title: Nonchemical influence of inspiratory pressure support on inspiratory activity in humans.
abstract: To determine whether nonchemical inhibition of respiratory activity occurs during inspiratory pressure support (IPS) ventilation (IPSV), respiratory motor output (in 9 subjects), obtained by calculating transdiaphragmatic pressure-time products, and central respiratory output (in 5 subjects), obtained by integrating the electromyographic activity of the diaphragm (EMGdi) during mechanical inspiratory time, EMGdi per minute, and electrical inspiratory time, as determined from onset to peak EMGdi, were compared during spontaneous ventilation (control) and IPSV with (IPS+CO2) and without (IPS) correction of hypocapnia. Both IPS and IPS+CO2 induced significant decreases in transdiaphragmatic pressure-time products (46 +/- 31 and 53 +/- 23%, respectively), EMGdi during mechanical inspiratory time (49 +/- 12 and 57 +/- 14%, respectively), EMGdi per minute (65 +/- 22 and 69 +/- 15%, respectively), and electrical inspiratory time (73 +/- 8 and 65 +/- 6%, respectively). Because correction of hypocapnia failed to eliminate the marked inhibition of both respiratory and central motor output seen with IPS, we conclude that nonchemical inhibition of respiratory activity occurs during IPSV.
authors.affiliation: Service de Physiologie, Explorations Fonctionnelles, Institut National de la Santé et de la Recherche Médicale U 492, Hôpital Henri Mondor, 94010 Créteil, France.
authors.forename: B
authors.initials: B
authors.lastname: Fauroux
authors.forename: D
authors.initials: D
authors.lastname: Isabey
authors.forename: G
authors.initials: G
authors.lastname: Desmarais
authors.forename: L
authors.initials: L
authors.lastname: Brochard
authors.forename: A
authors.initials: A
authors.lastname: Harf
authors.forename: F
authors.initials: F
authors.lastname: Lofaso
mesh_terms: D000328:Adult; D003964:Diaphragm / Q000502:physiology; D004576:Electromyography; D005260:Female; D006801:Humans; D016857:Hypocapnia / Q000503:physiopathology; D007385:Intermittent Positive-Pressure Ventilation; D008297:Male; D015656:Respiratory Mechanics / Q000502:physiology*