Pharyngeal peristaltic pressure variability, operational range, and functional reserve.

The present understanding of pharyngeal motor function remains incomplete. Among the remaining gaps of knowledge in this regard is the magnitude of variability of pharyngeal peristaltic pressure amplitude. Although variability can pose difficulty in interpretation of manometric findings, its magnitude can inform the operational range and reserve of the pharyngeal contractile function. We aimed to define the intra- and intersubject and intersession variability of select pharyngeal manometric parameters and, using this information, determine the number of swallow repetitions for acquiring reliable pharyngeal manometric data. We recorded pharyngeal peristalsis in 10 healthy subjects (age: 50 ± 25 yr, 5 women) by high-resolution manometry during two separate sessions of 20 sequences of 0.5-ml water swallows. Two-way ANOVA showed significant variation in the mean peak peristaltic pressure value across sites ( < 0.0001) as well as within the data at each site ( < 0.0001). Similarly, the pharyngeal contractile integral exhibited significant inter- ( = 0.003) and intrasubject ( < 0.001) variability. The Shapiro-Wilk normality test showed mixed results, in that some sites showed normally distributed data, whereas others did not. A robust Monte Carlo simulation showed that the nominal sample size was different for various tested metrics. For a power of 0.8, commonly accepted as an adequate threshold for acceptable statistical power, the optimal sample size for various peristaltic parameters ranged between 3 and 15. There is significant intra- and intersubject variability in site-specific and integrated parameters of pharyngeal peristalsis. The observed variance indicates a significant operational range and reserve in pharyngeal contractile function while necessitating parameter-specific sample size for reliable results. Intra- and intersubject variability are significant and different at various sites within the contractile pharynx. In addition, significant swallow-to-swallow and subject-to-subject variability exists in pharyngeal contractile integral. The range of intrasubject variability indicates the existence of broad operational range and reserve. Lastly, our variability studies informed Monte Carlo and power analyses, yielding estimates of sample size that would ensure accurate representation of pressure metric variability.