The manometric profile of cough and throat clearing in reflux monitoring studies

Background: The current trend in reflux-cough symptom correlation analysis is to use physiological signals rather than event marker activation for cough detection. This has been done by acoustic analysis. However, cough and throat clearing may be difficult to differentiate by sound alone, potentially confounding the analysis. The aim of this study was to investigate the manometric profiles of cough and throat clearing in pressure topography studies to explore this as an adjuvant method for differentiating cough and throat clearing with high resolution manometry (HRM). Methods: Ten healthy asymptomatic volunteers (7 females, mean age 31.1) underwent a HRM protocol using a 36 channel 360 HRM catheter (Given Imaging, Duluth, Georgia) after being trained to simulate cough and throat clearing in a randomized order every six minutes after a baseline recording. Intra-esophageal pressure, intra-gastric pressure and gastric-esophageal pressure gradient were analyzed 5 seconds before the event and during the cough and throat clearing events. The pattern of the events and the duration of the pressure changes were assessed using the 30 mmHg isobaric contour to determine whether distinct patterns could be identified. Manometric measures of cough and throat clearing were compared using the Mann-Whitney test. Results: Fifty cough and 50 throat clearing events were analyzed. Typical pressure topography of cough and throat clearing are illustrated in Figure 1. Both events began with a decrease in esophageal pressure, followed by a distal excursion of the esophagogastric junction (EGJ) high-pressure zone and an abrupt increase in gastric pressure that is transmitted into the esophagus. The comparison of the manometric profile between cough and throat clearing (Table 1) revealed a higher gastro-esophageal pressure gradient within 5 seconds before coughing (p=0.048). Additionally, there were higher intra-gastric (p<0.001) and intra-esophageal pressures (p<0.001) during cough. The distal gastroesophageal junction shift was more pronounced during the cough (p<0.001). The duration of sustained pressure increase was also significantly longer in cough than throat clearing (p<0.001) and cough was typically associated with more repetitive pressurizations. Cough and throat clearing were equally followed by swallows (52.9% vs 43.4%, p=0.391), whereas the latter had a shorter latency for swallows following the event (3.5 s vs 1.5 s, p=0.036). Conclusions: The profile of cough and throat clearing in pressure topography recordings revealed a similar qualitative pattern of pressurization. However, pressure changes associated with cough were more vigorous and associated with a greater rate of repetitive pressurizations. These findings suggest that although throat clearing and cough may be mechanistically similar, they can be differentiated by quantitative metrics on HRM. (Table presented).