Motor and Sensory Function as a Predictor of Respiratory Function Associated With Ventilator Weaning After High Cervical Cord Injury

Predicting extubation in patients with traumatic cervical spinal cord injury using the diaphragm electrical activity during a single maximal maneuver

BACKGROUND

The unsuccessful extubation in patients with traumatic cervical spinal cord injuries (CSCI) may result from impairment diaphragm function and monitoring of diaphragm electrical activity (EAdi) can be informative in guiding extubation. We aimed to evaluate whether the change of EAdi during a single maximal maneuver can predict extubation outcomes in CSCI patients.

METHODS

This is a retrospective study of CSCI patients requiring mechanical ventilation in the ICU of a tertiary hospital. A single maximal maneuver was performed by asking each patient to inhale with maximum strength during the first spontaneous breathing trial (SBT). The baseline (during SBT before maximal maneuver), maximum (during the single maximal maneuver), and the increase of EAdi (ΔEAdi, equal to the difference between baseline and maximal) were measured. The primary outcome was extubation success, defined as no reintubation after the first extubation and no tracheostomy before any extubation during the ICU stay.

RESULTS

Among 107 patients enrolled, 50 (46.7%) were extubated successfully at the first SBT. Baseline EAdi, maximum EAdi, and ΔEAdi were significantly higher, and the rapid shallow breathing index was lower in patients who were extubated successfully than in those who failed. By multivariable logistic analysis, ΔEAdi was independently associated with successful extubation (OR 2.03, 95% CI 1.52-3.17). ΔEAdi demonstrated high diagnostic accuracy in predicting extubation success with an AUROC 0.978 (95% CI 0.941-0.995), and the cut-off value was 7.0 μV.

CONCLUSIONS

The increase of EAdi from baseline SBT during a single maximal maneuver is associated with successful extubation and can help guide extubation in CSCI patients.

Respiratory Complications and Weaning Considerations for Patients with Spinal Cord Injuries: A Narrative Review

Respiratory complications following traumatic spinal cord injury are common and are associated with high morbidity and mortality. The inability to cough and clear secretions coupled with weakened respiratory and abdominal muscles commonly leads to respiratory failure, pulmonary edema, and pneumonia. Higher level and severity of the spinal cord injury, history of underlying lung pathology, history of smoking, and poor baseline health status are potential predictors for patients that will experience respiratory complications. For patients who may require prolonged intubation, early tracheostomy has been shown to lead to improved outcomes. Prediction models to aid clinicians with the decision and timing of tracheostomy have been shown to be successful but require larger validation studies in the future. Mechanical ventilation weaning strategies also require further investigation but should focus on a combination of optimizing ventilator setting, pulmonary toilet techniques, psychosocial well-being, and an aggressive bowel regimen.

Spinal cord injury and degenerative cervical myelopathy

Spinal cord injury (SCI) often results in impaired respiratory function. Paresis or paralysis of inspiratory and expiratory muscles can lead to respiratory dysfunction depending on the level and severity of the injury, which can affect the management and care of SCI patients. Respiratory dysfunction after SCI is more severe in high cervical injuries, with vital capacity (VC) being an essential indicator of overall respiratory health. Respiratory complications include hypoventilation, a reduction in surfactant production, mucus plugging, atelectasis, and pneumonia. Respiratory management includes mechanical ventilation and tracheostomy in high cervical SCI, while noninvasive ventilation is more common in patients with lower cervical and thoracic injuries. Mechanical ventilation can negatively impact the function of the diaphragm and weaning should start as soon as possible. Patients can sometimes be weaned from mechanical ventilation with assistance of electrical stimulation of the phrenic nerve or the diaphragm. Respiratory muscle training regimens may also improve patients' inspiratory function following SCI. Despite the critical advances in preventing, diagnosing, and treating respiratory complications, they continue to significantly affect persons living with SCI. Additional studies of interventions to reduce respiratory complications are likely to further decrease the morbidity and mortality associated with these injuries.

Separation from mechanical ventilation and survival after spinal cord injury: a systematic review and meta-analysis

BACKGROUND

Prolonged need for mechanical ventilation greatly impacts life expectancy of patients after spinal cord injury (SCI). Weaning outcomes have never been systematically assessed. In this systematic review and meta-analysis, we aimed to investigate the probability of weaning success, duration of mechanical ventilation, mortality, and their predictors in mechanically ventilated patients with SCI.

METHODS

We searched six databases from inception until August 2021 for randomized-controlled trials and observational studies enrolling adult patients (≥ 16 years) with SCI from any cause requiring mechanical ventilation. Titles and abstracts were screened independently by two reviewers. Full texts of the identified articles were then assessed for eligibility. Data were extracted independently and in duplicate by pairs of authors, using a standardized data collection form. Synthetic results are reported as meta-analytic means and proportions, based on random effects models.

RESULTS

Thirty-nine studies (14,637 patients, mean age 43) were selected. Cervical lesions were predominant (12,717 patients had cervical lesions only, 1843 in association with other levels' lesions). Twenty-five studies were conducted in intensive care units (ICUs), 14 in rehabilitative settings. In ICU, the mean time from injury to hospitalization was 8 h [95% CI 7-9], mean duration of mechanical ventilation 27 days [20-34], probability of weaning success 63% [45-78] and mortality 8% [5-11]. Patients hospitalized in rehabilitation centres had a greater number of high-level lesions (C3 or above), were at 40 days [29-51] from injury and were ventilated for a mean of 97 days [65-128]; 82% [70-90] of them were successfully weaned, while mortality was 1% [0-19].

CONCLUSIONS

Although our study highlights the lack of uniform definition of weaning success, of clear factors associated with weaning outcomes, and of high-level evidence to guide optimal weaning in patients with SCI, it shows that around two-thirds of mechanically ventilated patients can be weaned in ICU after SCI. A substantial gain in weaning success can be obtained during rehabilitation, with additional duration of stay but minimal increase in mortality. The study is registered with PROSPERO (CRD42020156788).