| Part 1 Establishment of a rat model of unilateral diaphragmatic paralysis Experiment 1 Anatomy of accessory phrenic nerve in ratObjective:To observe the gross anatomy of accessory phrenic nerve (APN) in rat.Methods:Twenty-eight female SD rats were used. Phrenic nerve (PN) and accessory phrenic nerve (APN) were exposed on both sides in the neck. Incidence, location, course, and diameter of APN were recorded.Results:The incidence of accessory phrenic nerve was 92.8% on left side and 89.3% on right side.9.8%,23.53%,49.02% and 17.65% of accessory phrenic nerves leave brachial plexus from C6 root, upper trunk, the root of anterior division of upper trunk and the anterior division of upper trunk respectively. After running a short distance in the same direction as the nerves to the upper limb, the accessory phrenic nerve turned towards the upper thoracic aperture lateral to the main phrenic nerve.78.43% of accessory phrenic nerves passed over C7 at the medial two thirds with 21.57% at the lateral one third. Diameter of the accessory phrenic nerve was 0.14±0.01mm, which was about 44% of the phrenic nerve.Conclusion:Incidence of the accessory phrenic nerve is high in rat. It leaves brachial plexus at different site. Some of them run far lateral to the main phrenic nerve.Experiment 2 Establishment and evaluation of a rat model of unilateral diaphragmatic paralysisObjective:To construct a reliable rat model of unilateral diaphragmatic paralysis by means of transection of phrenic and accessory phrenic nerve in the neck.Methods:Twenty-four female SD rats were randomly divided into three groups. EMG at five sites of each hemidiaphragm was recorded as baseline before surgery. In group A, both phrenic and accessory phrenic nerves on the left side were transected in the neck. In group B, only left phrenic nerve was transected. Group C was a control group, in which phrenic and accessory phrenic nerve were identically exposed. EMG was recorded again 30min post-surgery. Pulmonary function, electrophysiological and pathological measurements were carried out 4 weeks post-surgery.Results:1. Thirty minutes post-surgery, ipsilateral hemidiaphragm in group A was completely paralyzed. Partially paralysis of ipsilateral hemidiaphragm was obtained in group B. EMG of contralateral hemidiaphragm increased in both A and B group compared with baseline (pre-surgery).2. Four weeks post-surgery, complete paralysis of ipsilateral hemidiaphragm persisted in group A with reduced TV compared with group B and group C. Regions of ipsilateral hemidiaphragm, which had spontaneous EMG activity, enlarged in group B compared with 30min post-surgery. No myelinated fiber was observed in ipsilateral phrenic nerve of group A while 78±13 myelinated fibers with normal appearance were present in that of group B. Muscle fiber atrophy was detected in every site of ipsilateral hemidiaphragm in group A, while in group B, muscle fibers atrophy was found only at sternal site.Conclusion:Unilateral diaphragmatic paralysis can be induced in rat by transection of both phrenic and accessory phrenic nerve respectively in the neck. group A, both phrenic and accessory phrenic nerves on the left side were transected in the neck. In group B, only left phrenic nerve was transected. Group C was a control group, in which phrenic and accessory phrenic nerve were identically exposed. EMG was recorded again 30min post-surgery. Pulmonary function, electrophysiological and pathological measurements were carried out 4 weeks post-surgery.Part 2 Effect of unilateral diaphragmatic paralysis on pulmonary function in ratObjective:To evaluate the effect of unilateral diaphragmatic paralysis on pulmonary function in rat during quiet and loaded breathing.Methods:One hundred and thirty two female SD rats were used and randomly divided into 4 groups. Group A, left phrenic and accessory phrenic nerve were transected in the neck. Group B, after left phrenic and accessory phrenic nerve transection, motor branches of the 3rd and 4th intercostal nerves were transferred to the distal end of phrenic nerve in the neck by nerve grafting. Group C, left phrenic, accessory phrenic, and motor branches of the 3rd and 4th intercostal nerves were transected. Group D was a control group. Pulmonary function during quiet breathing and loaded breathing (induced by moderate aerobic exercise) was measured at 1,2,4, 8,12 and 24-week post-surgery. Incremental exercise testing was performed as well to evaluate capability of intensive activity.Results:Compared with the control group, pulmonary function impairment during quiet breathing in group A, B and C was permanent characterized by PIF decrement. Bur adequate ventilation maintained with unaltered breathing pattern. Pulmonary function among group A, B, and C did not differ significantly. In the dynamic observation of pulmonary function pre-and post-exercise, F, MV immediately after exercise in group A was lower than that in group D (P<0.05) while F during 12-15min post-exercise was higher than that in group D at 1-week post-surgery. No significant difference in all pulmonary function parameters was detected among four groups at 2, 4,8,12,24-week post-surgery. The maximal exercise time to exhaustion at each time point post-surgery did not differ significantly among groups as well.Conclusion:1. Pulmonary function impairment during quiet breathing after unilateral diaphragmatic paralysis is permanent without minute ventilation loss and alteration of breathing pattern.2. Ventilatory decrement and prolonged recovery in response to moderate aerobic exercise is present shortly after unilateral diaphragmatic paralysis. Restoration can be obtained thereafter. Capability of intensive exercise is kept.3. No further pulmonary function impairment occurs when phrenic nerve and two intercostal nerves are injured at the same time.4. There is no obvious advantage of ipsilateral hemidiaphragm reinnervation on pulmonary function after unilateral diaphragmatic paralysis. 8,12 and 24-week post-surgery. Incremental exercise testing was performed as well to evaluate capability of intensive activity.Part 3 Effect of unilateral diaphragmatic paralysis on diaphragmatic function in ratObjective:To investigate the effect of unilateral diaphragmatic paralysis on diaphragmatic function.Methods:One hundred and thirty two female SD rats were used and randomly divided into 4 groups. Group A, left phrenic and accessory phrenic nerve were transected in the neck. Group B, after left phrenic and accessory phrenic nerve transection, motor branches of the 3rd and 4th intercostal nerves were transferred to the distal end of phrenic nerve in the neck by nerve grafting. Group C, left phrenic, accessory phrenic, and motor branches of the 3rd and 4th intercostal nerves were all transected. Group D was a control group. Physiological, electrophysiological and pathological measurements were carried out at 1,2,4,8,12 and 24-week post-surgery.Results:1. There was no significant difference in esophageal pressure (Peso) during quiet breathing among groups at each time point post-surgery. EMG of contralateral hemidiaphragm in group A, B, C was stronger than that in group D at 1,2-week post-surgery while no difference existed thereafter. EMG of ipsilateral hemidiaphragm was detected only in group B, which was less than that of group D at 8,12-week and became similar at 24-week post-surgery.2. Peso and EMG during sneeze did not significantly differ among groups at each time point.3. Analysis of EMG power spectrum of contralateral hemidiaphragm showed no difference among groups in H/L. Fc in group A, C had been lower than that in group D since 4-week post-surgery while Fc in group B had been similar with group D since 8-week post-surgery.4. CMAP could be recorded in ipsilateral hemidiaphragm of group B at 8,12, and 24-week post-surgery. All of them showed lower Amp and prolonged Lat.5. Obvious ipsilateral hemidiaphragm atrophy was found in group A, C at 4,8,12, and 24-week post-surgery while no atrophy in group B was present at 8,12, and 24-week post-surgery.6. Area density of interalveolar septum did not differ among groups at each time point.7. The number of myelinated fibers in ipsilateral phrenic nerve just before entering diaphragm muscle was less in group B than that in group D at 4,8,12 and 24-week post-surgery. No myelinated fiber was detected in group A and C at each time point.Conclusion:1. Normal Peso during quiet breathing can be maintained after unilateral diaphragmatic paralysis without fatigue of contralateral hemidiaphragm.2. Phrenic nerve combined with 2 intercostal nerves transfer to repair brachial plexus is safe.3. Compared with unilateral diaphragmatic paralysis with unrepaired phrenic nerve, there is no functional advantage of phrenic nerve repair. |
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