In Reply:--Guyton is puzzled by the mechanism by which the "gills" in our new tracheal tube attain a seal at the level of the glottic opening. The glottic portion (alone) of the new, thin-walled tracheal tube is deformed to approximate the roughly pentagonal shape of the glottic opening. This alone greatly reduces air leak. We then attached to this so deformed section of the tracheal tube numerous, very thin, soft, and pliable polyurethane rings ("gills"), with a thickness of 25-75 micro meter. The purpose of those "gills" was to deform and, together with ever present mucus, fill voids between the glottic opening and the tracheal tube. The "gills" themselves do not exert any pressure on the glottis, except through added bulk. Hence, the term "no pressure cuff." Any pressure on the glottic structures is exerted through the tracheal tube. By eliminating the tracheal cuff, as in our study, mucosal lesions were greatly reduced/eliminated, aspiration was effectively prevented, and the laryngeal lesions were similar to those caused with conventional tracheal tubes.
We believe the "gills" produce an effective seal, different from the "parachute cuff." Whereas the parachute cuff produces effective seal only during the inspiratory period of ventilation, the "gills" attain an effective seal during both inspiration and expiration, effectively preventing aspiration.
Chiara Reali-Forster, M.D.; Theodor Kolobow, M.D.; Matteo Giacomini, M.D.; Tomayoshi Hayashi, M.D., Ph.D.; Koji Horiba, M.D., Ph.D.; Victor J. Ferrans, M.D., Ph.D.; National Institutes of Health; National Heart, Lung, and Blood Institute/IR PB; Building 10, Room 5D17; 10 Center Drive, MSC 1412; Bethesda, Maryland 20892-1412
(Accepted for publication April 1, 1996.)