Forced Oscillatory Parameters of the Canine Respiratory System with Altered Vagal Tone

Total respiratory impedance was obtained by forced oscillations ranging from 0.9 to 16 Hz in six anesthetized intubated dogs during a control period, after bilateral vagotomy, and during bilateral vagal stimulation. Values for forced oscillatory resistance, compliance, and inertance were calculated using regression analysis with a linear model. Mean values ±SD for the control period were 2.49 ±0.18 cmH2O ·L¿1 ·s, 0.0254 ±0.0039 L ·cmH2O¿1, and 0.0849 ±0.0055 cmH2O ·L¿1·s2, respectively. These were similar to previously reported values. Vagotomy produced only small changes in these parameters. Vagal stimulation produced a 33 percent increase in resistance, a 20 percent decrease in compliance, and an 8 percent increase in inertance. Changes in resistance and compliance were consistent with reported effects in the literature. Thus, the transient mechanical changes induced by vagal stimulation can be characterized by this technique.