The Pharyngeal Airway CHEST Atul Malhotra, MD, FCCP, James P. Butler, PhD, Andrew Wellman, MD  CHEST  Volume 141, Issue 6, Pages 1372-1375 (June 2012) DOI: 10.1378/chest.11-2989 Copyright © 2012 The American College of Chest Physicians Terms and Conditions

Figure 1 A, The phenomenon of negative effort dependence (NED) between breaths. B, The phenomenon of NED within breaths. A, Physiologic signals during an applied pressure drop in an experiment. Note the marked progressive lowering of airflow with increasing driving pressure (more negative PEPI) that occurs following the pressure drop (ie, between-breath NED). The genioglossus increases activity in response to negative pressure, but ostensibly the force output from the muscle is insufficient to preserve airflow. B, During spontaneous apnea, note the clear spike and plateau in the flow signal, which is consistent with the concept of NED within breaths. The reductions in airflow with increases in driving pressure are in contrast to the constant flow that would be predicted by classic Starling resistor behavior. Flow is measured via sealed mask using a pneumotachograph in L/min. EMGGG = genioglossus electromyogram; PEPI = pressure measured at the epiglottis in cm H2O; PMASK = mask pressure measured at the airway opening in cm H2O; SaO2 = oxygen saturation measured via pulse oximetry; VT = tidal volume. CHEST 2012 141, 1372-1375DOI: (10.1378/chest.11-2989) Copyright © 2012 The American College of Chest Physicians Terms and Conditions