Implantation eines Phrenicus-Stimulators bei zentraler Atemlähmung

Neoplastic or traumatic lesions of the brain stem or the upper spinal cord frequently cause respiratory insufficiency necessitating permanent mechanical ventilation. If the integrity of the diaphragm and its nerves is not affected, adequate ventilation can be achieved by electric stimulation of the phrenic nerves [1, 3, 5, 6]. Diaphragm pacing systems mean the patients can be independent of ventilator treatment. This is a psychological advantage for the patient, giving him or her the option of living in less specialized medical care units and perhaps even at home [4, 9]. Case report. We report the case of a 47-year-old man with a brain stem tumour, which was resected in large pieces. During the postoperative period an increasingly severe respiratory insufficiency developed, which finally made continuous mechanical ventilation necessary. After the viability of the phrenic nerves and contractility of the diaphragm had been shown by direct stimulation of the nerves to be still intact, it was decided that a diaphragm pacer system should be implanted. A “Diaphragm Pacer System S232 G” (Avery Laboratories, Glen Cove, N.Y., USA: external transmitter, antenna, implanted electrode and receiver) was implanted. Using a supraclavicular approach, phrenic nerve electrodes were placed around each nerve and connected with subcutaneous implants of radio signal receivers. Six days after implantation phrenic nerves were stimulated for a first short period. External antenna loops were taped to the skin over the implanted receiver sites (Fig.?3). The impulses produced by the transmitter were delivered via these antenna loops and led to contraction of the diaphragm, providing almost normal respiration. The duration of stimulation was increased stepwise from 1?h a day to full-time stimulation. Three weeks after implantation of the diaphragm pacer system the patient could be totally weaned from mechanical ventilation. After a further 2 weeks it was possible to discharge him from the intensive care unit, and he was then transferred to a rehabilitation centre.     

Effect of brachial plexus co-activation on phrenic nerve conduction time

BACKGROUND: Diaphragm function can be assessed by electromyography of the diaphragm during electrical phrenic nerve stimulation (ES). Whether phrenic nerve conduction time (PNCT) and diaphragm electrical activity can be reliably measured from chest wall electrodes with ES is uncertain. METHODS: The diaphragm compound muscle action potential (CMAP) was recorded using an oesophageal electrode and lower chest wall electrodes during ES in six normal subjects. Two patients with bilateral diaphragm paralysis were also studied. Stimulations were deliberately given in a manner designed to avoid or incur co-activation of the brachial plexus. RESULTS: For the oesophageal electrode the PNCT was similar with both stimulation techniques with mean (SE) values of 7.1 (0.2) and 6.8 (0.2) ms, respectively (pooled left and right values). However, for surface electrodes the PNCT was substantially shorter when the brachial plexus was activated (4.4 (0.1) ms) than when it was not (7.4 (0.2) ms) (mean difference 3.0 ms, 95% CI 2.7 to 3.4, p<0.0001). A small short latency CMAP was recorded from the lower chest wall electrodes during stimulation of the brachial plexus alone. CONCLUSIONS: The results of this study show that lower chest wall electrodes only accurately measure PNCT when care is taken to avoid stimulating the brachial plexus. A false positive CMAP response to phrenic stimulation could be caused by inadvertent stimulation of the brachial plexus. This finding may further explain why the diaphragm CMAP recorded from chest wall electrodes can be unreliable with cervical magnetic stimulation during which brachial plexus activation occurs.     

Mapping the phrenic nerve motor point: the key to a successful laparoscopic diaphragm pacing system in the first human series

BACKGROUND: For patients with high spinal cord injury and chronic respiratory insufficiency, electrically induced diaphragm pacing is an alternative to long-term positive pressure ventilation. The goal of this study was to laparoscopically assess the phrenic nerve motor point of the diaphragm and then implant electrodes to produce chronic negative pressure ventilation. METHODS: Patients undergoing elective laparoscopic procedures (volunteer patient group) underwent a series of electrical stimuli (2 to 24 mA at 100-microsecond pulse widths) with a mapping probe to identify the motor point through qualitative visualization of diaphragm motion and quantitative measurement of the abdominal pressure to assess the strength of the contraction. After Food and Drug Administration and Institutional Review Board approval, tetraplegic patients (spinal cord injured patient group) who were ventilator dependent underwent mapping and implantation of electrodes for pacing in both diaphragms. RESULTS: In the volunteer group, 28 patients underwent 3 to 50 stimulations per diaphragm to identify the motor points. Throughout this series the surgical tools and software were improved to allow rapid motor point location with a grid-mapping algorithm. In the spinal cord injured group, 5 of 6 patients had electrodes successfully implanted at the motor point to produce adequate tidal volumes. The one failure caused a change in our inclusion criteria to include fluoroscopic confirmation of diaphragm movement during surface nerve stimulation. Three patients are completely free of the ventilator, and the other 2 are progressively increasing their time off the ventilator with conditioning. CONCLUSIONS: Mapping and implantation of the electrodes can be done laparoscopically, providing for a low-risk, cost-effective, outpatient, diaphragm pacing system that will support the respiratory needs of patients.     

Microstimulators and intramuscular hook electrodes for the stimulation of respiratory muscles

BACKGROUND/OBJECTIVES: We determined the feasibility of stimulating the major muscles of respiration with different types of electrodes. Intramuscular hook electrodes, model microstimulators (M-Micro) developed in our laboratory, and commercial radiofrequency microstimulators (RFM) (Alfred Mann Foundation, Valencia, CA), were employed in this investigation. METHODS: In 8 anesthetized dogs, M-Micro were placed bilaterally on the diaphragm and in the abdominal muscles, and hook electrodes were placed in the 3rd and 5th intercostal regions adjacent to the intercostal nerves known to support inspiration. In 3 of the 8 animals, RFMs (Alfred Mann Foundation) in addition to the M-Micros were sutured to each hemidiaphragm at the same optimal site for phrenic nerve stimulation. During a hyperventilation-induced apnea, 2-second stimulations were applied to the diaphragm and with various combinations of diaphragm plus supporting muscles, both thoracic and abdominal. RESULTS: Diaphragm stimulation alone provided tidal volumes adequate for basal alveolar ventilation. However, implantation of the RFM required greater contact with the muscle. Stimulating other respiratory muscles along with the diaphragm further increased tidal volumes. The hook electrodes, M-Micro, and RFM performed equally well. CONCLUSIONS: In the acute dog model, M-Micro and hook electrodes can provide an implant system for the maintenance of ventilation. Support of the intercostal and abdominal muscles has the potential to reduce the contraction requirements of the diaphragm with decreased likelihood of diaphragm fatigue and hypoventilation. Whether the electrodes under investigation could provide an implant system for long-term ventilation needs to be determined.     

FK506局部缓释膜片促进周围神经再生的临床应用研究

目的临床观察在神经缝合口周围置入FK506高分子缓释膜片后对神经再生的影响。方法?选取同一时间段(4个月内)，在腕横纹至肘上5cm处因切割伤而导致正中神经或尺神经断伤的急诊病例16例。结合病人是否接受FK506治疗的意愿分为实验组及对照组，每组8例。实验组用9-0无创尼龙缝线将神经两断端作端端缝合，并将含有20mg FK506的高分子可生物降解膜片环绕神经缝合口一圈后用筋膜等软组织覆盖修复的神经和膜片。将膜片制成以1mg／d的速度释放，共20d。对照组仅用同法修复神经。结果术后1周起随访至2年。实验组在术后14周肌电图检测即有新生电位出现，较对照组提前4周。术后3～12个月测定，实验组感觉神经再生速度平均为3．1mm／d，明显快于对照组的1．7mm／d。实验组远期功能恢复的优良率也优于对照组。结论从FK506的药理作用和应用结果分析，FK506具有针对性促进周围神经再生的作用。     

Characterization of the human diaphragm muscle with respect to the phrenic nerve motor points for diaphragmatic pacing

Diaphragm pacing from laparoscopically placed electrodes is an alternative to conventional phrenic pacers that use electrodes placed in direct contact with the nerve in the neck or chest. The challenge with the laparoscopic approach is determining where to implant the electrodes, as the phrenic nerves are not visible from the abdomen. The objective of this study was to locate the phrenic nerve "motor points" in the human diaphragm muscle from an abdominal perspective. Twenty-five cadavers were examined by excising the diaphragm muscle and assessing for the thickness of the muscle, the motor point area, and the accessibility of the motor point from the abdominal approach. The data indicate the average thickness of the muscle in the motor point region was 3.0 mm for the left and 2.9 mm for the right hemidiaphragm. The average motor point area was 73 mm2 for the left and 58.7 mm2 for the right hemidiaphragm. The motor points were accessible from an abdominal approach, but the motor point on the right hemidiaphragm was located on the central tendon in many cases (12 of 25). Thus, although the nerves branch prior to entry into the muscle on the right side, several well-placed electrodes could still activate the entire nerve. In this study, we have characterized the human diaphragm muscle in the motor point region and found that it is feasible to place laparoscopically intramuscular electrodes in the motor point region. This is the foundation for the laparoscopically placed diaphragm pacing device that has been utilized in a small series of patients.     

Repetitive stimulation of phrenic nerves in myasthenia gravis.

BACKGROUND: In the investigation of patients with myasthenia gravis, repetitive supramaximal stimulation of an affected peripheral nerve is commonly performed to detect abnormal transmission at the neuromuscular junction. A study was undertaken to determine whether abnormal transmission could similarly be detected during stimulation of the phrenic nerves. METHODS: The phrenic nerves were stimulated supramaximally with surface electrodes in 13 patients with myasthenia gravis and in 16 control subjects (six control patients with diaphragmatic weakness but not with myasthenia and ten normal subjects). The amplitude of diaphragm muscle action potentials was measured with surface electrodes during phrenic nerve stimulation at frequencies of 1-5 Hz for 3-4 seconds. RESULTS: In five patients with myasthenia gravis, a significant decrement (15-43% decrease) occurred in the amplitude of diaphragm muscle action potential during stimulation at 3 Hz. When stimulation frequency was reduced to 1 Hz, diaphragm muscle action potentials returned to their original amplitude within 4-5 seconds. The decrement in the amplitude of the diaphragm muscle action potential was reduced temporarily in three of four patients after the administration of intravenous edrophonium chloride (Tensilon). There was no significant change (< 10% decrease) in the amplitude of diaphragm muscle action potentials during stimulation at increased frequencies either in the 16 control subjects or in eight of the patients with myasthenia gravis. CONCLUSION: A significant reduction in the amplitude of diaphragm muscle action potential occurred in five of 13 patients with myasthenia gravis during phrenic nerve stimulation at 3 Hz but in none of the control subjects. This may be a useful and non-invasive method for identifying patients with myasthenia gravis in whom weakness of the diaphragm is suspected.     

Feasibility of diaphragm pacing in patients after bilateral lung transplantation

Recent animal studies and intraoperative studies in humans suggested that phrenic nerve stimulation could attenuate ventilator‐induced diaphragm dysfunction. The purpose of the present study is to examine the safety and feasibility of diaphragm pacing during the weaning process after bilateral lung transplantation. Four patients, suffering from chronic pulmonary disease, were included, and diaphragm pacing was evaluated after lung transplantation. Implantation of electrodes at the end of the lung transplant procedure was possible in three of the four patients. In all implanted patients, stimulation of the diaphragm could trigger the ventilator. Implanted electrodes were completely removed by percutaneous retraction after up to 7 days of pacing. Adverse events related to pacing included occurrence of pain. Diaphragm pacing with temporary electrodes, inserted during surgery, is feasible and is able to trigger the ventilator in patients after bilateral lung transplantation. The use of intradiaphragmatic electrodes creates the additional opportunity to monitor the evolution of diaphragm electromyography during the postoperative weaning process.     

Thoracoscopic placement of phrenic nerve electrodes for diaphragmatic pacing in children

Background/Purpose: Diaphragmatic pacing can provide chronic ventilatory support for children who suffer from congenital central hypoventilation syndrome (CCHS) or cervical spinal cord injury. The authors report a new thoracoscopic approach for establishing diaphragm pacing. Methods: Between 1997 and 2000, 9 children ranging in age from 5 to 15 years and suffering from these disorders underwent thoracoscopic placement of bilateral phrenic nerve electrodes. A 3- or 4-trocar technique was used to dissect the phrenic nerve in the midchest and suture a phrenic nerve electrode (Avery Laboratories I-110A, Commack, NY) into place. The electrode was tunneled to a subcutaneous pocket in the upper abdomen and attached to an implanted pacing unit. Results: Bilateral electrodes were placed successfully into all patients. The average procedure time was 3.3 hours (range, 2.5 to 4.6), and average hospital stay was 4.2 days (range, 3 to 5). Four patients experienced postoperative complications (pneumonia, atelectasis, bradycardia, and pneumothorax). Average follow-up has been 30 months (range, 15 to 49). Eight patients have reached their long-term pacing goals. Conclusions: Phrenic nerve electrodes can be implanted thoracoscopically and allow the successful use of diaphragmatic pacing therapy. Avoidance of thoracotomy with its associated perioperative morbidity and scarring may encourage wider utilization of diaphragmatic pacing in children. J Pediatr Surg 37:974-978.     

The Learning curve for investigational surgery: lessons learned from laparoscopic diaphragm pacing for chronic ventilator dependence

Background Electrical stimulation of the phrenic nerve motor point of the diaphragm through laparoscopic implantation of a pacing system is an option for high spinal cord–injured patients with chronic respiratory insufficiency. This study assesses the operative learning curve for the initial series of patients.Method A series of six patients underwent laparoscopic placement of a diaphragm pacing system. The operative procedure was divided into the following four steps for analysis and rapid adjustment after each operation: exposure of the diaphragm, mapping of the phrenic nerve motor point, implantation of the pacing electrodes, and final routing of the wires to the external system.Results The first case required two operations, and the second case was unsuccessful because of a nonfunctioning phrenic nerve that led to a change in the preoperative screening criteria. The operative time decreased from 469 min for the first operation to 165 min for the sixth operation. The significant time decrease can be attributed to changes in the mapping and routing aspects of the operation. Key changes during this series that helped to reduce the operative time include abandonment of a software-dependent mapping technique, development of a grid algorithm for mapping, software improvement to increase the speed of stimulation and mapping, refinement of the mapping probe to maintain adequate suction on the diaphragm, shortening of the electrode lengths, and experience with the implantation of connections to the external electrodes. Presently, all five of the successfully implanted patients can be maintained on prolonged ventilatory support with the device.Conclusion Analysis of every step of this investigational procedure enabled us to make rapid changes in surgical protocol, leading to decreases in operative times and expectant improvements in patient safety and efficacy. In this series, analysis was the key to developing a low-risk cost-effective outpatient diaphragm pacing system.Presented at the scientific session of the annual meeting of the Society of American Gastrointestinal Endoscopic Surgeons (SAGES), Denver, CO, USA, 2 April 2004     

Taking the laparoscope to the laboratory for ventilatory research

Chronic ventilatory support by phrenic nerve stimulation has been accomplished, but potential permanent phrenic nerve injury has limited its therapeutic use. Prior work from the authors' laboratory has demonstrated that direct muscle stimulation can be safely performed for prolonged periods. Thus, in 1983, a laparoscopic technique was devised for the direct implantation of diaphragm pacing electrodes in the canine. During the subsequent four years, 16 animals (10 acute and 6 chronic) have undergone diaphragm pacing. Under general anesthesia, diaphragm pacing electrodes loaded into 19-gauge needles were implanted under direct laparoscopic visualization in both hemidiaphragms. In each animal, tidal volume, transdiaphragmatic pressure, arterial blood gas, impedence, cardiac activation, and histology of electrode placement site have been evaluated. Chronically paced animals were subjected to daily 8- to 24-hr per day pacing. The longest paced animal has been 179 days with continuous 24-hour per day pacing. In both acute and chronic experiments, maximal evoked tidal volume has approached 400 per cent of resting tidal volume. Cardiac ectopy has not occurred. This work has demonstrated the safety and feasibility of direct muscular diaphragm activation using the laparoscope. It has provided the basis for embarking upon a clinical study of this modality as a method of chronic ventilatory support. The laparoscopic technique of electrode placement may have a variety of other potential applications.     

Differential Sensitivity of Abdominal Muscles and the Diaphragm to Mivacurium: An Electromyographic Study

Background : Respiratory muscles are considered to be more resistant to muscle relaxants as compared with peripheral muscles. However, the relative sensitivity of respiratory muscles participating to the pump function has not been compared. We used electromyography to compare pharmacodynamic parameters of the diaphragm and abdominal muscles after mivacurium.

Methods : Forty adults undergoing elective surgery were randomly allocated in five dosing groups of mivacurium (50, 100, 150, 200, and 250 [mu]g/kg). Patients anesthetized with propofol and fentanyl underwent intubation without relaxants. Anesthesia was maintained with nitrous oxide and propofol. The right phrenic nerve, the left 10th intercostal nerve, and the ulnar nerve were stimulated. Electromyography of the diaphragm and abdominal muscles was recorded from surface electrodes. Mechanomyography was used to measure adductor pollicis evoked contraction. After a 5-min stable recording period, patients received a single intravenous bolus (20 s) dose of mivacurium. By using log dose-probit effect regression analysis, dose-response curves were constructed. Effective doses and 95% confidence intervals were derived for the diaphragm and abdominal muscles and were compared.

Results : The dose-response regression line of abdominal muscles differed from that of the diaphragm. Calculated ED50 and ED90 were higher for the diaphragm than for the abdominal muscles (104 [82-127] and 196 [177-213] [mu]g/kg, and 67 [51-82] and 161 [143-181] [mu]g/kg, respectively). The onset of block was faster and recovery of control responses were shorter at the diaphragm than at the abdominal muscles.     

Differential sensitivity of abdominal muscles and the diaphragm to mivacurium: an electromyographic study.

BACKGROUND: Respiratory muscles are considered to be more resistant to muscle relaxants as compared with peripheral muscles. However, the relative sensitivity of respiratory muscles participating to the pump function has not been compared. We used electromyography to compare pharmacodynamic parameters of the diaphragm and abdominal muscles after mivacurium. METHODS: Forty adults undergoing elective surgery were randomly allocated in five dosing groups of mivacurium (50, 100, 150, 200, and 250 microg/kg). Patients anesthetized with propofol and fentanyl underwent intubation without relaxants. Anesthesia was maintained with nitrous oxide and propofol. The right phrenic nerve, the left 10th intercostal nerve, and the ulnar nerve were stimulated. Electromyography of the diaphragm and abdominal muscles was recorded from surface electrodes. Mechanomyography was used to measure adductor pollicis evoked contraction. After a 5-min stable recording period, patients received a single intravenous bolus (20 s) dose of mivacurium. By using log dose-probit effect regression analysis, dose-response curves were constructed. Effective doses and 95% confidence intervals were derived for the diaphragm and abdominal muscles and were compared. RESULTS: The dose-response regression line of abdominal muscles differed from that of the diaphragm. Calculated ED50 and ED90 were higher for the diaphragm than for the abdominal muscles (104 [82-127] and 196 [177-213] microg/kg, and 67 [51-82] and 161 [143-181] microg/kg, respectively). The onset of block was faster and recovery of control responses were shorter at the diaphragm than at the abdominal muscles. CONCLUSION: Diaphragm and abdominal muscles have differential sensitivity to mivacurium. The diaphragm is more resistant to mivacurium than abdominal muscles are.     

阿珠莫林和丹曲洛林在不同型骨骼肌的肌肉松弛效应

目的　检查阿珠莫林 (azumolene)和丹曲洛林 (dantrolene)在家兔膈肌、前胫骨肌和比目鱼肌的不同肌肉松弛效应。方法　 2 4只家兔平均分成三组 ,静脉麻醉后分别游离膈神经 膈肌、胫神经 前胫骨肌和腓总神经 比目鱼肌 ,在膈肌表面和肢体肌远端肌腱固定连接肌张力换能测定装置以及在上述神经固定神经刺激电极 ,给予频率为 0 1Hz,持续 0 1ms,间隔 10s的超强刺激。采用 2倍递增给药法静脉注射阿珠莫林和丹曲洛林 ,对照组注射潘库溴铵 ,记录刺激神经所诱发的肌肉等张颤搐强度来评价药物在 3种肌肉不同肌肉松弛效应。结果　药物在膈肌、前胫骨肌和比目鱼肌的ED50 值所示 ,3种药物在不同肌肉作用强度顺序为阿珠莫林 :前胫骨肌 >比目鱼肌 >膈肌 ;丹曲洛林和潘库溴铵 :前胫骨肌 >膈肌 >比目鱼肌。药物间肌肉松弛效应强度为潘库溴铵 >丹曲洛林 >阿珠莫林。结论　阿珠莫林和丹曲洛林在这些肌肉所表现的不同肌肉松弛作用基本类似 ,在骨骼肌白纤维作用强 ,红纤维作用弱。这两种药物作用特点与潘库溴铵比较具有较大区别     

Minimally invasive trans-mediastinal endoscopic approach to insert phrenic stimulation electrodes in the human diaphragm: a preliminary description in cadavers

Objective: Diaphragm pacing by phrenic nerve (PN) stimulation is currently used for patients with central respiratory paralysis to be weaned from mechanical ventilation. Electrodes are inserted either through bilateral thoracotomy or through four ports laparoscopy. The aim of this experimental work is to demonstrate the feasibility of trans-mediastinal bilateral implantation of PN electrodes using a flexible gastroscope introduced through a cervical incision in human cadavers. Methods: Ten refrigerated and non-embalmed cadavers were used. The gastroscope was introduced through a cervical incision into the latero-tracheal space and then subsequently into both pleura by opening the mediastinal pleura. After identification of the PN, electrodes were introduced through an intercostal space to the desired diaphragmatic location using a long, pliable needle with the electrode loaded in its lumen. Results: Results are described for each hemi-diaphragm not for an anatomic subject. Mediastinal exploration and introduction of the video gastroscope into the pleural cavities proved easy in all subjects. Pleural adherences were present in five hemi-diaphragms. The central tendon of both hemi-diaphragms could be identified unambiguously in all the subjects. Identification of the entry point of the phrenic nerve into the diaphragm was straightforward in 10 hemi-diaphragms. In the remaining 10, this proved more difficult because of mediastinal fat or lung parenchyma. Introduction of the electrode-holding needles through the intercostal space and their insertion close to the phrenic nerve entry point was also easy. Withdrawal of the needle from the diaphragm and ‘capture’ of the hook were successful on the first attempt in 14 hemi-diaphragms, but failed in six others in whom a second attempt was necessary. Conclusion: Trans-mediastinal implantation of PN stimulation electrodes is possible using a flexible endoscope. This application of endoscopic surgery could allow a minimally invasive placement of PN electrodes in patients with central respiratory paralysis, for example, at the time of tracheostomy.     

Unilateral magnetic stimulation of the phrenic nerve.

BACKGROUND--Electrical stimulation of the phrenic nerve is a useful non-volitional method of assessing diaphragm contractility. During the assessment of hemidiaphragm contractility with electrical stimulation, low twitch transdiaphragmatic pressures may result from difficulty in locating and stimulating the phrenic nerve. Cervical magnetic stimulation overcomes some of these problems, but this technique may not be absolutely specific and does not allow the contractility of one hemidiaphragm to be assessed. This study assesses both the best means of producing supramaximal unilateral magnetic phrenic stimulation and its reproducibility. This technique is then applied to patients. METHODS--The ability of four different magnetic coils to produce unilateral phrenic stimulation in five normal subjects was assessed from twitch transdiaphragmatic pressure (TwPDI) measurements and diaphragmatic electromyogram (EMG) recordings. The results from magnetic stimulation were compared with those from electrical stimulation. To determine whether the magnetic field affects the contralateral phrenic nerve as well as the intended phrenic nerve, EMG recordings from each hemidiaphragm were compared during stimulation on the same side and the opposite side relative to the recording electrodes. The EMG recordings were made from skin surface electrodes in five normal subjects and from needle electrodes placed in the diaphragm during cardiac surgery in six patients. Similarly, the direction of hemidiaphragm movement was evaluated by ultrasonography. To determine the usefulness of the technique in patients the 43 mm mean diameter double coil was used in 54 patients referred for assessment of possible respiratory muscle weakness. These results were compared with unilateral electrical phrenic stimulation, maximum sniff PDI, and TwPDI during cervical magnetic stimulation. RESULTS--In the five normal subjects supramaximal stimulation was established for eight out of 10 phrenic nerves with the 43 mm double coil. Supramaximal unilateral magnetic stimulation produced a higher TwPDI than electrical stimulation (mean (SD) 13.4 (2.5) cm H2O with 35 mm coil; 14.1 (3.8) cm H2O with 43 mm coil; 10.0 (1.7) cm H2O with electrical stimulation). Spread of the magnetic field to the opposite phrenic nerve produced a small amplitude contralateral diaphragm EMG measured from skin surface electrodes which reached a mean of 15% of the maximum EMG amplitude produced by ipsilateral stimulation. Similarly, in six patients with EMG activity recorded directly from needle electrodes, the contralateral spread of the magnetic field produced EMG activity up to a mean of 3% and a maximum of 6% of that seen with ipsilateral stimulation. Unilateral magnetic stimulation of the phrenic nerve was rapidly achieved and well tolerated. In the 54 patients unilateral magnetic TwPDI was more closely related than unilateral electrical TwPDI to transdiaphragmatic pressure produced during maximum sniffs and cervical magnetic stimulation. Unilateral magnetic stimulation eliminated the problem of producing a falsely low TwPDI because of technical difficulties in locating and adequately stimulating the nerve. Eight patients with unilateral phrenic nerve paresis, as indicated by a unilaterally elevated hemidiaphragm on a chest radiograph and maximum sniff PDI consistent with hemidiaphragm weakness, were all accurately identified by unilateral magnetic stimulation. CONCLUSIONS--Unilateral magnetic phrenic nerve stimulation is easy to apply and is a reproducible technique in the assessment of hemidiaphragm contractility. It is well tolerated and allows hemidiaphragm contractility to be rapidly and reliably assessed because precise positioning of the coils is not necessary. This may be particularly useful in patients. In addition, the anterolateral positioning of the coil allows the use of the magnet in the supine patient such as in the operating theatre or intensive care unit.     

Comparison of the effects of mivacurium on the diaphragm and geniohyoid muscles

Although subjects often report difficulty with swallowing shortly after receiving neuromuscular blocking agents, difficulty with swallowing during recovery from neuromuscular blocking agents appears to be infrequent. We have used electromyography to compare onset and recovery at the diaphragm and geniohyoid airway muscles after an intubating dose of mivacurium (0.2 mg kg-1) to determine if the geniohyoid muscles were particularly sensitive to neuromuscular blocking agents. Twelve adults undergoing elective surgery were anaesthetized with propofol and fentanyl and the trachea intubated without neuromuscular blocking agents. The left hypoglossal and right phrenic nerves were stimulated with percutaneous needle electrodes and the electromyogram recorded with surface electrodes. EMG responses were measured after a bolus dose of mivacurium 0.2 mg kg-1. Recordings were also made of the mechanical response of the adductor pollicis to supramaximal ulnar nerve stimulation. There was no difference in the rate of onset of block for geniohyoid muscles and the diaphragm, but recovery to 25% and 90% of the control response was shorter at the diaphragm (median 14.5 (95% confidence limits 12.9-15.3) min and 23.8 (21.7-26) min) than at the geniohyoid muscle (19.4 (15.6-20.1) min and 29.2 (26.3-31.4) min), respectively (P < 0.05). When the train-of-four ratio of the mechanical response of the thumb reached 70%, the diaphragm and geniohyoid muscles had recovered completely in all patients.      

Functional restoration of the paralyzed diaphragm in high cervical quadriplegia via phrenic nerve neurotization utilizing the functional spinal accessory nerve

The authors report a case of functional improvement of the paralyzed diaphragm in high cervical quadriplegia via phrenic nerve neurotization using a functional spinal accessory nerve. Complete spinal cord injury at the C-2 level was diagnosed in a 44-year-old man. Left diaphragm activity was decreased, and the right diaphragm was completely paralyzed. When the level of metabolism or activity (for example, fever, sitting, or speech) slightly increased, dyspnea occurred. The patient underwent neurotization of the right phrenic nerve with the trapezius branch of the right spinal accessory nerve at 11 months postinjury. Four weeks after surgery, training of the synchronous activities of the trapezius muscle and inspiration was conducted. Six months after surgery, motion was observed in the previously paralyzed right diaphragm. The lung function evaluation indicated improvements in vital capacity and tidal volume. This patient was able to sit in a wheelchair and conduct outdoor activities without assisted ventilation 12 months after surgery.     

Complete worldwide operative experience in laparoscopic diaphragm pacing: results and differences in spinal cord injured patients and amyotrophic lateral sclerosis patients

Background  Diaphragm movement is essential for adequate ventilation, and when the diaphragm is adversely affected patients face lifelong positive-pressure mechanical ventilation or death. This report summarizes the complete worldwide multicenter experience with diaphragm pacing stimulation (DPS) to maintain and provide diaphragm function in ventilator-dependent spinal cord injury (SCI) patients and respiratory-compromised patients with amyotrophic lateral sclerosis (ALS). It will highlight the surgical experiences and the differences in diaphragm function in these two groups of patients. Methods  In prospective Food and Drug Administration (FDA) trials, patients underwent laparoscopic diaphragm motor point mapping with intramuscular electrode implantation. Stimulation of the electrodes ensued to condition and strengthen the diaphragm. Results   From March of 2000 to September of 2007, a total of 88 patients (50 SCI and 38 ALS) were implanted with DPS at five sites. Patient age ranged from 18 to 74 years. Time from SCI to implantation ranged from 3 months to 27 years. In 87 patients the diaphragm motor point was mapped with successful implantation of electrodes with the only failure the second SCI patient who had a false-positive phrenic nerve study. Patients with ALS had much weaker diaphragms identified surgically, requiring trains of stimulation during mapping to identify the motor point at times. There was no perioperative mortality even in ALS patients with forced vital capacity (FVC) below 50% predicted. There was no cardiac involvement from diaphragm pacing even when analyzed in ten patients who had pre-existing cardiac pacemakers. No infections occurred even with simultaneous gastrostomy tube placements for ALS patients. In the SCI patients 96% were able to use DPS to provide ventilation replacing their mechanical ventilators and in the ALS studies patients have been able to delay the need for mechanical ventilation up to 24 months. Conclusion   This multicenter experience has shown that laparoscopic diaphragm motor point mapping, electrode implantation, and pacing can be safely performed both in SCI and in ALS. In SCI patients it allows freedom from ventilator and in ALS patients it delays the need for ventilators, increasing survival. Presented as an oral presentation at the Plenary Session of SAGES 2008 Scientific Session, Philadephia.