temperature), participant characteristics, confounding variables such as genetic taster status, and methods of measurement. Most studies had a high risk of at least one type of bias and were of fair or poor quality. Interpretation is limited by wide variability in methods, taste stimulation, confounding factors, and lower-quality evidence. Existing studies suggest that taste can modulate swallowing, but more rigorous and standardized research is needed.

Saliva transit in patients with gastroesophageal reflux disease

Saliva is an important factor in the neutralization of the acidity of the refluxed material that comes from the stomach to the esophagus. The impairment of saliva transit from oral cavity to distal esophagus may be one of the causes of esophagitis and symptoms in gastroesophageal reflux disease (GERD). With the scintigraphic method, the transit of 2 mL of artificial saliva was measured in 30 patients with GERD and 26 controls. The patients with GERD had symptoms of heartburn and acid regurgitation, a 24-hour pH monitoring with more than 4.2% of the time with pH below four, 26 with erosive esophagitis, and four with non-erosive reflux disease. Fourteen had mild dysphagia for solid foods. Twenty-one patients had normal esophageal manometry, and nine had ineffective esophageal motility. They were 15 men and 15 women, aged 21-61 years, mean 39 years. The control group had 14 men and 12 women, aged 19-61 years, mean 35 years. The subjects swallowed in the sitting and supine position 2 mL of artificial saliva labeled with 18 MBq of (99m) Technetium phytate. The time of saliva transit was measured from oral cavity to esophageal-gastric transition, from proximal esophagus to esophageal-gastric transition, and the transit through proximal, middle, and distal esophageal body. There was no difference between patients and controls in the time for saliva to go from oral cavity to esophageal-gastric transition, and from proximal esophagus to esophageal-gastric transition, in the sitting and supine positions. In distal esophagus in the sitting position, the saliva transit duration was shorter in patients with GERD (3.0 ± 0.8 seconds) than in controls (7.6 ± 1.7 seconds, P = 0.03). In conclusion, the saliva transit from oral cavity to the esophageal-gastric transition in patients with GERD has the same duration than in controls. Saliva transit through the distal esophageal body is faster in patients with GERD than controls.

EFFECT OF SWALLOWED BOLUS VISCOSITY AND BODY POSITION ON ESOPHAGEAL TRANSIT, CONTRACTION AND PERCEPTION OF TRANSIT

Background The esophagus has a different response in relation to the characteristics of a swallowed bolus. Bolus viscosity and body position may affect esophageal contraction and transit. Objectives To investigate the effect of bolus viscosity and body position on esophageal contraction, transit and perception. Methods Esophageal contraction, transit and perception of transit were evaluated in 26 asymptomatic volunteers, 13 men and 13 women aged 18-60 years, mean: 33.6 (12.2) years. Esophageal contraction (manometry) and transit (impedance) were measured with a solid state catheter with sensors located 5, 10, 15, and 20 cm from the lower esophageal sphincter. Each volunteer swallowed in duplicate and in random sequence a 5 mL low viscous (LV) liquid bolus of an isotonic drink with pH 3.3, and a 5 mL high viscous (HV) paste bolus, which was prepared with 7.5 g of instant food thickener diluted in 50 mL of water (pH: 6.4). Results Total bolus transit time, in the sitting position, was longer with the HV bolus than with the LV bolus. Esophageal transit was longer in the supine position than in the sitting position. Bolus head advance time was longer with the HV bolus than with the LV bolus in both positions. Contraction esophageal amplitude was higher in the supine position than in the sitting position. The perception of bolus transit was more frequent with the HV bolus than with the LV bolus, without differences related to position. Conclusions The viscosity of the swallowed bolus and body position during swallows has an influence on esophageal contractions, transit and perception of transit.

ACIDIC AND NEUTRAL LIQUID INGESTION IN PATIENTS WITH GASTROESOPHAGEAL REFLUX DISEASE

Context Sour acidic liquid has a slower distal esophageal transit than a neutral liquid. Our hypothesis was that an acidic sour bolus has a different ingestion dynamic than a neutral bolus. Method In 50 healthy volunteers and 29 patients with gastroesophageal reflux disease (GERD), we evaluated the ingestion dynamics of 100 mL of acidic sour liquid (concentrated lemon juice, pH: 3.0) and 100 mL of water (pH: 6.8). The time to ingest the total volume, the number of swallows to ingest the volume, the interval between swallows, the flux of ingestion and the volume ingested in each swallow was measured. Results In both groups, healthy volunteers and patients in treatment for GERD, the acidic liquid took longer to be ingested, a higher number of swallows, a slower flux of ingestion and a smaller volume in each swallow than the neutral bolus. There was no difference between healthy volunteers and patients with GERD. The ingestion in women was longer than in men for acidic and neutral liquids. Conclusion Acidic liquid has a different dynamic of ingestion than the neutral liquid, which may be consequence of the slower transit through the distal esophageal body or an anticipation to drink a sour bolus. Patients with GERD have the same prolonged ingestion of the acidic liquid bolus as seen in healthy volunteers.