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Background: A frequent complication of Fontan operations is unilateral diaphragmatic paresis, which leads to hemodynamic deterioration of the Fontan circulation. A potential new therapeutic option is the unilateral diaphragmatic pacemaker. In this study, we investigated the most effective stimulation location for a potential fully implantable system in a porcine model., Methods: Five pigs (20.8 ± 0.95 kg) underwent implantation of a customized cuff electrode placed around the right phrenic nerve. A bipolar myocardial pacing electrode was sutured adjacent to the motor point and peripherally at the costophrenic angle (peripheral diaphragmatic muscle). The electrodes were stimulated 30 times per minute with a pulse duration of 200 µs and a stimulation time of 300 ms. Current intensity was the only variable changed during the experiment., Results: Effective stimulation occurred at 0.26 ± 0.024 mA at the phrenic nerve and 7 ± 1.22 mA at the motor point, a significant difference in amperage (p = 0.005). Even with a maximum stimulation of 10 mA at the peripheral diaphragm muscle, however, no effective stimulation was observed., Conclusion: The phrenic nerve seems to be the best location for direct stimulation by a unilateral thoracic diaphragm pacemaker in terms of the required amperage level in a porcine model., (© 2024. The Author(s).)

Background: Diaphragm Pacing(DP) demonstrates benefits over mechanical ventilation(MV) for spinal cord injured(SCI) patients. The hypothesis of this report is that phrenic nerve conduction study(PNCS) results cannot differentiate success or failure in selection of patients for DP. Direct surgical evaluation of the diaphragm should be performed., Methods: Observational report of prospective databases of patients undergoing laparoscopic evaluation of their diaphragms to assess for ability to stimulate to cause contraction for ventilation., Results: In 50 SCI patients who could not be weaned from MV, PNCS results showed latencies in stimulated patients (n = 44) and non-stimulated(n = 6) overlapped (7.8 ± 2.5 ms vs 9.4 ± 2.8 ms) and the null hypothesis cannot be rejected (p-value>0.05). Amplitudes overlapped (0.4 ± 0.2 mV vs 0.2 ± 0.2 mV) and the null hypotheses cannot be rejected (P-value >0.05). In 125 non SCI patients with diaphragm paralysis, there were 78(62.4%) with false negative PNCS., Conclusion: PNCS are inadequate pre-operative studies. Direct laparoscopic evaluation should be offered for all SCI patients to receive the benefit of DP., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Phrenic nerve injury (PNI) from birth trauma is a recognized phenomenon, generally occurring with ipsilateral brachial plexus palsy (BPP). In severe cases, PNI results in diaphragm paresis (DP) and respiratory insufficiency. Surgical diaphragmatic plication (SDP) is a potential management strategy for patients with PNI and DP, but timing and outcomes associated with SDP have not been rigorously studied., Methods: Records from 49 tertiary United States pediatric hospitals in the Pediatric Health Information System from 2004 to 2018 were analyzed. The study cohort included patients diagnosed with BPP from birth trauma who were documented to have PNI or DP. Patients who underwent congenital cardiac operations were excluded., Results: A total of 5832 patients were identified with BPP from birth trauma during the study period, 122 (2%) of whom were found to have concomitant DP. Of those, 65 (53%) were male, 39 (32%) were infants of diabetic mothers, 80 (65%) required mechanical ventilation, and 33 (27%) underwent SDP. SDP was performed at a median (range) age of 36 (7-95) days. Median (range) total and postoperative hospital lengths of stay (LOS) were 34 (6-180) and 15 (4-132) days, respectively. There was also an observed increase in post-operative LOS with increase in age at operation., Conclusion: Neonatal DP is rare and is managed with SDP in a minority of instances. Age at repair affects total and postoperative length of stay, proxies for resource utilization and morbidity. Repair prior to 45 days of life appears to result in a shorter postoperative hospital stay. This analysis will help guide surgeons with respect to indications and operative timing for infant DP., Type of Study: Retrospective Comparative Study., Level of Evidence: Level III., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The diaphragm is the main breathing muscle and contraction of the diaphragm is vital for ventilation so any disease that interferes with diaphragmatic innervation, contractile muscle function, or mechanical coupling to the chest wall can cause diaphragm dysfunction. Diaphragm dysfunction is associated with dyspnoea, intolerance to exercise, sleep disturbances, hypersomnia, with a potential impact on survival. Diagnosis of diaphragm dysfunction is based on static and dynamic imaging tests (especially ultrasound) and pulmonary function and phrenic nerve stimulation tests. Treatment will depend on the symptoms and causes of the disease. The management of diaphragm dysfunction may include observation in asymptomatic patients with unilateral dysfunction, surgery (i.e., plication of the diaphragm), placement of a diaphragmatic pacemaker or invasive and/or non-invasive mechanical ventilation in symptomatic patients with bilateral paralysis of the diaphragm. This type of patient should be treated in experienced centres. This review aims to provide an overview of the problem, with special emphasis on the diseases that cause diaphragmatic dysfunction and the diagnostic and therapeutic procedures most commonly employed in clinical practice. The ultimate goal is to establish a standard of care for diaphragmatic dysfunction., (Copyright © 2018 Sociedade Portuguesa de Pneumologia. Published by Elsevier España, S.L.U. All rights reserved.)

Neuralgic Amyotrophy (NA) or Parsonage-Turner syndrome is an idiopathic neuropathy commonly affecting the brachial plexus. Associated phrenic nerve involvement, though recognised, is thought to be very rare. We present a case series of four patients (all male, mean age 53) presenting with dyspnoea preceded by severe self-limiting upper limb and shoulder pain, with an elevated hemi-diaphragm on clinical examination and chest X-ray. Neurological examination of the upper limb at the time of presentation was normal. Diaphragmatic fluoroscopy confirmed unilateral diaphragmatic paralysis. Pulmonary function testing demonstrated characteristic reduction in forced vital capacity between supine and sitting position (mean 50%, range 42-65% predicted, mean change 23%, range 22-46%), reduced maximal inspiratory pressures (mean 61%, range 43-86% predicted), reduced sniff nasal inspiratory pressure (mean 88.25, range 66-109 cm H 2 O) and preserved maximal expiratory pressure (mean 107%, range 83-130% predicted). Phrenic nerve conduction studies confirmed phrenic nerve palsy. All patients were managed conservatively. Follow-up ranged from 6 months to 3 years. Symptoms and lung function variables normalised in three patients and improved significantly in the fourth. The classic history of severe ipsilateral shoulder and upper limb neuromuscular pain should be elicited and thus NA considered in the differential for a unilateral diaphragmatic paralysis, even in the absence of neurological signs. Parsonage-Turner syndrome is likely to represent a significantly under-diagnosed aetiology of phrenic nerve palsy. Conservative management as opposed to surgical intervention is advocated as most patients demonstrate gradual resolution over time in this case series.

Amyotrophic neuralgia is an uncommon neuropathy characterized by severe unilateral shoulder pain. Isolated or concomitant involvement of other peripheral motor nerves depending on the brachial plexus such as phrenic or laryngeal nerves is unusual(1). Its etiology is unknown, yet several explanatory factors have been proposed. Phrenic nerve involvement, either unilateral or bilateral, is exceedingly rare. Diagnosis relies on anamnesis, functional and imaging investigations and electromyogram. We report the case of a 48-year-old woman with a past history of renal transplantation due to proliferative glomerulonephritis with subsequent transplant rejection, who was eventually diagnosed with amyotrophic neuralgia with bilateral phrenic involvement, and who required sustained non-invasive mechanical ventilation., (Copyright © 2015 Elsevier España, S.L.U. All rights reserved.)

Introduction: Diaphragmatic paralysis (DP) due to phrenic nerve injury is a complication which occurs in association with congenital cardiac surgery and may be a life-threatening event in infants and young children. Information about this complication is still scarce from the developing countries., Methods: Retrospective study evaluated the incidence of DP among 414 patients who underwent congenital cardiac surgery in Abo Elriesh Children's Specialized Hospital, Cairo University, Egypt, in the duration from April 2009 to December 2011., Results: Incidence of DP was 3.6% (15 of 414 cases). Median age of affected patients was 10 months (ranged from 1 month to 13 years). Diagnosis of DP was observed after ventricular septal defect repair (3.9%), Glenn anastomosis (8.6%), Tetralogy of Fallot repair (4.3%), Senning operation (10%), arterial switch operation (3.2%), Fontan procedure (33%), coarctation of the aorta repair (7%), and pulmonary artery banding (6.4%). Diaphragmatic plication was performed in 4 of 15 cases. Patients with DP had significantly prolonged mechanical ventilation duration as compared to unaffected patients (median 120, range 48-600 vs 4, range 0-48 hours, P < .000). They also had a higher incidence of nosocomial pneumonia in 8 of 15 (53%) cases, longer duration of intensive care unit stay (median 15, range 4-62 days, P < .006), and significant mortality in 7 of 15 (46%; P < .004). Mortality among patients who underwent diaphragm plication was 1 of 4 (25%)., Conclusion: Diaphragmatic paralysis is a relatively rare complication of congenital cardiac surgery in children. Its occurrence is associated with increased morbidity and mortality. A high index of clinical suspicion, utilization of bedside diagnostic tools, and a policy of early plication for certain patients may lead to improved outcomes.

Background: The etiology of diaphragm paralysis is often elusive unless an iatrogenic or traumatic injury to the phrenic nerve can be clearly implicated. Until recently, there has been little interest in the pathophysiology of diaphragm paralysis since few treatment options existed., Methods: We present three cases of symptomatic diaphragm paralysis in which a clear clinico-pathologic diagnosis could be identified, specifically a vascular compression of the phrenic nerve in the neck caused by a tortuous or adherent transverse cervical artery., Results: In two patients the vascular compression followed a preceding traction injury, whereas in one patient an inter-scalene nerve block had been performed. Following vascular decompression, all three patients regained diaphragmatic motion on fluoroscopic chest radiographs, and experienced a resolution of respiratory symptoms., Conclusion: We suggest that vascular compression of the phrenic nerve in the neck may occur following traumatic or iatrogenic injuries, and result in symptomatic diaphragm paralysis., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Tetraplegia can lead to chronic respiratory failure. The need for tracheostomy mechanical ventilation significantly increases the cost of care, decreases the quality of life of the patient, and decreases life expectancy in spinal cord injury (SCI) because of pneumonias. Phrenic nerve stimulation was initially developed in the 1960s and diaphragm pacing was developed in the 1990s; both have the ability to remove a patient from positive pressure ventilation and allow them to breathe with their own diaphragm, decreasing posterior lung lobe atelectasis and pneumonia risk. This chapter summarizes the current surgical techniques, ventilator weaning options, and long-term results of functional electrical stimulation in restoring respiratory function., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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., (Copyright © 2011 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.)

Background: Phrenic pacing is an alternative to positive-pressure ventilation in selected patients, mostly in cases of upper spinal cord injury. We evaluated results of phrenic pacing performed by video-assisted thoracic surgery (VATS)., Method: Between 1997 and 2007, after complete neuromuscular investigations, 20 patients requiring full-time ventilation were selected for phrenic pacing (19 with posttraumatic tetraplegia and 1 with congenital central hypoventilation syndrome). Quadripolar cuff electrodes were fixed around each intrathoracic phrenic nerve via bilateral VATS. They were connected to a subcutaneous radiofrequency receiver coupled to an external radiofrequency transmitter. All patients participated in a reconditioning program beginning 2 weeks after implantation and continued until ventilatory weaning., Results: Phrenic pacing was successful in all cases. No intraoperative complications or perioperative mortality were observed. Intraoperative testing detected stimulation thresholds in 19 patients (range, 0.05-2.9 mA). Ventilatory weaning was obtained in 18 patients. Median diaphragm reconditioning time was 6 weeks (2 weeks-11 months). Reconditioning was still in process in a young woman and was not achieved in an elderly woman with a 4-year history of tetraplegia. All the patients weaned from mechanical ventilation reported improved quality of life. Failure or delay in recovery of effective diaphragm contraction was due to nonreversible amyotrophy., Conclusions: VATS implantation of 4-pole electrodes around the intrathoracic phrenic nerve is a safe procedure. Ventilatory weaning correlates with the degree of diaphragmatic amyotrophy. Phrenic pacing, performed as soon as neurologic and orthopedic stabilization is achieved, is the most important prognostic factor for successful weaning., (Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)

Purpose: Diaphragm pacing (DP) has been shown to successfully replace mechanical ventilators for adult tetraplegic patients with chronic respiratory insufficiency. This is the first report of DP in ventilator-dependent children., Methods: This was a prospective interventional experience under institutional review board approval. Diaphragm pacing involves outpatient laparoscopic diaphragm motor point mapping to identify the site where stimulation causes maximum diaphragm contraction with implantation of 4 percutaneous intramuscular electrodes. Diaphragm conditioning ensues to wean the child from the ventilator., Results: Six children were successfully implanted ranging from 5 to 17 years old with the smallest 15 kg in weight. Length of time on mechanical ventilation ranged from 11 days to 7.6 years with an average of 3.2 years. In all patients, DP provided tidal volumes above basal needs. Five of the patients underwent a home-based weaning program, whereas one patient who was implanted only 11 days post spinal cord injury never returned to the ventilator with DP use. Another patient was weaned from the ventilator full time but died of complications of his underlying brain stem tumor. The remaining patients weaned from the ventilator for over 14 hours a day and/or are actively conditioning their diaphragms., Conclusion: Diaphragm pacing successfully replaced mechanical ventilators, which improves quality of life., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Phrenic nerve stimulation is a technique whereby a nerve stimulator provides electrical stimulation of the phrenic nerve to cause diaphragmatic contraction. The most common indications for this procedure are central alveolar hypoventilation and high quadriplegia. This paper reviews the available data on the 19 patients treated with phrenic nerve stimulation in Australia to date. Of the 19 patients, 14 required pacing due to quadriplegia, one had congenital central hypoventilation syndrome and one had brainstem encephalitis. Information was unavailable for the remaining three patients. Currently, 11 of the pacers are known to be actively implanted, with the total pacing duration ranging from 1 to 21 years (mean 13 years). Eight of the 19 patients had revision surgeries. Four of these were to replace the original I-107 system (which had a 3-5-year life expectancy) with the current I-110 system, which is expected to perform electrically for the patient's lifetime. Three patients had revisions due to mechanical failure. The remaining patients' notes were incomplete. These data suggest that phrenic nerve stimulation can be used instead of mechanical ventilators for long-term ongoing respiratory support., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Context: Diaphragm pacing in ventilator-dependent tetraplegic subjects is usually achieved by the placement of phrenic nerve electrodes via thoracotomy. However, this technique may be accomplished less invasively via laparoscopic placement of IM electrodes, at a lower cost and with less risk of injury to the phrenic nerve., Objective: To assess the feasibility of laparascopic placement of IM diaphragm electrodes to achieve long-term ventilatory support in ventilator-dependent tetraplegic subjects., Design, Setting, and Participants: Two IM diaphragm electrodes were placed laparoscopically in each hemidiaphragm in five subjects with ventilator-dependent tetraplegia. Studies were performed either on an outpatient basis or with a single overnight hospitalization. Ventilator-dependent tetraplegic subjects were identified in whom bilateral phrenic nerve function was present, as determined by phrenic nerve conduction studies. Following electrode placement, subjects participated in a conditioning program to improve the strength and endurance of the diaphragm over a period of 15 to 25 weeks. The duration of the study was variable depending on the time necessary to determine the maximum duration that individuals could be maintained without mechanical ventilation support., Main Outcome Measures: Magnitude of inspired volume generation and duration of ventilatory support with bilateral diaphragm pacing alone., Results: In four of the five subjects studied, initial bilateral diaphragm stimulation resulted in inspired volumes between 430 and 1,060 mL. Reconditioning of the diaphragm over several weeks resulted in substantial increases in inspired volumes to 1,100 to 1,240 mL. These subjects were comfortably maintained without mechanical ventilatory support for prolonged time periods by diaphragm pacing, by full-time ventilatory support in three subjects, and 20 h per day, in the fourth subject. No response to stimulation was observed in one subject, most likely secondary to denervation atrophy., Conclusions: Diaphragm pacing in ventilator-dependent tetraplegic subjects can be successfully achieved via laparascopic placement of IM electrodes.

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.

We report four patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who presented with phrenic nerve palsy, which was unilateral in two instances. The two patients with bilateral phrenic nerve involvement required mechanical ventilation. After treatment with intravenous immunoglobulins (i.v.Ig) or steroids, the sensorimotor deficit and respiratory parameters improved in three patients, but the fourth patient remained ventilator dependent and died from pulmonary infection. Although rare, phrenic nerve palsy may be a feature of CIDP and may be responsive to treatment with i.v.Ig or steroids.

The hypothesis proposed is that restoration of functional capacity of denervated diaphragm may be achieved by reinervating it with vagus nerve. Following trauma, carcinomatose infiltration, and/or large thoracic surgery and neck surgery, phrenic nerve is frequently injured. Reinervation even in the most favourable conditions would not follow and diaphragm would rest permanently denervated and paralysed. This results in unilateral or bilateral paralysis of diaphragm. In principle, intermittent electrical stimulation of the phrenic nerve or diaphragm could elicit regular diaphragm contractions and maintain satisfactory respiration. While this technique could be used in upper motor neurone injury, in lower motor neurone injury and denervated diaphragm, that imposes too high electrical resistance, direct diaphragm pacing is practically impossible. In these cases, long term artificial ventilation is often necessary. Nevertheless, those patients are at high risk to suffer from atelectasis and respiratory infections. We project a hypothesis that reinervation of denervated diaphragm by vagus nerve could re-establishes its sensitivity to intramuscular electrical stimulation and may allow stimulation of the diaphragm by implanted pace-maker electrodes. An appropriate electrical stimulation might then be possible and diaphragm pacing could replace prolonged artificial ventilation in those patients. Restoration of functional capacity of denervated diaphragm could open a perspective for long term diaphragm pacing in patients with irreversible phrenic nerve injury and diaphragm paralysis.

Restoration of respiratory motion by stimulation of the phrenic nerve was investigated. Respiratory motion was restored successfully by introducing a breathing pacemaker to a patient with respiratory disturbance due to upper cervical spinal cord injury. Breathing pacemakers are considered to be more similar to physiological conditions compared to mechanical ventilators. Although the system is very expensive, its cost effectiveness may be excellent, provided that it can be used for long hours each day over an extended period. The system is effective in improving patient QOL because it dramatically increases patient mobility. From these findings, it is concluded that breathing pacemakers should be used more frequently in Japan, and that various forms of support are necessary to cope with economic and other concerns.

Phrenic pacing can restore diaphragmatic contractions in patients with central respiratory paralysis. It relies on radiofrequency transmission of energy from an external unit to implanted receivers through circular coil antennas. The case of a patient is reported in whom severe hypoventilation occurred following the use of a metallic rescue blanket. The phenomenon was confirmed in two subsequent patients and during benchmark tests. Possible mechanisms include reflection and diffusion of high frequency waves by a Faraday-like effect. Patients with implanted devices relying on telemetric control or powering, and their care givers, should be warned against the use of metallic rescue sheets.

Objectives: We sought to determine the prevalence and clinical impact of diaphragmatic paralysis caused by phrenic nerve injury after cardiothoracic surgery in children., Methods: A search of cardiology, radiology, and hospital databases identified 170 episodes of diaphragmatic paralysis after cardiothoracic surgery in 168 children operated on from 1985 to 1997. Medical records were reviewed to determine demographics, details of the operation and postoperative course, diagnostic features and management of diaphragmatic paralysis, and follow-up status., Results: The prevalence of diaphragmatic paralysis was 1.6% (95% confidence interval 1.4%-1.8%). Median age at operation was 6 months (range <1 day-14.4 years). Median time from the operation to the initial investigation was 5 days (range <1 day-61 days), with 57% of patients receiving mechanical ventilation at diagnosis. Diaphragmatic plication was performed in 40% of the patients at a median interval from the initial investigation of 15 days (range 3 days-11.1 months). Significant independent factors associated with increased postoperative hospital stay were lower patient weight at operation, previous cardiothoracic operations, bilateral diaphragmatic paralysis, increased interval from operation to investigation, mechanical ventilation at the time of investigation, and diaphragmatic plication. Confirmed recovery of diaphragmatic function was noted before hospital discharge in only 15 episodes., Conclusions: Diaphragmatic paralysis complicating cardiothoracic surgery continues to occur in the current era, with a significant impact on morbidity. Smaller patients with bilateral hemidiaphragmatic paralysis, requiring mechanical ventilation, may represent a higher risk subgroup to target for increased diagnostic suspicion and more aggressive management; early spontaneous recovery is rare.

Phrenic nerve injury following cardiac surgery is variable in its incidence depending on the diligence with which it is sought. Definitive studies have shown this complication to be related to cold-induced injury during myocardial protection strategies and possibly to mechanical injury during internal mammary artery harvesting. The consequences are also variable and depend to a large extent on the underlying condition of the patient, particularly with regard to pulmonary function. The response of the patient may range from an asymptomatic radiographic abnormality to severe pulmonary dysfunction requiring prolonged mechanical ventilation and other associated morbidities and even mortality. Two cases are presented to demonstrate the variability in clinical responses to diaphragmatic dysfunction secondary to phrenic nerve injury from cardiac surgery. In addition, treatment strategies are reviewed including early tracheostomy and diaphragmatic plication, which appear to be the most effective options for patients who are compromised by phrenic injuries.

In this article, the anatomy of the diaphragm and phrenic nerves is discussed, together with related surgical implications. Since the major cause of phrenic nerve injury is surgery, usually for congenital or acquired heart disease, incisions in the diaphragm that do not injure major branches of the phrenic nerve are also discussed. Diaphragmatic plication is usually required in infants less than 3 months of age, and older children may be managed by ventilatory support if electrophysiologic studies document the possibility of return of nerve function. In adults with normal pulmonary function, unilateral diaphragmatic paralysis is usually asymptomatic.

Objective: We describe the postoperative respiratory failure due to the phrenic nerve injury in the setting of concomitant cardiac and pulmonary operation., Experimental Study: Prospective study., Setting: Department of Cardiac and Thoracic Surgery Osaka University Medical School., Patients and Interventions: From January 1984 to December 1993, 5 patients (1.4%) underwent the concomitant cardiac and pulmonary operation out of 359 patients who received surgical treatment for lung cancer at our institution., Measures and Results: Three (60%) out of 5 patients required prolonged mechanical ventilation despite the absence of cardiac complication, lung edema or pneumonia. Diaphragm function and work of breathing were measured in two patients before and after weaning from mechanical ventilation. Phrenic nerve dysfunction was consistent with the result that trans-diaphragmatic pressure (delta Pdi) was low, a ratio of gastric to esophageal pressure swing (delta Pga/delta Pes) was abnormally negative, and work of breathing (WOB) was high. Phrenic nerve function restored associated with clinical improvement., Conclusions: Diaphragm dysfunction and an increase in work of breathing may be potential causes of respiratory failure in patients after concomitant cardiac and pulmonary operation. This compromise in respiratory mechanics should not be overlooked in the postoperative care, which may lead to the best management in postoperative respiratory care.

Diaphragm pacing (DP) by electrical stimulation of the phrenic nerve offers important advantages to a highly select group of patients with respiratory paralysis. The patient wears an external radiofrequency (RF) transmitter over an implanted receiver, and a stimulating current is induced without the need for any transcutaneous wires. We review the conditions and requirements of patients who may benefit most from DP. We outline the preoperative evaluation and procedures for surgical implantation. We discuss the risk of diaphragmatic fatigue posed by initiation of DP and the use of gradual conditioning to limit this problem. Other problems encountered by patients in the course of DP can be minimized by well-instructed home caregivers and by systematic medical follow-up. Although a few patients derive considerable benefit from DP, many patients with respiratory paralysis are better treated by less invasive means such as nasal bilevel positive airway pressure or intermittent positive pressure ventilation, which we also review.

Background: Phrenic nerve pacing is a recognized substitute to positive pressure ventilation via tracheotomy in patients with high cervical cord lesions or central hypoventilation. Although its indications are infrequent, reliable strategies need to be used in the determinations of patients who may benefit from this treatment; contraindications should be carefully respected., Study Objectives: To determine whether modern and noninvasive means to study the motor pathway to the diaphragm, namely cortical magnetic stimulation (CxMS) and cervical magnetic stimulation (CMS), can contribute to the selection of patients who may benefit from phrenic pacing., Design and Setting: Prospective study (18 months), on a consecutive basis, of patients referred for possible phrenic pacing to a 10-bed ICU associated with a respiratory neurophysiology laboratory., Patients: Seven patients (high cervical cord injury, n = 5; central hypoventilation following neurosurgery, n = 1; idiopathic acquired central hypoventilation, n = 1). INTERVENTION, MEASUREMENTS, AND RESULTS: Electromyography of the diaphragm and transdiaphragmatic pressure were assessed in response to CxMS and CMS. In three cases, no interruption of the corticodiaphragmatic pathway was evidenced, the decision of pacing was postponed, and the patients eventually recovered a spontaneous breathing activity. In two cases, the diagnosis of irreversible peripheral phrenic dysfunction was reached and pacing was denied. In two cases, complete interruption of the corticodiaphragmatic pathway and integrity of peripheral conduction led to the decision of phrenic pacemaker implantation., Conclusion: CxMS and CMS can be used to refine the assessment of patients proposed for phrenic pacing. CxMS can possibly identify those in whom there is a possibility for eventual recovery, and therefore substantiate a decision to postpone the pacing.

Background: Electrophrenic pacing can be used in the management of ventilatory failure in quadriplegic patients. A study was undertaken to determine the pattern of transdiaphragmatic pressure (PDI) during the conditioning phase of electrophrenic pacing to see if it had a possible role in optimising the process of conditioning., Methods: The tidal volume (TV) and PDI were measured in a group of six quadriplegic patients commencing ventilation by low frequency pulse stimulation (7-10 Hz) and low respiratory rate stimulation (< 10 breaths/min)., Results: Tidal volume increased between baseline and month 1 (4.33 ml/kg, p < 0.001) and between months 1 and 2 (3.00 ml/kg, p < 0.05) and then stabilised. PDI was higher during bilateral diaphragmatic pacing (mean (SD) 1.73 (0.30) kPa) than with either left (1.15 (0.34) kPa) or right (0.86 (0.37) kPa) unilateral pacing. PDI varied throughout the observation period, probably by interaction between recovery of the diaphragmatic fibres and the pacing regimen., Conclusions: Patients with quadriplegia due to high spinal injury can be maintained with ventilation by continuous electrophrenic pacing. The control criteria used in this study for pacing were tidal volume and the patient's tolerance, and the PDI measurement did not contribute any additional information to help with managing the conditioning process.

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. 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. 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.

A bilateral phrenic nerve paralysis after open heart surgery with cold cardioplegia in a 78-year-old patient is reported. This injury is observed after aortic valve replacement without use of an ice slush around the pericardium and no surgical or other direct nerve trauma. The diagnosis of clinical and radiologic abnormalities suggestive of phrenic dysfunction is assisted by portable sonography and measurement of the diaphragmatic compound muscle action potential after cervical transcutaneous phrenic nerve stimulation. This bilateral phrenic nerve paralysis required prolonged mechanical ventilation for 68 days with incomplete regression of the neuropathy five months after surgery.

It is presented the clinical record of a female newborn of 39 weeks of gestational age, with birth weight of 4600 g, with diaphragmatic palsy eight days after birth. Were realized diaphragmatic plicature and the clinical course was without any complication. Were reviewed the causes of diaphragmatic palsy and was described the relationship, with vein cannulation for parenteral nutrition.

During an 8-month period, 86 consecutive infants and children under 2 years of age underwent palliative or corrective cardiac surgery, of whom 11 subsequently developed phrenic nerve injury (PNI). This was seen most frequently following classic or modified Blalock-Taussig shunts. The diagnosis was established by ultrasound screening of the diaphragm, and patients were initially managed expectantly with ventilatory support. In nine patients no further management was necessary with demonstrated return of diaphragmatic function. The remaining two patients underwent plication of the diaphragm. The mean time to diaphragmatic recovery was 40.8 days and was more prolonged in patients with paradoxical, as opposed to absent, diaphragmatic movement. There were no deaths in the series. A further retrospective review of 241 patients of similar age undergoing similar surgery over the preceding 2 years revealed evidence of PNI in 11 (4.6%). Recovery of diaphragmatic function was documented in all except one patient who died. Based on these results we believe that although PNI is associated with considerable morbidity, and frequently a long stay in Intensive Care, there is evidence of spontaneous recovery of diaphragmatic function in 90% of the patients. Consequently, plication of the diaphragm can usually be avoided. Ultrasound scanning is extremely useful in establishing the diagnosis and offers assistance in predicting prognosis and deciding management.

We clarified the problems in respiratory management in patients with phrenic nerve palsy (PNP) after open heart surgery. From December 1988 to March 1991, 248 adult patients underwent open heart surgery with topical myocardial cooling. In these patients PNP was diagnosed in 17 patients (6.9%). Age of these patients at operation ranged from 25 to 76 years with a mean age of 57 years. 9 patients were valvular heart disease (7 were reoperation), 7 were coronary artery disease, and one patient was aortic aneurysm. PNP was diagnosed by chest roentgenogram or percutaneous phrenic nerve stimulation test (PNST). Frequency of long-term intubation (> 14 days) was higher in complete PNP patients than incomplete PNP patients. 2 patients, who were observed effort dyspnea at the time of respiratory weaning, were extubated followed by respiratory and circulatory deterioration, and were reintubated. PNP were confirmed after reintubation by PNST. These patients died of pneumonia. Another 2 patients were observed effort dyspnea during respiratory weaning, and were doubted of PNP. PNP were confirmed by PNST before extubation. After hemodynamic stabilization and respiratory physiotherapy, these patients were extubated without any trouble. One patient, who required repeated intubation, was diagnosed PNP by PNST. This patient was extubated after confirmation of improvement of PNP by follow-up PNST. The incidence of PNP was higher in patients with previous open heart surgery than without previous operation. We supposed that the dissection around the heart might be one of major cause of postoperative PNP. So, in recent 4 cases of mitral reoperation, we attempted to reach mitral valve through atrial septum with minimum dissection.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: To investigate the feasibility of negative extrathoracic pressure ventilation as a respiratory support following phrenic nerve palsy after cardiac surgery., Design: An uncontrolled pilot study., Patients: 14 patients aged one week to 30 months (median 5.3 months) with phrenic nerve palsy diagnosed by phrenic nerve conduction tests and diaphragmatic electromyograms. Four had bilateral and 10 unilateral palsy. Before treatment all required oxygen and 10 were receiving positive pressure ventilation. One of the patients with bilateral and four of the patients with unilateral palsies had undergone a plication before negative pressure ventilation was started., Intervention: Treatment was started 6-65 days (median 23) after operation with a newly designed system which included a Perspex chamber, which gave easy access to the child, and an elastic latex neck seal. Continuous negative pressure was used in conjunction with intermittent positive pressure ventilation while continuous or intermittent negative pressure ventilation was used in extubated infants., Results: All four patients with bilateral palsy survived with long-term intermittent negative pressure ventilation and did not require further surgery. Of the 10 with unilateral lesions, seven required no further surgery, two underwent plication, and one had a re-plication. Three patients with unilateral palsy died of non-respiratory causes. The duration of positive pressure ventilation after starting negative pressure ranged from 0 to 23 days (median 6). Treatment with negative pressure lasted for 3-241 days (median 32) and was predominantly administered off the intensive care unit, including at home., Conclusions: Negative pressure ventilation may be an alternative to positive airway pressure ventilation in the management of phrenic nerve palsy. A multicentre randomised controlled trial is now required to assess further the role of negative pressure ventilation in phrenic nerve palsy.

Phrenic stimulation is reserved for the rare patients with central neurogenic apnea due to isolated upper spinal cord injuries. Presenting a series of ten cases the authors describe the indications for phrenic stimulation, the technique of implantation and the conditions for diaphragmatic training by the use of stimulation by low frequency trains allowing for an increase in the number of low muscular fibers. The continuation of accompanying neurological rehabilitation and nursing of these severely handicapped patients is not to be neglected because of the length of the training protocole as the aim is their return home. This technique, therefore, seems particularly suitable for application in a few specialized centers where research for material totally implantable and adapted to the physiological requirements of the patient can be conducted parallel to treatment.

In anesthetized rabbits the efficiency of phrenic nerve stimulation with trains of electric current was studied either when ventilation was effected entirely by bilateral nerve stimulation (electrophrenic ventilation) or during unilateral nerve stimulation when animals were ventilated with a pump and open chest. Trains of rectangular electric pulses (RPT) with constant amplitude and frequency or sine waves, both the amplitude and frequency of which were modulated and controlled by a computer (MSWT), were used with each animal. MSWT closely reproduced the physiological shape of transdiaphragmatic pressure waves. Diaphragm fatigue, as determined from the decrease in the maximal relaxation rate of twitches, occurred after 20 minutes of bilateral or unilateral nerve stimulation with RPT, but only after 60 min (unilateral stimulation) or 98 min (bilateral stimulation) with MSWT. These data show the importance of the motor signal pattern in long-lasting nerve stimulation.

A multi-channel phrenic nerve stimulator developed in Tampere has been implanted into seven patients with C2-tetraplegia and into three patients with central sleep apneas. Six bipolar cuff electrodes were implanted bilaterally into the neck. Two four-pole cuff and 14 four-pole noncuff electrodes were used in seven patients and to replace one bipolar electrode. Four-pole electrodes were implanted within the thorax. Seven patients achieved total independence from conventional ventilators within 4 months of implantation, and one for 18 hours each day. Two patients died 12 days and 3 months after implantation and two patients after having achieved independence from mechanical ventilators from causes unrelated to the stimulators. Reoperations were necessary because of dislocation of receivers, electrodes, electrode lesions, nerve injuries, and technical failures in seven patients. Most of the problems appeared in two patients with obesity and in three patients with very thin phrenic nerves. Single unit prototypes failed technically more frequently than units of prototype serial fabrication. New electrode design, progress in the manufacture of receivers, and improved implantation technique should help to diminish failures in future.

Artificial ventilation by electric stimulation of the phrenic nerves has become clinically significant within the past 20 years and, in the world as a whole, approximately 700 patients have been treated with implanted diaphragmatic pacemakers. The two first patients in whom diaphragmatic pacemakers were implanted in Denmark, had sustained accidental fractures of the second cervical vertebra with subsequent high cervical spinal cord lesions with not only tetraplegia but also respiratory arrest. In both patients, diaphragmatic pacemakers were implanted bilaterally and these were employed for 12-14 hours daily while ventilation with a respirator was employed at night. The main indications for diaphragmatic pacing are paralysis of respiration following high cervical spinal traumata and the chronic central hypoventilation syndrome (sleep apnoea of Undine's curse). Diaphragmatic pacing may improve the mode of ventilation and the quality of life for patients with tetraplegia and respiratory insufficiency. On account of the potential technical problems, the risk of complications and the limited number of patients in whom this operation is suitable, implantation of diaphragmatic pacemakers should be concentrated in a few centres and probably only one in Denmark.

We implanted electrophrenic respiration (EPR) units in 15 apneic quadriplegic patients with brain stem or high cervical cord injury. 11 of the patients achieved full-time respiration with EPR and another 2 achieved half-time respiration. Despite the loss of patients due to unrelated problems, 7 now use EPR continuously, 1 for 18 years. The factors involved in the significant success rate with EPR are discussed from the point of view of a neurosurgeon.