Exsufflation With Negative Pressure (E.W.N.P.)

THE ELIMINATION of radiopaque material from the tracheobronchial tree of anesthetized dogs was reported in a previous paper.1This was accomplished by two devices which produced high-volume expiratory-flow rates simulating the natural cough.* Studies of bronchial dynamics by serial bronchography revealed a twofold dilatation of the medium-sized bronchi in animals subjected to an inflationary pressure of + 40 mm. Hg. The restoration to normal of the blood gas values found in obstructive dyspnea, reported by Cherniack, Gordon, and Drimmer,5may be explained in part by the marked dilatation of the bronchi. The development of a more effective technique, whereby there is slow inflation of the lungs, followed by an "explosive expiration," resulted in a total pressure-drop of approximately 100 mm. Hg, with expiratory-flow rates that surpassed those attainable by the most vigorous cough of normal human subjects.6A positive pressure blower served to inflate the lungs to a