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Spinal Cord Injury (SCI) / Myelopathy
OUTCOMES OF CONVENTIONAL MANAGEMENT
With acute high-level spinal cord injuries, most apneic individuals die before making it to a hospital. Therefore, when ventilatory failure develops and ventilatory support is needed, it usually happens during the first week of hospitalization as the vital capacity (VC) temporarily decreases because of swelling of the spinal cord into higher areas of the spine or due to other respiratory complications like pneumonia. Typically, as patients become short of breath or develop airway secretions, instead of being provided with noninvasive ventilatory support and mechanical insufflation-exsufflation (NVS and MIE), they receive O2. The supplemental O2 renders oximetry essentially useless as a gauge of alveolar ventilation and airway secretion congestion (see oximetry feedback protocol). In addition, sedatives and narcotics, which are typically given along with O2, dull ventilatory drive leading to shallow breathing and increased CO2 retention. Once secretions and hypoventilation cause distress, instead of using full ventilator setting with NVS and MIE, the patient is conventionally intubated.
Intubated patients, even if intubated for only a few days, are typically told that tracheotomy is needed, especially when surgery and general anesthesia are planned and autonomous breathing is not possible. While surgical interventions and general anesthesia, and inadequate respiratory muscle strength to breathe can necessitate intubation, tracheostomy is not always necessary (JBCV157). Even when not quickly undergoing tracheotomy, patients who fail ventilator weaning parameters and spontaneous breathing trials or extubation attempts are usually informed that tracheotomy is necessary for extubation even though alert, cooperative patients can also inevitably be extubated to CNVS and MIE. Patients with SCI can and should be intubated for one month or more if cognitively intact with functioning bulbar (throat) musculature because such patients are excellent candidates for extubation to CNVS and MIE. Such patients have no more likelihood of complications to the airways, and possibly less likelihood, than the patients who undergo tracheotomy (SCI1). Unfortunately, most acute SCI patients’ conditions are complicated by traumatic brain injury, chest trauma, complicating orthopedic and medical conditions, severe anxiety, and/or need for aggressive narcotic therapy for pain management that dulls respiratory drive, can render NVS ineffective, at least temporarily and can warrant tracheotomy.
Thus, the great majority of ventilator users with SCI are discharged from intensive care units on tracheostomy mechanical ventilation (TMV). This occurs even though studies indicate that airway complications are more frequent for intubated patients undergoing tracheotomy than when simply maintaining intubation. While 7.5% of SCI patients with no history of tracheostomy had dysphagia, 20% did whose tubes were removed before admission to rehabilitation and 38.3% had dysphagia when they had tracheostomy tubes upon admission to rehabilitation (SCI2). Even when weaned from ventilator use and decanulated, 7% of patients with a history of tracheotomy have dysphagia and aspirate for the rest of their lives.
It is well known that the life expectancy of CTMV dependent high level tetraplegics is significantly lower than for tetraplegics without tracheostomy tubes:
Unaffected 10 year olds can expect to live another 68.4 years.
For paraplegics (presumably without tracheostomy tubes or TMV use) surviving at least one year after injury, this figure is only 55.2 years.
For C1 to C4 tetraplegics, 46.4 years.
But for users of invasive ventilation with any SCI level, only 31.7 years.
The corresponding mortality figures for 60 year olds are 22.4, 13.2, 8.6, and 3.2 years, respectively (SCI3). Since none of these statistics include SCI patients dependent on CNVS and MIE rather than tracheotomy tubes, all died prematurely due to the tracheostomy tubes. Although SCI patients have a higher risk of mortality from skin ulcers, renal failure, heart failure and other causes, it is unclear why these non-respiratory related risks would be greater for patients dependent on CTMV, so the greatly increased risk of premature mortality for these CTMV dependent patients is most likely due to the CTMV itself. Reasons for death for the CTMV users were not studied unlike for ALS CTMV users for whom the great majority die from complications related to the invasive tubes (JBCV193). Therefore, it is likely that the majority of excess deaths of the SCI CTMV users is also due to the nature of invasive mechanical ventilation.
OUTCOMES OF NONINVASIVE RESPIRATORY MANAGEMENT
Since the great majority of SCI patients retain normal or almost normal bulbar-innervated (throat) muscle function and the ability to think and cooperate, with optimal nonininvasive management, intubation can be avoided for some uncomplicated cases and almost all people, even when continuously ventilator dependent, can be decanulated and safely managed noninvasively. While there are no comparable life expectancy and mortality statistics for CNVS dependent people with SCI, they, like ventilator dependent people with neuromuscular disease, consider noninvasive management to be safer and more desirable than invasive management. In fact, all who have required CTMV for at least 1 month and were decanulated to CNVS preferred the latter for speech, swallowing, convenience, comfort, safety, security, and overall (JBCV66). Whereas CTMV users must always be frightened of accidental disconnections from the ventilator and from the ventilator failing suddenly, 70% of CNVS users with good bulbar-innervated muscle function can master glossopharyngeal breathing (GPB) sufficiently to breathe independently of ventilators and even awaken using GPB so they never have to worry about this (JBCV24,JBCV28).
ACUTE INJURY PERIOD:
AVOIDANCE OF INTUBATION
Besides O2 sat, all SCI patients’ VCs and CO2 (end-tidal CO2) should be monitored every 8 hours in ambient air and if decreasing, any appearance of dyspnea should be treated by mouthpiece NVS without supplemental O2 administration. NVS should be delivered at full ventilatory support settings, that is, volume-preset at 700 to 1300 mL and physiologic backup rates or pressure-preset at about 20 cm H2O. If such patients are incorrectly administered oxygen, then the CO2 soars leading to unnecessary intubatation. Use of NVS and MIE is the ideal solution for acute respiratory distress caused by decreasing VC or airway mucus plugging.
If the O2 sat is normal, whether using NVS or not, the VC should be measured every 8 hours until it is clearly not decreasing (stable). If decreasing and the patient is not already using NVS, a portable ventilator should be used. Use of full ventilator support settings (rather than bi-level PAP) is necessary to optimally rest the inspiratory muscles, relieve dyspnea, and avert intubation for ventilatory failure.
Supplemental O2 should be avoided if the O2 sat is normal. Using NVS and MIE as needed, the oximeter provides feedback on status of alveolar ventilation, airway congestion, and intrinsic lung disease (see oximetry feedback protocol). The oximetry protocol works on the principle that it is impossible to develop severe CO2 retention or acute respiratory failure when the O2 sat remains greater than 94% without supplemental O2 administration. Any O2 sat less than 95% indicates marked hypercapnia, airway congestion, and if the latter is not expeditiously cleared, intrinsic lung disease develops (e.g. atelectasis and/or pneumonia). Thus, it should be immediately determined whether any desaturation below 95% is due to hypercapnia, thereby indicating need for NVS or a change in NVS settings and delivery, whether due to airway secretions which necessitate aggressive MIE to return O2 sat to normal, or due to acute lung/airways disease (most often pneumonia) for which the O2 sat baseline cannot be re-normalized without supplemental O2 administration. If, despite optimal use of NVS/CNVS and MIE the O2 sat baseline remains below 95%, the patient will probably need to be intubated. Uncomplicated patients managed by full setting NVS can avoid intubation despite becoming CNVS dependent and by avoiding the invasive tube may not develop airway congestion or require MIE (Figure SCI1) (JBCV157).
A 15-year-old developed shortness of breath as his VC fell to 750 mL and PaCO2 rose to 50 mmHg approximately 24 hours after hospital admission for high level SCI. Initially, he used a chest shell ventilator but was switched to NVS to permit access to his chest for Halo traction (JBCVBook7). His VC decreased further to 480 mL and he had no ventilator-free breathing ability. After trying nasal, oral, and lipseal NVS, he chose to use mouthpiece NVS (Figure) when awake and lipseal NVS for sleep. After 11 days of dependence on CNVS, he weaned entirely as his VC recovered to exceed 1500 mL. Since he was never intubated, he never developed any difficulties with airway secretions.
ACUTE INJURY PERIOD:
EXTUBATION OF "UNWEANABLE" PATIENTS
Intubated ventilator dependent SCI patients are managed optimally in accordance with indications in Table 1:
Adequate neck function involves sufficient lip and neck control to rotate, flex, and extend the neck to grab and use a mouthpiece for NVS; inadequate bulbar function (-) results in saliva aspiration that causes the O2 sat baseline to decrease below 95% (JBCV211).
Ventilator dependent SCI patients who have cognitive impairment or multi-organ dysfunction or develop lung disease despite optimal use of NVS and MIE, or who require surgery, usually require intubation. Even patients who require multiple surgeries, however, are likely to be better off remaining intubated for one month rather than undergo tracheotomy to avoid the complications caused by going from intubation to tracheotomy (SCI1). Also, it is much easier to extubate unweanable patients than to decanulate them. Once surgeries are completed, the patient is medically stable and cooperative, and specific extubation criteria are met, he or she can be extubated to CNVS and MIE as described (see extubation) (JBCV197,JBCV235).
In fact, in the New Jersey and Porto centers, ventilator “unweanable” adult patients intubated for 77 days (and babies with other conditions for over 5 months) are routinely successfully extubated to CNVS without upper airway complications of prolonged intubation. Likewise, more than 215 “unweanable” patients with neuromuscular weakness including 19 out of 19 with SCI were extubated without resort to tracheotomy, most after failing extubation at other facilities because of insufficient post-extubation ventilatory support (extubation to CPAP or low span bi-level PAP) and failure to use MIE. (JBCV197, JBCV235). Upon arrival for extubation to CNVS, baseline ambient air O2 sat was below 95% for over 80% because of hypercapnia and/or airway secretions. Ventilator settings were immediately adjusted to normalize CO2 and aggressive MIE instituted up to every 60 minutes via the tube until the O2 sat baseline remained 95% or greater, so that the patient was ready for successful extuabtion.
Following removal of any naso- or orogastric tube, patients are extubated directly to CNVS on assist/control 800 to 1500 mL, rate 10 to 14 breaths per minutes on ambient air. Volume cycling is preferred to permit air stacking to maintain pulmonary compliance and to augment cough flows as well as to maintain normal lung ventilation. None of the patients with SCI had lost the ability to swallow food safely but for any patients who might, radiographically inserted or open gastrostomy can be done without intubation (JBCV196). Virtually all patients with pre-extubation VCs of 250 mL regained at least some ventilator-free breathing ability by up to 3 weeks post-extubation; many continue to benefit from sleep NVS after discharge. Patients whose VCs remain less than 250 mL may require CNVS indefinitely. Post-extubation NVS is provided nocturnally via oral, nasal, or occasionally oronasal interfaces (Figures SCI2-5). Daytime support is usually delivered via 15-mm angled mouthpiece.
Patients wean themselves, when possible, by taking fewer and fewer intermittent positive pressure breaths as tolerated via a mouthpiece or nasal interface or by using nasal NVS for increasingly shorter periods of time. For episodes of O2 sat less than 95%, ventilator positive inspiratory pressure, interface or tubing air leakage, CO2 retention, ventilator settings, and airway secretions are considered. The care providers and especially the family provide MIE via oro-nasal interfaces up to every 30 minutes upon patient demand and for dips in O2 sat below 95% until O2 sat no longer dips below 95% and the patient remains clear of secretions. The success rate using this protocol for first attempts at extubation in individuals with high cervical SCI unable to pass spontaneous weaning trials either before or after extubation has been 100% (32/32) (JBCV197,JBCV235,MRCV101).
DECANULATION OF PEOPLE WITH SCI
Since intensivists are quick to tracheostomize SCI patients, virtually all who require intubation and who do not wean from support almost immediately undergo tracheotomy for CTMV and airway suctioning. The tracheostomy tube hinders ventilator weaning by increasing airway secretions, causing ventilator associated pneumonias due to chronic pathogenic bacterial colonization and invasive airway suctioning, chronic inflammation and airway irritation, hyperventilation possibly by bypassing upper airway afferents, etc. (SCI1,JBCVBook7). Thus, patients often go to rehabilitation facilities with tracheostomy tubes and often using TMV or CTMV.
In 1990, 24 high level SCI patients were decanulated to CNVS and MIE. Fifteen patients were unweanable and supported by continuous nonininvasive ventilatory support for 1 month or more before 8 weaned to sleep only NVS. Seven patients depended on CNVS for 12.4 ± 6.3 years (range 1 to 22). MIE was used at 40 to -40 mmHg to help clear airway secretions. Four with VCs as low as 50 mL were CNVS dependent with no ventilator-free breathing ability indefinitely. Six of the seven patients mastered GPB sufficiently to use it for ventilator-free breathing up to all day (JBCV24).
In another report on SCI patients from two centers (Dallas Rehabilitation Institute and University Hospital, Newark, New Jersey), 24 additional SCI patients were decanulated and switched from CTMV to continuous noninvasive ventilation and their ostomies allowed to close despite VCs of 608 ± 458 mL (range 0 to 1150). Eleven had no ventilator-free breathing ability and 4 had no measurable VC. Five patients with VCs averaging 402 mL used GPB to volumes of 2205 mL and used it for ventilator-free breathing up to all day long to give perfect security in the event of ventilator failure or disconnection that is not possible for CTMV users (JBCV28).
Subsequently, despite the challenge to rehabilitation spinal cord services made in 2006, only 11 other ventilator “unweanable” SCI patients have been reported to have been decanulated to CNVS and MIE in two centers (Newark, New Jersey and Porto, Portugal) (JBCV177,JBCV232,MRCV101). However, there are apparently others (Buenos Aires, Argentina via verbal communication of Dr. Eduardo DeVito).
LATE-ONSET VENTILATORY FAILURE
At the 14th Annual Scientific Meeting of the American Spinal Injury Association on May 2, 1988 in San Diego, Bach, Sortor, and Sipski reported that high cervical quadriplegic patients developed severe sleep blood gas derangements with age (Proc 1988:102-103). Whereas a 20-year-old with a VC of 1000 mL is likely to have normal sleep O2 sat and CO2, this is not often the case for a 50-year-old with the same VC. With time, many SCI patients become symptomatic for hypoventilation and possibly obstructive sleep apneas, and this is especially true when obesity or scoliosis complicates the clinical picture (JBCV62,JBCVLetter12).
Hypercapnic patients not using NVS, and especially those receiving supplemental oxygen after being evaluated for “sleep disordered breathing,” can eventually develop CO2 narcosis and stop breathing. Instead of evaluating and treating all of these patients for sleep disordered breathing with often inadequate supplemental O2, CPAP, and low span bi-level PAP, all symptomatic patients with markedly diminished VCs should be introduced to NVS at full support settings to ease symptoms by resting inspiratory muscles during sleep. When symptoms are questionable, home nocturnal end-tidal CO2 (EtCO2) and O2 sat monitoring that demonstrates CO2 > 50 cm H2O and multiple hourly desaturations below 95% indicates the need for a trial of nocturnal NVS to clear symptoms and normalize blood gases. Simple daytime EtCO2 measurement along with EtCO2 or transcutaneous CO2 (TcCO2) and O2 sat sleep monitoring are more useful than polysomnograms because the latter are not programmed to distinguish obstructive apneas from inspiratory muscle dysfunction and both can be successfully treated by NVS (without expiratory positive airway pressure).
When sleep-only NVS is no longer adequate and patients become short of breath when discontinuing it in the morning, especially when symptomatic daytime hypoventilation results in O2 sat < 95%, which happens most often when patients do not use sleep NVS, daytime ventilation can be normalized by wearing a pulse oximeter and setting the O2 sat alarm at 94% (JBCV62). The patient sees that by taking slightly deeper breaths, O2 sat will exceed 95% within seconds and hypercapnia diminishes. As this becomes too fatiguing if used throughout the day, the patient is instructed to maintain normal O2 sat by supplementing breathing with mouthpiece NVS. With age, co-morbidities, and weakening inspiratory muscles, the person can require increasing periods of daytime NVS to maintain adequate ventilation. In this manner, an oximeter can help to reset central ventilatory drive and NVS dependence can become continuous (CNVS) without hospitalization, episodes of acute respiratory failure, or resort to tracheostomy (JBCVLetter12).
While sufficient VC to breathe is usually attained for SCI patients with complete lesions below C3, unassisted cough flows are generally ineffective for all cervical and many thoracic SCI patients. As noted, a full conventional battery of pulmonary function studies and polysomnograms are suboptimal for SCI patients with decreased VC. These patients require ongoing annual monitoring of oximetry, EtCO2 or TcCO2, spirometry, and cough flow analyses as described (see evaluation and management).
Because they usually have intact bulbar innervated musculature, SCI patients can usually air stack very effectively and have manually assisted cough peak flows over 300 L/min which are usually adequate to clear the airways. All patients with VCs less than 1500 mL need to air stack to a maximally deep lung volumes before abdominal thrusts are applied for assisted coughing.
In 28 evaluations of patients with SCI, mean age 47 ± 13 years, with assisted CPF < 300 L/min, with mean VC in the sitting position 1031 ± 354 mL using accessory muscles and mean VC supine 512 ± 207 mL, the mean maximum insufflation capacity (MIC) was 1795 ± 948 mL, and although unassisted CPFs were 1.4 ± 0.6 L/second mean, assisted CPF were 3.5 ± 1.7 L/second (JBCV146,JBCV208). Although this can be the difference between coughing effectively to prevent pneumonia and acute respiratory failure or not, the relatively low assisted CPF of these patients warranted access to MIE during intercurrent respiratory infections. Indeed, all patients whose assisted and unassisted CPF cannot exceed 5 L/min should have oximeters at home for continuous monitoring and access to MIE to maintain SpO2 ≥ 95% during intercurrent infections as described (see oximetry feedback protocol). Older, obese, and scoliotic SCI patients are especially likely to require MIE for adequate cough flows when ill.
No one with spinal cord injury at any level of damage to the cord has been shown to be safer or better off with a tracheostomy tube than when managed noninvasively by CNVS, MIE, and occasionally with a phrenic nerve stimulator. One of our patients injured at birth in 1949 developed acute respiratory failure from pneumonia in 1975, underwent tracheotomy but was decanulated despite having a VC of only 730 mL. After multiple hospitalizations for chronic alveolar hypoventilation, cor pulmonale, and right heart failure, in 1977, she began ongoing nightly sleep lipseal NVS but soon required daytime periods of mouthpiece NVS, and required CNVS and MIE during daytime hours for all intercurrent respiratory tract infections. Since 2003, when her VC had decreased to 620 mL and with severe scoliosis, she became CNVS dependent with minimal ventilator-free breathing ability as she is today with a VC of 210 ml. Nevertheless, she has the ability to air stack to 1350 mL (see Figure 3 illustration in JBCV197).
The longest anyone with SCI has been CNVS dependent is a man who, at the age of 17, fell from a horse in a school gymnasium and sustained a fracture of C1 on C2 and complete C2 tetraplegia. He was immediately apneic and became permanently ventilator dependent on CTMV with no ventilator-free breathing ability. Bilateral phrenic pacemakers were placed but were ineffective. He remained in intensive care for 10 months due to pulmonary infections then was transferred for rehabilitation. His tracheostomy tube cuff had 12 mL of air and he developed severe trachiectasis with a cuff to trachea diameter ratio of 3:1. He had frequent airway mucus plugging that led to a cardiorespiratory arrest and cortical blindness. He was, therefore, very motivated to be decanulated. He was placed continuous noninvasive ventilatory support including mouthpiece NVS during the day with the tube capped on CMV pressure 20 cm H2O rate 18 breaths per minute. He also mastered glossopharyngeal breathing. Despite having 420 mL of VC using accessory muscles, unmeasurable VC supine, and no ventilator-free breathing ability during two years of CTMV, after another two episodes of pneumonia, he was decanulated, his pacemaker removed, and was maintained on continuous noninvasive ventilation including daytime mouthpiece CNVS for the next 29 years. Glossopharyngeal breathing permitted him breaths to 1700 mL and many hours of ventilator-free breathing ability. During the 29 years of noninvasive management, he had two episodes of pneumonia and had to be intubated once, but was extubated back to noninvasive management. After living with complete C2 tetraplegia, blind, and ventilator dependent in a nursing facility for 31 years, he requested and was granted assisted suicide, but was always grateful that his tracheostomy tube had been removed.
After regaining the ability to breathe independently 2.4 ± 2.2 years (range 1-8) after the acute injury, six patients were described who developed late-onset ventilatory insufficiency and required CNVS during intercurrent respiratory tract infections. These patients used mouthpiece NVS for daytime support. Three eventually lost all ventilator-free breathing ability to require lifetime CNVS (JBCV24,JBCV62). Subsequently, 16 of the Newark center SCI patients who weaned from ventilator use following the acute injuries at mean 27.9 years of age (range 0-61) began sleep NVS for symptomatic hypoventilation at age 39 (range 3 months to 63 years) with mean VCs of 1334 mL (range 640-3040) and cough peak flows of mean 3.1 L/min (range 0-495), thus, 11.6 years post-SCI (range 3 months to 28 years). The longest NVS user was injured at age 18, began NVS at age 21 with 850 mL of VC and has been using it for 34 years.
In summary, as noted in the challenge to SCI rehabilitation units in 2006, no alert, cooperative person with SCI at any level below the brain stem should need a tracheostomy tube for ventilatory support. Most such people without tracheostomy tubes who use some combination of CNVS and at times phrenic pacing can master glossopharyngeal breathing for ventilator-free breathing giving them security that is impossible when using CTMV. All TMV and CTMV users are candidates for decanulation to NVS provided that their upper airways are sufficiently open to permit at least 120 L/min of cough flows whether they be unassisted or assisted.