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Percentage change in PE-ratio as a function of the head and neck positions (hyperflexion, reference, elevation and unrestrained). There was a significant difference (p < 0.01) between the relative change in PE-ratio in the unrestrained head-neck position and the other contact positions investigated. The boxes defined the upper and lower quartiles with the medians marked by the horizontal lines, the whiskers indicated the minimum and maximum values (n = 40).
