Lateral pharyngeal fat pad pressure during breathing in anesthetized pigs

It has been hypothesized that the pressure in tissues surrounding the upper airway is one of the determinants of the size and shape of the upper airway. To our knowledge, this pressure has not been measured. The purpose of this study was to test whether the pressure in a tissue lateral to the upper airway, the lateral pharyngeal fat pad pressure (Pfp), differs from atmospheric and pharyngeal pressures and whether it changes with breathing. We studied six male lightly sedated pigs by inserting a transducer tipped catheter into their fat pad space by using computerized tomographic scan guidance. We measured airflow with a pneumotachograph attached to a face mask and pharyngeal pressure with a balloon catheter. Pfp differed from atmospheric pressure, generally exceeding it, and from pharyngeal pressure. Pfp correlated positively with airflow and with pharyngeal pressure, decreasing during inspiration and increasing during expiration. Changes in Pfp with ventilation were eliminated by oropharyngeal intubation. We conclude that Pfp differs from atmospheric and pharyngeal pressures and that it changes with breathing.