title: Thoracic gas volume measurements in paralyzed mice.
abstract: We have previously measured thoracic gas volume (VTG) in spontaneously breathing mice using a whole body plethysmograph and have now extended our technique to allow for V(TG) measurements during paralysis. BALB/c mice were anesthetized and placed in a body-box and ventilated via a tracheostomy cannula through the box wall. Box pressure (Pb) and tracheal pressure (Pao) were measured during spontaneous breathing, and again after paralysis while mechanically compressing the chest. V(TG) was much larger after paralysis (0.49+/-0.06 ml, positive end-expiratory pressure = 2 cmH2O) when compared with spontaneous breathing (0.31+/-0.01 ml). External chest compression produced looping in the plots of Pb versus Pao that was attributable to gradual changes in Pb upon release of the mechanical chest compression and had the character of thermal transients. Under the assumption that the rate of heating of the air in the chamber was proportional to the pressure applied to the animal's chest, and that any increase in air temperature was dissipated by heat absorption by the chamber walls, we developed an algorithm that corrected for the thermal events. This yielded similar results for V(TG) (0.30+/-0.02 ml) as obtained during spontaneous efforts. Our method may prove particularly useful when paralysis is required for the precise measurement of lung mechanics.
authors.affiliation: Vermont Lung Center, University of Vermont, Burlington, VT, USA. lennart.lundblad@uvam.edu
authors.forename: Lennart K A
authors.initials: LK
authors.lastname: Lundblad
authors.forename: John
authors.initials: J
authors.lastname: Thompson-Figueroa
authors.forename: Timothy
authors.initials: T
authors.lastname: Leclair
authors.forename: Charles G
authors.initials: CG
authors.lastname: Irvin
authors.forename: Jason H T
authors.initials: JH
authors.lastname: Bates
mesh_terms: D000818:Animals; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D008176:Lung Volume Measurements / Q000379:methods*; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D010991:Plethysmography / Q000379:methods*; D011175:Positive-Pressure Respiration / Q000379:methods; D012133:Respiratory Paralysis / Q000175:diagnosis* / Q000503:physiopathology*; D013909:Thorax / Q000503:physiopathology*; D013990:Tidal Volume