title: Effectiveness of a load-imposing device for cyclic stretching of isolated human bronchi: a validation study.
abstract: BACKGROUND
  Mechanical ventilation may induce harmful effects in the airways of critically ill patients. Nevertheless, the effects of cyclic stretching caused by repetitive inflation-deflation of the bronchial compartment have not been well characterized in humans. The objective of the present study was to assess the effectiveness of a load-imposing device for the cyclic stretching of human bronchi.
  
  
  METHODS
  Intact bronchial segments were removed from 128 thoracic surgery patients. After preparation and equilibration in an organ bath, bronchi were stretched repetitively and cyclically with a motorized transducer. The peak force imposed on the bronchi was set to 80% of each individual maximum contraction in response to acetylcholine and the minimal force corresponded to the initial basal tone before stretching. A 1-min cycle (stretching for 15 sec, relaxing for 15 sec and resting for 30 sec) was applied over a time period ranging from 5 to 60 min. The device's performance level was assessed and the properties of the stretched bronchi were compared with those of paired, non-stretched bronchi.
  
  
  RESULTS
  Despite the intrinsic capacities of the device, the targets of the tension adjustments remained variable for minimal tension (156-178%) while the peak force set point was unchanged (87-115%). In the stretched bronchi, a time-dependent rise in basal tone (P < .05 vs. non-stretched) was apparent after as little as 5 min of cyclic stretching. The stretch-induced rise in basal tone continued to increase (P < .01) after the stretching had ended. Only 60 min of cyclic stretching was associated with a significant (P < .05) increase in responsiveness to acetylcholine, relative to non-stretched bronchi.
  
  
  CONCLUSIONS
  Low-frequency, low-force, cyclic loading of human bronchi is associated with elevated basal tone and acetylcholine responsiveness. The present experimental model is likely to be a useful tool for future investigations of the bronchial response to repetitive stress during mechanical ventilation.
authors.affiliation: Research Unit UPRES EA220, University Versailles Saint-Quentin, Hôpital Foch, 40 rue Worth, F-92150, Suresnes, France; Departement of Anesthesiology, Hôpital Foch, 40 rue Worth, F-92150, Suresnes, France.
authors.forename: Morgan
authors.initials: M
authors.lastname: Le Guen
authors.affiliation: Research Unit UPRES EA220, University Versailles Saint-Quentin, Hôpital Foch, 40 rue Worth, F-92150, Suresnes, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Naline
authors.affiliation: Research Unit UPRES EA220, University Versailles Saint-Quentin, Hôpital Foch, 40 rue Worth, F-92150, Suresnes, France.
authors.forename: Stanislas
authors.initials: S
authors.lastname: Grassin-Delyle
authors.affiliation: Research Unit UPRES EA220, University Versailles Saint-Quentin, Hôpital Foch, 40 rue Worth, F-92150, Suresnes, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Devillier
authors.affiliation: Research Unit UPRES EA220, University Versailles Saint-Quentin, Hôpital Foch, 40 rue Worth, F-92150, Suresnes, France; Medical Intensive Care Unit, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, University Sorbonne Paris Cité, 20 rue Leblanc, F-75908, Paris, Cedex 15, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Faisy
mesh_terms: D001696:Biomechanical Phenomena; D001980:Bronchi / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D013997:Time Factors; D015625:Tissue Expansion Devices / Q000592:standards*; D014159:Transducers