SELECTIVE RESECTION OF THE PHRENIC-NERVE ROOTS IN RABBITS .2. RESPIRATORY EFFECTS

This study evaluates the delayed respiratory consequences of selective resection of one or several roots of the right phrenic nerve in rabbi ts. A total of 50 animals were operated on according to five modalitie s of root resection. A total of 11 animals served as control. The brea thing pattern was analysed 8 weeks after surgery. Transdiaphragmatic p ressure was measured during transjugular supramaximal stimulation of t he phrenic nerve, unilaterally or bilaterally and during prolonged tra cheal occlusion (PImax). No difference was observed between the esopha geal pressure observed during bilateral phrenic nerve stimulation (Bil Peso) in control animals when compared to animals with resection of th e highest root of the right phrenic nerve (16.2 +/- 1.0 versus 14.5 +/ - 1.0 cmH(2)O (mean +/- SE). Resection of the two highest or of the tw o lowest roots of the right phrenic nerve resulted in a similar BilPes o (11.3 +/- 0.8 versus 11.1 +/- 1.2 cmH(2)O). Preservation of only the accessory phrenic nerve (APN) resulted in a low value of BilPeso (9.8 +/- 1.0 cmH(2)O) similar to that obtained with complete denervation o f the right hemidiaphragm. Ventilation and PImax were not different be tween the denervated or intact rabbits during quiet breathing. We conc lude that in rabbits: (1) Diaphragmatic function is preserved after re section of the highest root of the phrenic nerve. (2) Diaphragmatic fu nction is altered if only the APN is preserved. (C) 1997 Elsevier Scie nce B.V.