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Mechanical Ventilation and Weaning Protocols

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The indications for mechanical ventilation and the acute management of respiratory issues in SCI are outside the scope of this review which focuses on rehabilitation.  However, the long-term complications associated with chronic ventilator dependency need to be mentioned in order to highlight their importance.  The overall life expectancy for individuals with SCI who are ventilator dependent has been increasing, especially for those individuals who survive the first year following injury (DeVivo and Ivie 1995). Despite advances, mortality for individuals with ventilator dependency remains high (DeVivo and Ivie 1995).

In general, subjects with complete neurologic injuries at C2 and above have no diaphragmatic function and are ventilator dependent. Subjects with complete neurologic injuries at C3 or C4 have variable diaphragmatic function. Although they may have the potential for ventilator weaning, it is difficult to predict whether they will ultimately be successfully weaned. Subjects with complete injuries at C5 and below have intact diaphragmatic function. They may require ventilatory support initially post-injury, but are usually able to wean from the ventilator.

The approach to ventilator weaning in SCI remains an important and somewhat neglected issue. The PVA Consortium for Spinal Cord Medicine—Respiratory management following spinal cord injury: a clinical practice guideline for health-care professionals (2005) suggests the consideration of “progressive ventilator free breathing over synchronized intermittent mandatory ventilation”.

Table 8: Weaning protocols

Discussion

Peterson et al. (1994) retrospectively compared weaning methods in 52 subjects with C3 and C4 SCI. Overall 83% of subjects were successfully weaned with progressive ventilator free breathing (PVFB, also known as T-piece weaning) being the most successful technique. However, most of the PVFB trials occurred at a single institution and in subjects who were longer post-injury whereas most of the intermittent mandatory ventilation trials (IMV) occurred in a variety of institutions in subjects who were earlier post-injury.

Gutierrez et al. (2003) developed an evidence based resistive and endurance protocol to improve ventilatory muscle strength and endurance in subjects with ventilator-dependent cervical SCI.  The evidence was based on SCI literature where possible, but was also derived from the general respiratory literature where required. The protocol included 4 daily phases with rests in between each phase: pre-training optimization (Trendelenberg positioning, trachea suctioning, bronchodilator use, and lung hyperinflation); inspiratory/expiratory resistive training; on-ventilator endurance training; and off-ventilator endurance training.  Although the pilot study only included 7 subjects, it did show promising results with respect to increasing inspiratory pressure, expiratory pressure and VC and ultimately ventilator weaning, especially in subjects with low tetraplegia (C4-C7) (Gutierrez et al. 2003).

Onders et al. (2010) evaluated diaphragm pacing (DP) as a weaning method in 20 subjects who also had cardiac pacemakers, and found no immediate or long-term device-to-device interactions. All patients could go >4 hours without mechanical ventilators, and 71% could go 24 hours continuously with DP.

Wong et al. (2012) retrospectively analyzed the charts of 24 individuals with high cervical SCI (C1-C4) who underwent high tidal volume ventilation (HVtV) treatment, high frequency percussive ventilation (HFPV) treatment and/or and mechanical insufflation-exsufflation (MIE) treatment in a specialised SCI treatment unit. All patients showed improvements in their respiratory status with implementation of these treatments. Overall, 14 patients were successfully weaned from their ventilators.

Prospective studies on weaning protocols are required to determine the best way to assess, treat and wean subjects requiring mechanical ventilation following SCI.

Conclusion

There is level 3 evidence (from 1 retrospective analysis) (Wong et al. 2012) that the implementation of specialized respiratory management (HVtV, HFPV, MIE) resulted in improvement of respiratory status in all study subjects.

There is level 4 evidence (from 1 case series study) (Peterson et al. 1994) that progressive ventilator free breathing (PFVB) protocol is more successful for weaning subjects with C3 and C4 spinal cord injuries than intermittent mandatory ventilation (IMV).

There is level 4 evidence (from 1 case series study) (Onders et al. 2010) that DP serves as an effective weaning protocol in all subjects.

There is level 4 evidence (from 1 pre-post study)(Gutierrez et al. 2003) that a resistive and endurance protocol increases inspiratory pressure, expiratory pressure and VC especially in low tetraplegia (C4-C7).

  • Progressive ventilator free breathing protocol should be considered for ventilator dependent subjects with tetraplegia who are appropriate for ventilator weaning.
  • Resistance and endurance training should be considered in subjects who are candidates for ventilator weaning.