title: Transdiaphragmatic pressure control of airway pressure support in healthy subjects.
abstract: 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.
authors.affiliation: Service d'Explorations Fonctionnelles, Hôpital Raymond Poincaré, Garches, France.
authors.forename: Tarek
authors.initials: T
authors.lastname: Sharshar
authors.forename: Gilbert
authors.initials: G
authors.lastname: Desmarais
authors.forename: Bruno
authors.initials: B
authors.lastname: Louis
authors.forename: Gilles
authors.initials: G
authors.lastname: Macadou
authors.forename: Raphael
authors.initials: R
authors.lastname: Porcher
authors.forename: Alain
authors.initials: A
authors.lastname: Harf
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Raphaël
authors.forename: Daniel
authors.initials: D
authors.lastname: Isabey
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lofaso
mesh_terms: D000328:Adult; D003964:Diaphragm / Q000503:physiopathology*; D004867:Equipment Design; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology* / Q000628:therapy*; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011312:Pressure; D012123:Pulmonary Ventilation / Q000502:physiology; D012121:Respiration, Artificial / Q000379:methods*; D012122:Ventilators, Mechanical; D014939:Work of Breathing / Q000502:physiology