Long Term Results Of Respiratory Function After Unilateral Phrenicectomy

Background The treatment of brachial plexus avulsion injury(BPAI) is a demanding and difficult area of trauma surgery.Nerve transfer is the main method to treat BPAI now and phrenic nerve(PN) transfer has been widely used in many centers because of its better efficacy than other options.However,during the cardiac and thoracic surgeries,it is believed that impaired phrenic nerve function will seriously affect ventilation.And it is reported that some patients experience dyspnea and orthopnea with impairment of pulmonary function,even need unilateral diaphragmatic plication.Therefore,the respiratory function after phrenic nerve transfer has become an urgent question.In the recent decades,several short-or-mid-term follow-up have been conducted and showed only some compensable damage took place on patient's pulmonary function,most of which gradually recovered to pre-operative levels within 1～3 years.But little is known about the long term result of respiratory function after unilateral phrenicectomy.Object To investigate the long term result of respiratory function after phrenic nerve transfer so that we can determine the safe time of the operation.Methods From 1987 to 2000 with a follow-up of 8-20(mean 13.84) years,a total of 39 patients underwent phrenic nerve transfer in Hand Surgery Department of Huashan Hospital were enrolled in the study.Chest fluoroscopy to assess diaphragmatic excursion,diaphragm compound muscle action potential with surface electrodes to assess response to phrenic stimulation and pulmonary function testing were performed to assess ventilation and perfusion as well as maximal inspiratory pressure.Results Chest fluoroscopy showed that the diaphragm was raised in 94.9% (37/39) patients(2.03±1.03 intercostal spaces in deep inspiratory phase)(mean±standard deviation[SD]).No or little(＜0.5 intercostal spaces) diaphragmatic excursion was observed in 53.8%(21/39) patients.Compared with the contralateral side,66.7%(26/39) patients had decreased diaphragmatic movements,with 61.5% (24/39) more than 50%reduction.10.2%(4/39) patients had normal diaphragmatic excursion with no diaphragm raise.No paradoxical movement was observed in all patients.In the study of diaphragm compound muscle action potential,no diaphragm response was elicited in 59.5%(22/37) patients.21.6%(8/37) patients had more than 50%amplitude of the contralateral side.Maximal inspiratory pressure(Pimax/MIP) was decreased in all(32/32) patients with 53.1%(17/32) more than 70%reduction.There was no difference between right-side and left-side phrenic nerve transfer.A mild decrease was observed in the mean FVC,FEV1,and total lung capacity. There was also an increase in diffusing capacity(TLCO / VA).FEV1/FVC,FRC and TLCO-SB were in the normal range.The statistical test found the operation-age (op-age) was positively correlated with the reduction percentage(1 - FEV1%pred), with the linear regression equation:100×(1 - FEV1%pred) = op-age×0.69+10.865 (p＜0.001,Adj R-squared 0.278).Given FEV1%pred= 60%as the threshold,it was predicted that patients under the age of 41 would have low risks of the phrenic nerve injury.Moderate and severe smokers(smoking index＞200),compared with non-smokers and mild ones,had a negative influence on the FEV1 result.There is no difference between patients combined with multiple intercostal nerve transfer and the ones with the procedure of phrenic nerve transfer alone.Body position still significantly affected FVC in the phrenic nerve group.Conclusions Diaphragm function appears little recovery in the long term follow-up.Diaphragmatic paralysis still exists in most of phrenic nerve transferred patients.However,the damage to respiratory function is so mild that it can easily be compensated by the body itself,only if he/she has adequate cardiopulmonary reserves. Preoperative evaluation and postoperative care is important to minimize the abnormality of the respiratory system.