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Chest wall motion of infants during spinal anesthesia.

To test the extent to which diaphragmatic contraction moves the rib cage in awake supine infants during quiet breathing, we studied chest wall motion in seven prematurely born infants before and during spinal anesthesia for inguinal hernia repair. Infants were studied at or around term (postconceptional age 43 +/- 8 wk). Spinal anesthesia produced a sensory block at the T2-T4 level, with concomitant motor block at a slightly lower level. This resulted in the loss of most intercostal muscle activity, whereas diaphragmatic function was preserved. Rib cage and abdominal displacements were measured with respiratory inductance plethysmography before and during spinal anesthesia. During the anesthetic, outward inspiratory rib cage motion decreased in six infants (P less than 0.02, paired t test); four of these developed paradoxical inward movement of the rib cage during inspiration. One infant, the most immature in the group, had inward movement of the rib cage both before and during the anesthetic. Abdominal displacements increased during spinal anesthesia in six of seven infants (P less than 0.05), suggesting an increase in diaphragmatic motion. We conclude that, in the group of infants studied, outward rib cage movement during awake tidal breathing requires active, coordinated intercostal muscle activity that is suppressed by spinal anesthesia.

Anesthesia, Spinal↗

[Diaphragmatic fatigue and its role in the development of respiratory insufficiency and cor pulmonale in COPD].

Diaphragmatic function test was performed at rest and during maximal incremental exercise in six male normal non-smokers (Group A), sixteen male patients with COPD (58 +/- 8 yrs), including 4 with only small airway disorder (B) 6 with mild (C) and 6 with moderate airway obstruction (D) and eight patients with cor pulmonale complicated severe airway obstruction and chronic respiratory failure (E). Maximal transdiaphragmatic pressure (Pdi max) at rest in Group A, B, C, D, E were 13.6 +/- 2.9 kPa, 10.8 +/- 3.1 kPa, 9.9 +/- 3.4 kPa, 6.8 +/- 3.3 kPa and 5.3 +/- 2.5 kPa respectively, the latter two (D and E) being significantly lower than that of the normal control (D, P less than 0.05, E, P less than 0.01). Breathing pattern of the diaphragm at rest was similar to the normal control in all groups except that half of the patients in Group E (4/8) showed diaphragmatic paradoxical motion during inspiration. Ergometer test with incremental workload was performed in all groups except for Group E. During exercise, patients with COPD revealed some extent of diaphragmatic fatigue. All in group D(6/6) and most in group C(4/6) eventually developed inspiratory paradoxical motion of diaphragm before the ventilatory reserve was exhausted.

Aged↗

Sarcomeres are added in series to emphysematous rat diaphragm after lung volume reduction surgery.

STUDY OBJECTIVES: The diaphragm adapts to its shortened state in experimental emphysema primarily by losing sarcomeres in series, thus reducing its optimal operating length. One would expect improved diaphragmatic function after lung volume reduction surgery (LVRS) only if the muscle can readapt to its elevated, lengthened postoperative position by either adding back sarcomeres or lengthening sarcomeres. We used a model of elastase-induced emphysema in rats to test the hypothesis that sarcomere addition occurs following LVRS. DESIGN: A cohort of emphysematous rats was created by the intratracheal instillation of elastase. Five months after the instillation, one group of rats underwent measurement of in situ costal diaphragm length via laparotomy, the determination of optimal muscle fiber operating length (Lo) on stimulated diaphragm strips in vitro, and the measurement of sarcomere length by electron microscopy on strips fixed at Lo. Another group of rats underwent LVRS or sham sternotomy 5 months after the instillation, and 5 months following the operation these animals underwent the same series of diaphragmatic studies. RESULTS: Lo was significantly greater in rats that underwent LVRS than those that underwent sternotomy (mean [+/- SE] Lo after LVRS, 2.50 +/- 0.08 cm; mean Lo after sternotomy, 2.27 +/- 0.06 cm; p = 0.013). There was no significant difference in sarcomere lengths between the two groups (2.95 +/- 0.04 vs 3.04 +/- 0.04 microm, respectively; p = 0.10). Using Lo as the length basis, the mean sarcomere number was calculated to be 8,712 +/- 192 in animals that had undergone LVRS and 7,144 +/- 249 in animals that had undergone sternotomy (p < 0.001). CONCLUSION: Sarcomere length is not significantly altered but sarcomeres are added in series following LVRS in this experimental model of emphysema/LVRS. It is likely that this sarcomere addition is a prerequisite to the improvement in inspiratory muscle function that has been observed following LVRS in humans.

Animals↗

[Contusion ruptures of the ocular capsule along postoperative corneo-limbic scars].

Clinical picture, variants of surgical treatment, and anatomic and functional outcomes of contusion ruptures of the eyeball at the site of postoperative corneolimbic cicatrices are described. Such traumas can occur even 9-10 years after keratotomy. The majority of unfavorable outcomes in such patients are due to retinal and vitreous abnormalities, such as hemophthalmia or detachment of the retina. Ruptures of corneolimbic cicatrices in patients after cataract extraction with or without implantation of intraocular lenses are more frequent during the first months after surgery; an indirect contusion is sufficient to cause them. The incidence of fibrous capsule ruptures does not depend on the localization of the cicatrice and type of suture. Ruptures of cicatrices on artiphakic eyes almost always involve falling of intraocular lenses into the wound. An intact diaphragmatic function of the iris and transparent optic media are prognostically favorable factors in such patients.

Adult↗

Post cardiac surgery phrenic nerve palsy: value of plication and potential for recovery.

OBJECTIVES: Evaluation of an aggressive policy for the treatment of phrenic nerve palsy (PNP), following cardiac operations, with emphasis on early diaphragmatic plication. Attention was given to the incidence and predisposing factors for PNP and the potential for recovery following plication. METHODS: From 1 June 1991 to 1 January 1996 we prospectively screened patients for PNP following cardiac surgery. The diagnosis was suspected if difficulty was experienced in weaning the child from the ventilator. If abnormal elevation of the hemidiaphragm was present diaphragmatic plication was performed. Echocardiography was used to assess subsequent return of diaphragmatic function. RESULTS: Seventeen children (nine boys, eight girls), out of 867 (1.9%) children younger than 16 years of age, undergoing cardiac operations were found to have PNP. The mean age was 66 days (range 1-17 months) with 16 patients below 1 year out of a total of 285 patients (incidence 5.6%) and one patient 17 months old. The incidence following open procedures was 11/190, following closed procedures 2/95 and following reoperation 4/83. PNP was diagnosed from 2 to 44 days (mean 14 days) following surgery. It was present on the right side in seven cases, the left in nine and was bilateral in one patient. Two patients were extubated at the time of diagnosis, one patient could be extubated shortly thereafter. Fourteen children underwent diaphragmatic plication, at a median 5 days post diagnosis. Extubation was possible 1-60 days (mean 4 days) after plication. Mean follow-up was 19 +/- 5 months. Subsequent recovery of diaphragmatic movement was documented in seven (41%) children. Time to recovery following plication was 16 months, without plication 38 months. CONCLUSION: Prospective screening for PNP revealed an incidence in children younger than 1 year of 6%. Early plication substantially reduces the duration of ventilation, with its associated reduced morbidity and ICU stay.

Algorithms↗

Breathing patterns during curare-induced muscle weakness.

This study examines the pattern of breathing used by normal subjects to compensate for an acute decrease in muscle strength. A continuous infusion of curare was used to reduce peak inspiratory pressure in six normal subjects from normal control levels to -45 cm H2O (moderate weakness) and to -70 cm H2O (mild weakness). Before administration of curare, inspiratory pressure exceeded -120 cm H2O. A canopy-computer-spirometer system was used for noninvasive spirometry and measurements of gas exchange. Partial curarization to a mild level of muscle weakness did not produce significant changes in the respiratory functions studied. With a moderate level of muscle weakness, there were significant increases in tidal volume from 166 to 186 ml/m2 and in inspiratory time from 1.51 to 1.71 sec (P less than 0.05). Minute ventilation and inspiratory flow did not change. However, when given 3% CO2, both normal and partially curarized subjects increased minute ventilation, from 2.3 to 5.7 L/min/m2 and from 2.5 to 6.7 L/min/m2, respectively. The increases in both conditions were secondary to increases in tidal volume. There was also a small increase in respiratory frequency from 15.4 to 18 breaths/min, P less than 0.01 in the partially curarized group given 3% CO2. Because minute ventilation was preserved while vital capacity decreased, it is proposed that respiration is maintained in the presence of muscle weakness associated with curare by diaphragmatic function which remains relatively unaffected by curarization.

Adult↗

Diaphragmatic fatigue and breathing pattern during weaning from mechanical ventilation in COPD patients.

The medium-term outcome of weaning from mechanical ventilation in COPD patients is not easy to anticipate because a respiratory fatigue may eventually develop. We evaluated the diaphragmatic function and the breathing pattern during 40 weaning trials on 15 patients ventilated after acute respiratory failure. We formed two groups according to the success (group B, n = 18) or failure (group A, n = 19) of the medium-term attempt (group A/less than 10 hours; group B/more than 12 hours). Provided the patients showed the classic weaning criteria (tidal volume greater than 5 ml/kg, respiratory frequency less than 30 breaths per minute, PaO2 greater than 50 mm Hg), the study of the breathing pattern did not allow differentiation between the groups. However, the transdiaphragmatic pressure (Pdi) and the Pdimax, which gave an indication of the power of diaphragm contraction, dropped early in the group that could not stand weaning, with an increase in the Pdi/Pdimax ratio. In addition, this same group showed a diaphragmatic dysfunction attested for by a frequent negative gastric pressure associated with or shortly preceded by an abdominal paradoxic motion.

Aged↗

Diaphragm function after pulmonary resection. Relationship to postoperative respiratory failure.

We studied the lung mechanics and respiratory muscle function in 20 patients undergoing pulmonary resection. Transdiaphragmatic pressure (delta Pdi) during quiet breathing did not show any remarkable change after the operation (9.5 +/- 1.1 to 10.9 +/- 1.0 cm H2O), while the ratio of abdominal to transdiaphragmatic pressure changes (delta Pab/delta Pdi) revealed a significant difference between the preoperative and the early postoperative periods (0.32 +/- 0.06 to 0.00 +/- 0.11, p less than 0.05). The postoperative delta Pab/delta Pdi correlated significantly with the work of breathing (r = -0.60, p less than 0.01). The maximal transdiaphragmatic pressure (Pdimax) decreased significantly after operation (75.0 +/- 15.8 to 32.8 +/- 12.4 cm H2O, p less than 0.05), with no significant change in the maximal inspiratory mouth pressure (MIP) (74.2 +/- 16.8 to 39.5 +/- 11.6 cm H2O). Four of 20 patients developed respiratory failure postoperatively and required mechanical ventilation. delta Pab/delta Pdi in these patients was significantly lower than in the other patients (-0.62 +/- 0.24 versus 0.16 +/- 0.09, p less than 0.005). Our results suggested that during quiet breathing diaphragmatic function was preserved and intercostal/accessory muscles recruitment increased, but maximal strength of the diaphragm might be reduced in patients undergoing pulmonary resection.

Adult↗

Clinically relevant diaphragmatic dysfunction after cardiac operations.

Phrenic nerve injury and diaphragmatic dysfunction can be induced by cardiac operation. The clinical consequences are not well-established. We evaluated 13 consecutive patients over a 2-year period with unexplained and prolonged difficulties in weaning from mechanical ventilation. The mean time of measurement from the operation day was 31 +/- 19 days (range 8 to 78). With the same technique we also evaluated 12 control patients: four patients at day 1 after cardiac operation while they were still intubated; four normally convalescing patients at day 7 or 8 after cardiac operation; and four patients who required prolonged mechanical ventilation because of another identified cause after cardiac operation. Diaphragmatic function was evaluated at the bedside from esophageal and gastric pressure measurements. A low or negative ratio of gastric pressure swing to transdiaphragmatic pressure swing, indicative of diaphragm dysfunction, was found in all 13 patients (mean -0.39 +/- 0.64). The difference between the 13 patients and all control groups was found to be highly significant. Transdiaphragmatic pressure measured during a maximal voluntary inspiratory effort and transdiaphragmatic pressure measured during a short, sharp sniff were markedly diminished (28 +/- 18 cm H2O and 13 +/- 15 cm H2O, respectively) in the 13 patients, significantly different from values in the four control patients studied at day 7 or 8. Transdiaphragmatic pressure measured after magnetic stimulation in four patients was also markedly reduced (7 +/- 5 cm H2O) as compared with normal theoretic values. Aminophylline infusion had no effect on any of these parameters. In one of two patients evaluated a second time, about 5 weeks later, a marked improvement was observed. Estimating the prevalence of clinically relevant diaphragmatic dysfunction, we found it to be 0.5% when no topical cooling was used and 2.1% when iced slush with no insulation pad was added for myocardial protection (p < 0.005). The most striking finding was that the clinical course of the 13 patients was marked by severe intercurrent events, including cardiorespiratory arrest after early tracheal extubation in 5 patients, nosocomial pneumonia in 11, prolonged mechanical ventilation in all (58 +/- 41 days), and a fatal outcome in 3. We conclude that prolonged postoperative diaphragmatic dysfunction may cause severe life-threatening complications after cardiac operation and can be limited to some extent by avoiding the use of iced slush topical cooling of the heart.

Adult↗

The decreasing incidence of diaphragmatic dysfunction in liver transplantation: a probable advantage of the piggy-back liver transplant technique.

BACKGROUND: Pediatric orthotopic liver transplantation (OLT) has a low mortality. Some children, however, have an adverse outcome defined as a prolonged ventilatory support requirement and protracted pediatric intensive care unit (PICU) stay. The aim of this study was to determine if that adverse outcome related to the child's condition pre-OLT and/or the development of a pleural effusion or diaphragmatic dysfunction. METHODS: The study included 210 children with a median age at transplantation of 45.5 months (range 0.2-252 months). Fourteen had undergone retransplantation. The duration of ventilatory support (intermittent positive pressure ventilation [IPPV]) and PICU admission and development of a pleural effusion and/or diaphragmatic dysfunction were documented for each child. The patients were divided into three groups according to whether they had acute liver failure (ALF), chronic liver disease at home (CHOM), or chronic liver failure sufficiently ill to be in the hospital awaiting transplantation (CHOSP). RESULTS: The 36 children with ALF were of similar age to the 138 CHOM and 36 CHOSP children but required longer IPPV (P < 0.0001) and PICU stay (P < 0.0001). Overall, 17 children developed diaphragmatic dysfunction and 138 pleural effusions; affected children required longer IPPV and PICU stay (P <0.01). Regression analysis demonstrated that diaphragmatic dysfunction, but not pleural effusion development, was associated with prolonged ventilation (P <0.01) and protracted PICU stay (P <0.05). Other risk factors were ALF (P <0.01), retransplantation (P <0.01), and young age (P <0.05). CONCLUSION: Diaphragmatic dysfunction adversely influences PICU morbidity after OLT. Early assessment of diaphragmatic function, and if necessary aggressive management, might improve outcome.

Journal Article↗

Simplified operative technique for the long-segment atypical coarctation of the aorta.

Simplified operative technique for the long-segment atypical coarctation of the aorta was described. The main objective of this technique is to gain quick access to both thoracic and abdominal aorta with minimal blood loss, and preservation of diaphragmatic function. This procedure consists of standard thoracotomy and pararectal incision with an entry into the retroperitoneal space. Long prosthetic graft was anastomosed in an end-to-side fashion to bypass the coarctated aorta. The graft is placed through peripheral circumference of the left hemidiaphragm, where phrenic nerve injury is not likely to occur. This technique was successfully applied to two cases of long-segment atypical coarctation of the aorta due to Takayasu's aortitis. Retroperitoneal placement of the graft prevents fatal hemorrhage due to direct contact with the graft. Contamination with transintestinal exudate can also be avoided. Results of the ten-year follow-up of the similar procedure in the literature is encouraging.

Adult↗

Verapamil causes decreased diaphragm endurance but no decrease of nocturnal O(2) saturation in patients with chronic obstructive pulmonary disease.

OBJECTIVE: In animal studies, it has been shown that verapamil reduces strength and endurance of the diaphragm and inhibits the beneficial effects of theophylline. We examined whether the use of verapamil in patients with severe chronic obstructive pulmonary disease (COPD) who use theophylline leads to a deterioration of diaphragmatic function resulting in a decrease of nocturnal O(2) saturation. METHODS: A double-blind, placebo-controlled crossover study was designed in eight stabile severe COPD patients [forced expiratory volume in 1 s (FEV(1)) 0.9 +/- 0.1 l] taking theophylline. The doses of theophylline ranged from 600 mg daily to 1200 mg daily (7.0 mg/kg daily to 16.9 mg/kg daily). Nocturnal recordings, maximal respiratory muscle strength and endurance tests, lung function, blood pressure, electrocardiogram and arterial blood gas analysis were performed after 6 days of verapamil and after placebo. RESULTS: A significant decrease of the endurance time from 7.7 min to 6.4 min was found in the threshold loading test. However, the mean nocturnal saturation values did not change significantly: 89.8% and 89.6%, respectively. Results of pulmonary function tests, arterial blood gas analysis and routine blood samples also did not change. CONCLUSION: The decrease of the respiratory muscle endurance after the use of verapamil is in line with experiments in animal diaphragms. However, the nocturnal saturation did not change. This finding suggests that the effect found on diaphragm endurance is of no clinical significance and that verapamil can be given to COPD patients without risk of worsening nocturnal saturation. However, this must be confirmed by future larger scale studies.

Aged↗

Chest wall kinematics during chemically stimulated breathing in healthy man.

Chest wall compartment kinematics and respiratory muscle coordinate activity, during either hypercapnia or hypoxia, have not been comparatively assessed in healthy humans. We assessed the displacement volume of the chest wall (Vcw) in 5 normal subjects during hypoxic-normocapnic and hypercapnic-hyperoxic rebreathing by using linearized magnetometers. Vcw was divided into displacement volumes of the rib cage (Vrc) and the abdomen (Vab). Esophageal (Pes) and gastric (Pga) pressures were simultaneously recorded and transdiaphragmatic pressure (Pdi) was calculated by subtracting Pes from Pga. Pressure swings (sw) from end expiration (EE) to end inspiration (EI) were also calculated. During both hypoxia and hypercapnia, from quiet breathing to 40 L/min VE, Vrc,EI increased consistently but Vrc,EE, and Vab,EI did not. Moreover, Vab,EE decreased significantly during hypercapnia and remained unchanged during hypoxia. PesEI decreased (more negative values) and PesEE increased (less negative values) during either stimulus, while PgaEE increased with hypercapnia. Pdisw, calculated as the difference between PdiEE and PdiEI, increased significantly with both hypercapnia and hypoxia ( p = 0.002 for both). On the plot of Pes vs Pga, the slope of a line from end expiratory to end inspiratory lung volume between 20 and 40 L/min VE progressively increased during hypercapnia indicating increasing rib cage muscle (RCM) contribution to inspiratory pressure swings relative to the diaphragm. From these results we conclude that in healthy man: (i) with both chemical stimuli RCM contribution accounts for increase in Vrc displacement; (ii) with hypercapnia, the decrease in Vab,EE displacement indicates abdominal muscle (ABM) contribution to tidal volume; (iii) RCM and ABM assist the diaphragmatic function during hypercapnic stimulation.

Adult↗

Bilateral diaphragmatic paralysis with hypercapnic respiratory failure. A physiologic assessment.

Bilateral diaphragmatic paralysis was suspected in a patient presenting with hypercapnic respiratory failure who exhibited paradoxic (i.e., inward) abdominal movement on inspiration during tidal breathing in the supine posture; no paradoxic abdominal motion was observed at the bedside with the patient upright. Transdiaphragmatic pressure measurements established the diagnosis of diaphragmatic paralysis, although 20 cm H2O pressure developed across the diaphragm during the latter part of a forced expiration, presumably due to the development of passive tension in the diaphragm as it was stretched near residual volume. Analysis of the relative motion of the rib cage and abdomen during breathing by the use of magnetometers confirmed the presence of abdominal paradox throughout the breathing cycle when the patient was supine, and established that paradoxic motion of the abdomen also occurred when the patient was in the erect posture but only in the latter half of inspiration. Our findings confirm that the use of transdiaphragmatic pressure measurements and magnetometry will help to quantify diaphragmatic function, that passive tension develops in the paralyzed diaphragm near residual volume and should not be confused with active contraction, and that paradoxic motion of the abdomen may be masked from the clinician when the patient is erect.

Aged↗

Post cardiac surgery phrenic nerve palsy in pediatric patients.

From January 1978 to December 1988, 109 phrenic nerve paralyses (PNP) occurred in a total of 9149 cardiac operations performed in a population of patients younger than 15 years old (1.2%) whose age varied from 1 day to 15 years old and mean weight was 11.3 +/- 8.7 kg. PNP was diagnosed in 43 patients after closed procedures (1.2% of 3509 procedures) and in 66 patients after open heart operations (1.2% of 5640 operations). PNP was right sided in 49 cases and left sided in 60 cases. Open heart operations that predisposed to PNP were those which needed harvesting of autologous pericardium (P less than 0.0001) and wide exposure of the great vessels. The modified right Blalock-Taussig shunt was the main cause of PNP in closed procedures (P less than 0.02). Small children tolerated PNP less well. They needed longer ventilatory support (P less than 0.0005) and developed more respiratory complications. Seventeen children underwent plication of the affected hemidiaphragm and could be subsequently extubated. It is concluded that for prevention of PNP, a high level of attention should be exercised in neonates and small children, particularly when pericardium is harvested or when exposure needs extensive dissection of the great vessels and thymus resection, or at reoperation. We also prefer to avoid the use of iced slush lavage. PNP, when symptomatic, is best managed by continuous positive airway pressure (CPAP) ventilation. Diaphragmatic plication is recommended when after 2-3 weeks there is no recovery of diaphragmatic function or when there are troublesome respiratory complications.

Adolescent↗

Spontaneous crossed phrenic activity in the neonatal respiratory network.

Hemisection of the cervical spinal cord causes paralysis of the ipsilateral hemidiaphragm in adult rats. Activation of a latent crossed phrenic motor pathway can restore diaphragmatic function, although structural changes take place before the pathway can be activated. Since mechanisms are employed to eliminate non-functional projections during development, we predicted that this latent neural pathway might be active during development. Therefore, we examined the effect of spinal hemisection (C2) on respiratory-like activity bilaterally using the brainstem--spinal cord preparation from neonatal rats (0-4 days). Spontaneous crossed phrenic activity (respiratory-like activity recorded from the ipsilateral C4 or C5 ventral roots following C2 hemisection) was observed in an age-dependent manner; younger preparations exhibited more than older preparations. Increasing drive (increasing [K+] or superfusion of theophylline) either increased or induced crossed phrenic activity. Hemisection caused no change in the frequency, the burst area, duration or peak amplitude contralateral to hemisection. Unlike adult rats, this study shows that crossed phrenic activity is present in the in vitro respiratory network of neonatal rats suggesting that a crossed neural pathway may be functionally active in neonates.

Action Potentials↗

Influence of diaphragm and rib cage muscle fatigue on breathing during endurance exercise.

Inspiratory muscle fatigue (IMF) can develop during exhaustive exercise and cause tachypnea or rapid shallow breathing. We assessed the effects of rib cage muscle (RCM-F) and diaphragm fatigue (DIA-F) on breathing pattern and respiratory mechanics during high-intensity endurance exercise. Twelve healthy subjects performed a constant-load (85% maximal power) cycling test to exhaustion with prior IMF and a cycling test of similar intensity and duration without prior IMF (control). IMF was induced by resistive breathing and assessed by oesophageal and gastric twitch pressure measurements during cervical magnetic stimulation. Both RCM-F and DIA-F increased RCM and abdominal muscle force production during exercise compared to control. With RCM-F, tidal volume decreased while it increased with DIA-F. RCM-F was associated with a smaller increase in end-expiratory oesophageal pressure (i.e. decrease in lung volume) than DIA-F. These results suggest that RCM-F and not DIA-F is associated with rapid shallow breathing and that lowering the operating lung volume with DIA-F may help to preserve diaphragmatic function.

Adult↗

Neurogenic respiratory failure: a 5-year experience using implantable phrenic nerve stimulators.

During the past 5 years, 20 phrenic nerve stimulators have been implanted in 11 patients who were ventilator dependent because of neurogenic respiratory failure. Ten patients had traumatic spinal cord lesions; the remaining patient suffered from a progressive demyelinating disease. There was no operative mortality. Complications included 1 stimulator malfunction and 1 pneumothorax. In spite of adjacent tracheostomies, there were no infections or wound complications. Of the 20 stimulators implanted, 13 initially produced good diaphragmatic function, 2 had fair function, and 5 had little or not function. Three patients became completely independent of their ventilators; 6 became partially independent, thus simplifying nursing care. There were no late complications. As of December, 1979, 7 patients had benefited or were continuing to benefit from phrenic nerve stimulation.

Adolescent↗