Factors contributing to the increased threat to life following spinal cord injury

Pulmonary function and expiratory flow limitation in acute cervical spinal cord injury

OBJECTIVE

To identify the nature of the changes of respiratory mechanics in patients with middle cervical spinal cord injury (SCI) and their correlation with posture.

DESIGN

Clinical trial.

SETTING

Acute SCI unit.

PARTICIPANTS

Patients with SCI (N=34) at C4-5 level studied within 6 months of injury.

INTERVENTIONS

Patients were assessed by the negative expiratory pressure test, maximal static respiratory pressure test, and standard spirometry.

MAIN OUTCOME MEASURES

The following respiratory variables were recorded in both the semirecumbent and supine positions: (1) tidal expiratory flow limitation (TEFL); (2) airway resistances; (3) mouth occlusion pressure developed 0.1 seconds after occluded inspiration at functional residual capacity (P(0.1)); (4) maximal static inspiratory pressure (MIP) and maximal static expiratory pressure (MEP); and (5) spirometric data.

RESULTS

TEFL was detected in 32% of the patients in the supine position and in 9% in the semirecumbent position. Airway resistances and P(0.1) were much higher compared with normative values, while MIP and MEP were markedly reduced. The ratio of forced expiratory volume in 1 second to forced vital capacity was less than 70%, while the other spirometric data were reduced up to 30% of predicted values.

CONCLUSIONS

Patients with middle cervical SCI can develop TEFL. The presence of TEFL, associated with increased airway resistance, could increase the work of breathing in the presence of a reduced capacity of the respiratory muscles to respond to the increased load. The semirecumbent position and the use of continuous positive airway pressure can be helpful to (1) reduce the extent of TEFL and avoid the opening/closure of the small airways; (2) decrease airway resistance; and (3) maintain the expiratory flow as high as possible, which aids in the removal of secretions.

Comparison of immunoreactivities in 4-HNE and superoxide dismutases in the cervical and the lumbar spinal cord between adult and aged dogs

Aging shows slowly progressive changes and is associated with many functional and morphological changes in the central nervous system. The accumulation of reactive oxygen species causes age-related deterioration in neuronal function and contributes to the increase of disease susceptibility during normal aging. In the present study, we compared the neuronal distribution and immunoreactivities of 4-hydroxy-2E-nonenal (4-HNE, end product of lipid peroxidation), and superoxide dismutase 1 (SOD1) and SOD2 in the cervical and lumbar spinal cord between adult (2-3 years) and aged (10-12 years) dogs. No significant change in neuronal morphology was observed after cresyl violet staining. The number of NeuN (a marker for neurons)-immunoreactive neurons was not significantly changed in the aged group compare to the adult group. In addition, we could not find Fluoro-Jade B (a marker for degenerating neurons) positive cells in both the adult and aged dogs. However, numbers of 4-HNE-, SOD1- and SOD2-immunoreactive cells were significantly increased in both the cervical and lumbar spinal cord of the aged dog: The increase rates of these cells in the aged spinal cord were higher in the lumbar level than the cervical level. In brief, 4-HNE, SOD1 and SOD2 levels are much increased in the aged spinal cord compared to the adult spinal cord.

Lower thoracic spinal cord stimulation to restore cough in patients with spinal cord injury: results of a National Institutes of Health-sponsored clinical trial. Part I: methodology and effectiveness of expiratory muscle activation

OBJECTIVE

Evaluation of the capacity of lower thoracic spinal cord stimulation (SCS) to activate the expiratory muscles and generate large airway pressures and high peak airflows characteristic of cough, in subjects with tetraplegia.

DESIGN

Clinical trial.

SETTING

Inpatient hospital setting for electrode insertion; outpatient setting for measurement of respiratory pressures; home setting for application of SCS.

PARTICIPANTS

Subjects (N=9; 8 men, 1 woman) with cervical spinal cord injury and weak cough.

INTERVENTIONS

A fully implantable electrical stimulation system was surgically placed in each subject. Partial hemilaminectomies were made to place single-disk electrodes in the epidural space at the T9, T11, and L1 spinal levels. A radiofrequency receiver was placed in a subcutaneous pocket over the anterior portion of the chest wall. Electrode wires were tunneled subcutaneously and connected to the receiver. Stimulation was applied by activating a small portable external stimulus controller box powered by a rechargeable battery to each electrode lead alone and in combination.

MAIN OUTCOME MEASURES

Peak airflow and airway pressure generation achieved with SCS.

RESULTS

Supramaximal SCS resulted in high peak airflow rates and large airway pressures during stimulation at each electrode lead. Maximum peak airflow rates and airway pressures were achieved with combined stimulation of any 2 leads. At total lung capacity, mean maximum peak airflow rates and airway pressure generation were 8.6+/-1.8 (mean +/- SE) L/s and 137+/-30 cmH2O (mean +/- SE), respectively.

CONCLUSIONS

Lower thoracic SCS results in near maximum activation of the expiratory muscles and the generation of high peak airflow rates and positive airway pressures in the range of those observed with maximum cough efforts in healthy persons.

Lower thoracic spinal cord stimulation to restore cough in patients with spinal cord injury: results of a National Institutes of Health-Sponsored clinical trial. Part II: clinical outcomes

OBJECTIVE

To evaluate the clinical effects of spinal cord stimulation (SCS) to restore cough in subjects with cervical spinal cord injury.

DESIGN

Clinical trial assessing the clinical outcomes and side effects associated with the cough system.

SETTING

Outpatient hospital or residence.

PARTICIPANTS

Subjects (N=9; 8 men, 1 woman) with cervical spinal cord injury.

INTERVENTIONS

SCS was performed at home by either the subjects themselves or caregivers on a chronic basis and as needed for secretion management.

MAIN OUTCOME MEASURES

Ease in raising secretions, requirement for trained caregiver support related to secretion management, and incidence of acute respiratory tract infections.

RESULTS

The degree of difficulty in raising secretions improved markedly, and the need for alternative methods of secretion removal was virtually eliminated. Subject life quality related to respiratory care improved, with subjects reporting greater control of breathing problems and enhanced mobility. The incidence of acute respiratory tract infections fell from 2.0+/-0.5 to 0.7+/-0.4 events/subject year (P<.01), and mean level of trained caregiver support related to secretion management measured over a 2-week period decreased from 16.9+/-7.9 to 2.1+/-1.6 and 0.4+/-0.3 times/wk (P<.01) at 28 and 40 weeks after implantation of the device, respectively. Three subjects developed mild hemodynamic effects that abated completely with continued SCS. Subjects experienced mild leg jerks during SCS, which were well tolerated. There were no instances of bowel or bladder leakage.

CONCLUSIONS

Restoration of cough via SCS is safe and efficacious. This method improves life quality and has the potential to reduce the morbidity and mortality associated with recurrent respiratory tract infections in this patient population.

Spinal cord stimulation: a new method to produce an effective cough in patients with spinal cord injury

Patients with spinal cord injury have an increased risk of developing respiratory tract infections as the result of expiratory muscle paralysis and consequent inability to cough. We have developed a method by which the expiratory muscles can be activated via lower thoracic and upper lumbar spinal cord stimulation to produce an effective cough mechanism. In a tetraplegic patient who required frequent (8.57+/-2.3 times per week [mean+/-SEM]) caregiver assistance to facilitate airway clearance and expectoration of secretions, three epidural electrodes were applied in the T9, T11, and L1 spinal cord regions. During stimulation at the T9 and L1 levels, airway pressures were 90 and 82 cm H2O, respectively. Peak expiratory flow rates were 6.4 L/s and 5.0 L/s; respectively. During combined (T9+L1) stimulation, airway pressure and expiratory flow rate increased to 132 cm H2O and 7.4 L/s, respectively. Addition of the third lead did not result in further increases in pressure generation. These values are characteristic of those observed with a normal subject. Because the patient is able to trigger the device independently, he no longer requires caregiver support for airway management. If confirmed in additional patients, spinal cord stimulation may be a useful method to restore an effective cough mechanism in patients with spinal cord injury.

Vieillissement chez les blessés médullaires

OBJECTIVE

Literature review of the data on aging with spinal cord injury.

METHOD

Interrogation on Medline using the following keywords: aging, spinal cord injuries, paraplegia, quadriplegia, mortality, morbidity, quality of life, survival, health status.

RESULTS

The expectation of life of the spinal cord injury patients improved even though it remains even lower than that of the general population. The effects of aging add to the specific complications which are numerous and alter almost every function. Respiratory complications became the first cause of death especially for tetraplegics. Urinary and cutaneous complications remain important as well as osteo-articular pathologies (particular upper limbs) whose consequences can be serious on the functional capacities. Studies on the quality of life show that adaptation to the handicap is done in a continuous way and a long time after the initial phase of rehabilitation. They underline the importance of professional resources, psychological reactions and previous experiences of the spinal cord injury patients in appreciating the quality of life after the traumatism.

CONCLUSION

The specificities of the aging of the spinal cord injury patients require to be well known and underline the importance and the necessity of an adequate and specific follow-up. On a more general plan, they imply a reflection on the strategies of initial rehabilitation, not to compromise the future of these spinal cord injury patients.