Published ahead of print on May 28, 2003, doi:10.1164/rccm.200203-241OC
American Journal of Respiratory and Critical Care Medicine Vol 168. pp. 760-769, (2003)
© 2003 American Thoracic Society
Transdiaphragmatic Pressure Control of Airway Pressure Support in Healthy Subjects
Tarek Sharshar,
Gilbert Desmarais,
Bruno Louis,
Gilles Macadou,
Raphaël Porcher,
Alain Harf,
Jean-Claude Raphaël,
Daniel Isabey and
Frédéric Lofaso
Services d'Explorations Fonctionnelles, de Réanimation Médicale et Centre d'Innovations Technologiques, Hôpital Raymond Poincaré, Garches; Ecole Supérieure d'Ingénieurs en Electrotechnique et Electronique, Noisy le Grand; Département de Biostatistique et Informatique Médicale, Hôpital Saint-Louis, Paris; Service de Physiologie, Explorations Fonctionnelles, Hôpital Henri Mondor et Institut National de la Santé et de la Recherche Médicale, Faculté de Médecine, Créteil, France
Correspondence and requests for reprints should be addressed to Frédéric Lofaso, M.D., Ph.D., Service d'Explorations Fonctionnelles, Hôpital Raymond Poincaré, 104, boulevard Raymond Poincaré, 92380 Garches, France. E-mail: f.lofaso{at}rpc.ap-hop-paris.fr
We designed a new servoventilator that proportionally adjusts airway pressure to transdiaphragmatic pressure (Pdi) generated by the subject during inspiration. Each cycle is triggered by either a preset Pdi increase or a preset inspiratory flow value (whichever is reached first), whereas cycling-off is flow-dependent. We evaluated the servoventilator in seven healthy subjects at normocapnia and three levels of hypercapnia (normocapnia + 3, + 6, and + 9 mm Hg) comparatively with spontaneous breathing. Triggering was by Pdi in six subjects and flow in one. At all end-tidal carbon dioxide pressure levels, time from onset of diaphragm electromyographic activity to inspiratory flow was similar with and without the servoventilator. Airway pressure increased proportionally to Pdi variation during servoventilator breathing. Flow, tidal volume, respiratory rate, intrinsic positive end-expiratory pressure, and esophageal and transdiaphragmatic pressure–time products increased significantly with hypercapnia with and without the servoventilator. Breathing pattern parameters were similar in the two breathing modes, and no differences were found for intrinsic positive end-expiratory pressure or gastric pressure variation during exhalation. Esophageal and transdiaphragmatic pressure–time products were lower with than without the servoventilator. The Pdi-driven servoventilator was well synchronized to the subjects effort, delivering a pressure proportional to Pdi and reducing respiratory effort at normocapnia and hypercapnia.
Key Words: triggering • servoventilator • respiratory drive
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Copyright © 2003 American Thoracic Society
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