The diaphragm before and after lung transplantation (LT)

The diaphragm is the main respiratory muscle. Because possible abnormality of phrenic nerve conduction is reported after cardiothoracic surgery, we aimed to evaluate the function of the diaphragm after LT. Thirty patients (age:42 yrs, LAS:36) were evaluated before, one month(T 1 ) and 3 months(T 2 ) after LT. At each visit, the diaphragm was evaluated in terms of weakness (supine fall of forced vital capacity), electrical activity (CMAPa:compound motor action potential area during phrenic nerve stimulation(PNS)), force (maximal inspiratory pressure and sniff pressure), displacement (abdominal contribution to tidal volume in supine) and mobility (excursion of the dome assessed by ultrasound). The latency during PNS was also quantified. All the diaphragmatic parameters deteriorated at T1, and at T2 CMAPa was further reduced.While spirometry continuously improved,77% of patients needed nocturnal ventilatory support at T1, 36% at T2 (figure1). LT, per se, reduces the function of the diaphragm in terms of force, weakness, activation and displacement.We assume that the use of ice during LT may induce stupor of the phrenic nerve,as shown by low CMAPa that results from loss of motorneurons. The main consequence is the need of nocturnal ventilation, because during the REM phase of sleep ventilation depends on a functioning diaphragm. Our results suggest the importance of an integrated approach after TX in all patients,even in case of proper clinical course and good spirometry.