The effect of tidal volumes on the time to wean persons with high tetraplegia from ventilators

Abstract

Study design: Retrospective review of patient medical records comparing the outcomes of two groups of individuals with high-level (C3-4) tetraplegia ± those with high-volume and those with low-volume mechanical ventilation. Objectives: To determine if higher volume mechanical ventilation contributes to faster weaning from the ventilator with fewer complications in individuals with ventilator dependent high-level tetraplegia. Setting: A Model Spinal Injury Center, located in Colorado, USA, which treats patients referred from throughout the Rocky Mountain region as well as other states. Methods: The medical records of 42 individuals with ventilator dependent C3-4 tetraplegia, admitted consecutively to the Rocky Mountain Regional Spinal Injury System between 1983 and 1993, were reviewed. All had required full-time mechanical ventilation upon admission, but had successfully weaned by discharge. They were divided into two groups that di ered with respect to the ventilator tidal volumes used during their treatment and weaning: a large volume group (420 mls/kg of body weight) and a smaller volume group (520 mls/kg of body weight). Results: Though the two groups were equivalent in neurological level and completeness, muscular function, initial spontaneous vital capacity, the weaning method used (T-piece), and ®nal spontaneous vital capacity, those in the large tidal volume group successfully weaned an average of 21 days faster than the lower tidal volume group (37.6 days vs 58.7 days, P=0.02). They also had signi®cantly less atelectasis (P=0.01) than the lower tidal volume group. Conclusion: This research suggests that the use of higher ventilator tidal volumes may speed up the weaning process and lessen respiratory complications. Because of the potential for this to decrease the length and cost of the rehabilitation programs for persons with high-level tetraplegia, further large-scale research is needed to verify these single-center ®ndings.

A comparison of high vs standard tidal volumes in ventilator weaning for individuals with sub-acute spinal cord injuries: a site-specific randomized clinical trial

“…A retrospective concurrent cohort comparison study of SCI patients found that higher Vts (mean Vt 25.3 ml kg − 1 IBW) were associated with earlier weaning from mechanical ventilation and more rapid resolution of atelectasis than lower Vts (mean Vt 15.5 ml kg − 1 IBW). 11 A more recent retrospective review also suggested that the use of higher Vts resulted in fewer days on mechanical ventilation. 17 Large Vts prevent small-airway closure by stretching airway smooth muscle and reduce surface tension by expanding the surface area of pulmonary surfactant.…”

“…Sub-acute SCI patients are generally not felt to be at the same risk for ARDS, as acute SCI patients and higher Vts have been safely used in these patients for many years. 10,11,17 Current clinical practice guidelines even advocate higher Vts in SCI patients 5 because higher Vts have been associated with improved outcomes. A retrospective concurrent cohort comparison study of SCI patients found that higher Vts (mean Vt 25.3 ml kg − 1 IBW) were associated with earlier weaning from mechanical ventilation and more rapid resolution of atelectasis than lower Vts (mean Vt 15.5 ml kg − 1 IBW).…”

“…9 High Vts have been safely used in the sub-acute SCI population for many years and are believed to help prevent atelectasis, minimize pulmonary complications, augment speech and enhance weaning. 10,11 This study addresses the safety of using higher Vt in a pre-designated minimum 14-day protocol of ventilator weaning for sub-acute SCI patients who were not felt to be at risk for ARDS.…”

Respiratory alkalosis and associated electrolytes in long-term ventilator dependent persons with tetraplegia

“…3 A similar approach is taken by other centres experienced in the management of tetraplegic respiratory failure and it has been shown that ventilating with at least 20 ml/kg and an interposed dead space can hasten the slow wean of tetraplegic patients on short-term ventilatory support. 4 Despite the addition of a breathing system with dead space it is often di cult to avoid a degree of respiratory alkalosis in patients with paralysis and low metabolic rates. Persons with tetraplegia may on occasion have episodes of dizziness which can usually be attributed to postural hypotension, autonomic hypere¯exia with hypertension or hypoglycaemia.…”

Abdominal stimulation for respiratory support in tetraplegia: A tutorial review

“…Weaning: Most patients can be weaned from the ventilator but this is often a tedious process lasting several weeks [29]. Surface FES of abdominal muscles could be used as part of the weaning program to potentially reduce weaning times and overall stays.…”