A Comparison of High vs. Low Tidal Volumes in Ventilator Weaning for Individuals With Cervical Spinal Cord Injuries
Condition: Spinal Cord Injury; Respiratory Insufficiency
MeSH terms: Respiratory Insufficiency; Spinal Cord Injuries; Wounds and Injuries
Study type: Interventional

Summary: 
      The study will compare outcomes between individuals with sub-acute, ventilator-dependent
      tetraplegia using high (20 cc/kg) vs. low (10 cc/kg) tidal volumes during mechanical
      ventilator support.
    

Detailed description: 
      While respiratory failure in people with SCI is common, clinicians have not come to a
      consensus on the best strategy to manage the mechanical ventilation of these individuals or
      whether to manage people with SCI differently from other patients. The Consortium for Spinal
      Cord Medicine has developed Clinical Practice Guidelines using protocols established at Craig
      Hospital in the 1980s and 1990s, but these are based only on clinical experience and
      retrospective, cohort data using historical controls.

      These guidelines suggest that patients should be ventilated with tidal volumes (VT)of 20-25
      cc/kg of ideal body weight (IBW). This recommended VT is at least twice as large as
      conventional VT used for general medical and surgical patients requiring mechanical
      ventilation. However, there is a clinical belief that people with SCI should be ventilated at
      higher VT to prevent atelectasis, to decrease the risk of pneumonia, and to facilitate
      weaning. This belief was fostered by a retrospective, concurrent cohort comparison study of
      individuals with SCI, which found that the use of high VT on the ventilator (mean 25.3 cc/kg,
      PAP<40) was associated with more rapid resolution of atelectasis and more rapid weaning from
      mechanical ventilation than the use of low VT (mean 15.5). Therefore, people with SCI have
      been clinically managed using high VT for the past 2-3 decades without prospective data to
      confirm these clinical impressions.

      At the same time that these ventilator strategies evolved in the care of patients with SCI,
      several clinical studies in general medical and surgical patients requiring mechanical
      ventilation suggested that high VT leading to higher airway pressures could actually promote
      lung injury. This occurred when higher VT increased the risk of over-distending the airways
      and creating volume-related trauma.16-19 In multiple studies, VT of only 10-15 cc/kg IBW was
      found to produce alveolar over-distention, stretch injury and barotrauma. This work led to
      the belief that low VT of 6-8 cc/kg IBW could be helpful in protecting mechanically
      ventilated individuals from ventilator-induced lung injury.

      Whether these findings and recommendations apply to individuals with SCI requiring mechanical
      ventilation is unclear. At least one study of mechanically ventilated individuals without
      acute respiratory distress syndrome suggests that the use of low VT (6 cc/kg) increases the
      risk of atelectasis.

      With the lack of prospective, evidence-based data regarding optimal VT for persons with a SCI
      who are ventilator-dependent, clinicians may be inclined to use lower VT to prevent lung
      injury, unless there is more definitive data to show that higher volumes are as safe as low
      VT and that higher VT facilitate more rapid weaning from mechanical ventilation.

      This is a prospective randomized, controlled study to compare outcomes between individuals
      with sub-acute, ventilator-dependent tetraplegia using high (20 cc/kg) tidal volume (VT) vs.
      low (10 cc/kg) VT during mechanical ventilator support. While the use of lower tidal volumes
      in the general pulmonary community is more common, we and others in the SCI rehabilitation
      community have used 20 cc/kg IBW tidal volumes or higher to manage and attempt to wean
      individuals with SCI on mechanical ventilation. This study will address the safety and
      efficacy of using higher VT in ventilator weaning. A series of objective measures and
      standardized protocols are implemented to ensure equivalent pulmonary management and weaning
      processes in individuals, regardless of their randomization status.

        -  For individuals with sub-acute ventilator-dependent tetraplegia, providing high tidal
           volumes (VT = 20 cc/kg) will result in more rapid weaning from mechanical ventilation
           than use of low tidal volumes (VT = 10 cc/kg) in an 8-week trial.

        -  For these individuals, use of high tidal volumes will result in fewer episodes of
           atelectasis and ventilator acquired pneumonia (VAP) compared to use of low tidal
           volumes.

        -  There will be no difference in the incidence of a) barotrauma or b) ARDS between those
           using high tidal volumes compared to those using low tidal volumes.
    

Intervention name(s): Tidal volume used in mechanical ventilation
Intervention type(s): Procedure
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: spinal cord injury; ventilator dependency; ventilator weaning; tidal volume