One of the most important avenues of respiratory management is mechanical ventilation. Over the past 40 years, there has been an increase in the incidence of cervical cord injuries and, as a result, an increase in the use of mechanical ventilation (Devivo, 2012; Jackson et al. 2004). Patients can be ventilated with non-invasive mask ventilation or more invasive endotracheal or transtracheal (with a tracheostomy) ventilation. Often these more invasive procedures are needed to allow for the ability to suction excess secretions to prevent the development of complications such as atelectasis or pneumonia (Gregoretti et al. 2005). Patients may experience more than one type of ventilation during their hospital stay as their needs adjust (i.e., they may initially be intubated with endotracheal ventilation and later proceed to transtracheal intubation to assist in ventilator weaning).
In addition to the delivery of ventilation, there are several modes of ventilation used for patients that vary in the amount of volume or pressure controlled based on pre-set variables to maximize lung function. For example, intermittent positive pressure breathing is one of the oldest ventilation strategies in which all inspirations are provided through the application of positive pressure to the airway. Its use is common in acute SCI patients, yet its general efficacy is still largely unknown (Denehy & Berney, 2001) and is understudied in the SCI population. Intubation for mechanical ventilation often occurs at the time of injury to manage respiratory failure or to protect the airway in cases of complete SCI between C1 and C5 (Berney et al. 2011). In contrast, incomplete injuries lower than C5, where the airway is not immediately compromised or at risk, ventilation is often still initiated approximately four days after injury when levels of carbon dioxide rise in the blood due to difficulty expiring (Galeiras Vázquez et al. 2013). Although ventilatory needs are unique for each patient, it is useful to determine which factors predict the need for mechanical ventilation in an effort to develop practice guidelines and reduce overall hospital stay (Casha & Christie, 2011).
Neuromuscular weakness due to SCI typically results in restrictive lung disease as opposed to acute lung injury. These patients experience different breathing capabilities than do other critical care patients on mechanical ventilation (Raurich et al. 2014). For this reason they may require unique approaches to their ventilatory needs. High tetraplegia, complete SCI, a high number of operations, pneumonia, atelectasis, and excessive sputum are all predictors for a patient requiring mechanical ventilation (Claxton et al. 1998; Lertudomphonwanit et al. 2014; McCully et al. 2014). Furthermore, the presence of a tracheostomy has been documented to require and to prolong mechanical ventilation (Kornblith et al. 2014; Leelapattana et al. 2012; McCully et al. 2014), but this relationship is reversed if patients receive the tracheostomy early (within 10 days of injury; Choi et al. 2013; Romero-Ganuza et al. 2011; Romero et al. 2009).
While most studies focusing on mechanical ventilation to date have been retrospective in nature, two prospective controlled trials have been conducted which evaluated the effectiveness of mechanical ventilation during acute SCI. Stiller et al. (1992) evaluated intermittent positive pressure breathing and reported that it indeed increases lung volume and vital capacity in SCI patients to allow for better breathing. Gregoretti et al. (2005) compared transtracheal open ventilation with endotracheal invasive ventilation and found that transtracheal open ventilation is just as effective and a more comfortable alternative to patients. Although there are several other methods of ventilation, no studies yet exist that evaluate their efficacy in SCI patients.
There is level 4 evidence (from two case series; Lertudomphonwanit et al. 2014; Claxton et al. 1998) that complete injuries and injuries above level C5 predict the need for mechanical ventilation in acute SCI patients.
There is level 2 evidence (from one cohort study, one case control and one case series; Leelapattana et al. 2012; McCully et al. 2014; Kornblith et al. 2014) that acute SCI patients who have had a tracheostomy experience a longer duration of mechanical ventilation compared to those who have not had a tracheostomy.
There is level 4 evidence (from three case series; Choi et al. 2013; Romero-Ganuza et al. 2011a; Romero et al. 2009) that patients who have had an early tracheostomy experience a shorter duration of mechanical ventilation compared to those who have had a late tracheostomy.
Complete injuries, as well as injuries C4 and above, have been identified as factors predictive of the need for mechanical ventilation during the acute phase post SCI.
Tracheostomy procedures increase the duration of required mechanical ventilation, although this may be reduced if they are performed early (<10 days post injury or hospital admission).