title: [Modifications of diaphragmatic activity induced by midline laparotomy and changes in abdominal wall compliance].
abstract: OBJECTIVE
  Diaphragmatic activity varies with the initial length of the muscle. Our objective was to evaluate the influence of surgery and changes in abdominal wall compliance on diaphragmatic activity.
  
  
  METHODS
  Both phrenic nerves in 7 mongrel dogs were stimulated electrically with single supramaximal pulses (twitch). The gastric (Pga) and transdiaphragmatic (Pdi) pressures generated and muscle shortening (sonomicrometry) were used to evaluate diaphragmatic activity, which was determined at baseline, after midline laparotomy, with an elastic abdominal bandage, and with a rigid circular cast. Abdominal pressure was then gradually increased in order to induce progressive lengthening of the diaphragm.
  
  
  RESULTS
  After laparotomy, the pressures were somewhat lower (by 12%) than at baseline. The elastic bandage produced a slight increase in the pressure generated by the diaphragm (mean [SE] values: Pga, from 4.2 [0.3]cm H(2)O to 6.3 [0.9]cm H(2)O, P<.01; Pdi(tw), from 12.1 [2.0]cm H(2)O to 15.4 [1.8]cm H(2)O, P<.05]), and these values increased even further with the rigid cast (Pga, to 12.6 [1.5]cm H(2)O; Pdi, to 20.2 [2.3]cm H(2)O; P<.01 for both comparisons); this occurred despite smaller degrees of muscle shortening: by 57% [5%] of the initial length at functional residual capacity at baseline, by 49% [5%] with the bandage (P<.05), and by 39% [6%] with the cast (P<.01). With progressive lengthening of the muscle, its contractile efficacy increased up to a certain point (105% of the length at functional residual capacity), after which it began to decline.
  
  
  CONCLUSIONS
  Abdominal wall compliance plays an important role in the diaphragmatic response to stimulation. This appears to be due mainly to changes in its length at rest.
authors.affiliation: Hôpital de Notre-Dame, Université de Montréal, Montréal, Quebec, Canadá. jgea@imim.es
authors.forename: Joaquim
authors.initials: J
authors.lastname: Gea
authors.forename: Juan Bautista
authors.initials: JB
authors.lastname: Gáldiz
authors.forename: Norman
authors.initials: N
authors.lastname: Comtois
authors.forename: Ercheng
authors.initials: E
authors.lastname: Zhu
authors.forename: Igor
authors.initials: I
authors.lastname: Salazkin
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Fiz
authors.forename: Alejandro
authors.initials: A
authors.lastname: Grassino
mesh_terms: D034861:Abdominal Wall / Q000502:physiology*; D000818:Animals; D003187:Compliance; D003964:Diaphragm / Q000502:physiology*; D004285:Dogs; D007813:Laparotomy / Q000379:methods*